EP4106937A1

EP4106937A1 - Laser-center-dependent exposure strategy

Info

Publication number: EP4106937A1
Application number: EP21706253.8A
Authority: EP
Inventors: Sarah Brandt; Alexander Frey
Original assignee: EOS GmbH
Current assignee: EOS GmbH
Priority date: 2020-02-18
Filing date: 2021-02-17
Publication date: 2022-12-28
Also published as: CN115135436A; DE102020201995A1; US20230077127A1; WO2021165305A1

Abstract

In a method for controlling an energy input device (20) of an additive manufacturing device for manufacturing a three-dimensional object by means of same, a beam deflection center (23) above the build plane (7) is assigned to each of the number of beams, proceeding from which center said beam is directed at the build plane (7), wherein each beam deflection center (23) is assigned a projection center (23') corresponding to a perpendicular projection of the position of the beam deflection center (23) onto the build plane (7), wherein at least in a portion of an object cross-section the directions of the motion vectors of the number of beams (22) during scanning of the trajectories (54) are defined such that at each of the solidification locations in said portion the motion vector is at an angle with respect to a connection vector from said solidification location toward the projection center (23') of the beam (22) used, which angle is less than a predetermined maximum angle γ1.

Description

Exposure strategy depending on the laser center

The present invention relates to a method for controlling an energy input device of an additive manufacturing device, a correspondingly adapted additive manufacturing method, a corresponding device for controlling an energy input device of an additive manufacturing device, a correspondingly adapted additive manufacturing device and an object produced by the correspondingly adapted additive manufacturing method.

Additive manufacturing devices and associated methods to which the invention relates are generally characterized in that objects are manufactured in them layer by layer by solidifying a shapeless construction material (eg a metal or plastic powder). The solidification can be brought about, for example, by supplying thermal energy to the building material by irradiating it with electromagnetic radiation or particle radiation (eg laser sintering (SLS or DMLS) or laser melting or electron beam melting). For example, during laser sintering or laser melting, a laser beam is moved over those points of a layer of the building material which correspond to the object cross-section of the object to be produced in this layer, so that the building material is solidified at these points. After the building material has been melted or sintered at one point by the supply of thermal energy, the building material is no longer in a shapeless state, but as a solid body after cooling. After all points of an object cross-section to be solidified have been scanned, a new layer of the building material is applied and also solidified at the points corresponding to the cross-section of the object in this layer. In particular when processing metal powder as a build-up material, impurities (e.g. metal vapors, smoke or spatter) occur during the melting process, which are deposited on the layer to be solidified or hinder the supply of radiation. Such impurities are undesirable since they can lead, for example, to an undesirable scatter in the mechanical properties of the objects produced. In the prior art, attempts are therefore made to minimize the effects of these impurities on the properties of a manufactured object by directing a gas stream over the point to be solidified during the scanning process.

In WO 2014/125280 A2 it is proposed to match the direction of movement of the beam when scanning the layer to the direction of the gas flow in order to achieve object properties that are as homogeneous as possible. Although an improvement in the object properties is already achieved through such a procedure, the procedure described is still in need of improvement, since on the one hand the coordination of the movement of the beam and the direction of the gas flow to each other sometimes complicates the manufacturing process and on the other hand, especially in the case of extensive construction areas, there is still inhomogeneity of the Object properties were observed.

It is therefore an object of the present invention to provide a method and a device for controlling an energy input device of an additive manufacturing device, by means of which an improved homogeneity of the properties of additively manufactured objects can be achieved.

The object is achieved by a method for controlling an energy input device according to claims 1, 5 and 10, an additive manufacturing method according to claim 24, a device for controlling an energy input device according to claims 25, 26 and 27, an additive manufacturing device according to claim 28 and an object according to Claim 29. Further developments of the invention are claimed in the dependent claims. In particular, a device according to the invention can also be further developed by the features of the method according to the invention below or as set out in the dependent claims vice versa. Furthermore, the features described in connection with a device according to the invention can also be used to develop another device according to the invention, even if this is not explicitly stated.

Additive manufacturing devices and methods to which the present invention relates are in particular those in which energy is selectively supplied as electromagnetic radiation or particle radiation to a layer of a shapeless building material. The working level (also referred to as the construction level) is a level in which the top of the layer to which the energy is supplied lies. In this case, the energy input device can have a laser or an electron beam source, for example. The radiation supplied to the building material heats it up and thereby causes a sintering or melting process.

In particular, the present invention relates to laser sintering, laser melting, and electron beam melting devices and their associated methods.

Although the invention can be used both in connection with plastic-based construction material and in connection with metal-based construction material, one application of the invention is in connection with additive manufacturing methods and devices in which a metallic or at least metal-containing construction material is used, for example a metal powder or metal alloy powder , of particular advantage.

It should be noted at this point that by means of an additive manufacturing device according to the invention, not only one object, but also several objects can be manufactured at the same time. When the production of an object is mentioned in the present application, then it goes without saying that the respective description can also be applied in the same way to additive production methods and devices in which several objects are produced at the same time.

The term “beam” is used here instead of “beam” in order to express that the diameter of the beam does not necessarily have to be very small, in particular if the radiation strikes the building material at an angle or but radiation is used, which is intended to cover a larger surface area when it hits the building material.

A beam deflection center can be, for example, a scanner with one or more galvanometer mirrors for deflecting a laser beam. Several different bundles of rays can also be assigned to one and the same bundle of rays deflection center or scanner, which e.g. are directed alternately from this bundle of rays to the construction plane, although normally one bundle of rays to be directed to the plane of construction is assigned to a bundle of rays deflection center. It should be noted at this point that in the present application the term “number” is always to be understood in the sense of “one or more.” For a projection of the position of the beam deflection center onto the building level, for example, a plumb line can be set up on the building level which passes through a point of the beam deflection center from which the beam directed by the beam deflection center onto the building plane starts. The projection center is then that place in the building plane at which the plumb bob was erected that in the case of several bundles of rays which are assigned to a bundle of rays deflection center, any differences in position of the points at which the bundles of rays originate are negligible.

In the method according to the invention, to produce at least a number of cross-sections of the object, preferably for the production of the entire object, the energy input device is controlled based on a data model of an object cross-section in such a way that the points to be consolidated corresponding to the object cross-section are provided by the energy input device Building material necessary energy is supplied. In particular, the chronological order in which the points are to be solidified, i.e. a scan line or a trajectory in the building plane along which the beam is to be moved, is specified and the number of beam deflection centers for moving the beam bundles assigned to them is controlled accordingly . A trajectory of a beam bundle that is predetermined when the energy input device is activated corresponds to a solidification path in the building plane, along which the building material is to be solidified by displacing the melt pool in a direction essentially parallel to the building plane. In this case, so much energy is supplied to the, preferably powdery or pasty, building material at a solidification point by the beam that the building material sintered or completely melted at this point as a result of exceeding a melting temperature, i.e. a solidus and / or liquidus temperature, in order to then cooled state no longer in the formless state, but to be present as a solid. Consolidation tracks are therefore areas in which, when the building material is scanned by the at least one beam, consolidation and not just heating of the same is actually brought about. A consolidation sheet can e.g. B. be a straight stretch of a certain width, but there are also cases in which when moving a beam along the consolidation path one or more changes in direction take place, in particular the consolidation path is geometrically as a curved line of a certain width. If in the present application reference is made to scanning with a beam, then this always means an action of the beam on the building material, which causes a solidification of at least one top layer of the building material, i.e. not just preheating or reheating the building material.

If an angle between two vectors is mentioned in this application, this is always understood to mean an angle between the directions of the two vectors, the value of which is less than or equal to 180 °.

A section of an object cross-section to which the invention relates does not necessarily have to relate only to a partial area of an object cross-section or a single object cross-section, but can also encompass the entire object to be produced.

In a method according to the invention for controlling an energy input device of an additive manufacturing device for manufacturing a three-dimensional object by means of the same, the object is produced by means of the additive Manufacturing device produced by applying a building material layer on layer and solidifying the building material in a building level by means of the energy input device by supplying radiant energy to solidification points in each layer, which are assigned to the cross section of the object in this layer, by connecting these solidification points with a number of from the energy input device provided ray bundles are scanned along a plurality of trajectories in the building plane, each of the number of ray bundles being assigned a ray bundle deflection center above the building plane, from which this ray bundle is directed onto the building plane, a projection center being assigned to each ray bundle deflection center, which corresponds to a perpendicular projection of the position of the beam deflection center on the building plane, wherein at least in a section of an object cross section, the directions of the motion vectors of the number A number of beam bundles when scanning the trajectories are set so that at each of the solidification points in this section the motion vector has an angle with respect to a connection vector from this solidification point to the projection center of the beam bundle used, which is smaller than a predetermined maximum angle g1.

A connection vector from a consolidation point to the projection center is a vector directed along the shortest possible straight connecting line between the consolidation point and the projection center to the projection center, the length of which corresponds to the distance between the consolidation point and the projection center.

With the method according to the invention, objects with improved homogeneity can be produced additively. This applies not only to the homogeneity of the material properties within an object, but also with regard to the reproducibility of the properties from object to object when the same objects are manufactured at different locations in the additive manufacturing device at the same time. The inventors explain this by the fact that, during a manufacturing process, the beam bundle is almost always at an angle different from 90 ° Angle hits the building plane. The beam bundle actually only hits the projection center at right angles. According to the findings of the inventors, if the bundle of rays impinges at an angle, there may be a displacement of build-up material at the solidification point. For example, the inventors were able to observe that when the bundle of rays impinging at an angle, the more build-up material is displaced, the more pronounced the movement of the bundle of rays away from the projection center. A displacement of building material leads to the fact that the solidified material volume fluctuates, which results in an inhomogeneity of the mechanical properties. Avoiding directions of movement of the beam that essentially point away from the projection center therefore has advantages. In particular, these advantages arise independently of the respective orientation of a gas flow over the construction field with respect to the motion vector of a beam.

It should be noted that it is also possible to specify different values for the maximum angle g1 for motion vectors that lie on different sides of the connection vector.

The predetermined maximum angle g1 preferably has a value that is less than or equal to 135 °, preferably less than or equal to 90 °.

In order to achieve good results, a maximum angle of 90 ° is preferably chosen. However, even with a maximum angle between 90 ° and 135 °, satisfactory results can still be achieved. The lower the maximum angle, the better results can be achieved. Therefore, depending on the quality requirements, a maximum angle of 75 °, 60 °, 45 °, etc. can also be selected.

More preferably, different maximum angles g1 are defined for different values of a beam deflection angle a, with a beam deflection angle being defined as the arctangent of the quotient of the distance between the solidification point and the projection center and the length of the projection line of the beam deflection center, the projection line of the beam Deflection center is a plumb line precipitated on the building level, which connects the projection center with the beam deflection center.

A beam deflection angle a is defined here as the angle between the direction of propagation of the beam and the perpendicular to the building plane. The more obliquely the beam strikes the building plane, i.e. the larger the beam deflection angle a, the more pronounced the effects will be when the beam strikes the building material (in particular a material displacement) and the smaller the maximum angle g1 should be selected. It is therefore advantageous to use a smaller maximum angle g1 as a basis in regions which are further away from the projection center of a beam deflection center. It is already advantageous if at least two different values of the maximum angle g1 are used as a basis, whereby a gradation with three, four or five different values of the maximum angle g1 depending on the beam deflection angle a leads to even better results.

It is further preferably specified in the method that at least two adjacent trajectories are scanned in the same or different directions, and different beam bundles are used to scan adjacent trajectories.

The advantage of this procedure is particularly evident when the different beam bundles are assigned to different beam bundle deflection centers. A scanning process can then proceed more quickly because, regardless of the temporal advantage of simultaneous scanning of different points of the object cross-section for each solidification point, that beam can always be selected for scanning which, due to the position of the associated projection center, is favorable for implementing the preferred mode of exposure. In particular, it is then possible to scan neighboring trajectories in alternating directions, it being possible for this to be carried out with an increased time offset, if necessary. When manufacturing a three-dimensional object with the additive manufacturing device, it is possible to guide a gas flow over the respective solidification point during the scanning. In this case, the directions of the motion vectors of the number of beam bundles when scanning the trajectories are preferably set in the at least one section of an object cross section such that a directional component of the gas flow is opposite to the direction of the motion vectors of the number of beam bundles.

In particular, the angle between each of the motion vectors and the direction of the gas flow can be greater than 90 °, preferably greater than 135 °, more preferably greater than 150 °. The optimal case would be if the direction of the gas flow were exactly opposite to that of the motion vectors.

As a result, it is possible to further improve the results that can be achieved with the invention by additionally taking into account the orientation of the gas flow.

In a further method according to the invention for controlling an energy input device of an additive manufacturing device for manufacturing a three-dimensional object by means of the same, the object is manufactured by means of the additive manufacturing device by applying a building material layer on layer and solidifying the building material in a building plane by means of the energy input device by supplying radiant energy Solidification points in each layer, which are assigned to the cross section of the object in this layer, in that these solidification points are scanned with a number of beam bundles provided by the energy input device along a plurality of trajectories in the building plane, each of the number of beam bundles having a beam deflection center above is assigned to the building level from which the beam is directed onto the building level, with each beam deflection center having a projection center is assigned which corresponds to a perpendicular projection of the position of the beam deflection center on the building plane, whereby at least one section of an object cross-section is solidified, sub-area by sub-area, wherein in at least one of the sub-areas, the solidification points of which are scanned with a beam bundle assigned to this sub-area, the sequence of the scanning of the trajectories is determined so that trajectories that are closer to the projection center of the beam bundle are to be scanned in front of trajectories that are further away from the projection center.

The sub-areas mentioned can in principle have any shape. A rectangular or square shape is preferably chosen, since then the trajectories in a partial area are often of the same length or essentially the same length, as a result of which better homogeneity can be achieved during solidification. Two trajectories are essentially parallel when they are parallel to one another for at least 80%, preferably at least 95% of the length of the shorter of the two.

If the same method for determining their spatial distance from the projection center is used as the basis for all trajectories present in a sub-area, there are no restrictions on how the distance is to be determined. For example, an average value of the distances of all points on a trajectory to the projection center can be defined as the distance of the trajectory from the projection center. However, it would be conceivable, for example. also to define the minimum of the distances of all points on a trajectory from the projection center as the distance of the trajectory from the projection center.

In the method according to the invention, which can lead to additively manufactured objects with improved homogeneity, the advantage results from the fact that a non-isotropic deposition of material is taken into account when a beam of rays hits the building plane at an angle. In particular, in the case of a bundle of rays impinging obliquely during the melting process, impurities (eg partially melted material) are preferably deposited towards the projection center in the building plane. When trajectories that are closer to the projection center are followed by trajectories that are closer to the projection center greater distance from the projection center are scanned, then this leads to the trajectories being scanned in a partial area, one after the other, starting with the one closest to the projection center and ending with the one farthest away from the projection center. This leads to the fact that impurities arising during the scanning of a trajectory are always deposited on already solidified building material (towards the projection center). This improves the homogeneity of the solidified object, since the impurities cannot affect the solidification process of the subsequent trajectory, as would be the case with the reverse scanning sequence. In particular, there is an improved homogeneity regardless of the respective orientation of a gas flow over the construction field.

In a sub-area in which the trajectories run essentially parallel to one another and the sequence of the scanning of the trajectories is determined in such a way that trajectories that are closer to the projection center of the beam are scanned before trajectories that are further away from the projection center are preferred, the directions of the motion vectors along the trajectories are set so that at each of the solidification points the motion vector has an angle with respect to a connection vector from this solidification point to the projection center of the beam used for this sub-area, which is smaller than a predetermined maximum angle g1.

The procedure described combines the advantages of an advantageous choice of the direction of the motion vector when scanning the trajectories with those of an advantageous choice of the scanning sequence of the trajectories, so that even more homogeneous components can be achieved. In order to achieve good results, a maximum angle g1 of 90 ° is preferably chosen. However, even with a maximum angle between 90 ° and 135 °, satisfactory results can still be achieved. The lower the maximum angle, the better results can be achieved. Therefore, depending on the quality requirements, a maximum angle of 75 °, 60 °, 45 °, etc. can also be selected. In order to determine the proximity of a trajectory to the projection center for each of the trajectories, a reference point connection vector is preferably constructed from a reference point on the respective trajectory, preferably from a starting point of the respective trajectory, to the projection center and the length of the component of the perpendicular to the trajectory Reference point connection vector determined, whereby it is established that for each two trajectories in which the length of the component perpendicular to the trajectory differs, that trajectory is closer to the projection center of the beam, in which the length of the component perpendicular to the trajectory is smaller is.

A reference point on a trajectory is a point whose distances from the start and end points of the trajectory meet a predefined ratio. In particular, this can be the starting point or the end point of the trajectory. If neighboring trajectories are traversed in opposite directions, the reference point can, for example, be defined as that point which is at the same distance from the starting point and the end point. The procedure described for determining the distances between the trajectories and the projection center is particularly advantageous when the trajectories are not perpendicular to the connection vectors from the projection center to the respective starting points of the trajectories.

More preferably, in a sub-area in which the trajectories run essentially parallel to one another and the order of the scanning of the trajectories is determined in such a way that trajectories that are closer to the projection center of the beam are scanned before trajectories that are further away from the projection center , the motion vector at at least one solidification point an angle with respect to a connection vector from this solidification point to the projection center of the beam bundle used, which is greater than a predetermined minimum angle g2.

If the motion vector of the beam when scanning the trajectories has a small angle with respect to the connection vector of a solidification point on the trajectory to the projection center, then when it hits at an angle of the beam on the building level, the impurities are deposited approximately along the trajectory itself. An impairment of neighboring trajectories is then not so great. It is therefore sensible to define a minimum angle g2 and to determine a specific sequence for scanning the trajectories only when this minimum angle is exceeded. A value of 45 ° can preferably be selected for the minimum angle, more preferably a value of 60 °, even more preferably a value of 75 °.

It should also be noted that it is also possible to specify different values for the minimum angle g2 for motion vectors which lie on different sides of the connection vector.

Preferably, different minimum angles g2 are set for different values of a beam deflection angle a, a beam deflection angle being defined as the arctangent of the quotient of the distance between the solidification point and the projection center and the length of the projection line of the beam deflection center, the projection line of the beam deflection center being defined on the construction plane is a precipitated plumb line that connects the projection center with the beam deflection center.

The more obliquely the beam hits the building plane, the more pronounced the deposition of impurities will be in a preferred direction. It is therefore advantageous to use a smaller minimum angle g2 as a basis in regions which are further away from the projection center of a beam deflection center. It is already advantageous if at least two different values of the minimum angle g2 are used as a basis.

When manufacturing a three-dimensional object with the additive manufacturing device, it is possible to guide a gas flow over the respective solidification point during the scanning. In this case, a beam deflection center is preferably selected for scanning the solidification points in the at least one of the subregions, for which a directional component of the gas flow from the Shows solidification points to the projection center assigned to the beam deflection center.

In particular, the angle between the direction of the gas flow and the connecting line between the solidification point and the projection center can be selected to be less than 90 °, preferably less than 45 °, more preferably less than 30 °. The optimal case would be when the gas flow points exactly to the center of the projection.

In a further method according to the invention for controlling an energy input device of an additive manufacturing device for manufacturing a three-dimensional object by means of the same, the object is manufactured by means of the additive manufacturing device by applying a building material layer on layer and solidifying the building material in a building plane by means of the energy input device by supplying radiant energy Solidification points in each layer, which are assigned to the cross section of the object in this layer, in that these solidification points are scanned with a number of beam bundles provided by the energy input device along a plurality of trajectories in the building plane, each of the number of beam bundles having a beam deflection center above is assigned to the building level from which the beam is directed onto the building level, with a projection center for each beam deflection center which corresponds to a perpendicular projection of the position of the beam deflection center onto the building plane, with at least one section of an object cross-section being solidified, sub-area by sub-area, the chronological sequence of the scanning of sub-areas whose solidification points are scanned with a beam assigned to these sub-areas , is determined in such a way that sub-areas, which are closer to the projection center of the beam, are scanned in front of subregions which are further away from the projection center.

The sub-areas mentioned can in principle have any shape. Furthermore, the sub-areas can in principle have any shape and the areas of the different sub-areas can also be of different sizes. Furthermore, the building material does not necessarily have to be solidified along straight trajectories within the partial areas. Scanning along a cycloid path would also be conceivable (referred to as "wobbling" in technical jargon). However, if the trajectories in a sub-area are selected to be essentially parallel and essentially of the same length, a rectangle or square shape of the sub-areas is preferably selected at the same time A parallel course of two trajectories exists when they are parallel to one another for at least 80%, preferably at least 95% of the length of the shorter of the two. that are adjacent to each other without any gaps.

If the same method for determining their spatial distance from the projection center is used as a basis for all sub-areas, there are no restrictions on how the distance is to be determined. For example, a mean value of the distances from all points to be solidified within a sub-area from the projection center can be defined as the distance of the sub-area from the projection center. However, it would be conceivable, for example. also to define the minimum of the distances between all points to be consolidated within a sub-area from the projection center as the distance of the sub-area from the projection center.

In the method according to the invention, which can lead to additively manufactured objects with improved homogeneity, the advantage also results from the fact that a non-isotropic or spatially unevenly distributed deposit of impurities is taken into account when a beam hits the building plane at an angle. As already mentioned above, in the case of a beam impinging at an angle, the impurities are preferred to the Projection center deposited in the building level. If sub-areas to which the same beam bundle is assigned for a scan are scanned in such a way that those sub-areas that have a smaller distance from the projection center of the beam are scanned before sub-areas that are a greater distance from the projection center, then this leads to that the partial areas are scanned one after the other, starting with the one closest to the projection center and ending with the one furthest away from the projection center. This has the result that impurities that arise during the scanning of a partial area are always deposited on already solidified building material (towards the projection center). This improves the homogeneity of the solidified object, since the impurities cannot impair the solidification process of the subsequent sub-area, as would be the case with the reverse scanning sequence. In particular, there is an improved homogeneity regardless of the respective orientation of a gas flow over the construction field.

In the subregions for which the temporal sequence of scanning is defined, the motion vector at each of the solidification points preferably has an angle with respect to a connection vector from this solidification point to the projection center of the beam used for this partial area, which is smaller than a predetermined maximum angle g1.

The procedure described combines the advantages of an advantageous choice of the direction of the motion vector when scanning the trajectories with those of an advantageous choice of the scanning sequence of the partial areas, so that even more homogeneous components can be achieved. In order to achieve good results, a maximum angle g1 of 90 ° is preferably chosen. However, even with a maximum angle between 90 ° and 135 °, satisfactory results can still be achieved. The lower the maximum angle, the better results can be achieved. Therefore, depending on the quality requirements, a maximum angle of 75 °, 60 °, 45 °, etc. can also be selected. Preferably, in at least one sub-area whose solidification points are scanned with a beam bundle assigned to this sub-area, the sequence of scanning of the trajectories is set in such a way that trajectories that are closer to the projection center of the beam are scanned before trajectories that are further away from the projection center .

If the same method for determining their spatial distance from the projection center is used as the basis for all trajectories present in a sub-area, there are no restrictions on how the distance is to be determined. For example, an average value of the distances of all points on a trajectory to the projection center can be defined as the distance of the trajectory from the projection center. However, it would be conceivable, for example. also to define the minimum of the distances of all points on a trajectory to the projection center as the distance of the trajectory from the projection center.

The procedure described combines the advantages of an advantageous selection of the scanning sequence of the trajectories within a sub-area, preferably within each of the sub-areas, with those of an advantageous selection of the scanning sequence of the sub-areas, whereby more homogeneous components can be achieved.

More preferably, the minimum of the distances between the solidification points in the partial area from the projection center is used as the measure for the distance of a sub-area from the projection center.

With the described definition of the distance of a sub-area from the projection center, a scanning sequence of the sub-areas can be defined in a simple manner.

The section further preferably has a plurality of sub-areas which have a rectangular shape in a plan view of the building plane, the trajectories in the section running essentially parallel to one another and essentially parallel to the transverse sides of the sub-areas, with one as a measure of the distance Subarea from the projection center the length of a perpendicular from the projection center to a straight line running through a subarea parallel to a longitudinal side is used.

With such a definition of the distance of a sub-area from the projection center, a scanning sequence can be established in a defined manner, in particular for rectangular sub-areas lying next to one another.

More preferably, when cross-sections of the object present in different layers are solidified, the longitudinal sides of the plurality of subregions in the different layers have a changed orientation in the building plane.

A changed orientation of the sub-areas in the building plane from layer to layer can lead to a reduction in the anisotropy of the properties of the manufactured objects. The more frequently the subregions are rotated from layer to layer, the more isotropic properties can be achieved in a plane parallel to the building plane. If the orientation of the trajectories in the sub-areas is chosen such that the trajectories always intersect the long sides of the sub-areas at a specified angle, then the different orientation of the sub-areas from layer to layer also results in a different orientation of the trajectories in them from layer to layer Layer. This can result in a different definition of the scanning sequence of the sub-areas from layer to layer and in particular a different assignment of laser beam deflection centers to sub-areas in order to ensure an optimized direction of the motion vectors and scanning sequences in relation to the respective projection center. In particular, a slice rotation angle d, by which the subregions are rotated from slice to slice, can be defined as a function of a maximum angle g1 and / or minimum angle g2 predetermined for the subregions.

More preferably, in each of the sub-areas for which the temporal sequence of the scanning is defined, the motion vector has one at a solidification point Angle with respect to a straight connecting line from this solidification point to the projection center of the beam bundle used, which is greater than a predetermined minimum angle g2.

If the direction of the trajectories has a small angle with respect to the connection vector of a solidification point on the trajectory towards the projection center, then when the beam hits the building plane at an angle, the impurities are deposited approximately along the trajectory itself. An impairment of neighboring trajectories is then not so great. It is therefore sensible to define a minimum angle g2 and to determine a certain sequence of scanning of the partial areas only when this minimum angle is exceeded. A value of 45 ° can preferably be selected for the minimum angle, more preferably a value of 60 °, even more preferably a value of 75 °.

When manufacturing a three-dimensional object with the additive manufacturing device, it is possible to guide a gas flow over the respective solidification point during the scanning. In this case, a beam deflection center is preferably selected for scanning the solidification points in the at least one section of an object cross-section, for which a directional component of the gas flow points from the solidification points to the projection center assigned to the beam deflection center.

A method according to the invention is also preferably carried out for a section which has at least one solidification point when it is scanned a beam deflection angle exceeds a minimum deflection angle a1, where a beam deflection angle is defined as the arctangent of the quotient of the distance between the solidification point and the projection center and the length of the projection line of the beam deflection center, the projection line of the beam deflection center being a perpendicular precipitated on the building plane, which is the Projection center connects with the beam deflection center.

The more obliquely the beam hits the building plane, the more pronounced the deposition of impurities will be in a preferred direction. Therefore, for small beam deflection angles, the procedure according to the invention can be dispensed with. To determine the minimum deflection angle a1, preliminary tests can be carried out with the construction material to be used and the beam parameters to be used (e.g. laser power, beam diameter, etc.). The minimum deflection angle a1 will also depend on the extent of inhomogeneities in the solidified building material that is acceptable in the object to be produced. Experience has shown that for most of the metal-containing powders used as building material, for the usual requirements for component homogeneity, a minimum deflection angle a1 can be set that is greater than or equal to 16 °, preferably greater than or equal to 13 °, more preferably greater than or equal to 10 °, particularly preferably greater than or equal to 7.5 ° is, can choose.

For the scanning of the construction material along a trajectory, a beam is also preferably used, the beam deflection angle a of which does not exceed a predetermined maximum deflection angle a2, a beam deflection angle being defined as the arctangent of the quotient of the distance of a solidification point from the projection center and the length of the projection line of the beam deflection center where the projection line of the beam deflection center is a plumb line precipitated on the building plane, which connects the projection center with the beam deflection center.

The procedure described is appropriate in cases in which there are a plurality of beam deflection centers. When the building material is scanned, there may be increased unilateral deposition of impurities on the Construction level can be avoided. The maximum deflection angle a2 is preferably identical to that minimum deflection angle a1, which should be followed in accordance with the invention if it is exceeded.

More preferably, different energy input parameter values are specified for a larger value of a beam deflection angle a than for a smaller value of the beam deflection angle a, a beam deflection angle being defined as the arctangent of the quotient of the distance of a solidification point from the projection center and the length of the projection line of the beam deflection center, where the The projection line of the beam deflection center is a plumb line precipitated on the building level, which connects the projection center with the beam deflection center.

The inventors were able to determine that by changing the energy input parameters, e.g. the laser power, the deflection speed when scanning with a beam, etc., the increased deposition of impurities on the construction level with increasing beam deflection angle can be counteracted.

Furthermore, the number of changes from one beam to another beam is preferably limited to a maximum value M during the scanning of the trajectories in the section.

When scanning a section with several bundles of rays, which originate from different bundle deflection centers, a scan of a first solidification point with a first beam and a second solidification point immediately next to the first solidification point with a second beam understood. In particular, if an interruption of the scanning process with a first beam and the continuation of the scanning process with a second beam ensure an optimized direction of the motion vector during scanning, then this can lead to a temporal extension of the scanning process, which is why the Establishing a maximum value M for the number of changes, it can be ensured that a desired production time of the object to be produced is not exceeded.

Furthermore, the maximum value M is preferably determined as a function of specifications for a quality of the section and / or a production time of the object.

Preferably, specifications for a quality or homogeneity of the section and / or a production time of the object are made by means of an operator input on an input terminal, in particular a graphical operator interface. As a result, an operator can individually determine for an object to be manufactured which sections of an object cross-section must have a high degree of homogeneity and which specifications are made with regard to the construction time (= production time).

In particular, there is the possibility that an operator selects one of n predetermined successive quality or homogeneity levels by means of an operator input at an input terminal, in particular a graphical user interface, in order to specify the quality or homogeneity. Here, n is a natural number greater than one and is preferably, but not necessarily, equal to the number of beam bundles or beam-bundle deflection centers available for scanning a section. It is also assumed that the specified quality or homogeneity levels are subject to an order relationship and that they are all different from one another. The specification of discrete homogeneity levels facilitates the usability on the one hand and the adaptability of the method according to the invention to a given additive manufacturing device on the other hand. Instead of the production time of the object, a production time of the section of the object cross-section can also be explicitly specified or selected from a spectrum of possible production times. The specified or selected production time directly influences the production time of the object.

More preferably, the number of beam bundles is assigned to the trajectories in such a way that the maximum time difference between the periods of time that the Need laser beam for the scanning of their associated consolidation points within the section, a minimum is achieved.

In general, the beam bundle to be assigned to a trajectory or a partial area for a scan can either be selected at random or else be selected according to a rule established in advance. The rule can in particular depend on the value of a slice rotation angle if the orientation of the subregions in the building plane changes from slice to slice by a predetermined slice rotation angle. The rule can also depend on the specified maximum angles g1 and / or minimum angles g2 (these can also be selected differently in the different layers).

A method according to the invention is preferably carried out for a section which is at least partially part of a floor area of an object cross-section, a floor area being defined by the fact that no solidification of building material is specified in at least one of p layers below the floor area, where p is a predetermined natural number and / or is at least partially part of a top surface area of an object cross-section, a top surface area being defined in that no solidification of building material is specified in at least one of q layers above the top surface area, where q is a predetermined natural number.

Achieving a good surface quality is particularly important in floor and top surface areas, since these surfaces are visible from the outside.

With this development, a significant improvement in the surface quality can already be observed for p = 1 and q = 1, but there can also be an influence on the consolidation behavior if unconsolidated building material is in the next but one or a further layer. Effects on the quality of external surfaces can, however, already be observed if a value less than 5, preferably less than 10 or even less than 25 is selected for p and / or q. Specific values for the parameters p and q, which specify when there is still an influence of Unconsolidated building material is present, can be determined depending on experience with a certain building material and a certain generative layer construction device, for example after preliminary tests.

The method is also preferably carried out for a section which is at least partially part of a contour region of an object cross-section.

A contour area is an edge area of an object cross-section which, after completion of the object, forms part of the outer surface of the object and should therefore be of high quality. Usually, one tries to achieve high quality by scanning the edge of the object cross-section in one go, if possible. According to this development of the invention, there is a deviation from the conventional procedure in that when the surface area is scanned, the position of the individual solidification points with respect to the projection center is taken into account, as described above. In particular, the direction of the motion vector with respect to the projection center and / or the sequence in which the parts of the contour area to be solidified are scanned relative to the projection center are taken into account. This can ensure an improved surface quality. The section can include not only part of the contour area, but also the entire contour area.

In an additive manufacturing method according to the invention for manufacturing a three-dimensional object, the object being manufactured by means of an additive manufacturing device by applying a building material layer on layer and solidifying the building material in a building plane by means of an energy input device by supplying radiant energy to solidification points in each layer that correspond to the cross-section of the object in this layer by scanning these solidification points with a number of beam bundles provided by the energy input device along a plurality of trajectories in the building plane Control of an energy input device of an additive manufacturing device controlled.

In particular, the energy input device can have a number of laser sources, from which laser beams are fed to a number of scanners (in particular galvanometer scanners) as beam deflection centers.

In the additive manufacturing process, it is possible to direct a gas flow over the respective solidification point during the scanning. In this case, it is advantageous if the manufacturing method is carried out in such a way that a directional component of the gas flow from the solidification points to the projection center points in the at least one section of an object cross-section and / or is opposite to the direction of the motion vectors of the number of beam bundles.

Either the movement of the beam bundles can be aligned to a predetermined direction of the gas flow or, if this is possible with the additive manufacturing device, the direction of the gas flow is adapted to the movement of the beam bundles.

Furthermore, the angle between each of the motion vectors and the direction of the gas flow can be greater than 90 °, preferably greater than 135 °, more preferably greater than 150 °. The optimal case would be if the direction of the gas flow were exactly opposite to that of the motion vectors.

As a result, it is possible, through a favorable choice of the orientation of the gas flow, to further improve the results that can be achieved with the invention. A device according to the invention for controlling a

Energy input device of an additive manufacturing device for manufacturing a three-dimensional object by means of the same, wherein the object is manufactured by means of the additive manufacturing device by applying a building material layer on layer and solidifying the building material in a building level by means of the energy input device by supplying radiant energy to solidification points in each layer, the Cross-section of the object in this layer are assigned in that these solidification points are scanned with a number of beam bundles provided by the energy input device along a plurality of trajectories in the building plane, each of the number of beam bundles being assigned a beam deflection center above the building plane, from which starting from this beam is directed onto the building plane, has an assignment device which assigns a projection center to each beam deflection center, which is a perpendicular projection of the position of the beam deflection center on the building plane, and a scanning control unit which is designed so that it defines the trajectories and the directions of the motion vectors of the number of beams when scanning the trajectories at least in a section of an object cross-section that at each of the solidification points in this section the motion vector has an angle with respect to a connection vector from this solidification point to the projection center of the beam bundle used which is smaller than a predetermined maximum angle g1.

The device for controlling an energy input device is able to implement the above-described method for controlling an energy input device, in which the direction of the movement vectors is determined along the trajectories. The individual components of the device, that is to say in particular the assignment device and the scanning control unit, can be implemented solely by software or solely by hardware or by means of a mixture of hardware and software. Another device according to the invention for controlling an energy input device of an additive manufacturing device for manufacturing a three-dimensional object by means of the same, the object being manufactured by means of the additive manufacturing device by applying a building material layer on layer and solidifying the building material in a building plane by means of the energy input device by supplying radiant energy Solidification points in each layer, which are assigned to the cross section of the object in this layer, in that these solidification points are scanned with a number of beam bundles provided by the energy input device along a plurality of trajectories in the building plane, each of the number of beam bundles having a beam deflection center above is assigned to the building level, from which the beam is directed onto the building level, has an assignment device, which each beam Deflection center assigns a projection center, which corresponds to a perpendicular projection of the position of the beam deflection center on the building plane, and a scanning control unit which is designed such that it specifies a consolidation of at least a section of an object cross-section section by section, with the Trajectories run essentially parallel to one another and in at least one of the sub-areas, the solidification points of which are scanned with a beam bundle assigned to this sub-area, the sequence of the scanning of the trajectories is determined in such a way that trajectories that are closer to the projection center of the beam bundle are followed by trajectories that are further away from the center of the projection.

This device for controlling an energy input device is able to implement the method described above for controlling an energy input device, in which the sequence of the scanning of the trajectories within a partial area is established. The individual components of the device, that is to say in particular the assignment device and the scanning control unit, can be implemented solely by software or solely by hardware or by means of a mixture of hardware and software. Another device according to the invention for controlling an energy input device of an additive manufacturing device for manufacturing a three-dimensional object by means of the same, the object being manufactured by means of the additive manufacturing device by applying a building material layer on layer and solidifying the building material in a building plane by means of the energy input device by supplying radiant energy Solidification points in each layer, which are assigned to the cross section of the object in this layer, in that these solidification points are scanned with a number of beam bundles provided by the energy input device along a plurality of trajectories in the building plane, each of the number of beam bundles having a beam deflection center above is assigned to the building level, from which the beam is directed onto the building level, has an assignment device, which each beam Deflection center assigns a projection center, which corresponds to a perpendicular projection of the position of the beam deflection center on the building plane, and a scanning control unit which is designed so that it specifies a consolidation of at least a section of an object cross-section section by section, the chronological order of the Scanning of sub-areas whose solidification points are scanned with a beam bundle assigned to these sub-areas is determined in such a way that sub-areas which are closer to the projection center of this beam are scanned in front of sub-areas which are further away from the projection center.

This device for controlling an energy input device is able to implement the method described above for controlling an energy input device, in which the sequence of the scanning of the partial areas is determined. The individual components of the device, that is to say in particular the assignment device and the scanning control unit, can be implemented solely by software or solely by hardware or by means of a mixture of hardware and software. An additive manufacturing device according to the invention for manufacturing a three-dimensional object, the object being manufactured by means of the additive manufacturing device by applying a building material layer on layer and solidifying the building material in a building plane by means of an energy input device by supplying radiant energy to solidification points in each layer that correspond to the cross section of the Objects in this layer are assigned in that these solidification points are scanned with a number of beam bundles provided by the energy input device along a plurality of trajectories in the building plane to apply already existing, preferably already selectively solidified, building material layer, and an energy input device which is suitable for solidifying radiation energy Points in each layer, which are assigned to the cross-section of the object in this layer, by scanning these solidification points with a number of beam bundles provided by the energy input device along a plurality of trajectories in the building plane, the additive manufacturing device being a device according to the invention for control an energy input device of an additive manufacturing device and / or is signal-connected to a device according to the invention for controlling an energy input device of an additive manufacturing device.

In particular, the device for controlling an energy input device present in the additive manufacturing device can also be integrated into a control device that is present in the additive manufacturing device and controls an additive manufacturing process. In particular, the device for controlling an energy input device present in the additive manufacturing device can also be a computer program with which a CPU present in the control device is controlled. With a signaling Connection is a connection by means of physical lines that can transmit control signals, or a radio connection.

An object according to the invention is by means of an additive according to the invention

Manufacturing process can be produced.

Further features and usefulnesses of the invention emerge from the

Description of exemplary embodiments on the basis of the attached figures.

1 shows a schematic, partially sectioned view of an exemplary device for the additive manufacture of a three-dimensional object according to the invention.

FIG. 2 shows schematically an example of the procedure according to the invention when consolidating strip-shaped partial areas of an object cross-section ("hatches").

3 illustrates the position of a beam deflection center and a projection center of the same with respect to consolidation points in the building plane.

4 shows an example of a procedure according to a first embodiment.

Fig. 5 shows schematically the result of studies on the influence of

Direction of movement of the beam when scanning the building material for the component quality.

6 shows an example of a procedure according to a second embodiment.

FIGS. 7a and 7b schematically show the result of examinations with regard to the sequence with which the trajectories are scanned within a partial area. 8 shows an example of a procedure according to a third embodiment.

9a and 9b each show schematically the impingement of a laser beam on the top layer of the building material for different inclinations of the beam during the scanning process.

10 illustrates a procedure in which the size of a beam deflection angle is taken into account.

11 shows an example of a variant of the procedure according to a second embodiment.

12a and 12b each show schematically the processes during melting of the building material for different trajectory sequence directions.

13 shows the schematic structure of a device according to the invention for controlling an energy input device.

For a description of the invention, an additive manufacturing device according to the invention will first be described below using the example of a laser sintering or melting device with reference to FIG. 1.

To build up an object 2, the laser sintering or laser melting device 1 contains a process chamber or construction chamber 3 with a chamber wall 4. A construction container 5, which is open at the top and has a container wall 6, is arranged in the process chamber 3. A working plane 7 (also called a construction plane) is defined through the upper opening of the construction container 5, the area of the working plane 7 lying within the opening, which can be used to construct the object 2, being referred to as construction field 8. In the building container 5 there is arranged a carrier 10 which is movable in a vertical direction V and to which a base plate 11 is attached, which closes the container 5 at the bottom and thus forms its bottom. The base plate 11 can be a plate formed separately from the carrier 10 and attached to the carrier 10, or it can be formed integrally with the carrier 10. Depending on the powder and process used, a construction platform 12 can also be attached to the base plate 11 as a construction base, on which the object 2 is built. The object 2 can, however, also be built on the base plate 11 itself, which then serves as a construction base. In FIG. 1, the object 2 to be formed in the container 5 on the building platform 12 is shown below the working plane 7 in an intermediate state with several solidified layers, surrounded by building material 13 that has remained unsolidified.

The laser sintering or melting device 1 furthermore contains a storage container 14 for a building material 15, in this example a powder that can be solidified by electromagnetic radiation, and a coater 16 movable in a horizontal direction H for applying the building material 15 within the building field 8. Optionally, in A heating device, for example a radiant heater 17, can be arranged in the process chamber 3, which is used to heat the applied building material. An infrared radiator, for example, can be provided as the radiant heater 17.

The exemplary additive manufacturing device 1 also contains an energy input device 20 with a laser 21 which generates a laser beam 22 which is deflected via a beam deflection center 23, for example one or more galvanometer mirrors including the associated drive, and via a focusing device 24 via a coupling window 25, which is attached to the top of the process chamber 3 in the chamber wall 4, is focused on the working plane 7. In particular, it is also possible to provide a plurality of lasers and / or beam deflection centers. As a result, a manufacturing process can take place in a shorter time, since the building material can then be scanned and solidified at different points at the same time with a plurality of beam bundles. The specific structure of a laser sintering or melting device shown in FIG. 1 is therefore only exemplary for the present invention and can of course also be modified, in particular when using a different energy input device than that shown. In order to make it clear that the area of the radiation impingement area on the building material does not necessarily have to be very small (“punctiform”), the term “beam” is often used synonymously with “beam” in this application.

The laser sintering device 1 furthermore contains a control device 29, via which the individual components of the device 1 are controlled in a coordinated manner in order to carry out the construction process. Alternatively, the control device can also be attached partially or entirely outside of the additive manufacturing device. The control device can contain a CPU, the operation of which is controlled by a computer program (software). The computer program can be stored separately from the additive manufacturing device in a storage device, from where it can be loaded (e.g. via a network) into the additive manufacturing device, in particular into the control device.

During operation, the carrier 10 is lowered layer by layer by the control device 29, the coater 16 is controlled to apply a new powder layer and the energy input device 20, i.e. in particular the beam deflection center 23 and possibly also the laser 21 and / or the focusing device 24, controlled to solidify the respective layer at the points corresponding to the respective object by scanning these points with the laser. Here, in the present application, reference is made to a unit 39 within the control device 29 responsible for controlling the energy input device 20 as a device 39 for controlling an energy input device. Nevertheless, it should be emphasized that a device for controlling an energy input device can also be present outside the control device 29 in the same way (also as a computer program), provided that it is ensured that the device 39 for controlling an energy input device for the additive production of Objects can sufficiently interact with the control device 29, so in particular can exchange signals.

Although the invention relates primarily to laser sintering or laser melting methods or devices, application to electron beam melting is also possible.

When activating the energy input device, a consolidation of points of a building material layer is established in a chronological sequence which corresponds to the movement of a beam along a trajectory over the building material. In this regard, FIG. 13 shows a schematic structure of the already mentioned device 39 for controlling an energy input device, in which a scanning control unit 39b defines the time sequence, FIG. 2 giving an example of the procedure. In FIG. 2, an object cross-section 50 to be solidified, which in this example has a rectangular shape, is divided into an inner area or core area 52 and a contour area 51, with the contour area 51 generally being assigned different parameters for the energy input into the building material than the inner area 52. For example, the contour area 51 is scanned with a laser beam (as an example of a beam) in such a way that the trajectory runs along the contour. In this example, the inner area 52 is consolidated in such a way that it is divided into sub-areas 53, which usually have an approximately rectangular or square shape and are therefore also referred to as "strips" or "squares", and subsequently a scanning of the building material sub-area for Partial area is specified. In the example of FIG. 2, the laser beam is moved along parallel trajectories (hatch lines) 54 over the building material in each sub-area 53, resulting in a hatching-like movement pattern when each sub-area 53 is scanned with the laser beam. This process is also known as "hatching" in technical jargon. In FIG. 2, the direction of movement of the laser beam along a trajectory is illustrated in each case by an arrow.

According to the invention, the horizontal position of a beam deflection center is taken into account when controlling the energy input device. In the Device 39 for controlling an energy input device is provided with an assignment device 39a for this purpose. The procedure is explained below with reference to FIG. 3, which schematically shows a beam deflection center 23 above the construction field 8. A projection center 23 ′ in the construction plane 7 is assigned to the beam deflection center 23 through a perpendicular projection of the beam deflection center 23 onto the construction field 8 (or the construction level 7). As shown in the figure, a projection line 23k is a plumb line precipitated on the building plane 7, which connects the projection center 23 ′ with the beam deflection center 23.

By defining the projection center 23 ', the scanning procedure can be defined depending on the position of a point 64a, 64b, 64c to be consolidated within the construction field relative to the projection center 23', as will be explained below with the aid of several examples.

First embodiment

According to the first embodiment, the device for controlling an energy input device selects the direction of the movement vector of the beam for scanning a point to be solidified or solidification point in construction field 8 as a function of the position of the solidification point relative to projection center 23 '. The procedure is explained below with reference to FIG. 4.

4 shows a top view of the construction field 8 in which the position of the projection center 23 'of a beam deflection center 23 and the positions of four exemplary consolidation points 74a, 74b, 74c and 74d can be seen. Furthermore, the figure shows the respective motion vectors 75a, 75b, 75c and 75d during the movement of the ray bundle emanating from the ray bundle deflection center 23 over the solidification points 74a, 74b, 74c and 74d.

As can be seen, the device for controlling an energy input device defines the direction of the motion vector at points 74a, 74b and 74d in such a way that the motion vector has a component s pointing towards the projection center 23 '. To better illustrate the direction a straight connecting line 73a, 73b, 73c and 73d with the projection center 23 'is drawn in dashed lines in FIG. 4 for each solidification point 74a, 74b, 74c and 74d.

It can also be seen in FIG. 4 that the motion vector is fixed at the solidification point 74c in such a way that it has only one component q perpendicular to the connecting line 73c. In this case, the motion vector 75c forms an angle g of 90 ° with the connecting line 73c along a trajectory.

The background for the procedure described is that the inventors were able to determine a deterioration in the object properties for the case in which the motion vector has a large component pointing away from the projection center. For this purpose, FIG. 5 shows schematically the result of the examinations carried out in which a layer of a metal powder was applied in a conventional laser sintering device and was then scanned with a laser beam. For the investigation, the construction field 8 was divided into sixteen square sections A to P, as shown in the upper part of FIG. 5, in which the position of the projection center 23 'of the beam deflection center 23 used for scanning is marked. In this case, the scanning took place according to the procedure described with reference to FIG. 2. Different sub-areas 53 were thus scanned within a section in such a way that in each sub-area 53 the laser beam was moved along parallel trajectories (hatch lines) 54 over the building material.

The lower part of the figure shows a plan view of the section A after the described scanning. One can see within the section A sixteen partial areas 53 which, in contrast to FIG. 2, do not directly adjoin one another. In each sub-area, the direction in which the trajectories are traversed is indicated by an arrow. It should be noted that in each sub-area 53, the mutually parallel trajectories 54 are all traversed in the same direction, that is to say that the movement vectors in a sub-area each point in the same direction during the scanning. Furthermore, the illustrated position of the arrow within each sub-area 53 characterizes the position of the trajectory 54 scanned first within this sub-area. Finally, it should also be noted that, for reasons of clarity, only two of the sixteen partial areas are provided with the reference numerals 53 and 54 in the figure.

In the lower part of FIG. 5, scanned sub-areas 53 with three different hatching densities and sub-areas 53 without hatching can be seen. The different density of the hatching lines should indicate the different properties of the solidified building material. Dense hatching lines indicate greater local fluctuations in the solidified material volume in a sub-area 53 than less dense or even missing hatching lines in a sub-area 53.A lack of hatching lines therefore indicate the greatest possible flomogeneity or the highest volume percentage of solidified material achieved in a sub-area 53. In particular, it can be seen that a different direction of the motion vector in relation to the projection center 23 'leads to a different hatching density. The size of the component of the motion vector pointing towards the projection center or away from the projection center also plays a role. The more the motion vector is oriented towards the projection center or away from the projection center, the clearer the effect to be observed.

It should also be noted that the above investigation was carried out for different directions of a gas flow over the construction field and a result was always obtained which corresponds to that of FIG. 5.

The above investigation makes it clear that when scanning the building material with a beam, too large a directional component of the motion vector pointing away from the projection center should be avoided. Directional components of the motion vector that point away from the projection center should preferably be dispensed with at all. In practice, however, it can become apparent that the preferred procedure must be deviated from due to other boundary conditions, for example a specified manufacturing time that must not be exceeded for the manufacture of the object. It is therefore advisable in practice to choose the procedure described at least when the trajectory to be scanned falls below a maximum angle g1 with respect to the connection line to the projection center.

The inventors explain the observed behavior by the special features of the deep welding process used to melt the metal powder. In a deep penetration welding process, temperatures are generated in the material that are so high that evaporation occurs and, in particular, the radiation penetrates into a vapor capillary on the material surface. By multiple reflections at the edges of the vapor capillary, more energy in particular can then be introduced into the material. The temporarily formed vapor capillary is usually referred to as a "keyhole". As will be explained below with reference to FIG. 9, the observed behavior can be explained by the fact that when the laser beam strikes the building material at an angle, the keyhole forms differently depending on the direction of movement.

According to the explanatory model, FIGS. 9a and 9b each show schematically the impingement of a laser beam on the metal powder used. The beam bundle is moved in the horizontal direction (from left to right in FIGS. 9a and 9b), which is illustrated in each case by an arrow pointing to the right. Furthermore, in FIGS. 9a and 9b, the reference number 22 illustrates the beam which is in each case directed from a beam deflection center (not shown) onto the building material. While in FIG. 9a the beam moves away from the projection center of the beam deflection center (also not shown) when the building material is scanned, in FIG. 9b the beam moves towards the projection center when the building material is scanned.

Both in FIG. 9a and in FIG. 9b, the keyhole formed by the radiant energy supplied is shown schematically. This keyhole has approximately its greatest extent in the direction of incidence of the beam and consequently has an inclination with respect to the vertical in the case of a beam incident obliquely on the building material. As can be clearly seen in FIG. 9a, the not yet solidified powder material is undermined and displaced, while in FIG Fig. 9b this does not take place. As a result, the solidified layer in FIG. 9a shows poorer properties, in particular a partially reduced or strongly fluctuating layer thickness, which is not shown in the schematic illustration of FIG. 9a.

While FIG. 9 shows an example of the situation in which the motion vector of the beam exclusively has a directional component towards the projection center or away from the projection center, in practice there will usually also be a directional component perpendicular to the connecting line of a solidification point with the projection center. Correspondingly, with a sufficiently large directional component perpendicular to the connecting line, satisfactory results can also be achieved if there is a directional component that is not too large and not pointing away from the projection center, in other words, a maximum angle between the motion vector and the connecting line to the projection center is not reached.

As can be seen from the explanation given, the procedure according to the invention will achieve the most significant improvements in flomogeneity when a beam of rays strikes the building plane at an angle. This is illustrated with reference to FIG. 10.

The view of FIG. 10 is very similar to the view of FIG. 3. In particular, the position of a beam deflection center 23 above its associated projection center 23 'in the building plane is shown together with a schematic illustration of the directions 163a, 163b and 163c of a beam, if this is directed at the consolidation points 164a, 164b and 164c, respectively. The figure also shows a respective beam deflection angle a6, a1 and a4 between the respective direction 163a, 163b or 163c and the projection line 23k of the beam deflection center 23. The solidification point 164c is only shown for the sake of illustrating a minimum deflection angle a1. If, in the example of FIG. 10, it is determined how the energy input device is to be controlled in an additive manufacturing device for scanning the solidification points 164a and 164b, then the respective beam deflection angle a6 or a4 is first compared with the minimum deflection angle a1. Since the beam deflection angle a4 for the solidification point 164b is greater than the minimum deflection angle a1, the direction of the motion vector is set at the solidification point 164b so that a predetermined maximum angle between the motion vector and the connecting line to the projection center is not reached. The beam deflection angle a6 for the solidification point 164a is smaller than the minimum deflection angle a1. Therefore, at the solidification point 164a, a direction of the motion vector can be permitted in which the predetermined maximum angle between the motion vector and the connecting line to the projection center is exceeded.

Even if it was mentioned further above that the advantageousness of a procedure according to the first exemplary embodiment shows itself independently of the orientation of a gas flow which, for example, as in WO 2014/125280 A2 is directed over the construction field, ie the areas to be consolidated, shows as follows this does not mean that the results cannot be improved by additionally taking into account the orientation of the gas flow.

As already indicated above in connection with FIG. 9, it is disadvantageous if, when the laser radiation strikes the building material, the latter is displaced in such a way that it is deposited on the still unconsolidated building material at points that are still to be solidified. If, therefore, a gas flow is passed over the points to be solidified during scanning, the motion vectors of the number of beam bundles 22 should be determined when scanning the trajectories 54 so that a directional component of the gas flow is opposite to the direction of the motion vectors. In this way, the gas flow counteracts deposits on material that is still to be solidified. Alternatively, if the additive manufacturing device allows this, the direction or orientation of the gas flow can also be adapted. Second embodiment

The second exemplary embodiment relates to the usual procedure, explained above with reference to FIG. 2, of scanning the locations of a cross section, section by section. According to the second exemplary embodiment, the sequence in which the trajectories (hatch lines) are scanned within each sub-area is determined by the device for controlling an energy input device as a function of the position of the trajectories relative to the projection center. The procedure is explained below with reference to FIG. 6.

FIG. 6 is very similar to FIG. 2. In contrast to FIG. 2, the position of the projection center 23 ′ relative to the subregions 53 is shown. Furthermore, in each sub-area 53, the time sequence in which the trajectories 54 are scanned one after the other in this sub-area is each identified by an arrow, which indicates the trajectory sequence direction 86. It can be seen that in FIG. 6 in each sub-area 53 the trajectory arranged on the far right is traversed first and then all further trajectories 54 are traversed one after the other up to the trajectory arranged on the far left in the sub-area. The order in which the trajectories are scanned one after the other is determined in the example in FIG. 6 by the device for controlling an energy input device so that trajectories with a small distance from the projection center are scanned before trajectories with a greater distance from the projection center.

An exemplary possibility of defining the distance of the trajectories within a sub-area 53 to the projection center 23 'is that for each of the trajectories 54 in the sub-area 53 from the respective starting point of the trajectory a reference point connection vector 83 to the projection center 23' is constructed and the length the component 83s of the connection vector which is perpendicular to the trajectory is determined. For an essentially parallel alignment of the trajectories within a sub-area, a trajectory sequencing direction 86 perpendicular to the trajectories can then be determined on the basis of the lengths of the components 83s. As a result, trajectories that are closer to the projection center 23 'are scanned before those that are further away from the projection center 23 '. Of course, instead of the starting point, a different reference point on the trajectories can also be selected for the construction of the connection vector. In the event that not all trajectories within a partial area are exactly parallel to one another and / or are of exactly the same length, however, it is advantageous to refer to the starting point or end point as the reference point.

The inventors were able to determine that with the procedure described a more homogeneous consolidation of the building material could be achieved (recognizable e.g. by a lower surface roughness of the scanned areas) than when scanning the trajectories without observing the chosen strategy. Here, too, it was possible to achieve an improvement regardless of the direction in which a gas flow was present. FIG. 7 schematically shows an exemplary result of the investigations carried out by the inventors with regard to the sequence with which the trajectories are scanned within a partial area.

As in the investigation of FIG. 5, a layer of a metal powder was applied in a conventional laser sintering device and then scanned with a laser beam. 7a and 7b each show a top view of a square section of the construction field 8 after it has been scanned, as well as the position of the projection center 23 '. As in the lower part of FIG. 5, sixteen partial areas 53 can be seen which, in contrast to FIG. 2, do not directly adjoin one another. In each sub-area, an arrow 88 indicates the direction in which the trajectories are traversed by the laser beam during scanning, the mutually parallel trajectories being traversed in the same direction in all sub-areas 53, i.e. the movement vectors during scanning in the same direction demonstrate. For the sake of clarity, only one of the sixteen partial areas is provided with a reference symbol in FIGS. 7a and 7b.

7a and 7b differ in the position of the arrow indicating the scanning direction in the individual subregions. In Fig. 7a this arrow 88 is arranged on the left upper edge of the subregions 53, while in Fig. 7b the arrow is arranged in each case at the lower right edge of the sub-areas. The reason for the different arrangement is that both in FIG. 7 a and in FIG. 7 b the position of the arrow 88 is intended to simultaneously also identify the trajectory that was scanned first within a partial area. In FIG. 7a, the trajectories are scanned from top left to bottom right in each sub-area 53, while in FIG. 7b the trajectories are scanned from bottom right to top left in each sub-area 53.

Similar to the lower part of FIG. 5, scanned sub-areas 53 with three different hatching densities and sub-areas 53 without hatching can be seen in FIG. The different density of the hatching lines is intended to indicate the different quality that was achieved in the different sub-areas. Denser hatching lines in a sub-area 53 are intended to indicate a greater roughness of the surface compared to a sub-area 53 with less dense or even missing hatching lines. Missing hatching lines therefore indicate surfaces with a very low roughness. In particular, a comparison of FIGS. 7a and 7b shows that a higher quality (recognizable by the lower surface roughness) can be achieved if the direction in which the trajectories are scanned within a sub-area one after the other (trajectory sequencing direction) is a component which points away from the projection center 23 '. This result could be observed independently of the direction of a gas flow over the construction field during the scanning.

Furthermore, it can also be seen that an improvement is also achieved for those subregions 53 in which the motion vector of the beam has a directional component away from the projection center when the trajectories are scanned. This makes it clear that a procedure according to the second exemplary embodiment in itself, that is to say independently of the choice of the direction of the motion vector when scanning the individual trajectories, leads to an improved quality of the solidified areas. Correspondingly, an improvement in flomogeneity can also be achieved with the procedure illustrated in FIG shows. If a particularly high homogeneity of the components produced is desired, then the procedures according to the first exemplary embodiment and according to the second exemplary embodiment should be combined with one another, which is easily possible.

A possible explanation of the observed behavior is given with reference to FIG. In FIG. 12, similar to FIG. 9, the position of a keyhole that forms when a beam of rays hits the powdery building material is shown. In contrast to FIG. 9, however, the beam moves perpendicular to the connecting line from the respective solidification point to the projection center. In the left half of FIGS. 12a and 12b, a section through the keyhole and two adjacent consolidation tracks 54 'is shown perpendicular to the direction of movement of the beam, so the direction of movement of the beam is perpendicular to the plane of the drawing sheet. The difference between FIG. 12a and FIG. 12b is that in FIG. 12a the keyhole is inclined towards the unconsolidated powder material, whereas in FIG. 12b the keyhole is inclined towards the two consolidation tracks 54 'with already consolidated build-up material. In the right half of FIGS. 12a and 12b, a top view of a layer that is currently to be solidified is shown in each case. This top view shows that in FIG. 12a the trajectory succession direction points towards the projection center 23 '(not shown), while in FIG. 12b the trajectory succession direction points away from the projection center 23'.

In FIG. 12 (as in FIG. 9) the displacement of material from the keyhole is illustrated by means of two arrows on both sides of the respective keyhole. It can be seen that in FIG. 12a material from the keyhole is deposited on the not yet solidified powdery building material, whereas in FIG. 12b material from the keyhole is deposited on the solidification tracks 54 '. Accordingly, in the situation of FIG. 12a, the melting process is impaired when the subsequent adjacent trajectory is scanned, which leads to a deteriorated quality, for example a rougher surface of the associated solidification path. Similar to the first exemplary embodiment, it can become apparent in practice that the procedure according to the second exemplary embodiment must be deviated from due to other boundary conditions, for example a predetermined manufacturing time that must not be exceeded for the manufacture of the object. In such a case, a procedure according to the second exemplary embodiment can only be carried out in those partial areas in which a motion vector when scanning a trajectory within the partial area has an angle with respect to the connecting line to the projection center which exceeds a minimum angle g2. This is illustrated with reference to FIG. 11.

11 schematically shows a top view of the construction field 8, in which the position of a projection center 23 ′ relative to trajectories 154, 155 and 157 is shown in different subregions. The connection vector 181 to the projection center 23 ′ encloses an angle g2 with a motion vector along the exemplary trajectory 154, which in the example in FIG. 11 is defined as the minimum angle.

With such a definition of a minimum angle g2, the trajectory sequencing direction 186 is defined for the trajectories 155 such that trajectories that are closer to the projection center 23 'are scanned before trajectories that are further away from the projection center 23'. The reason is that when the trajectories 155 running in parallel are scanned, an angle g5 between the direction of the motion vector and the respective connection vector 183 to the projection center 23 ′ is greater than the minimum angle g2. The motion vectors along the trajectories 157 running parallel to one another enclose an angle g7 with the respective connection vector 188 which is smaller than the minimum angle g2. Correspondingly, a trajectory sequencing direction 187 can be permitted for the trajectories 157, in which trajectories which are closer to the projection center 23 ′ are scanned for trajectories which are further away from the projection center 23 ′.

In the case of the second exemplary embodiment, too, when the procedure according to the invention is used, the most significant improvements in the homogeneity will be achieved in the case of an oblique impingement of the beam on the building plane. In other words, it can be for a sufficiently perpendicular impingement of the beam, under certain circumstances, a procedure described in the second exemplary embodiment can be dispensed with if the accuracy requirements are not so high. The procedure illustrated with reference to FIG. 10 as a function of the beam deflection angle can therefore be used in the same way in connection with the second exemplary embodiment.

Similar to the first exemplary embodiment, the results can be improved if an orientation of the gas flow is also taken into account.

As already mentioned above in connection with FIG. 12a, it is disadvantageous if, when the laser radiation strikes the building material, material is displaced from the keyhole in such a way that it is deposited on building material that is not yet solidified at points that are still to be solidified. If, therefore, a gas flow is passed over the points to be solidified during the scanning, the trajectory succession direction should not only be selected so that it points away from the projection center 23 ', but a beam deflection center 23 should also be selected for the solidification associated projection center 23 ′ has a position which results in a directional component of the gas flow pointing from a solidification point in the direction of projection center 23 during the scan. In this way, the gas flow counteracts deposits on material that is still to be solidified. Alternatively, if the additive manufacturing device allows this, the direction or orientation of the gas flow can also be adapted.

Third embodiment

The third exemplary embodiment, like the second exemplary embodiment, relates to the usual procedure, explained above with reference to FIG. 2, of scanning the locations of a cross section, section by section. According to the third exemplary embodiment, the sequence in which the partial areas are scanned one after the other is controlled by the device for controlling a Energy input device determined as a function of the position of the sub-areas relative to the projection center. The procedure is explained below with reference to FIG. 8.

FIG. 8 is very similar to FIG. 6, but the trajectory sequence direction 86 is not specifically identified by an arrow in the subregions. In FIG. 8, the two partial areas provided with the reference numerals 53a and 53b are distinguished from one another by the appended lower case letter. This is intended to express that the sub-area 53a is scanned in front of the sub-area 53b, since it is at a smaller distance from the projection center 23 '.

An exemplary possibility of taking into account the distance between a sub-area and the projection center is to determine the minimum distance to the projection center for each sub-area and to scan the sub-areas with increasing size of the minimum distances, i.e. the sub-area with the smallest minimum distance first and the sub-area with the greatest minimum distance last. In FIG. 8, the minimum distance between the partial area 53a and the projection center 23 ′ is identified by a connection vector or a straight connection line 93.

Of course, the distance between a partial area and the projection center can also be determined in other ways. For example, as just described, the length of the shortest connecting line between a sub-area and the projection center could not be defined as the distance, but the component of the shortest connecting line that is perpendicular to the trajectories within the sub-area. A corresponding distance is provided with the reference symbol 93p in FIG. 8.

For a procedure in accordance with the third exemplary embodiment, the inventors were also able to determine that a more homogeneous solidification of the building material can be achieved than in comparison to disregarding the preferred time sequence just described for scanning the subregions one after the other. Also here left an improvement can be achieved regardless of the direction in which a gas flow is present.

As in the second exemplary embodiment, especially if there are additional boundary conditions, e.g. a predetermined manufacturing time for the manufacture of the object that must not be exceeded, a procedure according to the third exemplary embodiment can be limited to those subregions in which the trajectories to be scanned are at an angle with respect to the connecting line to the projection center which exceeds a minimum angle g2. The above explanations in connection with FIG. 11 can also be applied analogously to the third exemplary embodiment.

In the case of the third exemplary embodiment, too, when the procedure according to the invention is used, the most significant improvements in the homogeneity will be achieved when the beam strikes the building plane at an angle. In other words, for a sufficiently perpendicular impingement of the beam, under certain circumstances, the procedure described in the third exemplary embodiment can be dispensed with if the accuracy requirements are not so high. The procedure illustrated with reference to FIG. 10 as a function of the beam deflection angle can be applied in the same way in connection with the third exemplary embodiment.

Similar to the second exemplary embodiment, the results can be further improved if an orientation of the gas flow is also taken into account.

According to the third exemplary embodiment, the homogeneity of the properties of the manufactured objects is improved in that subregions which are closer to the projection center 23 ′ of the beam bundle 22 are scanned in front of subregions which are further away from the projection center 23 ′. In this case, too, the aim is to avoid material being deposited on building material that has not yet solidified as a result of the scanning. If, therefore, a gas stream is passed over the points to be solidified during scanning, a beam deflection center 23 should be selected for the solidification, its associated one Projection center 23 ′ has a position which results in a directional component of the gas flow pointing in the direction of projection center 23 from the solidification points in the partial areas during the scan. In this way, the gas flow counteracts deposits on material that is still to be solidified. Alternatively, if the additive manufacturing device allows this, the direction or orientation of the gas flow can also be adapted.

The procedures described in the first, second and third exemplary embodiments, including their modifications, can be combined with one another as desired. The greatest homogeneity of the properties of an additively manufactured object is achieved with a procedure which simultaneously implements the teachings of all three exemplary embodiments when controlling an energy input device. Finally, it should be noted that the maximum angle g1 described above and the minimum angle g2 described above are not symmetrical with respect to the

Connection vector must be chosen from a solidification point to the projection center. Rather, for motion vectors that lie on different sides of the connection vector, different values can be specified for the maximum angle g1 and / or the minimum angle g2.

Claims

1. A method for controlling an energy input device (20) of an additive manufacturing device for manufacturing a three-dimensional object by means of the same, the object being manufactured by means of the additive manufacturing device by applying a building material layer on layer and solidifying the building material in a building level (7) by means of the energy input device by supplying radiation energy to solidification points in each layer, which are assigned to the cross-section of the object in this layer, by creating these solidification points with a number of beam bundles (22) provided by the energy input device (20) along a plurality of trajectories (54) in the building plane (7), each of the number of beam bundles being assigned a beam deflection center (23) above the building plane (7), from which the beam is directed onto the building plane, with each beam deflecting center (23) having a project ctionszentrum (23 ') is assigned, which corresponds to a perpendicular projection of the position of the beam deflection center (23) on the building plane (7), wherein at least a portion of an object cross-section is consolidated, sub-area by sub-area, wherein in at least one of the sub-areas (53 ), the solidification points of which are scanned with a beam (22) assigned to this sub-area, the sequence of scanning of the trajectories (54) is determined so that trajectories that are closer to the projection center (23 ') of the beam before trajectories that are further away from the projection center (23 ') are scanned.

2. The method according to claim 1, wherein in a sub-area (53) in which the trajectories (54) run essentially parallel to each other and the order of the scanning of the trajectories is determined so that trajectories that are closer to The projection center (23 ') of the beam (22) are located before trajectories which are further away from the projection center (23') are scanned, the directions of the motion vectors along the trajectories are set so that the motion vector is at an angle opposite to each of the solidification points a connection vector from this solidification point to the projection center (23 ') of the beam bundle (22) used for this partial area, which is smaller than a predetermined maximum angle g1.

3. The method according to claim 1 or 2, in which to determine the proximity of a trajectory to the projection center (23 ') for each of the trajectories a reference point connection vector (83) from a reference point on the respective trajectory, preferably from a starting point of the respective trajectory, to the projection center (23 ') is constructed and the length of the perpendicular to the trajectory component (83s) of the reference point connection vector (83) is determined, whereby it is determined that for two trajectories in which the length of the on the trajectory perpendicular component (83s) distinguishes that trajectory closer to the projection center (23 ') of the beam (22), in which the length of the component (83s) that is perpendicular to the trajectory is smaller.

4. The method according to any one of claims 1 to 3, wherein in a partial area (53) in which the trajectories (54) run essentially parallel to each other and the order of the scanning of the trajectories is determined so that trajectories that are closer to the projection center ( 23 ') of the beam (22) lie, before trajectories which are further away from the projection center (23') are scanned, the motion vector at at least one solidification point is at an angle to a connection vector from this solidification point to the projection center (23 ') of the beam bundle used (22) which is greater than a predetermined minimum angle g2.

5. The method as claimed in claim 4, in which different minimum angles g2 are established for different values of a beam deflection angle a, a beam deflection angle being the arctangent of the quotient The distance of the solidification point from the projection center (23 ') and the length of the projection line (23k) of the beam deflection center (23) is defined, the projection line (23k) of the beam deflection center (23) being a plumb line precipitated on the construction plane (7) which connects the projection center (23 ') with the beam deflection center (23).

6. The method according to any one of claims 1 to 5, in which in the production of a three-dimensional object with the additive manufacturing device, a gas flow is passed over the respective solidification point during the scanning, wherein for the scanning of the solidification points in the at least one of the subregions (53) a beam deflection center (23) is selected for which a directional component of the gas flow points from the solidification points to the projection center (23 ') assigned to the beam deflection center (23).

7. A method for controlling an energy input device (20) of an additive manufacturing device for manufacturing a three-dimensional object by means of the same, the object being manufactured by means of the additive manufacturing device by applying a building material layer on layer and solidifying the building material in a building level (7) by means of the energy input device by supplying radiation energy to solidification points in each layer, which are assigned to the cross-section of the object in this layer, by creating these solidification points with a number of beam bundles (22) provided by the energy input device (20) along a plurality of trajectories (54) in the building plane (7) are scanned, each of the number of beams is assigned a beam deflection center (23) above the building plane (7), from which this beam is directed onto the building plane (7), each beam deflecting center (23) egg n projection center (23 ') is assigned, which corresponds to a perpendicular projection of the position of the beam deflection center (23) on the building plane (7), the directions of the motion vectors of the number of beam bundles (22) in at least one section of an object cross-section Sampling the Trajectories (54) are set so that at each of the solidification points in this section, the motion vector has an angle with respect to a connection vector from this solidification point to the projection center (23 ') of the beam (22) used, which is smaller than a predetermined maximum angle g1.

8. The method according to claim 7, wherein the predetermined maximum angle g1 has a value that is less than or equal to 135 °, preferably less than or equal to 90 °.

9. The method according to claim 7, in which different maximum angles g1 are set for different values of a beam deflection angle a, a beam deflection angle being the arctangent of the quotient of the distance between the solidification point and the projection center (23 ') and the length of the projection line (23k) des Beam deflection center (23) is defined, the projection line (23k) of the beam deflection center (23) being a plumb line precipitated on the building plane (7) which connects the projection center (23 ') with the beam deflection center (23).

10. The method according to any one of claims 7 to 9, in which it is established that at least two adjacent trajectories (54) are scanned in the same or different directions, and different beam bundles (22) are used to scan adjacent trajectories.

11. The method according to any one of claims 7 to 10, wherein in the production of a three-dimensional object with the additive manufacturing device during the scanning, a gas flow is passed over the respective solidification point, wherein in the at least one section of an object cross-section, the directions of the motion vectors of the number of beam bundles (22) when scanning the trajectories (54) are determined so that a directional component of the gas flow is opposite to the direction of the motion vectors of the number of beam bundles.

12. A method for controlling an energy input device (20) of an additive manufacturing device for manufacturing a three-dimensional object by means of the same, the object being manufactured by means of the additive manufacturing device by applying a building material layer on layer and solidifying the building material in a building level (7) by means of the energy input device by supplying radiation energy to solidification points in each layer, which are assigned to the cross section of the object in this layer, by creating these solidification points with a number of beam bundles (22) provided by the energy input device (20) along a plurality of trajectories (54) in the building plane (7) are scanned, each of the number of beams is assigned a beam deflection center (23) above the building plane (7), from which the beam is directed onto the building plane (7), each beam deflecting center (23) a pr ojektionszentrum (23 ') is assigned, which corresponds to a vertical projection of the position of the beam deflection center (23) on the building plane (7), wherein at least a portion of an object cross-section is solidified, sub-area by sub-area, the chronological order of the scanning of sub-areas (53), the solidification points of which are scanned with a beam bundle assigned to these partial areas, is determined in such a way that partial areas which are closer to the projection center (23 ') of the beam bundle (22) lie in front of partial areas which are further away from the projection center (23') to be scanned.

13. The method according to claim 12, wherein in the partial areas (53) for which the temporal sequence of the scanning is determined, at each of the solidification points, the motion vector has an angle with respect to a connection vector from this solidification point to the projection center of the beam used for this partial area, which is smaller than a predetermined maximum angle g1.

14. The method according to claim 12 or 13, wherein in at least one sub-area (53) whose solidification points are associated with this sub-area Beam bundles are scanned, the sequence of the scanning of the trajectories (54) is determined so that trajectories which are closer to the projection center (23 ') of the beam bundle (22) are scanned before trajectories which are further away from the projection center (23') will.

15. The method according to any one of claims 12 to 14, in which the minimum of the distances between the solidification points in the partial area from the projection center is used as a measure of the distance between a sub-area (53) from the projection center (23 ').

16. The method according to any one of claims 12 to 15, in which the section has a plurality of partial areas (53) which have a rectangular shape in a plan view of the building plane (7), the trajectories (54) in the section being essentially parallel run parallel to each other and essentially parallel to the transverse sides of the sub-areas, the length of a perpendicular (93p) from the projection center on a straight line running through a sub-area parallel to a longitudinal side being used as a measure of the distance of a sub-area (53) from the projection center (23 ') will.

17. The method according to claim 16, wherein during the consolidation of cross-sections of the object present in different layers, the longitudinal sides of the plurality of partial areas in the different layers have a changed orientation in the building plane.

18. The method according to any one of claims 12 to 17, wherein in each of the sub-areas (53) for which the temporal sequence of the scanning is determined, the motion vector at a solidification point at an angle with respect to a straight connecting line from this solidification point to the projection center of the beam bundle used which is greater than a predetermined minimum angle g2.

19. The method according to any one of claims 12 to 18, wherein in the production of a three-dimensional object with the additive manufacturing device during the scanning, a gas flow is passed over the respective solidification point, wherein for the scanning of the solidification points in the at least one section of an object cross-section a beam deflection center (23) is selected for which a directional component of the gas flow points from the solidification points to the projection center (23 ') assigned to the beam deflection center (23).

20. The method according to any one of the preceding claims, wherein the method is carried out for a section which has at least one solidification point, during the scanning of which a beam deflection angle exceeds a deflection minimum angle cd, a beam deflection angle as an arctangent of the quotient of the distance of the solidification point from the projection center (23 ') and the length of the projection line (23k) of the beam deflection center (23) is defined, the projection line (23k) of the beam deflection center (23) being a plumb line precipitated on the building plane (7) which defines the projection center (23') ) connects to the beam deflection center (23).

21. The method according to any one of claims 1 to 19, in which a beam (22) is used for scanning the building material along a trajectory, the beam deflection angle a of which does not exceed a predetermined maximum deflection angle a2, a beam deflection angle being the arctangent of the quotient from the distance a solidification point is defined by the projection center (23 ') and the length of the projection line (23k) of the beam deflection center (23), the projection line (23k) of the beam deflection center (23) being a perpendicular precipitated on the building plane (7), which connects the projection center (23 ') with the beam deflection center (23).

22. The method according to any one of the preceding claims, wherein for a larger value of a beam deflection angle α other

Energy input parameter values are specified as for a smaller value of the beam deflection angle α, where a beam deflection angle is defined as Arctangent of the quotient of the distance of a solidification point from the projection center (23 ') and the length of the projection line (23k) of the beam deflection center (23), the projection line (23k) of the beam deflection center (23) being on the construction level (7) is precipitated solder that connects the projection center (23 ') with the beam deflection center (23).

23. The method according to claim 21, wherein the number of changes from one beam to another beam is limited to a maximum value M during the scanning of the trajectories in the section.

24. The method according to claim 23, in which the maximum value M is determined as a function of specifications for a quality of the section and / or a production time of the object.

25. The method according to any one of the preceding claims, wherein the method is carried out for a section which is at least partially part of a bottom surface area of an object cross-section, wherein a bottom surface area is defined in that in at least one of p layers below the bottom surface area no solidification of building material ( 15) is specified, where p is a predetermined natural number, and / or is at least partially a component of a top surface area of an object cross-section, a top surface area being defined by the fact that no solidification of building material is specified in at least one of q layers above the top surface area, where q is a given natural number.

26. The method according to any one of the preceding claims, wherein the method is carried out for a section which is at least partially part of a contour region of an object cross-section.

27. Additive manufacturing process for manufacturing a three-dimensional object, the object being manufactured by means of an additive manufacturing device by applying a building material layer on layer and solidifying the building material in a building level (7) by means of an energy input device (20) by supplying radiation energy to solidification points in each layer, which are assigned to the cross section of the object in this layer, by creating these solidification points with a number of beam bundles (22) provided by the energy input device (20) along a plurality of trajectories in the building plane (7) are scanned, wherein the energy input device (20) is controlled by means of a method according to one of claims 1 to 23

28. Additive manufacturing method according to claim 27, in which during the production of a three-dimensional object with the additive manufacturing device, a gas flow is passed over the respective solidification point during scanning, the manufacturing method being carried out in such a way that a directional component of the Gas flow from the solidification points to the projection center (23 ') shows and / or is opposite to the direction of the motion vectors of the number of beam bundles.

29. Device for controlling an energy input device (22) of an additive manufacturing device for manufacturing a three-dimensional object by means of the same, the object being manufactured by means of the additive manufacturing device by applying a building material layer on layer and solidifying the building material in a building level (7) by means of the energy input device by supplying radiation energy to solidification points in each layer, which are assigned to the cross-section of the object in this layer, by creating these solidification points with a number of beam bundles (22) provided by the energy input device (20) along a plurality of trajectories (54) in the building plane (7) are scanned, each of the number of beam bundles being assigned a beam deflection center (23) above the building plane (7), from which the beam is directed onto the building plane (7), with an assignment device that assigns a projection center to each beam deflection center, which corresponds to a perpendicular projection of the position of the beam deflection center onto the building plane, and a scanning control unit which is designed to solidify at least a portion of an object cross-section for a partial area Partial area specified, wherein in each partial area (53) the trajectories (54) run essentially parallel to each other and in at least one of the partial areas, the solidification points of which are scanned with a beam assigned to this partial area, the sequence of the scanning of the trajectories (54) is determined that trajectories which are closer to the projection center (23 ') of the beam bundle (22) are scanned before trajectories which are further away from the projection center (23').

30. Device for controlling an energy input device (20) of an additive manufacturing device for manufacturing a three-dimensional object by means of the same, the object being manufactured by means of the additive manufacturing device by applying a building material layer on layer and solidifying the building material in a building level (7) by means of the energy input device by supplying radiation energy to solidification points in each layer, which are assigned to the cross-section of the object in this layer, by creating these solidification points with a number of beam bundles (22) provided by the energy input device (20) along a plurality of trajectories (54) in the building plane (7) are scanned, each of the number of beams is assigned a beam deflection center (23) above the building plane (7), from which this beam is directed onto the building plane (7), with an allocation device that each Beam deflection center assigns a projection center, which corresponds to a perpendicular projection of the position of the beam deflection center on the building plane, and a scanning control unit which is designed so that, at least in a section of an object cross section, the trajectories (54) and the directions the motion vectors of the number of beams (22) when scanning the Defines trajectories so that at each of the solidification points in this section the motion vector has an angle with respect to a connection vector from this solidification point to the projection center of the beam bundle used, which is smaller than a predetermined maximum angle g1.

31. Device for controlling an energy input device (20) of an additive manufacturing device for manufacturing a three-dimensional object by means of the same, the object being manufactured by means of the additive manufacturing device by applying a building material layer on layer and solidifying the building material in a building level (7) by means of the energy input device by supplying radiation energy to solidification points in each layer, which are assigned to the cross-section of the object in this layer, by creating these solidification points with a number of beam bundles (22) provided by the energy input device (20) along a plurality of trajectories (54) in the building plane (7), each of the number of beam bundles being assigned a beam deflection center (23) above the building plane (7), from which the beam bundle is directed onto the building plane (7), with an assignment device that assigns each Str a beam deflection center assigns a projection center, which corresponds to a perpendicular projection of the position of the beam deflection center on the building plane, and a scanning control unit which is designed so that it specifies a consolidation of at least a section of an object cross-section section by section, with the temporal Sequence of scanning of sub-areas (53), the solidification points of which are scanned with a beam (22) assigned to these sub-areas, is determined in such a way that sub-areas which are closer to the projection center (23 ') of this beam are before sub-areas which are further away from the projection center (23 ') are to be scanned.

32. Additive manufacturing device for manufacturing a three-dimensional object, the object being manufactured by means of the additive manufacturing device by applying a build-up material layer on layer and solidifying the Building material in a building level (7) by means of an energy input device by supplying radiant energy to solidification points in each layer, which are assigned to the cross-section of the object in this layer, in that these solidification points with a number of beam bundles (22) provided by the energy input device along a plurality of Trajectories (54) in the building plane (7) are scanned, the additive manufacturing device having: a layer application device (16) which is suitable for applying a layer of a building material to an already existing, preferably already selectively solidified, building material layer, and an energy input device ( 20), which is capable of generating radiant energy

Solidification points in each layer, which are assigned to the cross-section of the object in this layer, are supplied by these solidification points being scanned with a number of beam bundles provided by the energy input device along a plurality of trajectories (54) in the building plane, the additive manufacturing device being a device after one of the

Claims 29 to 31 and / or is signal-connected to a device according to one of Claims 29 to 31.

33. Object that can be produced by means of a method according to claim 27 or 28.