DE102021103118A1 - Method for producing a three-dimensional workpiece by selectively irradiating a plurality of layers of raw material powder - Google Patents

Abstract

A method of manufacturing a three-dimensional workpiece by selectively irradiating a plurality of raw material powder layers is provided. The method comprises creating a plurality of first structures in a number of N first raw material powder layers, where N is 1 or more. The plurality of first structures do not touch each other. At least 75% of an area consolidated for the plurality of first structures in a bottommost of the N first layers of raw material powder is in direct contact with non-solidified layer of raw material powder under the bottommost of the N first layers of raw material powder. The method further includes creating a plurality of second structures in a number of M second raw material powder layers, where M is 1 or more. The positions of the second structures are the same in the M second layers. The plurality of second structures do not touch each other. Each of the plurality of second structures is connected to at least two of the plurality of first structures via overlapping areas. The method further includes generating a surface of the three-dimensional workpiece such that the surface and the surface consolidated for the plurality of first structures in the bottom of the N first raw material powder layers at least partially overlap with respect to a viewing direction perpendicular to the raw material powder layers.

Description

The present invention relates to a method for manufacturing a three-dimensional workpiece by selectively irradiating a plurality of raw material powder layers.

Powder bed melting is an additive layer construction process that can be used to process powdered, in particular metallic and/or ceramic, raw materials into three-dimensional workpieces with complex shapes. For this purpose, a raw material powder layer is applied to a carrier and, depending on the desired geometry of the workpiece to be manufactured, radiation (e.g. laser or particle radiation) is applied to it in a location-selective manner. The radiation penetrating the powder layer causes heating and thus melting or sintering of the raw material powder particles. Further raw material powder layers are then successively applied to the already irradiated layer on the carrier until the workpiece has the desired shape and size. Powder bed melting can be used to manufacture prototypes, tools, spare parts, high value components or medical prostheses such as e.g. As dentures or orthopedic prostheses, are used on the basis of CAD data. Examples of powder bed melting processes are selective laser melting and selective laser sintering.

Devices for producing one or more workpieces using the above-mentioned method are known. For example, describe EP 2 961 549 A1 and EP 2 878 402 A1 a device for the production of a three-dimensional workpiece using the method of selective laser melting. The general principles described in these documents may also apply to the method of the present disclosure. However, the present disclosure is not limited to selective laser melting and can also be applied to other additive manufacturing processes in which layers of raw material powder are selectively irradiated and solidified, e.g. B. using one or more laser beams and / or particle beams.

When a workpiece is manufactured by any of the methods described above, the usual methods often require a support structure to dissipate the heat generated during the build process and/or to provide mechanical stability. In particular, horizontal surfaces of the workpiece or surfaces that form a small angle with respect to the carrier must be supported by a support structure in the known methods. However, support structures typically require a lot of material that cannot be reused. The fabrication of the support structures also requires additional time for irradiation. Also, the support structure must be removed in a post-processing step, which is often time-consuming and complex, and sometimes even impossible.

It is therefore an object of the invention to provide a method for producing a three-dimensional workpiece by selectively irradiating a plurality of raw material powder layers, which method avoids or reduces at least one of the above problems or a problem related thereto. In particular, it is desirable to avoid at least some of the support structure(s) produced by prior art methods.

This object is achieved by a method according to claim 1 and a method according to claim 10.

According to a first aspect, there is provided a method for manufacturing a three-dimensional workpiece by selectively irradiating a plurality of raw material powder layers. The method comprises creating a plurality of first structures in a number of N first raw material powder layers, where N is 1 or more. The plurality of first structures do not touch each other. At least 75% of an area consolidated for the plurality of first structures in a bottommost of the N first layers of raw material powder is in direct contact with non-solidified layer of raw material powder under the bottommost of the N first layers of raw material powder. The method further includes creating a plurality of second structures in a number of M second raw material powder layers, where M is equal to 1 or more. The plurality of second structures do not touch each other. Each of the plurality of second structures is connected to at least two of the plurality of first structures via overlapping areas. The method further includes generating a surface of the three-dimensional workpiece such that the surface and the area solidified for the plurality of first structures in the bottommost of the N first raw material powder layers at least partially overlap with respect to a viewing direction perpendicular to the raw material powder layers.

The method for producing the three-dimensional workpiece can include the usual steps of powder bed melting methods such as electron beam melting, selective laser melting or selective laser sintering. In particular, the method can involve the application of a first raw material powder layer to a carrier of a device for producing a three-dimensional work include pieces. The first layer (as well as the subsequent layers) can have a predefined layer thickness, wherein the layer thickness can be adapted from layer to layer depending on the type of powder application method used or can be fixed. The layers of powder can be applied using any suitable technique, with several methods and devices for producing layers of raw material powder being known in the art. After the application of the first raw material powder layer, predefined areas of the powder are irradiated with an energy beam, such as a laser beam or a particle beam (eg an electron beam), according to the CAD data of a workpiece to be produced and/or a support structure to be produced. In this way, a first layer of a workpiece to be produced can be irradiated directly on the carrier or on a support structure connected to the carrier and thereby solidified. In a further step, a second raw material powder layer is applied and predefined areas of this layer are irradiated and solidified. In this way, the workpiece is built up layer by layer.

Each of the structures can be essentially two-dimensional, e.g. H. only extend over one or a few (N or M) layers in one direction. The expansion of each structure in at least one dimension parallel to the raw material powder layers can be at least three times, at least five times, at least ten times or at least twenty times larger than the expansion of the structure along the construction direction. In this context, the "structures" may have essentially two-dimensional shapes, such as B. a filled circle, a filled square, etc.

In this disclosure, a Cartesian coordinate system is considered in which the building direction is a z-direction and each of the raw material powder layers extends in an x-y plane. Thus, the expression "perpendicular to the raw material powder layers" means parallel to the z-direction and the expression "parallel to the raw material powder layers" means parallel to an x-y plane. Since all raw material powder layers extend in an x-y plane, the above expressions are clearly defined. However, the phrase "perpendicular to the raw material powder layers" may be replaced by "perpendicular to a support" or "perpendicular to a lowermost one of the raw material powder layers". Likewise, the expression "parallel to the raw material powder layers" can be replaced by "parallel to a carrier" or "parallel to a lowermost of the raw material powder layers".

In the following description, the terms "raw material powder layers" and "powder layers" are used as synonyms. However, these "powder layers" are different from "layers of structures". The term "powder layer" means a layer of deposited (and optionally partially solidified) raw material powder. The term "layer of structures" (or "layer of first structures" etc.) refers to one or more (e.g. M or N) powder layers in which the plurality of structures are arranged. For example, there may be a layer of first structures followed by a layer of second structures, each of which two layers may be formed from one or more layers of powder.

As usual, the plurality of first structures means at least two. However, more or significantly more than two first structures can also be produced. A number of first structures can be at least 4, at least 9, at least 16, at least 25, at least 36, at least 49, at least 64, at least 81, at least 100, at least 500 or at least 1000. The same applies to the plurality of second structures. A number of second structures can be at least 4, at least 9, at least 16, at least 25, at least 36, at least 49, at least 64, at least 81, at least 100, at least 500 or at least 1000.

Furthermore, in addition to the “plurality of first structures” in the N first raw material powder layers, further structures can be produced. In other words, not all structures created in the N first layers of raw material powder need to be considered part of the “plurality of first structures”. It is important to take this into account because not all structures in the N first raw material powder layers have to be connected to at least two of the plurality of second structures. For example, there can be structures in edge regions of the plurality of structures arranged in the N first raw material layers, which are only connected to one or to none of the second structures. Likewise, not all structures created in the M second layers of raw material powder need to be considered part of the “plurality of second structures”. The arrangement of structures can therefore also be described as follows. A plurality of structures are generated in the N first raw material powder layers, all or only a part of these plurality of structures being regarded as “plurality of first structures”. This plurality of first structures can be significantly more than two (e.g. at least 64).

For the sake of simplicity, the description refers to a workpiece to be built. It is clear that more than one piece can be built in a single build order. So if from When talking about the workpiece, this also means several workpieces.

Among the N first raw material powder layers, a position, a size, a shape, and an orientation of an irradiated portion of each structure may be the same. In other words, each of the plurality of first structures can e.g. B. be a vertical cylinder. In other words, in each of the plurality of N first layers, a position, a size, a shape, and an orientation of the plurality of first structures can be the same. However, a position, a size, a shape, and/or an orientation of an irradiated surface for the plurality of first structures in the N first raw material powder layers may differ from powder layer to powder layer. This difference can be small (e.g. less than 20% or less than 10% for adjacent raw material powder layers). For example, a position, a shape, and an orientation in the N first raw material powder layers may be the same, but a size may differ by less than 20% or less than 10% when considering adjacent raw material powder layers. The above details and considerations regarding the plurality of first structures in the N first raw material powder layers may also apply to the plurality of second structures in the M second raw material powder layers.

Furthermore, each of the plurality of first structures can be formed in each of the N first powder layers. In other words, in each of the N first powder layers, for each of the plurality of first structures, a portion of the respective powder layer corresponding to the respective structure is solidified. However, in another embodiment, each of the plurality of first structures is not consolidated in each of the N first powder layers. Instead, a first portion of the plurality of first structures is consolidated in one of the N first powder layers and a second, different portion of the plurality of first structures is consolidated in another of the N first powder layers. For example, in a regular grid pattern, in a first of the N first powder layers, only every other one of the plurality of first structures is consolidated, and in a second of the N first powder layers, the remaining structures of the plurality of first structures are consolidated. In this way, not all structures are consolidated in each of the N first powder layers.

The individual structures of the plurality of first structures can all have the same shape, size and orientation. Alternatively, a shape, size, and/or orientation of at least two of the plurality of first structures may differ. In other words, the first structures may all have the same shape, size, and orientation, or a shape, size, and/or orientation of at least some of the structures may differ. For example, the plurality of first structures may include structures having two or more different shapes and/or two or more different sizes. The same applies to the plurality of second structures.

Thus, a size, an orientation, and a shape of the first structures can vary in the plurality of first structures. In other words, a size, orientation, and/or shape of all first structures need not be the same. However, a size, an orientation and/or a shape of the first structures can be the same. For example, a size, an orientation, and a shape of all first structures can be the same. However, it may also be the case that a size and a shape of the first structures are the same, but different orientations are present within the plurality of first structures (eg two different orientations rotated by 180° relative to one another). The above information on the first structures can also apply to the plurality of second structures.

The plurality of first structures do not touch each other. In other words, each of the first structures is not in contact with any other one of the first structures in the plurality of N first raw material powder layers. In other words, there is no lateral contact between the first structures. However, the first structures touch other structures (e.g., the second structures) in layers other than the N first raw material powder layers. This also applies to the plurality of second structures, which likewise do not touch one another.

The plurality of first structures can be arranged at corner points of a regular grid. The distances between adjacent vertices can all have the same value. The first structures can be arranged at the corner points in such a way that a focal point of the respective first structure is arranged at the respective corner point. The plurality of first structures may be arranged at vertices of a regular lattice, where the regular lattice is a square lattice, a hexagonal lattice, an equilateral triangle lattice, or other suitable shape. The plurality of first structures can form a regular pattern. The above also applies to an arrangement of the plurality of second structures.

In the number of N layers, a place in the raw material powder layers where the first Structures are formed to be identical from powder layer to powder layer. However, a part of a workpiece and/or other structures, in particular support structures, can be formed at a different location of the N powder layers, at which location the powder can be consolidated differently, e.g. B. by using a different irradiation strategy and/or by using an energy beam with a different energy distribution, a different energy density, a different spot diameter, a different spot shape, a different power and/or in the case of laser beams a different wavelength. The above information on the first structures can also apply to the plurality of second structures.

At least 75% of an area consolidated for the plurality of first structures in a bottommost of the N first layers of raw material powder is in direct contact with non-solidified layer of raw material powder under the bottommost of the N first layers of raw material powder.

Just for clarification - when the description refers to an "area consolidated for a plurality of structures", this means the sum of the areas that were actually consolidated for the creation of the structures and not the areas with possible loose powder between the Structures contain, in other words, it is not an area bounded by the outermost structures and containing the structures and loose powder between them.

In other words, the plurality of first structures are not built up directly on a carrier, but on at least one previously applied layer of powder. Further, a portion of this previously applied powder layer on which the plurality of first structures will be formed is not consolidated or only consolidated such that at least 75% of a consolidated area for the plurality of first structures in a bottommost of the N first powder layers is in direct contact with unsolidified raw material powder. In other words, at least a large part (at least 75%) of the first structures is built on a "free powder bed".

At least 85%, at least 90% or 100% of a consolidated surface for the plurality of first structures in a bottommost of the N first raw material powder layers may be in direct contact with unconsolidated raw material powder of a raw material powder layer under the bottommost of the N first raw material powder layers. Furthermore, an entire volume below the area consolidated for the plurality of first structures and extending to a carrier or a portion of the workpiece or another workpiece may be unconsolidated, or at least 75% of that volume, at least 85%, or at least 90% %. In other words, there may be support structures under the layer of first structures that support the first structures, but these support structures are attached to only a small fraction of a total area of the plurality of first structures.

The plurality of second structures may be arranged at the vertices of a regular lattice, wherein in a preferred embodiment the regular lattice of the second structures is the same as a regular lattice of the first structures, but offset laterally. A pattern formed by the plurality of second structures may be the same as a pattern formed by the plurality of first structures but shifted laterally. Laterally shifted means that it is offset (or shifted) parallel to the powder layers (i.e. within an x-y plane).

An orientation, a shape, and a size of each of the second patterns may be the same as an orientation, a shape, and a size of each of the first patterns. However, an orientation, a shape and/or a size of the plurality of second structures can differ with respect to the plurality of first structures. For example, the plurality of first structures can consist of circles, while the plurality of second structures consist of squares. As another example, the plurality of first features may be circles of a first size, while the plurality of second features are circles of a second, different size.

Each of the plurality of second structures is connected to at least two of the plurality of first structures via overlapping areas. This can mean that the second structures are formed in a powder layer that directly follows the N first powder layers of the first structures. However, one or more intermediate powder layers can be provided between the N first powder layers and the M second powder layers, with the laser melting and solidifying these intermediate powder layers during the irradiation of a first of the M second powder layers. Therefore, the first of the M second powder layers may be otherwise consolidated, e.g. B. by using a different irradiation strategy and/or by using an energy beam with a different energy distribution, a different energy density, a different spot diameter, a different spot shape, a different power and/or in the case of laser beams a different wavelength. In both options, the plural becomes second Structures connected to the plurality of first structures (either directly or via one or more intermediate powder layers). The overlap areas refer to an overlap between a first structure and a second structure with respect to the viewing direction perpendicular to the raw material powder layers.

The surface of the workpiece can be a plane. The surface of the workpiece may be a curved surface. The surface can also be only part of a total surface area of a workpiece. Furthermore, the term "surface" does not necessarily mean that this "surface" is an exterior surface of the workpiece in its final form. Additional structures such as B. the first and / or second structures and / or one or more support structures may be attached to the surface. These additional structures can be removed during post-processing. However, the additional structures do not necessarily have to be removed completely or cannot be removed at all, so that the "surface" in the final form of the workpiece is still covered with the additional structures.

The surface of the workpiece may be a surface forming a maximum angle of 45° or less, 30° or less, 20° or less, 10° or less, or 0° or less with the raw material powder layers.

In other words, the surface can be essentially horizontal in relation to its arrangement within a building cylinder of a corresponding device for producing the three-dimensional workpiece. Since the layers of powder are applied to a support, the angle can also be measured in relation to a surface of the support. The "maximum angle" means that a maximum angle is considered with respect to two surface normal vectors of the respective surfaces. If the surface of the workpiece is a plane, the maximum angle is the angle between the respective surface normal vectors. However, if the surface is curved, a surface normal of the surface is chosen that forms the greatest angle with the surface normal of the powder layers. When the angle is "not more than 0°", the surface can be made of a single layer of raw material powder.

The method may further comprise performing the following step one or more times: creating a plurality of third structures in a number of L third raw material powder layers, where L is 1 or more, wherein the plurality of third structures do not touch each other and where each of the plurality of third structures is connected to at least two of the plurality of structures in a layer of structures below the L third raw material powder layers.

The details explained above with regard to an arrangement of the first structures can also apply to the plurality of third structures. In other words, the steps of creating a plurality of "first structures" and optionally creating a plurality of "second structures" can be repeated one or more times, with the structures in these additional layers being generically referred to as "third structures". In this way, layers of structures can be formed on top of each other, with a layer of "first structures" following a layer of "second structures" and a layer of "second structures" following a layer of "first structures", etc. In this way several layers of first structures and second structures can be produced alternately. Each of these layers of structures can be created from one or more layers of powder (depending on the numbers N, M and L). if e.g. B. N=5, M=5 and L=5, each layer of structures is created from 5 layers of raw material powder. The “layer of structures under the L third raw material powder layers” may be a layer of second structures or a layer of third structures previously created.

The surface of the workpiece may be bonded to the plurality of second structures or to the plurality of third structures by bonding at least a portion of the surface directly to the second structures or to the third structures, depending on whether one or more layers of third structures is/are present.

In the above embodiment, when there are only two layers of structures, the surface is bonded to the second structures. If more than two layers of structures are present (ie, one or more layers of third structures are present), the surface is bonded to a top layer of those third structures. In other words, at least one of the second or third structures can be connected directly to the surface of the three-dimensional workpiece. If the surface of the three-dimensional workpiece is parallel to the N first layers (ie the angle between these layers is 0°), all of the second structures or third structures can be bonded directly to the surface of the three-dimensional workpiece. In this case the structure comprising the first and the second (and optionally the third) structures can be used as a direct support for the surface surface of the three-dimensional workpiece.

Furthermore, particularly when the surface of the workpiece is not exactly horizontal, it can happen that the second and/or the third structures, which are located in a powder layer lying closest to the surface, do not touch the surface directly. In other words, there may be unconsolidated raw material between an uppermost second or third structure and the surface. Additionally or alternatively, a size, shape, and/or orientation of a cross section of the second or third structures in a top layer of structures may be different compared to the previous layers of structures. For example, all first, second, and (optionally) third structures under the top layer of structures may have the same size, shape, and orientation. However, the structures of the top layer are modified, e.g. B. to better adhere to the surface of the workpiece.

The surface of the workpiece may be bonded to the plurality of second structures or to the plurality of third structures by providing at least one support structure between the surface and the second structures or the third structures, depending on whether one or more layers of third structures is/are present.

In the above embodiment, when there are only two layers of structures, the surface is connected to the second structures via the at least one support structure. If more than two layers of structures are present (i.e., one or more layers of third structures is/are present), the surface is bonded to a top layer of those third structures via the at least one support structure. The support structure can in particular be a rod-like, beam-like, wall-like or grid-like support structure. In this case, the structure comprising the first and second structures can be considered as a structure “floating” in the powder bed. This "floating" structure can be thought of as the base from which extends the support structure that supports the surface of the three-dimensional workpiece. The support structure can be connected directly to the surface of the three-dimensional workpiece.

A maximum extension of each of the first structures in at least one dimension parallel to the raw material powder layers can be 5 mm, 3 mm or 2 mm. A maximum extent of each of the second structures in at least one dimension parallel to the raw material powder layers can be 5 mm, 3 mm or 2 mm.

The maximum extent can mean that a base area of the respective structure within the respective plane is not greater than the specified value in at least one dimension parallel to the powder layers (i.e. parallel to an x-y plane). Furthermore, the maximum extent of each of the first and/or second structures in all directions parallel to the powder layers can be 5 mm, 3 mm or 2 mm. In this case, the respective structure fits into a circle with a diameter of 5 mm, 3 mm or 2 mm, viewed in the viewing direction perpendicular to the powder layers.

The size of the structures can depend on the material used for the raw material powder. In particular, it may depend on the material's tendency to develop stresses on cooling and/or to distort on cooling. The higher the tendency of the material to warp, the smaller the expansion of the structures can be in at least one dimension parallel to the raw material powder layers. For example, for a material with a lower tendency to warp such. B. TiAI6V4 an expansion in at least one dimension parallel to the raw material powder layers of even more than 5 mm can be used, while for a material with a higher tendency to warp such. B. Inconel 718 an extension in at least one dimension parallel to the raw material powder layers of less than 5 mm, 3 mm or 2 mm can be preferred.

Each of the first structures and/or second structures may have a cross section parallel to the raw powder layers in a filled geometric shape selected from the list consisting of a polygon, a hexagon, a rectangle, a square, an ellipse, a circle, a triangle, a cross and a star. If the area is sufficient, the cross-section can also consist of a belt along the perimeter of said geometric shapes.

Each geometric shape can be filled with a hatch pattern. The first structures do not necessarily all have the same shape. The same applies to the second structures.

Prior to the step of creating the plurality of first structures, a support structure or portion of the three-dimensional workpiece may be formed connecting a carrier to at least one of the plurality of first structures.

In other words, the structure comprising the first and the second structures can be of be supported by a support structure. This support structure can in particular be beam-like, rod-like, wall-like or grid-like. In a preferred embodiment, a base area of the support structure is smaller than an extension of the first structures in a plane parallel to the powder layers. For example, this base area covers only 25% or less of the extent of the first structures in the plane parallel to the powder layers.

Furthermore, at least a part of the plurality of first structures can be connected to a portion of a workpiece. In particular, the portion of the workpiece may include a vertical or substantially vertical plane adjacent to the plurality of first structures. Additionally or alternatively, at least a portion of the plurality of first structures may be built onto a portion of a workpiece. The workpiece can be the same workpiece that has the surface. In other words, similar to the support structure described above, the structure including the first and second structures can be supported by a portion of the workpiece. However, the arrangement described above is designed such that at least 75% of a consolidated area for the plurality of first structures in a lowermost of the N first raw material powder layers is in direct contact with unsolidified raw material powder of a raw material powder layer under the lowermost of the N first raw material powder layers. In other words, a portion of the workpiece that is in contact with the plurality of first structures occupies no more than 25% of the area consolidated for the plurality of first structures.

Each of the plurality of second structures can be connected to at least three or at least four of the plurality of first structures via overlapping regions.

For example, if the first structures are located at vertices of a first square lattice, the second structures may be located at vertices of a second square lattice, with the vertices of the second lattice being at the centers of the vertices of the first square lattice. In this case, each of the plurality of second structures may intersect with four of the first structures.

The plurality of first structures and/or the plurality of second structures can be irradiated in a direction radially inward toward a center of the surface of the three-dimensional workpiece. In other words, structures in areas remote from the center of the surface are irradiated first, and then structures closer to the center of the surface are irradiated. Alternatively, the plurality of first structures and/or the plurality of second structures may be irradiated in a radially outward direction away from a center of the surface of the three-dimensional workpiece. In other words, structures in areas near the center of the surface are irradiated first, followed by structures further from the center of the surface. The direction mentioned above can have an influence on the cooling behavior and the stress relaxation in the surface of the workpiece. Furthermore, the plurality of first structures and/or the plurality of second structures can be irradiated in a random order or in a shifted manner, in particular in order to improve the cooling behavior.

According to a second aspect, there is provided a method of manufacturing a three-dimensional workpiece by selectively irradiating a plurality of raw material powder layers. The method includes creating a plurality of first structures in a first raw material powder layer. The plurality of first structures do not touch each other. At least 75% of an area consolidated for the plurality of first structures in the first raw material powder layer is in direct contact with unsolidified raw material powder of a raw material powder layer under the first raw material powder layer. The method further includes after creating the plurality of first structures, solidifying a space between the first structures in the first raw material powder layer so that adjacent ones of the first structures are bonded together. The method further includes generating a surface of the three-dimensional workpiece such that the surface and the area solidified for the plurality of first structures in the first raw material powder layer at least partially overlap in relation to a viewing direction perpendicular to the raw material powder layers.

The method of manufacturing the three-dimensional workpiece according to the second aspect may comprise the usual steps of powder bed fusion methods as discussed above in relation to the first aspect.

Each of the first structures can be essentially two-dimensional, e.g. i.e. they only extend over one layer in one construction direction. In this context, the "structures" may have essentially two-dimensional shapes, such as B. a filled circle, a filled square, etc.

As usual, the plurality of first structures means at least two. However, more or significantly more than two first structures can also be produced. A number of first structures ren can be at least 4, at least 9, at least 16, at least 25, at least 36, at least 49, at least 64, at least 81, at least 100, at least 500 or at least 1000.

Furthermore, in addition to the “plurality of first structures” in the first powder layer, further structures can be produced. In other words, not all structures created in the first powder layer need to be considered part of the "plurality of first structures".

The individual structures of the plurality of first structures can all have the same shape, size and orientation. Alternatively, a shape, a size and/or an orientation of at least two of the first structures can differ. In other words, the first structures may all have the same shape, size, and orientation, or a shape, size, and/or orientation of at least some of the structures may differ. For example, the plurality of first structures may include structures having two or more different shapes and/or two or more different sizes.

Thus, a size, an orientation and/or a shape of the first structures can vary in the plurality of first structures. In other words, a size, orientation, and/or shape of all first structures need not be the same. However, a size, an orientation and/or a shape of the first structures can be the same. For example, a size, an orientation, and a shape of all first structures can be the same. However, it may also be the case that a size and a shape of the first structures are the same, but different orientations are present within the plurality of first structures (eg two different orientations rotated by 180° relative to one another).

The plurality of first structures do not touch each other. In other words, each of the first structures is not in contact with any other one of the first structures in the first powder layer. In other words, there is no lateral contact between the first structures. However, the first structures may touch other structures in layers other than the first powder layer.

The plurality of first structures can be arranged at the corner points of a regular grid. The distances between adjacent vertices can all have the same value. The first structures can be arranged at the corner points in such a way that a focal point of the respective first structure is arranged at the respective corner point. The plurality of first structures may be arranged at vertices of a regular lattice, where the regular lattice is a square lattice, a hexagonal lattice, an equilateral triangle lattice, or other suitable shape. The plurality of first structures can form a regular pattern.

At least 75% of an area consolidated for the plurality of first structures in the first raw material powder layer is in direct contact with unsolidified raw material powder of a raw material powder layer under the first raw material powder layer. In other words, the plurality of first structures are not built up directly on a carrier, but on at least one previously applied layer of powder. Further, a portion of this previously applied powder layer on which the plurality of first structures are formed is unconsolidated or only so consolidated that at least 75% of an area consolidated for the plurality of first structures in the first powder layer is in direct contact with unconsolidated raw material powder stand. In other words, at least a large part (at least 75%) of the first structures is built on a "free powder bed", i. H. an area containing only loose powder or multiple small structures with larger areas of powder in between.

At least 85%, at least 90%, or 100% of an area consolidated for the plurality of first structures in the first raw material powder layer may be in direct contact with unsolidified raw material powder of a raw material powder layer under the first raw material powder layer. Further, an entire volume below the consolidated area for the plurality of first structures and extending to a support may be unconsolidated, or at least 75% of that volume, at least 85%, or at least 90%. In other words, there may be support structures under the layer of first structures that support the first structures, but these support structures are attached to only a small fraction of a total area of the plurality of first structures.

The fact that adjacent ones of the first structures are bonded together means that the first structures are bonded together within the same powder layer. A solidification of the space between the first structures can mean that an entire space between the first structures is solidified. However, the space can also be only partially solidified, so that adjacent first structures are connected to one another. The space between the first structures may be smaller in area than the area of the first structures to avoid generation of stress upon cooling the. Additionally or alternatively, the space between the first structures can be consolidated in several steps, wherein only part of the space between the first structures is consolidated and another part of the space connected to the previously irradiated part is consolidated after a cooling phase .

The surface of the workpiece can be a plane. The surface of the workpiece may be a curved surface. Furthermore, the term "surface" does not necessarily mean that this "surface" is an exterior surface of the workpiece in its final form. Additional structures such as B. the first structures and / or one or more support structures can be attached to the surface. These additional structures can be removed during post-processing. However, the additional structures do not necessarily have to be removed completely or cannot be removed at all, so that the "surface" in the final form of the workpiece is still covered with the additional structures.

The surface of the workpiece may be a surface forming a maximum angle of 45° or less, 30° or less, 20° or less, 10° or less, or 0° or less with the raw material powder layers.

In this context, the above details relating to the first aspect may also apply to the second aspect.

The method may further comprise performing the following group of steps one or more times: creating a plurality of second structures in a second layer of raw material powder, wherein the plurality of second structures do not touch one another and wherein the second layer follows a previous layer of structures (in particular directly follows), and after generating the plurality of second structures, solidifying a space between the second structures in the second raw material powder layer such that adjacent ones of the second structures are connected to each other.

In other words, more than one layer of structures can be formed on top of each other. The second structures can be arranged at the same positions or at different positions with respect to the first structures. Also in each layer of the second structures, the structures are connected to each other by solidifying a space between the second structures.

The surface of the workpiece can be bonded to the plurality of first structures or to the plurality of second structures by bonding at least a portion of the surface directly to the first structures or to the second structures, depending on whether one or more layers of second structures is/are present.

In the above embodiment, when there is only one layer of structures, the surface is bonded to the first structures. If more than one layer of structures is present (i.e., one or more layers of second structures is/are present), the surface is bonded to a top layer of those second structures. In other words, at least one of the first or second structures can be connected directly to the surface of the three-dimensional workpiece. If the surface of the three-dimensional workpiece is parallel to the first layer of powder (i.e. the angle between these layers is 0°), all the first structures or second structures can be bonded directly to the surface of the three-dimensional workpiece. In this case, the structure comprising the first (and optionally the second) structures can be considered as direct support for the surface of the three-dimensional workpiece. If left connected to the workpiece, the structures can also be considered as the first layer of the workpiece.

The surface of the workpiece may be bonded to the plurality of first structures or to the plurality of second structures by providing at least one support structure between the surface and the first structures or the second structures, depending on whether one or more layers of second structures is/are present.

In the above embodiment, the surface is connected to the first structures via the at least one support structure when there is only one layer of structures. If more than one layer of structures is present (ie one or more layers of second structures is/are present), the surface is bonded to a top layer of those second structures via the at least one support structure. The support structure can in particular be a rod-like, beam-like, wall-like or grid-like support structure. In this case, the structure comprising the first structures can be considered as a structure “floating” in the powder bed. This "floating" structure can be thought of as the base from which extends the support structure that supports the surface of the three-dimensional workpiece. The support structure can be directly connected to the surface of the three-dimensional workpiece.

A maximum extension of each of the first structures in at least one dimension parallel to the raw material powder layers can be 5 mm, 3 mm or 2 mm.

The maximum extension can mean that the footprint of the respective structure within the respective plane is not larger than the specified value in at least one dimension parallel to the powder layers (i.e. parallel to an x-y plane). Furthermore, the maximum extent of each of the first structures in all directions parallel to the powder layers can be 5 mm, 3 mm or 2 mm. In this case, the respective structure fits into a circle with a diameter of 5 mm, 3 mm or 2 mm, viewed in the viewing direction perpendicular to the powder layers.

Each of the first structures may have a cross section parallel to the raw powder layers in a filled geometric shape selected from the list consisting of a polygon, hexagon, rectangle, square, ellipse, circle, triangle, cross and includes a star. If the area is sufficient, the cross-section can also consist of a belt along the perimeter of said geometric shapes.

Each geometric shape can be filled with a hatch pattern. The first structures do not necessarily all have to have the same shape.

The step of solidifying the space between the first structures may be performed by creating a plurality of filled geometric shapes, each of the geometric shapes being identical to a shape of each of the first structures. For example, each of the first structures and each of the filled geometric shapes of the "solidification step" can be a hexagon of the same size. Alternatively, rectangles, squares or triangles can also be used. The first structures can be created in a checkerboard pattern, and in the step of solidifying, a remaining space between the squares of the checkerboard pattern can be solidified.

In the step of solidifying the space between the first structures, an entire space between the first structures may be solidified so that a continuous area of solidified raw material powder is generated.

In other words, a portion of the first powder layer (e.g., having a rectangular shape) may be fully consolidated, which portion includes the plurality of first structures.

Prior to the step of creating the plurality of first structures, a support structure or portion of the three-dimensional workpiece may be formed connecting a carrier to at least one of the plurality of first structures.

In other words, the structure including the first structures can be supported by a support structure. This support structure can in particular be beam-like, rod-like, wall-like or grid-like. A base area of the support structure is smaller than an extension of the first structures in a plane parallel to the powder layers. For example, this base area covers only 25% or less of the extent of the first structures in the plane parallel to the powder layers.

The plurality of first structures can be irradiated in a direction radially inward toward a center of the surface of the three-dimensional workpiece. In other words, structures in areas remote from the center of the surface are irradiated first, and then structures closer to the center of the surface are irradiated. Alternatively, the plurality of first structures may be irradiated in a radially outward direction away from a center of the surface of the three-dimensional workpiece. In other words, structures in areas near the center of the surface are irradiated first, followed by structures further from the center of the surface. The direction mentioned above can have an influence on the cooling behavior and the stress relaxation in the surface of the workpiece.

According to both the first and the second aspect, at least one layer is formed from small structures (hereinafter also: “structures” or “flakes”). These structures can help reduce overheating of a surface of the three-dimensional workpiece to which the structures are connected. The metallic bond between the structures can help protect the surface of the three-dimensional object from cracking and warping. Furthermore, the one or more layers of structures can form a floating support within a stack of powder layers, so that a "classic" support structure does not have to be created between the carrier and the surface of the workpiece.

A possible advantage of the "flake" building strategy according to the first and the second aspect can be understood as follows. The flakes are built up independently of each other. After the flakes have been scanned (ie solidified), they also cool down independently of one another. During the cooling phase, the flake can be slightly deformed due to internal stress/thermal contraction. Due to the small size of the flake, the deformation can be minimal and cannot interfere with the powder reapplication process.

In the same powder layer (according to the second aspect) or in the next powder layers (according to the first aspect), the flake is then connected by further melting to form a full-area or nest-shaped layer with a certain strength. Since the flake has already deformed and the stress has been partially relieved, this layer is relatively stress-relieved and can lead to less deformation, allowing for a smooth build-up without disruption.

The "flake" structure can be built up during the process, e.g. B. for only some layers. It can be thin enough to stay with the main workpiece without having to remove it. On the other hand, it can also be considered as a first layer of the workpiece.

Structures including the first and second structures described above can be created at various vertical positions within the stack of powder layers (i.e., within a build space). More specifically, a plurality of such structures may be formed at different vertical and/or horizontal positions during a build job. A plurality of structures including the first and second structures mentioned above may be provided on different surfaces of a workpiece. In other words, more than one surface of the workpiece can be supported by such structures. Furthermore, structures including the first and second structures described above may be created for a plurality of workpieces in a build order.

• 1 eine schematische Darstellung einer Vorrichtung zur Herstellung eines dreidimensionalen Werkstücks zeigt, die zur Durchführung der Verfahren gemäß der hier beschriebenen Ausführungsformen verwendet werden kann;
• 2 ein Werkstück mit einer aus dem Stand der Technik bekannten Stützstruktur zeigt;
• 3 verschiedene Beispiele für Formen der hier beschriebenen Strukturen zeigt;
• 4 ein Beispiel für kreisförmige Strukturen zeigt, die in zwei aufeinanderfolgenden Schichten von Strukturen erzeugt werden;
• 5 ein Beispiel für quadratische Strukturen zeigt, die in zwei aufeinanderfolgenden Schichten von Strukturen erzeugt werden, wobei 5(a) eine Draufsicht der Strukturen und 5(b) eine perspektivische Ansicht des Werkstücks mit den Strukturen zeigt;
• 6 eine perspektivische Ansicht eines Werkstücks mit auf einer Oberfläche angeordneten Strukturen und mit einer zusätzlichen Stützstruktur zeigt, wobei 6(a) ein erstes Beispiel einer Stützstruktur und 6(b) ein zweites Beispiel einer Stützstruktur zeigt;
• 7 eine schematische Darstellung einer schwimmenden Struktur mit kleinen Strukturen und mit einer zusätzlichen Stützstruktur zeigt, die sich bis zu einer Oberfläche des Werkstücks erstreckt; und
• 8 vier verschiedene Beispiele für Formen und Anordnungen von Strukturen zeigt.

Preferred embodiments of the invention will be described in more detail with reference to the accompanying schematic drawings, in which

• 1 12 shows a schematic representation of an apparatus for producing a three-dimensional workpiece, which can be used to carry out the methods according to the embodiments described herein;
• 2 shows a workpiece with a support structure known from the prior art;
• 3 shows various examples of forms of the structures described herein;
• 4 shows an example of circular structures produced in two successive layers of structures;
• 5 shows an example of square structures produced in two consecutive layers of structures, where 5(a) a top view of the structures and 5(b) shows a perspective view of the workpiece with the structures;
• 6 shows a perspective view of a workpiece with structures arranged on a surface and with an additional support structure, wherein 6(a) a first example of a support structure and 6(b) shows a second example of a support structure;
• 7 Figure 12 shows a schematic representation of a floating structure with small features and with an additional support structure extending to a surface of the workpiece; and
• 8th shows four different examples of shapes and configurations of structures.

1 FIG. 12 shows a schematic representation of an apparatus 10 for manufacturing a three-dimensional workpiece 8 that is suitable for carrying out the methods according to the present disclosure. However, the present disclosure is not limited to methods associated with the device 1 be performed. The methods can be performed using any suitable apparatus. Such an apparatus may be, for example, a selective laser melting apparatus or a selective laser sintering apparatus in which one or more laser beams or other energy beams may be used to selectively irradiate and solidify successive layers of raw material powder. 7 FIG. 15, for example, shows another example of an apparatus that uses two laser beams (rather than one) to increase a footprint of a produced workpiece and/or reduce production time.

1 shows a device 10 for producing a three-dimensional workpiece 8 by selective laser melting. The device 10 comprises a process chamber 12. The process chamber 12 can be sealed against the ambient atmosphere, ie against the environment surrounding the process chamber 12. A powder application device 14 arranged in the process chamber 12 serves to apply a raw material powder onto a tray eng 16. A vertical movement unit 32 is provided so that the carrier 16 can be displaced in the vertical direction, so that the carrier 16 moves downwards in the vertical direction as the overall height of the workpiece 8 increases when it is built up in layers from the raw material powder on the carrier 16 can be moved below.

Since the mobility of the carrier 16 by means of the vertical movement unit 32 is known from the field of selective laser melting, it will not be explained in more detail here. As an alternative to the movable carrier 16, the carrier 16 (in particular with regard to the vertical z-direction) can also be designed as a stationary (or fixed) carrier, with the irradiation unit 20 (see below) and the process chamber 12 being designed in such a way that during the Construction process (ie with increasing height of the workpiece 8) are moved up. In addition, both the carrier 16 and the irradiation unit 20 can be individually movable along the z-direction.

A support surface of the support 16 defines a horizontal plane (an x-y plane), and a direction perpendicular to this plane is defined as a vertical direction or building direction (z-direction). Therefore, each top layer 28 of raw material powder extends in a plane parallel to the horizontal plane (x-y plane) defined above.

The device 10 also includes an irradiation unit 20 for selectively irradiating an uppermost layer 28 of the raw material powder applied to the carrier 16 with laser radiation. By means of the irradiation unit 20, the raw material powder applied to the carrier 16 can be exposed to laser radiation in a location-selective manner, depending on the desired geometry of the workpiece 8 to be produced.

The irradiation unit 20 includes a scanner unit 22 configured to selectively irradiate a laser beam 24 onto the raw material powder applied to the carrier 16 . The irradiation unit 20 includes at least one laser beam source (not shown), from which the laser beam 24 is directed onto the scanner unit 22 . The laser beam source can, for. B. be a diode-pumped ytterbium fiber laser that emits laser light with a wavelength of about 1070 to 1080 nm.

In addition to the scanner unit 22, the irradiation unit 20 can also include other optical components such as a beam expander for expanding the laser beam 24, focusing optics for focusing the laser beam 24 in one direction along the beam path and/or an objective lens. By means of the scanner unit 22, the position of the laser beam 24 can be moved over the x-y plane of the top layer 28 of the raw material powder. The scanning unit 22 can be implemented in the form of a galvanometer scanner. The objective lens may be an f-theta objective lens provided downstream of the scanner unit 22 in the optical path. The operation of the irradiation unit 20 is controlled by a control unit 27 . In addition, the control unit 27 is configured to control other components of the device 10, such as. B. the vertical movement unit 32, the powder application device 14 and other components of the device 10.

For the purposes of this disclosure, it is assumed that powder bed fusion processes are well known to those skilled in the art and therefore the details of these processes will not be discussed in detail. The device 10 described above for carrying out a method of selective laser melting can serve as an example. All techniques that are suitable for carrying out the methods described here have in common that a raw material powder is applied in layers and each layer is selectively irradiated and solidified in order to produce a layer of a workpiece to be produced. After removing excess powder and after optional post-processing steps (e.g. removing one or more support structures), the finished workpiece is obtained.

2 FIG. 1 shows a workpiece 8 with a support structure 34 according to a technique known from the prior art. As in 2 As shown, the workpiece 8 has a horizontal surface parallel to the xy plane. Current support methods require a large support structure 34 to support a horizontal surface 36 (e.g., for heat dissipation during production). In particular, the present disclosure relates to downward-facing surfaces 36 (also referred to as downskin surfaces), ie surfaces 36 of the workpiece 8 that face the carrier of the device 16 . In particular, horizontal surfaces 36 which are at an angle of 0° with respect to the carrier 16 are considered. However, the surface 36 may also form a small angle with respect to the carrier 16, e.g. B. less than 5 °, less than 10 °, less than 20 °, less than 30 ° or less than 45 °. The lower part of the support structure 34 is connected to the beam 16 or to another fixed part.

The construction of the support structure 34 costs material and time. It also requires the effort of post-processing, ie removal of the support structure 34. For some horizontal areas of the workpiece 8, it may even be impossible to use a tool to remove the support structure 34. With regard to the Ver drive the support structure 34 can be avoided or at least reduced.

The embodiments described herein can help to significantly reduce the size of a required support structure by using small structures 38, e.g. e.g. for several layers directly under the first fixed layer of the workpiece 8, or by replacing the first layers of the workpiece 8. Examples of different forms of “structures” 38 are given in 3 shown. As in 3 As shown, examples of structures 38 may be a square, circle, equilateral triangle, cross, heart, cloud, star, etc. Any suitable shape can be used for the structures 38 of the present disclosure. Filled shapes, as in 3 shown are advantageous.

An arrangement of a plurality of structures to be built is a "multi-small-pieces" arrangement. To build this assembly, a small piece of thin part is attached as a unit (structure 38) of the assembly. The size of the structure 38 is approximately 1 mm to 5 mm in the x/y direction and 20 μm to 200 μm in the z direction. This structure can be of any shape, like the examples in 3 demonstrate. In addition, the size and position of these structures can change with the layers of the structures. Different shapes can be mixed together to form the assembly within a layer of structures.

The arrangement includes a plurality of the small structures 38 and can arrange these structures 38 in certain predefined ways. One arrangement includes a partial overlapping of the structures 38 with each other. 4 Figure 3 shows an example of the arrangement of circular structures 38 to form the assembly to be built. The structures have areas of overlap with respect to successive layers of structures. The aim is to create a metallic bond between the structures 38 between successive layers to form a porous assembly. The entire surface does not have to be fully reflowed since there are unfused spaces between the structures 38 in this example. This arrangement is built up for several layers of structures immediately before the solid workpiece 8 is built.

4(a) 12 shows a first layer of structures 38a, the structures 38a of this first layer being referred to here as first structures 38a. In 4(a) Also shown is a part of the workpiece 8 which corresponds to a lower part of the workpiece 8 and which is not part of the horizontal or nearly horizontal surface of the workpiece 8 to be supported. In the 4(a) The powder layer shown is a layer within the stack of raw material powder layers, with one or more raw material powder layers being provided under the layer shown, in which an area in which the first structures 38a in the in 4(a) powder layer shown are built up, is not solidified. In the 4(a) The arrangement of first structures 38a shown can be produced in only one raw material powder layer or, in an identical manner, in a plurality of N layers, where N is any integer, e.g. B. 2, 5 or 10. In a powder layer that follows the number of N powder layers with the first structures 38a, a powder layer with second structures 38b is generated, as in FIG 4(b) shown. Similar to the arrangement of first structures 38a, the arrangement of second structures 38b may be repeated for a plurality of M layers of powder, where M is any integer and may be the same as N .

4(b) (as well as 4(a) ) is a plan view along a direction parallel to a surface normal of the powder layers, ie along the z-direction. As in 4(b) As can be seen, there are areas where the first structures 38a and the second structures 38b overlap. A metallurgical bond exists in these overlapping areas, and the first structures 38a are connected (ie, bonded) to the second structures 38b. As in the 4(a) and (b) each of the second structures 38b overlaps at least two of the first structures 38a, namely four. As in 4(b) As shown, however, there are edge regions of structures of the second layer of structures in which structures are provided that only overlap two of the first structures. These structures in the edge areas cannot be regarded as belonging to the plurality of second structures 38b.

After creating M layers of second structures 38b, L more layers of third structures can follow (these third structures are identical to the first structures), followed by L more layers of third structures (these third structures are identical to the second structures), and so on. In this way, first structures 38a and second structures 38b can be produced alternately.

From the 4(a) and 4(b) It can further be seen that the plurality of first structures 38a forms a regular two-dimensional pattern. In general, both the first structures 38a and the second structures 38b (in the case of 4(a) and (b): circles) at vertices of a regular grid, especially a quadrati cal grid, arranged. The distances between adjacent structures are equal. The pattern of structures is repeated. The pattern of the second structures 38b is shifted in the xy plane in such a way that the corner points of the grid of the second structures 38b lie on the centers of the squares of the square grid of the first structures 38a. In other words, the second structures 38b are positioned exactly between the first structures 38a when viewed in plan view (along the z-direction).

The arrangement according to 4 causes each of the second structures 38b to overlap with at least two of the first structures 38a and thereby the second structures 38b can be connected to the first structures 38a. In central areas of the second structures 38a, the second structures 38b overlap with four of the first structures 38a.

5 shows a different arrangement of structures. Similar to in 4 the first and second structures 38a and 38b are arranged at vertices of a regular square lattice. In contrast to the circles in 4 uses the in 5 However, in the arrangement shown, a square shape is provided for the plurality of first and second structures 38a and 38b. According to the arrangement 5 For example, a size, an orientation, and a shape of the first patterns 38a are the same as those of the second patterns 38b. 5(a) shows the first structures 38a and the second structures 38b in a state in which the second structures 38b have already been produced on the first structures 38a, so that the (square) overlapping areas are visible. Similar to the arrangement according to 4 each of the second structures 38b overlaps four of the first structures 38a.

5(b) shows the arrangement according to 5(a) , after a part of the workpiece 8 has been created on the second structures 38b. The workpiece 8 includes a horizontal surface 36 directly connected to the second structures 38b. In other words, the second structures 38b are directly connected to the surface 36 of the workpiece 8.

The arrangement of structures 38a and 38b covers the horizontal surface 36 substantially completely, as in FIG 5(b) shown. In other words, there is no room on the surface 36 for additional complete second structures 38b. When constructing the workpiece 8, the placement of structures 38a and 38b under the workpiece can help reduce surface 36 overheating. The metallic bonds between structures 38a and 38b can help prevent surface 36 from cracking and warping.

As stated above in relation to the structures 4 described, both the first structures 38a and the second structures 38b can be provided in multiple powder layers (M layers of first structures 38a and N layers of second structures 38b). In addition to the M layers of first structures 38a and N layers of second structures 38b, further layers of first and second structures 38a and 38b can be produced after the in 5(b) layers shown have been generated. In this way, alternating layers of first structures 38a and layers of second structures 38b can be produced. The structures in these additional layers are also referred to as third structures.

In order to fix the workpiece 8 on the carrier 16 and to conduct heat from the workpiece to the carrier via the structures, a support structure 34 may also be required. 6(a) 12 shows an example of a support structure 34 used for a small horizontal surface 36 and/or for a workpiece made of a material with a low tendency to crack or warp. 6(b) 12 shows an example of a support structure 34 used when the horizontal surface 36 is quite large and/or the workpiece is made of a material with a higher tendency to crack or warp. Compared to the in 2 shown conventional support structure 34 is a size of the required support structure 34 according to 6(a) and 6(b) significantly reduced. The in the 6(a) and (b) support structure 34 shown is disposed directly on carrier 16. In other words, the support structure 34 extends from the carrier 16 to a bottom layer with first or second structures 38a, 38b. A footprint of the support structure 34 (both in 6(a) as well as in 6(b) ) is significantly less (ie, less than 50%, less than 20%, or less than 10%) than a footprint of surface 36. Additionally, the footprint of support structure 34 is less than 25% of a consolidated area for plurality of first structures 38a. As in 6 As shown, there are a plurality of first structures 38a built entirely on the free (ie, unconsolidated) powder bed.

7 12 shows an embodiment in which the structures 38a or 38b are not directly connected to the surface 36 of the workpiece 8. FIG. Instead, the structures 38a and 38b are provided in a "floating" arrangement in the powder bed, and beam-like, rod-like, wall-like or grid-like support structures 40 extend from the second structures 38b to the surface 36. In this way, the surface 36 can be supported by a combination made of "classic" beam-like, rod-like, wall-like or lattice-like support structure ren 40 and the new type of small structures (comprising the first and second structures 38a, 38b). Since the structures 38a and 38b provide support within the powder bed, the support structures 40 need not extend all the way down to the carrier 16. In the event that the heat generated during production cannot be dissipated properly, it is of course possible for supporting structures to also extend from the carrier 16 to the structures 38a. As mentioned above, fewer support structures are required compared to the prior art.

7 shows a different device than that in 1 device 10 shown. The device according to FIG 7 can irradiate the powder bed with two lasers. However, these details of the device are of little importance for the production of the structures discussed here.

the 8(a) through (d) show four different configurations of structures that can be used for the methods of the present disclosure.

Any of the assemblies can be bonded directly to the surface 36 of the workpiece 8 (as e.g. in 5(b) shown) or may take the form of a "floating" arrangement, as in 7 shown, be provided.

8(a) shows a stripe pattern of stripes extending in two directions and forming an angle of 90°. 8(a) shows two layers of structures. More specifically, for M number of layers of raw material powder, stripes are produced, all stripes extending in the same direction and all stripes having the same width and the same distance from each other. The strips can be viewed as rectangular first structures 38a. Strips are then produced for a number N of consecutive layers of raw material powder, with all strips extending in the same direction and offset by 90° with respect to the direction of the first structures. These strips can also be viewed as rectangular second structures 38b. The strips of the second structures 38b overlap the strips of the first structures 38a in overlapping areas. The strips can extend several mm in one direction, but a width of the strips perpendicular to the direction of extension is e.g. B. less than 5 mm or less than 2 mm.

8(b) Figure 12 shows a first "layer" of first structures 38a, the first structures 38a being circular and arranged in a regular pattern. 8(b) therefore shows the example of 4(a) , wherein a second layer of circular second structures 38b according to 4(b) can follow.

Furthermore, an alternative embodiment with reference to FIG 8(c) to be viewed as. The first structures 38a are square structures that have the same size and orientation and are arranged at the vertices of a square grid. The first structures 38a thus form a checkerboard pattern. The corners of structures 38a are aligned with one another and do not touch.

A first raw material powder layer is according to the in 8(c) shown arrangement of the first structures 38a solidified. The square structures 38a do not touch at their corners. In a subsequent irradiation process within the same powder layer, the spaces between the first structures 38a are completely filled. As a result, a hardened surface is created. Since the first structures 38a initially, as in 8(c) shown, are irradiated, the first structures 38a have time to cool and relieve stress. During the subsequent irradiation process, the stresses have already been reduced, so that damage caused by cracking or warping can be reduced.

8(d) shows an arrangement similar to that referred to above 8(c) alternative embodiment discussed was generated. First, the first structures 38a marked with “1” are solidified. The first structures 38a are non-touching hexagons in this embodiment. In a subsequent irradiation process, the spaces between the first structures “1” 38a are solidified. In this subsequent irradiation process, first a second arrangement of hexagons "2" and then a third arrangement of hexagons "3" are consolidated. In this way, the entire area is filled with hexagons.

In the "alternative embodiments" mentioned above, a plurality of identical raw material powder layers can be produced in the same manner as described above. The arrangements of the "alternative embodiments" can be used for the same purpose as the other arrangements described herein. In this way they can be connected directly to a horizontal or substantially horizontal surface 36 of a workpiece 8 . Alternatively, they can also, as in 7 shown to serve as a "floating" structure.

QUOTES INCLUDED IN DESCRIPTION

This list of documents cited by the applicant was generated automatically and is included solely for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions.

Patent Literature Cited

• EP 2961549 A1 [0003]
• EP 2878402 A1 [0003]

Claims (18)

A method for producing a three-dimensional workpiece (8) by selectively irradiating a plurality of raw material powder layers, the method comprising: creating a plurality of first structures (38a) in a number of N first raw material powder layers, where N is 1 or more, wherein the plurality of first structures (38a) do not touch each other, and at least 75% of one for the plurality of first structures ( 38a) solidified surface in a bottommost of the N first raw material powder layers is in direct contact with non-solidified raw material powder of a raw material powder layer below the bottommost of the N first raw material powder layers; creating a plurality of second structures (38b) in a number of M second raw material powder layers, where M is 1 or more, the plurality of second structures (38b) not touching each other and each of the plurality of second structures (38b) having at least two connecting the plurality of first structures (38a) via overlapping areas; and Creating a surface (36) of the three-dimensional workpiece (8) in such a way that the surface (36) and the area solidified for the plurality of first structures (38a) are in the lowermost of the N first raw material powder layers in relation to a viewing direction perpendicular to the raw material powder layers at least partially overlap. procedure after claim 1 , wherein the surface (36) of the workpiece (8) is a surface having a maximum angle of not more than 45°, not more than 30°, not more than 20°, not more than 10° or does not form more than 0°. procedure after claim 1 or 2 , wherein the following step is performed one or more times: creating a plurality of third structures in a number of L third raw material powder layers, where L is 1 or more, wherein the plurality of third structures do not touch each other and each of the plurality of third structures with joining at least two of the plurality of structures in a layer of structures below the L third raw material powder layers. Procedure according to one of Claims 1 until 3 , wherein the surface (36) of the workpiece (8) with the plurality of second structures (38b) or with the plurality of third structures is connected by at least a portion of the surface (36) directly with the second structures (38b) or with connected to the third structures depending on whether one or more layers of third structures are present. Procedure according to one of Claims 1 until 3 , wherein the surface (36) of the workpiece (8) is connected to the plurality of second structures (38b) or to the plurality of third structures by at least one support structure (40) between the surface (36) and the second structures (38b ) or the third structures, depending on whether one or more layers of third structures are present. Procedure according to one of Claims 1 until 5 , wherein a maximum extension of each of the first structures (38a) in at least one dimension parallel to the raw material powder layers is 5 mm, 3 mm or 2 mm and wherein a maximum extension of each of the second structures (38b) in at least one dimension parallel to the raw material powder layers is 5 mm, 3 mm or 2 mm. Procedure according to one of Claims 1 until 6 , wherein each of the first structures (38a) and/or second structures (38b) parallel to the raw material powder layers has a cross section in a filled geometric shape selected from the list consisting of a polygon, a hexagon, a rectangle, a square, includes an ellipse, a circle, a triangle, a cross and a star. Procedure according to one of Claims 1 until 7 , wherein prior to the step of creating the plurality of first structures (38a), a support structure (34) or part of the three-dimensional workpiece is formed connecting a carrier (16) to at least one of the plurality of first structures (38a). Procedure according to one of Claims 1 until 8th , wherein each of the plurality of second structures (38a) is connected to at least three or at least four of the plurality of first structures (38a) via areas of overlap. Method for producing a three-dimensional workpiece (8) by selectively irradiating a plurality of raw material powder layers, the method comprising: creating a plurality of first structures (38a) in a first raw material powder layer, the plurality of first structures (38a) not touching one another, and wherein at least 75% of an area consolidated for the plurality of first structures (38a) in the first layer of raw material powder is in direct contact with unconsolidated raw material powder of a raw material powder layer under the first raw material powder layer; after generating the plurality of first struct structures (38a), solidifying a space between the first structures (38a) in the first raw material powder layer such that adjacent ones of the first structures (38a) are connected to each other; and creating a surface (36) of the three-dimensional workpiece (8) in such a way that the surface (36) and the area solidified for the plurality of first structures (38a) in the first raw material powder layer in relation to a viewing direction perpendicular to the raw material powder layers at least partially overlap. procedure after claim 10 , wherein the surface (36) of the workpiece (8) is a surface having a maximum angle of not more than 45°, not more than 30°, not more than 20°, not more than 10° or does not form more than 0°. procedure after claim 10 or 11 wherein the following group of steps is performed one or more times: creating a plurality of second structures in a second layer of raw material powder, wherein the plurality of second structures do not touch each other and wherein the second layer follows a previous layer of structures; and after generating the plurality of second structures, solidifying a space between the second structures in the second raw material powder layer such that adjacent ones of the second structures are connected to each other. Procedure according to one of Claims 10 until 12 , wherein the surface (36) of the workpiece (8) with the plurality of first structures (38a) or with the plurality of second structures is connected by at least a portion of the surface (36) directly with the first structures (38a) or with connected to the second structures depending on whether one or more layers of second structures are present. Procedure according to one of Claims 10 until 12 , in which the surface (36) of the workpiece (8) is connected to the plurality of first structures (38a) or to the plurality of second structures by at least one support structure (40) between the surface (36) and the first structures ( 38a) or the second structures, depending on whether one or more layers of second structures is/are present. Procedure according to one of Claims 10 until 14 , wherein the maximum extension of each of the first structures (38a) in at least one dimension parallel to the raw material powder layers is 5 mm, 3 mm or 2 mm. Procedure according to one of Claims 10 until 15 , wherein each of the first structures (38a) parallel to the raw material powder layers has a cross section in a filled geometric shape selected from the list consisting of a polygon, a hexagon, a rectangle, a square, an ellipse, a circle, a triangle , a cross and a star. Procedure according to one of Claims 10 until 16 wherein in the step of solidifying the space between the first structures (38a), an entire space between the first structures (38a) is solidified so that a continuous region of solidified raw material powder is generated. Procedure according to one of Claims 10 until 17 , wherein prior to the step of creating the plurality of first structures (38a), a support structure (34) or part of the three-dimensional workpiece is formed connecting a carrier (16) to at least one of the plurality of first structures (38a).

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