WO2018210436A1

WO2018210436A1 - Optimization of the energy input in the downskin

Info

Publication number: WO2018210436A1
Application number: PCT/EP2017/062195
Authority: WO
Inventors: Ludger HÜMMELER
Original assignee: Eos Gmbh Electro Optical Systems
Priority date: 2017-05-19
Filing date: 2017-05-19
Publication date: 2018-11-22

Abstract

A computer-aided method for providing control data for a generative layer construction apparatus has: a first step (S1) of accessing a plurality of layer data records each having a data model of a construction material layer to be selectively strengthened during production, characterized in that, in a second step (S2), an object section comprising at least one part of one or more object cross sections is determined, and the plurality of layer data records are modified in such a manner that values of at least one energy input parameter are allocated to a plurality of points corresponding to the object section in the plurality of layer data records in such a manner that the values change with a change in the distance to an edge section of the object section in a plurality of steps, preferably substantially monotonously, and, in a third step (S3), the plurality of layer data records modified in the second step are provided for the purpose of generating a control data record for the generative layer construction apparatus.

Description

Optimization of the energy input in the downskin

The invention relates to a method and a device for providing control data for a generative layer construction device, a correspondingly adapted generative layer construction method, a suitably adapted generative layer construction device and a correspondingly adapted computer program. Generative layer construction devices and related methods are generally characterized by fabricating objects in them by solidifying a shapeless building material layer by layer. The solidification can be brought about, for example, by supplying heat energy to the building material by irradiating it with electromagnetic radiation or particle radiation (eg laser sintering (SLS or DMLS) or laser melt or electron beam melting) or by inducing a crosslinking reaction in the building material (e.g. Stereolithography). The devices and processes originally used in prototype construction are increasingly used for series production, for which the term "additive manufacturing" has become common. German Offenlegungsschrift DE 10 2008 031 926 A1 describes the problem that when producing products in layers, for example by means of a laser melting process, in the edge area of products, in particular if a product section is laterally over or under product sections there is surface irregularity and imperfections in the peripheral area. The problem becomes more pronounced the greater the angle between an outer surface of a product section and a perpendicular to the layers. In particular, the problem occurs in outer surfaces facing down during the manufacturing process, since the non-solidified powder material under these laterally protruding outer surfaces dissipates the heat poorly, which leads to overheating in this area. To solve the problem is therefore proposed to co-build additional wedges on the corresponding outer surfaces, which are then removed by a mechanical process again. However, the method according to DE 10 2008 031 926 A1 has the disadvantage that a further method step, namely the mechanical removal of the wedges, is necessary, which makes the production process of objects very complicated.

In view of the problems described in the prior art, it is an object of the present invention to provide a method and a device by means of which the quality of edge portions of an object produced by a generative layer construction method can be ensured in a simple manner.

The object is achieved by a computer-assisted method according to claim 1, a generative layer construction method according to claim 19, a device for providing control data according to claim 21, a generative layer construction device according to claim 22 and a computer program according to claim 23. Further developments of the invention are described in FIGS dependent claims claims. In particular, a device according to the invention can also be developed by the features of the method according to the invention which are embodied below or in the dependent claims, and vice versa. Furthermore, the features described in connection with a device can also be used to develop another device according to the invention, even if this is not explicitly stated. A computer-aided method of providing control data for a generative layer building apparatus for producing a three-dimensional object, wherein the object is manufactured by the generative layer building apparatus by applying a building material layer by layer and solidifying the building material in a working plane by applying radiant energy to locations in each layer , which are assigned to the cross-section of the object in this layer by scanning these locations by means of the energy input device according to a set of energy input parameters with energy radiation, comprises a first step of accessing a plurality of layer data sets, each one selectively a data model during production to have to be solidified build-up material layer, wherein in each data model an object cross-section corresponding locations are marked, in which a solidification of Aufbauma terials in the associated layer should take place. The method is characterized in that, in a second step, an object section is defined which comprises at least part of one or more object cross sections, and the plurality of layer data sets is modified such that a plurality of locations corresponding to the object section in the plurality of layer data sets Values of at least one energy input parameter can be assigned such that the values change with a change in the distance of the locations to an edge section of the object section in several steps, preferably essentially monotonically, and in a third step the plurality of shift data sets modified in the second step the generation of a control data record for the generative layer building apparatus is provided.

Generative layer construction devices and methods to which the present invention relates are, in particular, those in which energy, such as electromagnetic radiation or particle radiation, is selectively applied to a layer of the building material. The working plane is a plane in which the upper side of the layer to which the energy is applied lies. In this case, the energy input device may for example comprise a laser or an electron beam source, but it would also be conceivable to use a UV light source, as used in particular in stereolithography. While in stereolithography, solidification of the building material is effected by applying to the building material In the case of other methods, in particular in laser sintering or laser melting or electron beam melting, heat which is applied to the building material is supplied with heat. In this case, the building material is partially or completely melted by means of the energy introduced by the radiation, whereby the constituents of the building material (for example powder grains) connect to one another. After cooling, the building material is then present as a solid. Since the transitions between superficial melting (sintering) and complete melting (melting) are fluid, the terms sintering and melting are used synonymously in the present application and do not distinguish between sintering and melting.

If, in this application, there are layers below or above an object cross-section, then this direction indication refers to a direction which is essentially perpendicular to the layer planes or lies perpendicular to the construction plane. The term "substantially" expresses here that the layer thickness may not be uniform in some cases, e.g. B. the layer thickness can change monotonically across the cross section of the object. It is assumed in this connection that underlying layers are applied temporally in front of the overlying layers and are therefore arranged below the overlying layers. It should also be noted at this point that by means of a generative invention

Layer construction device not only an object, but also several objects can be produced simultaneously. Whenever the present application is concerned with the manufacture of an object, it is to be understood that the respective description is equally applicable to generative layer construction methods and apparatus in which a plurality of objects are produced simultaneously.

As a control data set (often also referred to as a control command set), a sequence of instructions is here considered to apply layers of the building material successively and to scan regions of the respective layers which correspond to the cross section of an object to be produced with energy radiation in order to solidify the building material. In detail, a control data set is based on a computer-based model of the object (s) to be produced, preferably a CAD model. In particular, the control data set determines, for each build material layer during manufacture, the thickness of the layer application and the locations where solidification of the build material is to be effected by irradiation. In addition, a control data set often also contains production-specific information, for example regarding the position and orientation of the objects in the generative layer building apparatus or with respect to a diameter of the energy beam (bundle) when hitting the building material. As a rule, the control data set contains all the data required for controlling the energy input device, which, inter alia, determines the energy density of the energy radiation and optionally the travel speed of the beam over the building material and / or an irradiation pattern.

The control data set can thus be regarded as a totality of all control data predetermined for the control of the production process in a generative layer building apparatus. The control data relating to a single layer are also referred to below as a shift data record.

In the present application, a shift data record is considered as a data record which contains a data model of a build material layer to be consolidated at the locations of an object cross section during the production process. Such a layered data set is usually generated by decomposing a CAD model of the object to be produced into layers (referred to in the jargon as slicing). However, it is also conceivable to extract a two-dimensional representation of the object cross-section to be consolidated in one layer by means of one or more beams in a different way from the computer-based CAD model of the object. In the layer data set, locations of a building material layer to be consolidated are specified. In addition, but need not, even more information regarding the production of the object cross-section may be included, for. Example, the layer thickness or irradiation parameter values such as the diameter of a beam incident on the building material, etc. It should be emphasized that there are also special cases, in which a shift data record does not refer to a complete object cross-section, but only to a part of it.

When referring to an access to a plurality of shift data sets, it is meant that shift data records are read from a memory or the data corresponding to the shift data records are received via a network. The shift data sets do not necessarily have to be read together (ie simultaneously). It is also possible that there is a greater time interval between the access operations on the shift data sets, for example a shift data record is read in each case as required during a production process of an object and a modified shift data record is then integrated into the control data record during the production process.

The provision of the modified in the second step layer data set for the generation of a control record can, for. B. by the layer data record providing unit itself by integrating the modified layer data set in a control data record for the generative layer building apparatus. However, providing also includes forwarding the shift data record to a data processing device, which integrates the shift data record into a control data record, or a direct forwarding to a generative layer-building device. In particular, it is possible to dynamically provide shift data sets for object cross sections still to be produced during a production process in the generative layer construction device of this device. In particular, modified layer data sets according to the invention need not be provided individually for a generative layer construction process. Rather, several modified shift data sets can first be collected and then provided in their entirety for integration into a control data record.

As a result of the method according to the invention, abrupt changes or large differences on both sides of boundary surfaces, that is to say surfaces, can separate the edge sections of the solidified material from unreinforced construction material or border edge sections adjoin one another. zender object sections that are to be solidified with different energy input parameters can be avoided. The inventor has found that it is not sufficient merely to solidify the contour of an object section with particular parameters in order, for example, to take account of the different behavior of the unsolidified building material lying outside the object section. Rather, the inventor was able to determine that even areas in the solidified object, which have a certain distance to an edge portion, behave differently than areas that are farther away from edge portions. The object portion may also be limited to a building material layer or comprise the entire object.

The inventor was able to determine an improvement in the surface quality of objects, the mechanical properties (in particular in the edge region) and the dimensional accuracy of objects in which according to the invention the energy input was changed in at least two steps as a function of the distance of the points to be consolidated to an edge portion. The influence of the area outside the object section (that is, beyond the

Marginal portion) on the quality of the object, eg. B. homogeneity, mechanical properties, dimensional accuracy or color, it will be the lower, the more sites to be solidified in the object are removed from the edge portion. The edge section may be the entire edge area of the object section. However, the edge portion referred to in the assignment of energy input parameter values in the second step may also be only part of the edge region. This part of the border area can be selected either via a user default or automatically, for example according to the following criteria:

- Consideration of the bordering area adjacent to the building material to be left unconsolidated; In this case, the building material remaining unconsolidated can also be present in a cavity of the object to be produced or of the object section, ie adjacent to an inner edge (in this case, the topological boundary concept is used as a basis); Selection of a marginal portion which is of particular importance for the functionality of the object (for example the edges of turbine blades) or whose detail is of particular importance; Different distance definitions or metrics can be used to determine the distance. For example, the distance between the two locations in a given spatial direction (eg, the direction perpendicular to the working plane) can be defined as the distance between two locations of an object section. In this case, the distance from the edge section along a spatial direction which is the same for all points of the object section to be consolidated could then be used as the basis for the assignment of the at least one energy input parameter value. It is also conceivable, however, another distance definition, in which the predetermined spatial direction may be different for different sites to be consolidated. This is the case, for example, whenever the shortest distance between a point and the edge section of the assignment of an energy input parameter value is always used. The predetermined spatial direction at each point in this case is the direction of the solder from this point to the edge portion, whereby there is no uniform predetermined spatial direction at a curved edge portion, since the solders of the edge portion to be solidified points are not all parallel to each other. In general, the method is applicable to arbitrary edge sections of an object section. A predefined edge section is preferably such a region of the edge of the object section at which the energy input parameter values change greatly compared to the region outside this object section. The default of the edge portion may already be specified in the plurality of shift records accessed in the first step. However, it is also possible to make a specification of the edge section during the course of the method by a user. Furthermore, it is also possible that the edge portion is automatically set, for. B. as that edge surface of the object portion, which points during its production downwards or upwards, that is immediately adjacent to unbonded building material above or below. In this case, the plurality of points corresponding to the object section to which a value of an energy input parameter is assigned need not all to be solidified points of the object section include. Preferably, in the second step, at most all those points are assigned a value of an energy input parameter lying on a straight line which intersects the edge section and runs along a predetermined spatial direction introduced for the distance definition.

In any case, it is important that the energy input into the material with increasing distance from the edge portion is changed at least twice, so not only a contour line or edge line or surface is solidified at the edge portion with different energy than the interior of the object section. The quality of the regions of an object section near the edge section can be increased, in particular, by modifying the energy input in as many steps as possible with increasing distance to the edge section, for example, increasing it essentially monotonously. For example, the energy input is continuously increased with increasing distance to the edge portion up to a maximum energy input. Of course, however, in practice a continuous modification can only be approximated, since the change of the energy input and the change of the movement of an energy beam over the building material usually takes place in discrete steps (albeit very small ones).

"Substantially monotonic" is intended to express that smaller deviations from the monotonic variation of an energy input parameter are generally tolerable. Depending on the situation, it may be acceptable if the monotony is broken at a maximum of 10% or at most 20%, in some cases even at most 30%. This can be determined by preliminary tests. Of course, there may be cases in which no interruption of the monotonous course is allowed.

Possible energy input parameters in the set of energy input parameters are the energy density, ie the amount of radiation energy per unit area of an energy beam focused on the constituent material for solidification thereof, an energy density distribution over an impact surface of the energy beam on the constituent material, the velocity of movement of an energy beam over the constituent material, the frequent the energy input at one point, when using a laser as an energy source, the pulse duration and / or frequency of the laser pulses, the scanning pattern with which an energy beam is moved over the building material, etc. Even the variation of a diameter of an energy beam used to scan the building material or the temporal and spatial sequence of the scanning of sites to be solidified with energy radiation can lead to different melting behavior and can therefore also be energy input parameters whose value is changed.

In a further development of the method, in step S2 in the data models of the building material layers in at least one of the plurality of layer data sets, the values of an energy input parameter are assigned to the positions corresponding to the object section in segments, wherein a layer segment is a subregion of the building material layer and at least a layer segment, preferably at least in two layer segments, particularly preferably in all layer segments, all points of the object section in the layer segment is assigned the same value of the at least one Energieeintragabsameters depending on the distance of the layer segment to the edge portion of the object portion.

In the just mentioned development of the invention, an adaptation of the energy to be introduced into the building material takes place in an efficient manner, since the segment-wise allocation gives only a manageable number of different values of an energy input parameter which are assigned to different sites to be consolidated. The distance of a layer segment to an edge portion can be defined as the distance between a predetermined position in the layer segment and the edge portion.

It should be emphasized here that according to the development defined layer segments may also include outside of the object portion to be solidified areas. This is irrelevant for the assignment of values of an energy input parameter, since the data model of a shift data record specifies precisely those points at which solidification is to take place. In another development, the respective assignment of the layer segments to a layer data set is identical in at least two, preferably in all layer data sets of the plurality of layer data records that contain the object section, with regard to the shape and position of the layer segments in the working plane.

In particular, it is possible in this development, by means of the assignment of layer segments, to generate a grid of equally sized and identically oriented layer segments for a plurality of layers and the layer segments in the grid, so to speak the raster elements, energy input parameter values as a function of the distance to an edge section of the object or Assign object section. Such a procedure simplifies the execution of the method, since the sometimes complex geometry of an object section or object in the distance determination must be taken into account only limited. For the determination of the distance, it is preferable to use a distance in a spatial direction which is perpendicular to the working plane.

Furthermore, at least two different layer segments, in particular adjacent layer segments, can be assigned the same value for at least one energy input parameter, preferably all energy input parameters. In this further development, by assigning the same energy input parameter values, several layer segments within a building material layer can be combined into larger units (clusters), which are to be treated in the same way. Furthermore, areas with the same assigned energy input parameter values can also be introduced, which extend over several layer segments in different building material layers. The training thus allows a simplification of the method since

Values for energy input parameters, d. H. the energy input, be varied only very roughly.

In particular, the volume of the layer segments may increase with an increase in the distance to an edge portion of the object portion. In this way, it is possible to take into account the fact that the influence of a marginal section increases with increasing depreciation. stood to the edge portion fades and thus a detailed determination of the energy input in relation to the edge portion may no longer be necessary.

Furthermore, the layer segments can be assigned as a function of desired properties of the object section.

In this case, the size and shape of the layer segments is determined as a function of object-specific criteria, such as the required dimensional accuracy of an object section or the required mechanical properties. For example, a small size of the layer segments can be selected for particularly high demands on the dimensional accuracy and the mechanical properties of an object section, so that energy input parameters are assigned very finely tuned to the points to be solidified of the object. In what manner should be used in the assignment of layer segments, for example, if particularly high demands on compliance with defined quality specifications of the object section exist, can be specified by a user by means of a user input or automatically done, for. B. in the second step, an automatic analysis of the shape of the object is performed, from the z. B. due to the filigree structure of an object section shows that the dimensions of the layer segments should be chosen small.

In a further development of the method, the distance to an edge section of the object section in a direction perpendicular to the working plane is determined and the edge section comprises a region of a building material layer which directly adjoins unsolvable construction material in a layer above or below the edge section.

With this development of the method, it is possible to specifically consider marginal sections to unverfestigtem material out. Examples of this are edge sections that point downward during the manufacturing process of the object section (in the jargon downskin areas) or point upwards (in the jargon Upskin areas). In contrast to the prior art, the proximity to the unsolidified building material is not only in the The proximity to the unconsolidated building material adjacent layer is taken into account, but the proximity to the unconsolidated building material is taken into account in layers that are not directly adjacent to the unconsolidated building material. According to the method, layer segments are assigned in a plurality of layers, and energy input parameter values are assigned to the layer segments depending on the distance between a layer segment and the unconsolidated construction material below or above. The distance is here preferably defined as the distance in a direction perpendicular to the working plane. which, if not the thicknesses of the layers vary, is also perpendicular to the layer planes. The value of an energy input parameter to be assigned to a layer segment is thus z. B. is made dependent on whether the layer segment is in a layer of the next closest to the building material remaining unbonded, in the next but one layer, in the überübernächsten layer, etc. In how many layers are determined in this way layer segments and energy input parameter values are assigned, depends z. B. from the required quality of an object section.

Furthermore, the extent of each layer segment parallel to the layer plane can correspond at most to the extent of a region of the edge section which lies in a direction perpendicular to the working plane above or below the layer segment. If only a portion of a layer segment is above or below unconsolidated material, then it is difficult to determine what distance this layer segment has to the build-up material remaining unconsolidated. The procedure just described ensures that the layer segments are each selected so that they lie either completely or not at all above or below non-consolidatable building material.

Furthermore, at least 50%, more preferably at least 80%, even more preferably at least 95% of a maximum radiation energy per unit area W _{max can be} supplied to the sites to be solidified in a layer segment if construction material was solidified below the layer segment in at least n _max immediately preceding layers - where r is a natural number, and wherein the maximum irradiation energy amount per unit area W _max is a maximum amount of radiant energy per unit area applicable to the manufacturing process, depending on the building material used and the energy input device.

If the energy input to be supplied to the locations of the building material is monotonously increased with increasing distance from an edge section, then it makes sense to no longer increase the energy input per area from a certain distance to the edge section, otherwise a maximum amount of energy to be entered into the building material is exceeded and there are errors in solidification. This can be done by defining a maximum number n _m ax of layers that lie below a layer segment and in which the building material has been solidified. In such a case, it is assumed that the solidification in the layer segment is no longer influenced by the unassembled building material. Which value is to be selected for n _ma x depends on previous experience with the building material used and the energy input device used and can be determined, for example, within the framework of a limited number of preliminary experiments.

Furthermore, if less than n _m ax of immediately preceding layers of building material were solidified below a layer segment, the amount of radiation energy per unit area to be solidified in the layer segment can be chosen to be higher, the higher the number of immediately preceding layers which was solidified below the layer segment building material. In this approach, the amount of radiation energy to be input per unit area is not only increased monotonically with increasing distance to the edge portion, but even strictly monotonous.

Furthermore, the individual layer segments can each be assigned a position factor LF, depending on the respective number of immediately preceding layers which structural material has been solidified below the layer segment and a radiation energy quantity per unit area to be entered into the respective layer segment is selected as a function of the position factor LF. By the introduction of positional factors, which are, for example, numerical values which map the distance of a layer segment from the edge section or an underlying layer with unconsolidated building material, the distance to the unsolidified construction material or to the edge section does not have to be every time when energy input parameter values are assigned to the layer segments be determined again. This allows the assignment of energy input parameter values to be faster. In particular, this facilitates a further modification of already assigned energy input parameter values.

Furthermore, the edge portion may comprise a boundary of the object portion to at least one other portion of the object.

In this procedure, the edge portion of an object portion does not run at the edge or near the surface of the object, but within the object. Thus, it is possible to provide a soft transition in solidification for objects having sections that have different energy input parameter values such that the energy input parameter values do not abruptly change at the boundary within the object and inhomogeneities, particularly abrupt changes in properties in the solidified Material can be prevented. Furthermore, in the object section, the radiant energy per unit area may be supplied to the building material according to a predetermined first set of standard energy input parameter values and in a further object section adjacent to the object section the radiant energy per unit area may be applied to the building material according to a predetermined second set of standard energy input parameter values, and on the border between the two Object sections can be defined in at least one of the two object sections n intermediate sections, in which the energy input device respectively inputs the radiation energy per unit area such that the value of at least one energy input parameter lies between the values of this energy input parameter in the first and second set, where n is a natural number greater than One is.

As used herein, the term "standard energy input parameter values" is representative of energy input parameter values that are applied within that object portion, such as energy input parameter values specified in a data model of a slice dataset accessed in the first step. According to the described procedure, no abrupt transition of the energy input parameter values occurs at the boundary between two object sections with different standard energy input parameter values. Rather, intermediate boundaries are defined at the boundary in which the energy input parameter values have intermediate values between the values of the two sets of standard energy input parameter values. As a result, a jump in the material properties during solidification at the boundary between the object sections can be avoided.

In one development, n is greater than one and the energy input parameter values in the intermediate sections are such that at intermediate sections farther from the boundary between the two object sections, the value of at least one energy input parameter is closer to the value of the associated standard energy input parameter in that section of the object is located as intermediate sections within the same object section at a closer distance to the boundary.

This embodiment specifies more specifically that as the distance between the intermediate sections and the boundary between the two object sections increases, the values of at least one energy input parameter in these intermediate sections more and more approach the standard energy input parameter values defined for the object section. It should be emphasized that an intermediate section is not necessarily is an already mentioned single layer segment, since an intermediate section can also be defined to extend over several building material layers. Namely, the boundary between object sections may also be at an angle other than 90 ° to the planes of the building material layers.

Furthermore, the values of an energy input parameter to be assigned to those locations in the plurality of layer data sets that correspond to the object section can be determined in advance by means of simulation or by preliminary experiments. In particular, it is possible to select the layer segments or intermediate sections introduced in the second step in such a way that they are identical to areas which were used in advance for the determination of an energy input parameter value in the simulation or in the preliminary tests. Often, for a simulation or for preliminary tests, the section of an object to be simulated or examined is subdivided into smaller sections, and the simulation or examination is then carried out in regions such that the points within a section are treated the same or are regarded as indistinguishable.

Furthermore, an amount of radiation energy per unit area to be entered at one location can be determined using the equation

S = min ((W _mi n + Vf * LF) / W _max , 1.0) are determined, wherein the maximum amount of radiation energy per unit area W _m ax is a maximum applicable in the manufacturing process amount of radiation energy per unit area of the building material used and the energy input device, where S denotes a factor between 0 and 1 to multiply the maximum radiation energy per unit area W _m ax to obtain the amount of radiation energy to be entered per unit area, where W _m denotes a minimum amount of radiation energy per unit area to be entered and Vf designates a pre-factor determined in advance. By means of the analytical equation shown as an example, a radiation energy amount to be introduced can be determined in a particularly simple manner. Furthermore, in step S2, the assignment of values of an energy input parameter to results stored in a table of a simulation or a preliminary test can be used.

Even with this procedure, the values to be assigned can be assigned in a particularly simple and rapid manner.

In particular, the building material may contain a metal powder or metal alloy powder. Since in processes in which metal powder or metal alloy powder is used as the building material, a large part of the energy to be solidified is introduced into the material by the energy input device, the procedure described is of particular advantage for minimizing or controlled limitation during construction, especially for such construction materials Manufacturing process occurring temperature variations.

A generative layer construction method according to the invention for producing at least one three-dimensional object, wherein in the generative layer construction method the at least one object is produced by applying a building material layer by layer and solidifying the building material in a working plane by supplying radiant energy to locations in each layer corresponding to the cross section of the Assigned to objects in this layer, by scanning these locations by means of an energy input device according to a set of energy input parameters with energy radiation, includes a method according to the invention for providing control data. In particular, in the laminating method, during the selective solidification of a building material layer or between the selective solidification of different building material layers, the temperature may at least a location of a layer are measured, and a value of an energy input parameter is assigned to a location based on that measurement.

Feedback from a monitoring device about the actual conditions during the production process helps to correct the value of an energy input parameter to be assigned to a location as correctly as possible, ie. H. according to specified requirements. This applies in particular in a case in which the temperature was measured at this point before the allocation of an energy input parameter value to a location. The process for providing control data in this case will take place during the manufacturing process and will not be completed prior to the start of the manufacturing process.

A device according to the invention for providing control data for a generative layer building apparatus for producing a three-dimensional object, the object being produced by means of the generative layer building apparatus by applying a building material layer by layer and solidifying the building material in a working plane by supplying radiant energy to locations in each layer, which are assigned to the cross-section of the object in this layer by scanning these locations by means of the energy input device according to a set of energy input parameters with energy radiation, has a data access unit which is designed to access a plurality of

Layer data sets, which each have a data model of a build material layer to be selectively solidified during production, wherein in each data model an object cross-section corresponding locations are marked, at which a solidification of the building material to take place in the associated layer. The device according to the invention is characterized by a layer data record modification unit which is designed to define an object section which comprises at least part of one or more object cross sections and to modify the plurality of layer data records in such a way that a plurality of the points corresponding to the object section in the Plurality of layer data sets. Values of at least one energy input parameter are assigned such that the values increase with an increase in the distance to an edge section of the object section in a plurality of steps, preferably substantially monotone, and a slice data set providing unit configured to provide a plurality of slice records modified by the slice record modification unit to generate a control set for the generative slice building apparatus.

The provision of layered data sets modified in the third step for the production of the three-dimensional object can also take place in such a way that the layered data record providing unit itself integrates the modified layered data set into a control data record for the generative layering device. However, providing also includes forwarding one or more layer data sets to a data processing device which integrates the one or more layer data sets into a control data record, or a direct forwarding to a generative layer construction device. In particular, it is possible to dynamically provide shift data records for object cross sections still to be produced during a production process in the generative layer construction device of the generative layer construction device.

A generative layer building apparatus according to the invention for producing a three-dimensional object, wherein in the generative layer building apparatus the object is produced by applying a building material layer by layer and solidifying the construction material in a working plane by supplying radiant energy to locations in each layer corresponding to the cross section of the object in this layer are assigned by these points are scanned by means of an energy input device according to a set of energy input parameters with energy radiation, has an inventive device for providing control data.

A computer program according to the invention has program code means for carrying out all the steps of a method according to the invention when the computer program is executed by means of a data processor, in particular a data processor cooperating with a generative layer construction device. "Interaction" means here that the data processor is either integrated into the generative layer construction device or can exchange data with it. The implementation of the inventive method for providing control data and the associated device by means of software allows easy installation on various computer systems EDV at different locations (for example, the creator of the design of the object or the operator of the generative layer building apparatus).

In a computer-readable storage device according to the invention, the computer program according to the invention is stored. The storage device may be a portable storage medium, but in particular may also be a storage device present in a generative layer construction device or the energy input device.

Further features and advantages of the invention will become apparent from the description of embodiments with reference to the accompanying drawings.

Fig. 1 shows a schematic, partially in section view of an exemplary apparatus for generatively producing a three-dimensional

Object according to an embodiment of the invention, Fig. 2 shows schematically a section through a portion of an object during its manufacture to illustrate the different areas of a

Object section,

3 schematically shows a section through an exemplary section of an object during its production in order to illustrate the procedure,

4 shows a schematic plan view of an exemplary object cross-section for illustrating the procedure in the presence of an edge section within an object section, 5 illustrates the flow of a method for providing control data,

6 shows the schematic structure of a device for providing control data,

For a description of the invention, a generative layer building apparatus will first be described below with reference to FIG. 1, using the example of a laser sintering melting apparatus.

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. In the process chamber 3, an upwardly open building container 5 with a container wall 6 is arranged. A working plane 7 is defined by the upper opening of the construction container 5, wherein the area of the working plane 7 which lies within the opening and which can be used to construct the object 2 is referred to as construction field 8.

In the building container 5 a movable in a vertical direction V carrier 10 is arranged, on which a base plate 11 is mounted, which closes the container 5 down and thus forms its bottom. The base plate 11 may be a plate formed separately from the carrier 10, which is fixed to the carrier 10, or it may be formed integrally with the carrier 10. Depending on the powder and process used, a building platform 12 can still be mounted on the base plate 11 as a construction base on which the object 2 is built up. The object 2 can also be built on the base plate 11 itself, which then serves as a construction document. 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 a plurality of solidified layers surrounded by building material 13 which has remained unconsolidated.

The laser sintering or melting device 1 further comprises a storage container 14 for a building material 15, in this example an electromagnetic radiation solidifiable Powder, and a movable in a horizontal direction H coater 16 for applying the building material 15 within the construction field 8. Optionally, in the process chamber 3, a heater, such as a radiant heater 17 may be arranged, which serves to heat the applied building material. As radiant heating 17, for example, an infrared radiation can be provided.

The exemplary generative layer building apparatus 1 further comprises an exposure device 20 with a laser 21, which generates a laser beam 22, which is deflected by a deflection device 23 and by 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 level 7.

Furthermore, the laser sintering device 1 includes a control device 29, via which the individual components of the device 1 are controlled in a coordinated manner for carrying out the building process. Alternatively, the control device may also be mounted partially or completely outside the device. The controller may include a CPU whose operation is controlled by a computer program (software). The computer program can be stored separately from the device on a storage medium from which it can be loaded (for example via a network) into the device, in particular into the control device.

In operation, the carrier 10 is lowered layer by layer by the control device 29, the coater 16 is actuated to apply a new powder layer and the deflection device 23 and optionally also the laser 21 and / or the focusing device 24 are controlled to solidify the respective layer to the corresponding locations of the respective object by means of the laser by scanning these locations with the laser.

In laser sintering or laser melting, an exposure apparatus may, for example, comprise one or more gas or solid-state lasers or any other type of laser, such as laser diodes, in particular VCSELs (Vertical Cavity Surface Emitting Lasers) or VECSELs (Vertical Exposure Lasers). Ternary Cavity Surface Emitting Laser), or a line of these lasers. The specific structure of a laser sintering or melting apparatus shown in Fig. 1 is therefore exemplary only for the present invention and can of course be modified, especially when using a different exposure device than the one shown. To make it clear that the shape of the radiation incident surface on the building material may not necessarily be approximately punctiform, but also flat, the term "beam" is often used in the following synonymous with "beam".

All statements made in the further course apply not only to laser sintering or melting devices, but also to other types of generative layer construction devices in which heat energy in the form of radiation is introduced into the construction material.

In the generative layer construction device just described by way of example, a production process proceeds in such a way that the control unit 29 processes a control data record (often also referred to as a control instruction set). A first embodiment of the procedure according to the invention will be described below.

As shown in FIG. 6, a generative layer construction control data providing apparatus 100 includes a data access unit 101, a layer data set modification unit 102, and a layer data record preparation unit 103. The operation of the control data providing apparatus 100 will be described with reference to FIG 5 described.

In the device 100 for providing control data for a generative layer construction device shown in FIG. 6, the data access unit 101 first accesses a plurality of layer data sets, each of which has a data model of a build material layer to be selectively solidified during fabrication, in which an object cross-section corresponding points of the layer marked, at which building material to be solidified. In the process sequence shown in FIG. 5, this is the first step S1. In a second step S2 shown in FIG. 5, the slice data set modification unit 102 first selects an object portion included in the data models of the plurality of slice records. An example of such an object section is illustrated in FIG. 2, which is a side view of one through a generative one

Layer construction method to be produced object section, similar to the side view of the object 2 in Fig. 1st

The object section shown in FIG. 2 has seven cross sections in the layers n + 1 to n + 7, wherein the arrow on the right indicates the direction in which the object section is built up layer by layer ("z direction" in a transmission) In all layers, the region 70, in which the construction material remains unconsolidated, is shown without filling and with a dashed border line.

Furthermore, FIG. 2 shows so-called bottom surface regions 62 (often also referred to as downskin regions in technical jargon). These are areas of an object cross-section, which lie during the object production above building material that remains unconsolidated or under certain conditions on support structures - in the jargon supports - which in turn connect the object for the purpose of improved heat dissipation with a construction platform. The bottom surface areas 62 thus correspond to surface areas of the object which during its production downwards

(towards the carrier 10) show. The bottom surface regions 62 are indicated in FIG. 2 by slashes "/".

FIG. 2 likewise shows regions 61 identified by backslashes "\". These are regions of an object cross-section which are covered immediately after the object has been produced by building material that has remained unconsolidated or, in certain cases, may remain uncovered. Correspondingly, the regions 61 are referred to as cover surface regions (often referred to as upskin regions in the technical jargon), since these are surface regions of the object to be produced which point upwards (directed away from the support 10) during its production. Finally, FIG. 2 shows regions 63 still marked with circles "O". These are regions of an object cross-section above and below which the building material is to be solidified, for which reason the regions 63 are referred to as sandwich regions.

An embodiment is described below with reference to FIG. 3, in which edge regions which are specifically considered in step S2 are those regions of the edge of the object section in FIG. 2 which are in a direction perpendicular to the layers above or below lie unverfestigt remaining material. In FIG. 2, such an edge portion would be, for example, one of the downskin regions 62 in the layers n + 1, n + 2 and n + 3. The inventor has recognized that it is not sufficient for a satisfactory quality of the manufactured object if only changed energy input parameter values in a downskin region 62 with respect to the sandwich regions 63 are selected in order to take into account the different heat dissipation capacity of the underlying unconsolidated building material. Rather, the inventor has found that, for example, when solidifying the sandwich region 63 in the n + 2 layer in Figure 2, there is an effect on the material in the underlying n + 1 layer and the unconsolidated material in the underlying n layer. In particular, the build-up material in the layer n can be involuntarily partially solidified when the layer n + 2 solidifies, so that the object section in FIG. 2 after its solidification has a greater extent perpendicular to the layers than planned. In order to remedy this situation, it is possible to proceed as illustrated in FIG. 3. 3 shows, by way of example, an object section 300 which has a horizontal surface 303 pointing upwards during the construction process, a surface 304 which is substantially perpendicular to the building material layers during the construction process (facing away from the viewer) and a curved surface pointing downward during the production process 302. The layering shown in FIG. 3 shows a section through the object section 300 along a plane parallel to the side surface 305. In the example of Fig. 3, the object portion is formed by applying and solidifying eight building material layers n-7 to n, solidifying the layer n-7 before the n-6 layer, etc., and n last in the figure is solidified. In this example, the curved downwardly facing surface 302 is considered to be the edge portion of the object portion with respect to which the energy to be input to the building material is set.

FIG. 3 shows in each layer a plurality of layer segments 350, which are subregions of the layer. Furthermore, it can be seen that each layer segment is provided with a number 0, 1, 2, 3, etc. This number expresses how many layer segments in which building material is solidified lie between a layer segment and the unconsolidated material 13. In the example shown in FIG. 3, the horizontal expansions of the superimposed layer segments in different layers were chosen to be the same. The numerical value assigned to a layer segment can be regarded as the position factor LF expressing the distance to the edge section, which is used as the basis for the dimensioning of the energy amount to be entered in the layer segment.

In the example, the layer data set modification unit 102 sets the amount of energy per unit area to be entered into the layer segments as follows: Below the

Layer segment with the number 2 in the layer n is entered into the layer segment with the number 0 in the layer n-2 a reduced energy amount per unit area compared to a sandwich area. This takes into account that the unconsolidated building material 13 dissipates the registered thermal energy bad. In the layer segment with the number 1 in the layer n-1, an energy amount per area unit increased compared to the layer segment with the number 0 in the layer n-2 is entered, since this layer segment is further away from the unconsolidated building material. Finally, in the layer segment with the number 2 in the layer n, an energy amount per area unit which is further increased in comparison with the layer segment with the number 1 in the layer n-1 is entered. Thus, the entire object section in FIG. 3 is moved, whereby the material deposited in the building material is removed. The radiation energy per unit area is gradually increased with increasing distance from the unconsolidated building material 13. In short, it is proposed herein to define upskin regions 62 and downskin regions 61 so that they extend over several superimposed layers.

The energy to be introduced into the building material per unit area can be changed by varying the value of one or more energy input parameters. An energy input parameter is, for example, the energy density of the radiation energy directed onto a layer segment, that is to say the amount of energy deposited per unit area in the building material. Another possible energy input parameter is the speed with which, for example, an energy beam is moved over the building material. The shorter the time in which an energy beam sweeps over a specific location of the building material, the less energy is introduced at this point. Furthermore, it is also conceivable that each point is scanned several times with energy radiation. In this case, the number of energy inputs is also an energy input parameter that influences the en- ergy quantity entered. Further, another energy input parameter is the distance between two locations within a layer segment at which energy is sequentially introduced. The shorter the distance, the greater the mutual influence of the two points. In the example of FIG. 3, the maximum value of the position factor LF is five. However, this value is not mandatory. Depending on the building material used (in particular its heat dissipation capability) and on the manner of solidification in the generative layer construction method, the maximum value of the position factor LF may also be different. The value of the position factor LF here describes not only the number of solidified layer segments between unconsolidated building material 13 and a layer segment but also the number of steps in which the energy to be introduced into the building material, ie the value of at least one energy input parameter, increases with increasing distance to the unsolidified layer Construction material is increased. The inventor has found that normally a maximum value of 25 can be chosen for the position factor LF, since an influence of the unconsolidated building material (due to its heat dissipation capacity) can be selected. gen) or an unintentional change in the unconsolidated building material 13 when solidifying overlying layers are no longer detectable when 25 layers in which the material has solidified, lie between a layer segment and the unconsolidated building material. Depending on the construction material used and the layer construction method used, however, a maximum value of 15 or 10 or 8 or even a value greater than 25 may already be adequate. Conversely, improvements in the solidification behavior can already be observed if only a maximum value of the position factor of 2 is selected, ie the amount of energy per unit area to be entered in a layer segment is only increased in two steps until it reaches the value in the layer segments with the position factor 2 achieved within a sandwich area to be entered amount of energy per unit area.

As already mentioned, in FIG. 3, the extent of the layer segments within the layer planes was chosen to be the same in all illustrated layers. This facilitates the determination of a "distance" of a layer segment from an underlying edge section. As can be seen in Fig. 3, while the extension of the superimposed layer segments parallel to the layer plane was chosen so that it corresponds to the extension of lying on the edge portion layer segment (this is in each case with the numeral "0") parallel to the layer plane. The extent of the respective layer segment lying directly on the edge section is selected such that the edge section occupies the entire downwardly facing surface of the layer segment. Of course, the horizontal extent of the layer segment lying directly on the edge section can also be chosen to be smaller, so that the layer no longer has the full layer thickness in this layer segment, but preferably the horizontal extension of the layer segment lying directly on the edge section should not be so large that a part of the underside of such a layer segment lies above consolidated building material.

Basically, it is possible to introduce a grid, which one has to imagine as a two-dimensional grid, which is placed in thought over the surface of a building material layer, so that each point of a building material layer a certain (eg square) Raster element is assigned. The layer segments to be defined in the method described can correspond to individual raster elements or correspond to a combination of juxtaposed raster elements. Finally, in a step S3 shown in FIG. 5, the layer data set modified in step S2 is provided by the layer data record preparation unit 103 for the generation of a control data record.

The procedure described in connection with FIG. 3 is equally applicable to upskin regions 61. The position factor LF of the layer segments grows in such a case with increasing distance to the Upskin region, that is for segments in the layer n + 5 in Fig. 2 is usually greater than in the layer n + 6 in Fig. 2, etc .. ,

FIG. 4 shows an exemplary embodiment in which an edge section of an object section 50 to be taken into consideration lies within an object and not at the boundary with the building material remaining unconsolidated. It is understood that the object portion in Fig. 4 is kept very simple for the sake of ease of explanation, and the method is equally applicable to much more complicated object portions. The object portion 50 consists of a half 50a and a half 50b to be scanned with different energy input parameters and separated by a margin portion 55 (a boundary). In this example 50a intermediate sections 51a and 52a are defined in half and defined in half 50b intermediate sections 51b and 52b. In this case, the plan view of FIG. 4 shows only a cross section corresponding to the object section, and the sections of the object section which have already been solidified underneath it are not visible. Similarly, the intermediate sections illustrated in FIG. 4 are similar to the layer segments 350 illustrated in FIG. 3. However, unlike the layer segments of FIG. 3, the intermediate sections of FIG. 4 may comprise sections of multiple layers. Analogously to the procedure in the example of FIG. 3, the value of at least one energy input parameter is then set as a function of the distance of an intermediate section to the boundary 55. For example, if a radiation energy density value EDa to be entered is set for the left half 50a and a radiation energy density value EDb to be entered is set for the right half, in this example, an energy density value for the radiant energy to be inputted is selected in the intermediate portions 51a and 51b, which varies to both EDa and EDb. The intermediate sections 52a and 52b are then assigned energy density values which are closer to the values EDa and EDb, respectively. For the remaining portions 53a and 53b of the left and right halves 50a and 50b, the values of the energy densities EDa or EDb are specified. For example, the energy density values E3a, E2a, Ela, Elb, E2b, E3c could be assigned to regions 53a, 52a, 51a, 51b, 52b, 53b in FIG. 4 with E3a>E2a>Ela>Elb>E2b> E3c. By doing so, a gradual transition is created in solidifying the different halves 50a and 50b in the transition region near the boundary 55.

It is also possible to combine the procedure of FIG. 4 (edge section within an object or an object cross section) with the procedure according to FIG. 3, so that additionally the distance of a layer segment from unconsolidated building material is taken into account. In particular, it is also possible to proceed in such a way that the distance to the unconsolidated building material in an overlying or underlying layer is not taken into account, as in the example of FIGS. 2 and 3, but the distance to the unconsolidated building material at the edge of an object cross section for the definition of energy input parameter values is taken into account. Assuming, for example, in FIG. 4, that the object section 50 shown there at its upper and lower edge (with respect to the plane of the drawing in FIG. 4) adjoins unfixed building material, then layer segments could be introduced at this upper and lower edge, which would be assigned other values of radiant energy density.

In a modification of the procedure according to FIG. 4, intermediate sections are introduced in only one of the two halves 50a and 50b and energy input parameter values are thus assigned. indicated that they are closer to the standard energy input parameter values in the respective half as the distance from the boundary 55 increases. Generally, the amount of change of energy input parameter values in the transition from one intermediate section to the next intermediate section does not have to be the same in the left half and the right half of FIG. 4.

As regards the determination of the energy input parameter values to be assigned to the layer segments and intermediate sections, it is possible to base the determination on previously performed simulations of the production process of an object or results from preliminary investigations in which the solidification behavior was investigated close to edge sections of an object section. In the case of simulations, for example, a simulation can be based on the same raster, which is also used as a basis for defining slice segments. In this case, a simple transfer of the results of the simulation to the energy input parameter values is possible.

In order to simplify the definition of the energy density to be entered before the production of an object, it is useful to set up an analytical equation for the energy density to be entered. As an example of such an equation, here is the equation

S = min ((W _min + Vf * LF) / W _m ax, 1.0), wherein the maximum amount of radiation energy per unit area (Wmax) is a maximum amount of radiant energy per unit area applicable in the manufacturing process, which depends on the building material used and the Energy input device, where S denotes a factor between 0 and 1, with which the maximum amount of radiation energy per unit area (W _max ) is to be multiplied in order to obtain the amount of radiation energy to be input per unit area, where W _{m designates} a minimum amount of radiation energy per unit area and Vf designates a pre-factor determined in advance. Finally, it should be mentioned that a device 100 according to the invention for the provision of control data for a generative layer construction device is not limited to software components alone; but also by hardware components or mixtures of hardware and software can be realized. In particular, interfaces mentioned in the present application do not necessarily have to be designed as hardware components, but can also be realized as software modules, for example if the data fed in or output via them can be taken over by other components already realized on the same device or must be passed to another component only by software. Similarly, the interfaces could consist of hardware and software components, such as a standard hardware interface specifically configured by software for the specific application. In addition, several interfaces can also be combined in a common interface, for example an input-output interface.

Claims

A computer-aided method for providing control data for a generative layer building apparatus for producing a three-dimensional object, wherein the object is manufactured by the generative layer building apparatus by applying a building material layer by layer and solidifying the building material in a working plane by supplying radiant energy to locations in each layer associated with the cross-section of the object in that layer by scanning these locations with energy radiation by means of the energy input device according to a set of energy input parameters,

wherein the method for providing control data comprises:

a first step (S1) for accessing a plurality of layer data records, each of which has a data model of a build-up material layer to be selectively solidified during production, wherein in each data model, locations corresponding to an object cross section are identified, at which solidification of the building material (15) should take place in the associated layer,

characterized in that in a second step (S2) an object section is defined which comprises at least part of one or more object cross sections, and the plurality of layer data sets is modified such that a plurality of locations corresponding to the object section in the plurality of layer data sets at least an energy input parameter may be assigned such that the values change with a change of the distance to an edge section of the object section in a plurality of steps, preferably substantially monotonically, and

in a third step (S3), the plurality of shift data records modified in the second step is provided for the generation of a control data record for the generative layer building apparatus.

2. Method according to claim 1, wherein in step (S2) in the data models of the building material layers in at least one of the plurality of layer data sets, the values of an energy input parameter are assigned to the positions corresponding to the object section in segments, wherein a layer segment is a subregion of the building material layer is and at least in a layer segment, preferably at least in two layer segments, particularly preferably in all layer segments, all points of the object section in the layer segment in each case the same value of the at least one Energieeintragabsameters assigned depending on the distance of the layer segment to the edge portion of the object section.

3. The method of claim 2, wherein in at least two, preferably in all the layer data sets of the plurality of layer data sets containing the object section corresponding locations, the respective assignment of the layer segments to a layer data set in terms of shape and location of the layer segments in the working plane is the same.

4. The method of claim 2 or 3, wherein at least two different layer segments, in particular adjacent layer segments, the same value for at least one energy input parameter, preferably all energy input parameters assigned.

5. The method of claim 2, wherein the volume of the layer segments increases with an increase in the distance to an edge portion of the object portion.

6. The method according to any one of claims 2 to 5, wherein the layer segments are assigned as a function of desired properties of the object section.

7. The method according to claim 1, wherein the distance to an edge section of the object section is determined in a direction perpendicular to the working plane, and the edge section comprises a region of a building material layer, which is immediately adjacent. adjoining non-bonded building material in a layer above or below the edge portion.

8. The method according to claim 7, wherein the extent of each layer segment parallel to the layer plane corresponds at most to the extent of a region of the edge section lying in a direction perpendicular to the working plane above or below the layer segment.

9. The method of claim 8, wherein at least 50%, more preferably at least 80%, more preferably at least 95% of a maximum radiation energy amount per unit area (W _m ax) is supplied to the sites to be solidified in a layer segment, if below the layer segment in at least n _ma x immediately preceding layers of building material, where n _ma x is a natural number, and wherein the maximum amount of radiation energy per unit area (Wmax) is a maximum amount of radiation energy per unit area applicable in the manufacturing process, depending on the building material used and the energy input device.

10. The method of claim 9, wherein, if below a layer segment in less than n _m ax immediately preceding layers building material has been solidified, a set of sites to be solidified in the layer segment amount of radiation energy per unit area the higher, the higher the number of immediate preceding layers, in which building material was solidified below the layer segment.

11. The method according to claim 9 or 10, wherein the individual layer segments each a position factor (LF) is assigned as a function of the respective number of immediately preceding layers in which building material was solidified below the layer segment and to be entered in the respective layer segment radiation energy per unit area is selected as a function of the position factor (LF).

12. The method according to any one of claims 1 to 4, wherein the edge portion comprises a boundary of the object portion to at least one other portion of the object.

13. The method of claim 12, wherein in the object section, the radiant energy per unit area is supplied to the building material according to a predetermined first set of standard energy input parameter values, and in a further object section adjoining the object section, the radiant energy per unit area corresponds to the building material corresponding to a predetermined second one Set of standard energy input parameter values, and

n intermediate sections are defined at the boundary between the two object sections in at least one of the two object sections, in which the energy input device inputs the radiation energy per unit area such that the value of at least one energy input parameter lies between the values of this energy input parameter in the first and second set, where n is a natural number greater than one.

14. The method of claim 13, wherein n is greater than one, and the energy input parameter values in the intermediate portions are such that at intermediate portions farther from the boundary between the two object portions, the value of at least one energy input parameter is closer to the value of The associated standard energy input parameter in this object section is located as intermediate sections within the same object section with a smaller distance to the boundary.

15. The method according to claim 1, wherein the values of an energy input parameter to be assigned to those locations in the plurality of layer data sets which correspond to the object section are determined in advance by means of simulation or by preliminary tests.

16. The method of claim 15, wherein a to be entered at one point amount of radiation energy per unit area based on the equation

S = min ((W _min + Vf * LF) / W _m ax, 1.0) is determined, wherein the maximum amount of radiation energy per unit area (Wmax) is a maximum applicable in the manufacturing process amount of radiation energy per unit area, which depends on the building material used and the energy input device, where S denotes a factor between 0 and 1, with the maximum is to be multiplied by the quantity of radiation energy per unit area (W _m ax) in order to obtain the amount of radiation energy to be entered per unit area, where W _m denotes a minimum radiation energy quantity per unit area to be introduced and Vf denotes a pre-factor determined in advance.

17. The method of claim 15, wherein in step (S2) for the assignment of values of an energy input parameter used in a table results of a simulation or a preliminary test is used.

18. The method according to any one of the preceding claims, wherein the building material contains a metal powder or metal alloy powder.

19. Generative layer construction method for producing at least one three-dimensional object, wherein in the generative layer construction method, the at least one object is produced by applying a building material layer by layer and solidifying the building material in a working plane by supplying radiant energy to locations in each layer corresponding to the cross section of the Objects in this layer are assigned by these points are scanned by means of an energy input device according to a set of energy input parameters with energy radiation, wherein the generative layer construction method includes a method according to any one of claims 1 to 18.

20. The generative layer building method of claim 19, wherein during the selective solidification of a build material layer or between selectively solidifying different building material layers, the temperature of at least one location of a layer is measured and a value of an energy input parameter is assigned to a location based on that measurement.

21. A device for providing control data for a generative layer building apparatus for producing a three-dimensional object, wherein the object is produced by the generative layer building apparatus by applying a building material layer by layer and solidifying the building material in a working plane by supplying radiant energy to sites in each layer, associated with the cross-section of the object in that layer by scanning those locations by the energy input means in accordance with a set of energy input parameters with energy radiation, the apparatus for providing control data comprising:

a data access unit (101) adapted to access a plurality (M l) of layer data sets each having a data model of a build material layer to be selectively solidified during fabrication, wherein each data model identifies locations corresponding to an object cross section at which solidification of the Building material (15) to take place in the associated layer

characterized by a layer data set modification unit (102) configured to define an object portion including at least a part of one or more object cross sections and to modify the plurality of layer data sets such that a plurality of locations corresponding to the object portion in the plurality of layer data sets Values of at least one energy input parameter can be assigned such that the values change with an increase in the distance to an edge section of the object section in a plurality of steps, preferably substantially monotonically, and

a slice data set providing unit (103) configured to provide a plurality of slice records modified by the slice record modification unit (102) to generate a control set for the generative slice building apparatus.

22. Generative layer building apparatus for producing a three-dimensional object, wherein in the generative layer building apparatus the object is produced by applying a building material layer-by-layer and solidifying the building material in a working plane by supplying radiant energy to locations in each layer corresponding to the transverse layer. section of the object in that layer are scanned by means of an energy input device according to a set of energy input parameters with energy radiation, wherein the generative layer construction device comprises a device according to claim 21.

A computer program comprising program code means for performing all the steps of a method according to any one of claims 1 to 20, when the computer program is executed by means of a data processor, in particular a data processor cooperating with a generative layer construction device.