METHOD AND DEVICE FOR IMPROVING THE COMPONENT QUALITY OF OBJECTS MANUFACTURED BY AN ADDITIVE MANUFACTURING PROCESS

Description

[0001] The present application relates to a method and a device for providing control data for an additive manufacturing device, a correspondingly adapted additive manufacturing method, a corresponding device for controlling energy input devices of an additive manufacturing device, a correspondingly adapted additive manufacturing device, and a correspondingly adapted computer program. In particular, the component quality of the manufactured objects is to be improved.

[0002] In the field of laser beam welding, it is known that a crater can form at the end of a weld path at the point where the laser beam is switched off (see, for example, US 2004 / 0182836 A1). This crater can lead to reduced stability, i.e., poorer adhesion between the two welded parts. The present invention addresses the problem that, even in the field of selective laser sintering or melting, the structure of a manufactured object can be adversely affected if the laser beam is switched off abruptly. This behavior is surprising and not fully understood, especially since laser beam sintering or melting involves a completely different process than laser beam welding.

[0003] While laser welding typically involves joining two metal sheets, selective laser sintering or selective laser melting involves converting a powdered material into a solid by successively melting layers of material. While the crater in laser welding is theoretically caused by the molten material cooling so quickly that the melt can no longer fill the crater, this problem should not exist with selective laser sintering or laser melting, as a crater created by melting a layer is filled by the application of the subsequent layer of powdered material.The deep penetration welding process commonly used in selective laser sintering or laser melting typically produces a depth of molten pool created by a laser beam that is greater than the depth ("layer thickness") of the last applied powder layer, for example, twice or three times as great. A number of already selectively solidified layers located below the layer currently being selectively solidified are thus at least partially remelted, so that any crater in the layer immediately below can not only be filled with solid material (solidified melt), but the microstructure can also be re-formed.

[0004] Fig. 10 shows the usual procedure for the additive manufacturing of objects by irradiating them with electromagnetic radiation or particle radiation (e.g. laser sintering (SLS or DMLS) or laser melting or electron beam melting). In Fig. 10 An object cross-section 50 is divided into an inner region or core region 52 and a contour region 51, wherein the contour region 51 is generally assigned different parameters for the energy input into the construction material than the inner region 52. For example, the contour region 51 is scanned with a laser beam as an example of a beam bundle in such a way that the laser beam is moved along the course of the contour. The inner region 52 is usually solidified in such a way that the inner region 52 is divided into subregions 53, which usually have an approximately rectangular or square shape. The inner region 52 is then scanned subregion by subregion with the laser beam.

[0005] As in Fig. 10 As shown, in each partial area 53, the laser beam is moved in parallel paths (scan lines) 54 over the build-up material, resulting in a hatching-like movement pattern when scanning each partial area 53 with the laser beam. In Fig. 10 The direction of movement of the laser beam is illustrated by arrows. It can be seen that the directions of movement for adjacent scan lines 54 are opposite to each other.

[0006] Fig. 11 illustrates how such a movement pattern of the laser beam can be achieved. The laser beam enters Fig. 11 top left into the area 53 and scans the build-up material in the area 53 along the top scan line 54. At the end of the scan line, i.e. when the laser beam has reached the edge of the partial area 53, the laser beam is switched off and, without supplying radiation to the build-up material, the direction of movement of the laser beam is changed within the reversal area 55, so that the laser beam can then be moved along the second top scan line 54 in the opposite direction over the build-up material in the partial area 53. Following this movement pattern, the entire partial area 53 is then scanned, as shown in Fig. 11 is illustrated.

[0007] Although the procedure just described is generally used to obtain homogeneous, uniform components, the inventors have found that the procedure described may nevertheless result in component inhomogeneities in the reversal regions 55.

[0008] WO 2015 / 091875 A1 describes a method for producing three-dimensional objects in which the scanning speed of a beam used for solidification is increased outside the area to be solidified.

[0009] H. Yeung et al., Laser Path Planning and Power Control Strategies for Powder Bed Fusion Systems, Proceedings of the 27th International Solid Freeform Fabrication Symposium 2016, pages 113-127 describes a method for manufacturing three-dimensional objects in which laser power can be adjusted based on proximity to already solidified areas in order to avoid excessive heating there.

[0010] The object of the present invention is therefore to provide a method and a device by means of which the component homogeneity of objects produced by an additive manufacturing process can be improved.

[0011] The object is achieved by a computer-aided method according to claim 1, an additive manufacturing method according to claim 11, a device for providing control data according to claim 12, a device according to claim 13, an additive manufacturing device according to claim 14 and a computer program according to claim 15. Further developments of the invention are claimed in the dependent claims.

[0012] In particular, a device according to the invention can also be further developed by features of the methods according to the invention set out below or in the dependent claims, and vice versa. Furthermore, the features described in connection with a device according to the invention can also be used to further develop another device according to the invention, even if this is not explicitly stated.

[0013] A computer-aided method according to the invention for providing control data for an additive manufacturing device for producing a three-dimensional object, wherein the object is produced by means of the additive manufacturing device by applying a build-up material layer upon layer and solidifying the build-up material by supplying radiant energy to locations in each layer that are associated with the cross-section of the object in this layer by scanning these locations with at least one beam according to a set of energy input parameter values ​​along a number of solidification paths, comprises: a first step of accessing computer-based model data of at least one section of the object to be produced, a second step of generating at least one data model of a region of a building material layer to be selectively solidified for producing the at least one object section, wherein solidification of the building material by moving at least one beam along at least one solidification path is specified in the data model, wherein a set of energy input parameter values ​​is specified for the end point of the at least one solidification path, which sets a reference value for the radiation power per unit area in the radiation impact area of ​​the beam on the building material, which is lower than the reference value for the radiation power per unit area at other locations of the solidification path, and a third step,in which control data corresponding to the at least one data model generated in the second step are provided for the generation of a control data set for the additive manufacturing device. ,

[0014] Additive manufacturing devices and methods to which the present invention relates are, in particular, those in which energy is selectively supplied to a layer of the building material as electromagnetic radiation or particle radiation. The working plane is a plane in which the upper side of the layer to which the energy is supplied lies. The energy input device can comprise, for example, a laser or an electron beam source. In particular, the invention relates to methods and devices in which heat is supplied to the building material by means of radiation, such as laser sintering, laser melting, or electron beam melting.

[0015] Of particular advantage is an application of the invention in connection with additive manufacturing processes and devices in which a metallic or at least metal-containing construction material is used, for example a metal powder or metal alloy powder.

[0016] It should also be noted at this point that using an additive manufacturing device according to the invention, not only one object but also multiple objects can be manufactured simultaneously. Whenever the present application refers to the manufacture of one object, it is understood that the respective description is equally applicable to additive manufacturing methods and devices in which multiple objects are manufactured simultaneously.

[0017] A control data set (often also referred to as a control command set) is considered here to be a sequence of instructions to apply layers of the build-up material one after the other and to scan areas of the respective layers, which correspond to the cross-section of an object to be manufactured, with radiation in order to solidify the build-up material.

[0018] In detail, a control data set is based on a computer-based model of the object(s) to be manufactured, preferably a CAD model. The control data set specifies the locations for each layer during production at which the build-up material is to be solidified by the application of radiation, and optionally the thickness of the layer. Furthermore, a control data set often also contains manufacturing device-specific information, for example regarding the position and orientation of the objects in the additive manufacturing device or regarding the diameter of a radiation impact area of ​​a beam (bundle) when it strikes the build-up material. The control data set generally contains all the data required to control the energy input device, which, among other things,The energy density of the radiation, i.e., the energy per unit area, and / or the travel speed of the beam across the build material and / or an irradiation pattern can be specified. Here, the term "beam" is used instead of "beam" to express that the diameter of the radiation impact area on the build material does not necessarily have to be very small, but can also cover a larger area, particularly when the radiation strikes the build material at an angle or when radiation is used that is deliberately intended to cover a larger area upon impact with the build material (for example, when a line exposure unit is used).

[0019] The control data set can thus be viewed as the totality of all control data specified for controlling the manufacturing process in an additive manufacturing device. The control data related to an individual layer is also referred to below as a layer data set. In the present application, it is particularly assumed that a layer data set contains a data model of the locations of an object cross-section to be solidified during the manufacturing process. Such a data model is generally generated by dividing a CAD model of the object to be manufactured into layers (referred to in technical jargon as slicing). However, it is also conceivable to extract a two-dimensional representation of the object cross-section to be solidified in a layer using one or more beams from the computer-based CAD model of the object in another way.The layer data set specifies locations corresponding to an object cross-section that are to be solidified in the associated build-up material layer. Furthermore, further information regarding the production of the object cross-section can be included, in particular the chronological sequence in which locations corresponding to an object cross-section are to be solidified, i.e., a scan line or scanning track along which solidification is to take place, or, for example, the layer thickness or irradiation parameter values, such as the diameter or travel speed of a radiation exposure area of ​​a beam impinging on the build-up material, etc. It should be emphasized that there are also special cases in which a layer data set does not refer to a complete object cross-section, but only to a part of it.

[0020] The computer-based model data can, for example, be a model of the object section to be manufactured, which is available, for example, as a CAD model or converted into STL format, and does not yet contain any information about the decomposition into layers for layer-by-layer production. It is also conceivable for the model data to be present in a GML (Generative Modeling Language) description. Alternatively, it can be a number of layer data sets, each of which contains a data model of a region of a build-up material layer to be selectively solidified during production, corresponding to a cross-section of the object section. It should be noted here that in the present application, the term "number" is always to be understood as "one or more."Furthermore, it should be noted that the object section does not necessarily have to refer only to a part of the object to be manufactured, but can also include the entire object to be manufactured.

[0021] Access to the model data can take the form of the model data being read from a memory or being received via a network. The model data for the entire object section does not necessarily have to be read in at once. It is also possible for there to be a longer time interval between accessing parts of the model data. For example, parts of the model data can be read in as needed during a manufacturing process for the object section from a memory (which can also be accessed, for example, by the additive manufacturing device) or via a network, and a generated data model can then be integrated into the control data set during the manufacturing process. An additive manufacturing device can therefore modify the control data set for its own control based on the method according to the invention.

[0022] If the model data accessed in the first step already contains a number of layer data sets, then the generation of at least one data model in the second step can consist of modifying a data model of a building material layer already present in the model data. Otherwise, a data model of a building material layer (or part thereof) can be generated for the first time in the second step.

[0023] A solidification path corresponds to a section in the working plane along which the build material is to be solidified without temporal or spatial interruptions, i.e., in one go or, in other words, by continuously displacing the molten pool in a direction parallel to the build plane. Solidification paths can therefore be viewed in particular as those scan lines (sections) where, when the build material is scanned by at least one beam, the solidification of the material is actually effected, rather than merely its heating. A solidification path can, for example, be a straight section of a certain width along which the build material is solidified by scanning with a radiation exposure zone.However, there are also cases in which one or more changes in direction occur when moving a radiation exposure area along the solidification path, in particular the solidification path is geometrically present as a curved line of a certain width.

[0024] In the data model generated in the second step, the energy input parameter values ​​are specified for the radiation exposure area of ​​that at least one beam whose effect on the building material causes a solidification of at least one uppermost layer of the building material, i.e., which does not merely preheat or postheat the building material.

[0025] Preferably, a single beam is used to solidify the build-up material along a solidification path. As a result of the energy supplied by the beam as it scans the build-up material, the latter is partially or completely melted, causing the components of the build-up material (e.g., powder grains) to bond together. After cooling, the build-up material then exists as a solid.

[0026] It should be noted that there may be building materials, such as alloys, for which no clear melting point is defined, but rather a melting range. In principle, in such a case, partial melting can already be considered to have occurred if the solidus temperature, i.e., the lower limit of the melting range, is exceeded. However, the present invention is preferably applied to cases in which the building material is completely melted, i.e., the liquidus temperature or the upper limit of the melting range is exceeded.

[0027] Since the transitions between partial (in the case of powder grains, i.e. superficial) melting (liquid phase sintering) and complete melting (melting) are fluid, the terms sintering and melting are used synonymously in the present application and no distinction is made between sintering and melting.

[0028] When the build-up material is solidified along a solidification path using more than one beam, the build-up material is partially or completely melted by the combined action of several beams, causing the components of the build-up material (e.g. powder grains) to bond with one another. Here, too, the build-up material is solidified along the solidification path without any interruptions, i.e., in one go. For example, when using two beams, one of the beams could initially solidify an initial section of the solidification path on its own, with the other beam only being switched on at some distance from the starting point. The two beams would then simultaneously introduce energy into the build-up material for a certain section of the solidification path, with their impact areas at least partially overlapping.At some distance from the end point, the second beam could then be switched off again, so that the end section would then again be solidified only by the first beam.

[0029] The procedure is an example of a particular embodiment of the invention, in which the joint energy input of two or more beam bundles in the central section of a solidification path ensures that a higher reference value of the radiant power is supplied to the build material per unit area. For example, a constant reference value of the radiant power per unit area could be specified within the central section, which is higher than that at the starting or end point, where fewer beam bundles than in the central section or only one beam bundle inputs energy. The central section of the solidification path is understood to be a section of the solidification path that lies between the starting point and the end point of the solidification path with respect to the direction in which the solidification path is scanned.

[0030] The length of a consolidation path, for example, corresponds to the width of a (often strip-shaped or rectangular) sub-area of ​​a cross-section of the object to be manufactured that is to be solidified. If an object cross-section is solidified using a beam in the form of a hatch pattern, such consolidation paths are also referred to as "hatch lines." In particular, the length of a consolidation path can also correspond to the diameter of the object cross-section in the direction of the hatch lines, whereby the approximate width of a contour line framing the cross-section may also have to be subtracted from this diameter. Alternatively, the length of a consolidation path can also correspond to the distance between the edge of a (often rectangular or square) sub-area of ​​an object cross-section that is to be solidified and the edge of the object cross-section or the contour line.

[0031] When reference is made to a start or end point of a solidification path, this does not mean a point without extent, but rather a section at the start or end of a solidification path whose extent corresponds to that partial area of ​​the impact area of ​​a beam of radiation within which solidification is effected. Such a partial area is regarded as the radiation exposure area. Typically, locations of the build material to be irradiated are encoded in the control data for controlling the at least one beam of radiation as points within a coordinate system, which can be defined two-dimensionally (relative to a layer) and / or three-dimensionally (relative to a build volume of the production device, i.e. to a plurality of layers). However, information about a respective extent of the radiation exposure area of ​​the beam of radiation can be linked to these points.In a data space used to prepare a manufacturing process, a starting and / or end point of a solidification path may well exist as mathematical points, but not in an actual manufacturing process. The direction of scanning or solidification of the solidification path by at least one beam bundle usually runs from the starting point to the end point.

[0032] A radiation impact zone of a beam of radiation on the build material can be viewed as the area of ​​the working plane within which the incident radiation power per unit area is greater than a specified percentage of the maximum radiation power per unit area, whereby exceeding the specified percentage of the maximum radiation power per unit area results in a melting temperature or solidus and / or liquidus temperature of the build material being exceeded. Within the radiation impact zone, laser radiation or particle radiation, for example, can act on the build material. The specified percentage or the shape and size of the radiation impact zone can be determined either through previous manufacturing processes with the additive manufacturing device and / or with the build material or as part of preliminary tests in which test irradiations are carried out.

[0033] A radiation exposure area on the build material does not necessarily have to be circular, but can also have other shapes, such as oval, especially when the radiation impinges on the build material at an angle or when radiation is used that is deliberately intended to cover a larger area upon impact (for example, when a line exposure unit is used). In particular, the radiation output per unit area can be deliberately varied within the radiation exposure area.

[0034] The reference value for the radiant power per unit area in the radiation impact zone can be, for example, the output power of the radiation source used to generate the beam (e.g., a (pump) laser source) while directing the beam toward the radiation impact zone. Examples of other possible reference values ​​include the average radiant intensity in the beam, the maximum radiant intensity in the beam, the total radiant power in the beam, the integral radiant power per unit area in the radiation impact zone, or a value calculated from various radiometric base quantities.

[0035] In particular, if the radiant power per unit area varies within the radiation exposure zone, the maximum radiant power per unit area within the radiation exposure zone can also be used as a reference value, since a maximum can be determined for each local distribution of the radiant power per unit area. For example, if the radiant power per unit area is constant within the radiation exposure zone, the maximum would be the radiant power per unit area present at each location. Alternatively, an average radiant power per unit area within the radiation exposure zone could be chosen as the reference value.

[0036] What is used as the reference value for the radiant power per unit area within the radiation impact area is irrelevant to the concept of the present invention. The only important factor when determining the reference value for the radiant power per unit area in the radiation impact area is that the reference value is positively correlated with the radiant power per unit area at a position within the radiation impact area, i.e., that it increases monotonically with the radiant power per unit area in the radiation impact area.

[0037] If energy input parameter values ​​corresponding to a reference value for the radiant power per unit area are specified, this can be done in various ways. Firstly, a specified energy input parameter can be the reference value itself. For example, a value for the output power of the radiation source used to generate the beam (e.g., a (pump) laser source) can be specified. It is also possible to specify values ​​of energy input parameters that are not the reference value but that influence the reference value. An example of this would be the specification of the local distribution of the radiation intensity per unit area within the radiation exposure area, for example by specifying the focusing, i.e. the position of the focus in a direction perpendicular to the build plane.

[0038] How a reference value changes when the radiant power per unit area changes at a position in the radiation impact area can be determined in advance for the additive manufacturing device for which control data is to be provided, e.g. by examining a beam profile or an intensity distribution of the beam, by directly measuring the radiant power per unit area (e.g. using an IR camera or a sensor mounted close to the build plane), etc. If the relationship between the reference value and the radiant power per unit area is already known from previous manufacturing processes with the additive manufacturing device and / or the build material used, the aforementioned preliminary investigations can be dispensed with.

[0039] When scanning a solidification path with only one beam, the width of the solidification path is defined as the extent of the radiation exposure zone perpendicular to the direction of movement of the beam. Where multiple beams within a solidification path jointly cause solidification of the build-up material, depending on the procedure, the width of the solidification path can be defined by the intersection of the extents of the radiation exposure zones perpendicular to the direction of movement of the beams along the solidification path. Alternatively, the beam with the largest extent of the radiation exposure zone perpendicular to the direction of movement of the beams along the solidification path can also define the width of the solidification path.

[0040] The invention allows control data to be provided for additive manufacturing of objects with improved homogeneity in an additive manufacturing device. This can be explained with reference to the example of Figur 11 can be explained as follows: While solidification of the build-up material is to take place at the end point of a solidification path, solidification is to take place in the immediately adjacent reversal region 55. For this purpose, in the prior art, the laser beam is switched off in the reversal regions 55. This can, however, lead to undesirable inhomogeneities in the object or component at one end of a solidification path, the cause of which lies in the abrupt change in the laser parameters, in particular the power density, i.e. the radiation power per unit area. By reducing the reference value for the radiation power per unit area at the end point according to the invention, the change in the power density at these points is smaller, thereby reducing temperature inhomogeneities which, for example, can lead to structural inhomogeneities in the structure of the finished object or component.The reference value for the radiant power per unit area specified at other locations along the solidification path is higher than at the start and / or end points. At these other locations, less consideration needs to be given to temperature inhomogeneities. Of course, the reduction in the reference value for the radiant power per unit area does not have to be limited to the end point, but can also include other locations along the solidification path, although not all locations.

[0041] It should also be noted that the tax data provided for the generation of a tax data record can, on the one hand, consist of the at least one data model itself generated in the second step, but, on the other hand, the at least one data model can also be prepared in accordance with any format requirements for integration into the tax data record.

[0042] Preferably, the reference value for the radiation power per unit area in the radiation exposure area on the building material at the end point of a consolidation track is less than or equal to 50%, preferably less than or equal to 20%, more preferably less than or equal to 10%, even more preferably less than or equal to 5%, even more preferably at most 3%, even more preferably at most 2% of the reference value for the radiation power per unit area at the other points of the consolidation track.

[0043] The higher the percentage differences, the more positive the effect on object homogeneity can be.

[0044] Further preferably, the energy input parameter values ​​in the radiation exposure area at the end point of a solidification path are set such that a thermal conduction welding process takes place when the radiation acts on the build-up material, wherein a deep welding process takes place at least at one other point of the solidification path when the radiation acts on the build-up material.

[0045] A deep penetration welding process is defined here as a process in which the radiation power per unit area introduced into the build-up material by the radiation is so high that all of the build-up material's main components evaporate. For example, if reinforcement particles or fibers are used that are specifically designed to be non-melting, these are not considered main components. Due to the formation of a vapor capillary on the surface of the build-up material, the beam penetrates deeper below the surface of the layer to be solidified. This can lead to multiple reflections of the beam, which improves radiation absorption.

[0046] A conduction welding process is defined here as a process in which the radiation power per unit area introduced into the build material by the radiation is too low to cause vaporization of the build material. The energy spreads into the build material via thermal conduction, resulting in a reduced expansion of the molten pool perpendicular to the surface created by the radiation.

[0047] The inventors have discovered that a transition to a thermal conduction welding process at the end of the solidification path has a positive effect on object homogeneity. They explain this by stating that the material evaporation occurring during a deep welding process can lead to craters in the solidified build-up material. This can occur, in particular, if the radiation power per unit area is reduced too abruptly at the end of a solidification path, so that the applied energy per unit area drops below the energy per unit area required to melt the build-up material (for example, by switching off the beam). Due to the rapid solidification process of the molten build-up material, the temporarily formed vapor capillary, also known as a "keyhole," in the solidified object can no longer be filled with material.

[0048] As a solution, it is therefore proposed to specify energy input parameter values, particularly at the end point of a hardening path, which induce a thermal conduction welding process when the radiation hits the build-up material. Suitable energy input parameter values ​​for this purpose can be determined in preliminary tests for the build-up material to be used. During the preliminary tests, for example, the output power of the radiation source used to generate the beam, the local distribution of the radiation intensity per unit area within the radiation exposure zone, the movement speed of the radiation exposure zone in the working plane, or, for example, the focusing depth of the radiation relative to the working plane can be varied.

[0049] The type of welding process can be investigated, for example, by observing the radiation exposure area using a camera (optical, IR, UV), by analyzing the radiation emitted by the radiation exposure area, or by analyzing test objects produced during preliminary tests. The almost complete absence of emissions caused by the vapor capillary created during the deep welding process, i.e. spatter or jets as well as metal vapor, can be used as a criterion for the presence of a conduction welding process. A further criterion is the aspect ratio of the molten pool (diameter of the molten pool parallel to the working plane in relation to the depth, i.e. perpendicular to the working plane), which for conduction welding is above 1:1, ideally around 2:1, and in any case below 100:1, or / and the surface temperature of the build-up material. If the latter is below the evaporation point of one or more components, the temperature of the build-up material can be below the evaporation point of the component.of all components of the build-up material, then the "keyhole" required for the deep welding process cannot form.

[0050] Preferably, the energy input parameter values ​​in the radiation exposure zone for a period immediately before directing the beam onto the starting point of the solidification path are specified such that a reference value for the radiation power per unit area in the radiation exposure zone of the beam on the building material is a maximum of 50%, preferably a maximum of 20%, more preferably a maximum of 10%, even more preferably a maximum of 5%, even more preferably a maximum of 3%, and even more preferably a maximum of 2% of the reference value for the radiation power per unit area at the starting point. Preferably, the radiation power per unit area before directing the beam onto the starting point is below 0.05 MW / cm2.

[0051] As explained above, a solidification path extends between a starting point and an end point. The procedure just described can be used to prevent areas of the build-up material adjacent to the starting point from being solidified outside the specified solidification path before an impact area of ​​at least one beam reaches the starting point. The edges of the solidified area should generally be formed with a high level of detail, which is accompanied by a precise demarcation of the solidified area from unsolidified or previously solidified build-up material. The procedure described makes it possible to ensure a clear demarcation of the solidified area from surrounding unsolidified build-up material, since the difference in the radiation power applied per unit area is limited. Preference is given to areas outside the solidification path (e.g.In the already mentioned reversal areas) only so much energy is introduced that the build-up material is heated but no solidification is effected.

[0052] In particular, the energy input parameter values ​​in the radiation exposure zone within a section of the solidification path adjacent to the end point are preferably set such that a thermal conduction welding process takes place when the radiation acts on the building material, wherein preferably a maximum extent of the section corresponds to at most twenty times the maximum extent of the radiation exposure zone, more preferably at most ten times, even more preferably at most five times, particularly preferably at most twice the maximum extent of the radiation exposure zone.

[0053] By applying a heat conduction welding process within a section of the solidification path adjacent to the end point, it can be ensured that irregularities in the solidified build-up material are avoided even close to the end point.

[0054] Preferably, for the end point and / or a section of the at least one solidification path adjacent to the end point, a greater or equal maximum extent of the radiation exposure area perpendicular to the direction of movement of the beam is specified than at the other points of the solidification path and / or a different distribution of the radiation intensity per unit area within the radiation exposure area, in particular a greater value of the ratio of the radiation power per unit area at the edge of the radiation exposure area to the radiation power per unit area in the middle of the radiation exposure area is specified than at the other points of the solidification path.

[0055] A transition to a lower radiation output per unit area at the end point of the consolidation path can lead to a change in the consolidation width. This can be counteracted by the modifications mentioned. For example, with a reduction in the radiation output per unit area, the speed of movement of the radiation exposure zone across the build-up material can also be reduced and / or the focusing plane of the beam bundle can be changed relative to the working plane. Furthermore, the distribution of the radiation intensity in the beam bundle can be selected such that at the end point and / or in a section of the consolidation path adjacent to the end point, the ratio of the radiation output per unit area at the edge of the radiation exposure zone, on the one hand, to the radiation output per unit area in the center of the radiation exposure zone, on the other hand, is higher than at other points along the consolidation path.However, the changed distribution of radiation intensity per unit area does not necessarily mean that an absolute value of the radiation power per unit area at the edge is higher than an absolute value of the radiation power per unit area in the middle.

[0056] Further preferably, at the end point and / or within a section of the at least one solidification path adjacent to the end point, the beam bundle in the working plane performs a periodic or irregular movement of an amplitude which is less than five times, preferably less than three times, particularly preferably less than twice a maximum extent of the radiation exposure area in the working plane.

[0057] The amplitude of the movement is, in particular, the maximum distance between the center of the radiation exposure zone and the end point during the movement in the working plane. This measure can ensure a more even distribution of the applied radiation energy in the build-up material, thereby reducing any depressions or material accumulations that may exist at the end point of the solidification path.

[0058] Further preferably, in the second step, it is specified that for a period immediately before directing the beam to the starting point of the solidification path and / or for a period immediately after directing the beam to the end point of the solidification path, the beam is not directed to the build-up material.

[0059] If the beam is not directed at the build-up material immediately before or after a scanning process along a solidification path, this can ensure that no build-up material is inadvertently solidified anywhere. To this end, for example, the radiation source generating the radiation can be switched off or the beam can be deflected so that it does not hit the build-up material. If the beam is not directed at the build-up material immediately before the beam is directed at the start point of the solidification path and / or immediately after the beam is directed at the end point of the solidification path, then the greatest temperature differences between the areas of the build-up material to be solidified and those not to be solidified can potentially occur in the area of ​​the start and end of a solidification path.However, since the radiation power supplied to the build-up material per unit area is already reduced at the start and / or end point of the consolidation path compared to other points of the consolidation path, the procedure according to the invention is not expected to have such great disadvantages.

[0060] Further preferably, the energy input parameter values ​​of the beam for a period immediately after the beam is directed onto the end point of the solidification path are specified such that a reference value for the radiation power per unit area in the radiation impact area of ​​the beam on the building material is less than or equal to 50%, preferably less than or equal to 20%, more preferably less than or equal to 10%, even more preferably less than or equal to 5% of the reference value for the radiation power per unit area at the end point.

[0061] Preferably, the radiant power per unit area after directing the beam to the end point is below 0.05 MW / cm 2< .

[0062] As explained above, a solidification path extends between a starting point and an end point. The procedure just described can be used to prevent areas of the build-up material adjacent to the end point from being solidified outside the specified solidification path. The edges of the solidified area should generally be formed with a high level of detail, which is accompanied by a precise demarcation of the solidified area from unsolidified or previously solidified build-up material. The procedure described makes it possible to ensure a clear demarcation of the solidified area from the surrounding build-up material. Preferably, outside the solidification path (e.g., in the reversal areas mentioned above), the maximum amount of energy applied is sufficient to heat the build-up material but not to cause solidification.

[0063] Preferably, the energy input parameter values ​​are specified such that within the section of the solidification path adjacent to the end point, the reference value for the radiant power per unit area in the radiation impact area of ​​the beam decreases.

[0064] By increasing the radiant power per unit area in a section adjacent to the starting point, a gradual transition to larger reference values ​​for the radiant power per unit area can be ensured. The same applies to reducing the reference value for the radiant power per unit area in a section of the solidification track adjacent to the end point. In both cases, the change in the reference value for the radiant power per unit area can occur in stages and / or continuously (steplessly).

[0065] Preferably, the solidifying beam is directed onto the solidification path such that, when scanning the solidification path, the speed of movement of the radiation exposure area of ​​the beam on the building material increases within the section of the solidification path adjacent to the starting point and / or decreases within the section of the solidification path adjacent to the end point.

[0066] By adjusting the movement speed of the radiation exposure zone to the radiation power per unit area, as described above, the total amount of energy supplied to the build-up material per unit area can be adjusted. For example, at a lower movement speed, the radiation exposure zone will require a longer time to travel over a specific point on the build-up material layer, thus increasing the amount of energy applied (compared to a case where a relatively higher movement speed was selected).

[0067] Preferably, the speed is changed monotonically. For example, a continuous, in particular linear, decrease in the movement speed of the radiation exposure zone along the solidification path can be specified until the end point is reached. The same applies to an increase in speed from the starting point of the solidification path. Depending on the control device used, the speed can be changed according to a function specified by a control mechanism for the movement of the radiation exposure zone. Short-term increases in speed while the radiation exposure zone moves toward the end point of the solidification path, or short-term decreases in speed shortly after leaving the starting point of the solidification path, could also be conceivable.Finally, it is also possible to change the speed in stages, for example, after leaving the starting point of the solidification path, it is initially increased in stages until a maximum or specified target speed is reached. Likewise, the speed can be reduced in stages toward the end of the solidification path.

[0068] Further preferably, the beam is directed onto the solidification path in such a way that the speed of movement of the radiation exposure area of ​​the beam in the working plane increases by at least 10%, more preferably by at least 100%, even more preferably by at least 1000% within a section of the solidification path adjacent to a starting point and / or decreases by at least 20%, more preferably by at least 50%, even more preferably by at least 80% within the section of the solidification path adjacent to the end point.

[0069] The extent to which the speed of movement of the radiation exposure zone is reduced toward the end point of the solidification path or increased from the beginning of the solidification path can be linked to the conditions of a particular manufacturing process. It can depend, for example, on the energy input device used, e.g., a mirror system for deflecting laser beams, and / or the build material, for which, for example, specific melting conditions must be met.

[0070] The amount of energy introduced into the build-up material per unit area can be precisely adjusted, especially when the radiation output per unit area and the speed of movement of the radiation impact zone are changed together, especially simultaneously. A certain degree of flexibility may be available for the amount of energy introduced for solidification, e.g., when using a metallic or metal-containing or metal-based (metal content > 50 volume percent) powder as the build-up material. It may therefore be sufficient, when the radiation output per unit area and the speed of movement of the radiation impact zone are changed together, to keep the amount of energy introduced per unit area within a predetermined range of values. The term "amount of energy introduced per unit area" refers to, among other things,Surface energy, determined in advance, taking into account the absorption capacity of the building material, which is to be supplied to the building material to solidify it.

[0071] Further preferably, the speed of movement of the radiation exposure zone of the beam in the working plane within a section of the solidification path adjacent to a starting point and / or within the section of the solidification path adjacent to the end point is varied together with the reference value for the radiation power per unit area in the radiation exposure zone such that at least at one point the percentage change in the reference value for the radiation power per unit area per unit time is greater than the percentage change in the speed of movement per unit time.

[0072] Such an approach can ensure a continuous transition to a lower energy input per unit area at the beginning and end of a consolidation path.

[0073] Preferably, in the second step, it is specified that the radiation impact area of ​​the beam is moved from the end point of the solidification path to the starting point of another solidification path, wherein during this movement the energy introduced into the building material by the beam does not cause any solidification of the same and is preferably zero. As already mentioned, the invention is advantageous, for example, where there is a transition between solidifying and non-solidifying scanning of the building material, in particular when moving from one point of the building material layer to be solidified to another point to be solidified at a distance therefrom, i.e. the radiation impact area of ​​the beam on the building material is moved from one point of the building material layer to another point of the building material layer without any solidification of the building material being intended during this movement.To avoid solidification of the build-up material, for example, the radiation power per unit area can be significantly reduced during the transition to the starting point of another solidification path.

[0074] More preferably, in the second step, a movement of the at least one beam bundle along a plurality of mutually adjacent, preferably at least partially substantially parallel, solidification paths is specified in the data model. The method according to the invention can be used in connection with hatching regions of a building material layer. During hatching, the radiation exposure region of a beam bundle is generally moved along mutually parallel solidification paths, wherein at an end point of a solidification path, a movement of the beam bundle takes place without solidification of building material to the starting point of a next solidification path. The movement without solidification of building material can be associated with a reversal of the direction of movement, but this does not have to be the case. The solidification paths can be exactly parallel to one another, but this does not have to be the case.It is quite possible that the hardening paths are only essentially parallel to each other.

[0075] As already mentioned in the introduction to the description, inhomogeneities caused by switching off the laser beam should not be significant, since any depressions ("holes") that may have formed are filled by the application of the subsequent powder layer and the subsequent process step of selective melting. The inventors explain the problems that nevertheless arise by the fact that the powder column above a depression or hole, which is larger than a typical layer thickness, behaves differently during melting than the combination of powder in a newly applied layer and solidified build-up material in the underlying layer.The reason for the different melting behavior may be a significantly lower density of the material to be melted in the hole in the underlying layer compared to the already solidified material around the hole, resulting in a lower mass of material to be melted per unit volume. As a result, the laser penetrates the layer or underlying layers more quickly and deeply at the location of the hole, which means that the hole is not completely eliminated even after the subsequent layer has solidified.

[0076] Although the inventive procedure already leads to an improvement or homogenization of the structure of the object or component in the case just described, the most significant effects can be seen where, during additive manufacturing, points where the laser power is set to zero or at least significantly reduced lie one above the other in two or more immediately consecutive layers. Such a situation can occur when endpoints of hatch lines lie one above the other in two or more consecutive layers. It is precisely at these points that the inventive procedure is advantageous, especially when three or more endpoints of hatch lines lie directly above one another, i.e., have the same position in the build plane.

[0077] In particular, if the speed of movement of the radiation impact area on the build-up material increases within the section of the solidification path adjacent to the starting point and / or decreases within the section of the solidification path adjacent to the end point, the beam can move along a small curve radius when reversing direction. This can shorten the time required for the transition to the starting point of the next solidification path compared to a case where, for example, the beam's movement speed is only reduced after the end point and increased again to a constant target speed before the starting point of the next solidification path, whereby the impact area of ​​the beam on the build-up material generally travels a considerably longer distance.Naturally, more time is required to scan the trajectory when the radiation exposure zone of the beam moves at a reduced speed. However, the direction of movement in the reversal zone cannot be changed arbitrarily quickly, so at high beam speeds, the curve radius along which the beam moves when reversing direction is larger than at low speeds. The reduced path length when reversing direction at a reduced speed can ultimately result in a shorter overall time for solidifying a layer of build-up material.

[0078] Further preferably, in the second step, an energy input is specified in the data model in adjacent, preferably rectangular or square, irradiation areas, wherein, in one irradiation area, an energy beam is moved over the build-up material in essentially parallel solidification paths. As already mentioned, the inventive procedure is particularly suitable for the prior art solidification of the build-up material section by section, in which, in the individual sections (e.g., strips or squares, or a closed cross-sectional area, which may also be irregularly shaped), scanning takes place by hatching along solidification paths that are exactly or essentially parallel to one another.In these cases, the data model specifies an energy input in adjacent, preferably rectangular or square, irradiation areas, wherein in one irradiation area a beam of rays is moved over the build-up material in essentially parallel solidification paths.

[0079] In an additive manufacturing method according to the invention for producing a three-dimensional object, wherein the object is produced by means of an additive manufacturing device by applying a building material layer upon layer and solidifying the building material 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 with at least one beam according to a set of energy input parameter values ​​along a number of solidification paths, the sequence of the additive manufacturing method is controlled by a control data set which was generated using a computer-aided method according to the invention for providing control data for an additive manufacturing device for producing a three-dimensional object.

[0080] If control data provided according to the invention are used in a control data set generated for controlling an additive manufacturing process, in particular the control of a layer-by-layer additive manufacturing process, such as a layer-by-layer powder melting or sintering process, such as SLS or DMLS or SLM, then the component homogeneity of the object can be improved.

[0081] A device according to the invention for providing control data for an additive manufacturing device for producing a three-dimensional object, wherein the object is produced by means of the additive manufacturing device by applying a build-up material layer upon layer and solidifying the build-up material by supplying radiant energy to locations in each layer that are associated with the cross-section of the object in this layer by scanning these locations with at least one beam according to a set of energy input parameter values ​​along a number of solidification paths, comprises: a data access unit configured to access computer-based model data of at least one section of the object to be produced, a data model generation unit configured to generate at least one data model of a region of a building material layer to be selectively solidified for producing the at least one object section, wherein the data model specifies solidification of the building material by moving at least one beam along at least one solidification path, wherein, when directing the at least one beam onto the end point of the at least one solidification path, a set of energy input parameter values ​​is specified that effects a reference value for the radiation power per unit area in the radiation impact area of ​​the beam on the building material, which is lower than the reference value for the radiation power per unit area at other locations along the solidification path,and a control data providing unit configured to provide control data corresponding to the at least one data model generated by the data model generating unit for generating a control data set for the additive manufacturing device.

[0082] The provision of the data model generated in the second step for generating a control data set can be done by the control data provision unit itself by integrating the generated data model into a control data set for the additive manufacturing device. However, provision also includes forwarding the data model to a data processing device, which integrates the data model into a control data set, or forwarding it directly to an additive manufacturing device. In particular, it is possible to dynamically provide data models for object cross-sections yet to be manufactured in the additive manufacturing device during a manufacturing process. In particular, data models generated in the second step do not have to be provided individually for an additive manufacturing process.Rather, several generated data models can first be collected and then made available in their entirety for integration into a tax data set.

[0083] A device according to the invention for the computer-assisted control of a number of energy input devices of an additive manufacturing device for producing a three-dimensional object by means of the same, wherein the object is produced by means of the additive manufacturing device by applying a building material layer upon layer and solidifying the building material by supplying radiant energy to locations in each layer that are associated with the cross-section of the object in this layer by scanning these locations with at least one beam according to a set of energy input parameters along a number of solidification paths, is designed such that solidification of the building material takes place by moving at least one beam along at least one solidification path such that a set of energy input parameter values ​​is specified for the end point of the at least one solidification path,which results in a reference value for the radiation power per unit area in the radiation impact area of ​​the beam on the build-up material, which is lower than the reference value for the radiation power per unit area at other points on the consolidation track.

[0084] The device for computer-assisted control of a number of energy input devices can be implemented solely using software components, using a combination of hardware and software components, or even solely using hardware components. A device implemented solely using software components can, in particular, interact with a control device in an additive manufacturing device to produce a three-dimensional object or be integrated into such a control device. The device for computer-assisted control of a number of energy input devices can improve the component homogeneity of objects produced by an additive manufacturing process.In particular, the device can implement a production of objects by an additive manufacturing method based on a control data set that was generated by means of a method according to the invention for providing control data.

[0085] An additive manufacturing device according to the invention for producing a three-dimensional object, wherein in the additive manufacturing device the object is produced by applying a build-up material layer upon layer and solidifying the build-up material by supplying radiant energy to locations in each layer that are associated with the cross-section of the object in this layer by scanning these locations with at least one beam according to a set of energy input parameters along a number of solidification paths, comprises: a layer application device suitable for applying a layer of a building material to an already existing, preferably already selectively solidified, building material layer, an energy input device suitable for supplying radiant energy to the cross-section of the object in locations assigned to a layer by scanning these locations with at least one beam according to a set of energy input parameter values ​​along a number of solidification paths,wherein the additive manufacturing device comprises a device according to the invention for computer-assisted control of a number of energy input devices of an additive manufacturing device for producing a three-dimensional object by means of the same and / or is signal-connected to a device according to the invention for computer-assisted control of a number of energy input devices of an additive manufacturing device for producing a three-dimensional object by means of the same.

[0086] An energy input device can comprise a number of radiation sources for generating radiation, e.g., electromagnetic radiation or particle radiation, as well as a number of associated beam deflection or redirection devices for directing the radiation onto the building material. In particular, a beam deflection device is preferably assigned precisely one radiation exposure region on the building material. The radiation sources can be, for example, 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 External Cavity Surface Emitting Lasers), or a row of these lasers.

[0087] In particular, when generating the control data in the additive manufacturing device, the device can dynamically generate data models for object (partial) cross-sections still to be manufactured during a manufacturing process by means of the data model generation unit.

[0088] A computer program according to the invention has program code means for executing all steps of a method according to a computer-aided method according to the invention for providing control data for an additive manufacturing device for producing a three-dimensional object when the computer program is executed by means of a data processor, in particular a data processor cooperating with an additive manufacturing device.

[0089] "Interaction" here means that the data processor is either integrated into the additive manufacturing device or can exchange data with it. Implementing the inventive method for providing control data and the associated device using software enables easy installation on various IT systems at different locations (for example, at the creator of the object's design or at the operator of the additive manufacturing device).

[0090] Further features and advantages of the invention will become apparent from the description of embodiments with reference to the accompanying figures. Fig. 1 shows a schematic, partially sectioned view of an exemplary device for additively manufacturing a three-dimensional object according to an embodiment of the invention, Fig. 2 shows schematically an example of the procedure according to the invention for solidifying a strip-shaped partial area of ​​an object cross-section, Fig. 3a shows schematically the change in the magnitude of the speed of a jet bundle along the upper solidification path in Fig. 2 , Fig. 3b shows schematically the change of the reference value for the radiation power per unit area of ​​a beam along the upper solidification path in Fig. 2 , Fig. 4a shows schematically the change in the magnitude of the speed of a jet bundle along the second highest solidification path in Fig. 2 , Fig. 4b shows schematically the change of the reference value for the radiation power per unit area of ​​a beam along the second highest solidification path in Fig. 2 , Fig. 5 shows schematically the variation of the reference value for the radiation power per unit area of ​​a beam along a solidification path according to a variant, Fig. 6 shows schematically the variation of the reference value for the radiation power per unit area of ​​a beam along a solidification path according to another variant, Fig. 7 illustrates the process of providing tax data, Fig. 8 shows the schematic structure of a device for providing control data, Fig. 9 shows a specific embodiment of the invention. Fig. 10 shows a procedure known to the applicant for scanning an object cross-section with energy radiation, Fig. 11 serves to further explain the Fig. 10 procedure shown.

[0091] For a description of the invention, an additive manufacturing device according to the invention will first be described below using the example of a laser sintering or melting device with reference to Fig. 1 be described.

[0092] For constructing an object 2, the laser sintering or laser melting device 1 contains a process chamber or build chamber 3 with a chamber wall 4. Arranged within the process chamber 3 is a build container 5 open at the top and with a container wall 6. A work plane 7 is defined by the upper opening of the build container 5, with the area of ​​the work plane 7 located within the opening, which can be used to construct the object 2, being referred to as the build field 8.

[0093] Arranged within the construction container 5 is a carrier 10 movable in a vertical direction V, to which a base plate 11 is attached, which closes off the container 5 at the bottom and thus forms its base. The base plate 11 can be a plate formed separately from the carrier 10 and fastened to the carrier 10, or it can be formed integrally with the carrier 10. Depending on the powder and process used, a construction platform 12 can also be attached to the base plate 11 as a construction base, on which the object 2 is built. However, the object 2 can also be built on the base plate 11 itself, which then serves as the construction base. Fig. 1 the object 2 to be formed in the container 5 on the construction platform 12 is shown below the working level 7 in an intermediate state with several solidified layers, surrounded by unsolidified building material 13.

[0094] The laser sintering or melting device 1 further includes a reservoir 14 for a build material 15, in this example a powder that can be solidified by electromagnetic radiation, and a coater 16 movable in a horizontal direction H for applying the build material 15 within the build field 8. Optionally, a heating device, e.g., a radiant heater 17, can be arranged in the process chamber 3. An infrared radiator, for example, can be provided as the radiant heater 17.

[0095] The exemplary additive manufacturing device 1 further includes an energy input device 20 with a laser 21, which generates a laser beam 22, which is deflected via a deflection device 23 and is focused onto the working plane 7 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.

[0096] In laser sintering or laser melting, an energy input device can comprise, for example, one or more gas or solid-state lasers or any other type of laser such as laser diodes, in particular VCSEL (Vertical Cavity Surface Emitting Laser) or VECSEL (Vertical External Cavity Surface Emitting Laser), or a row of these lasers. Fig. 1 The specific design of a laser sintering or melting device shown is therefore only exemplary for the present invention and can, of course, also be modified, particularly when using a different energy input device than the one shown. To emphasize that the area of ​​the radiation impact on the construction material does not necessarily have to be very small ("point-shaped"), the term "beam bundle" is often used synonymously with "beam" in this application.

[0097] The laser sintering device 1 further includes a control device 29, via which the individual components of the device 1 are controlled in a coordinated manner to carry out the construction process. Alternatively, the control device can also be mounted partially or entirely outside the additive manufacturing device. The control device can include a CPU whose operation is controlled by a computer program (software). The computer program can be stored separately from the additive manufacturing device in a storage device, from where it can be loaded (e.g., via a network) into the additive manufacturing device, in particular into the control device.

[0098] During operation, the control device 29 lowers the carrier 10 layer by layer, controls the coater 16 to apply a new powder layer, and controls the deflection device 23 and, if appropriate, also the laser 21 and / or the focusing device 24 to solidify the respective layer at the locations corresponding to the respective object by means of the laser by scanning these locations with the laser.

[0099] All statements made below apply not only to laser sintering or melting devices, but also to other types of additive manufacturing devices in which heat energy is introduced into the build material by means of radiation.

[0100] In the additive manufacturing device just described as an example, a manufacturing process takes place in such a way that the control unit 29 processes a control data set.

[0101] The control data set specifies to an energy input device, in the case of the above laser sintering or laser melting device specifically the deflection device 23, at each point in time during the solidification process, at which point of the working plane 7 the radiation is to be directed. As in Fig. 8 As shown, a device 100 for providing control data for an additive manufacturing device includes a data access unit 101, a data model generation unit 102, and a control data provision unit 103. The operation of the device 100 for providing control data is explained with reference to Fig. 7 described as an example.

[0102] In the Fig. 8 In the device 100 shown for providing control data for an additive manufacturing device, the data access unit 101 first accesses a number, i.e. one or more, of layer data sets, each of which has a data model of a region of a building material layer to be selectively solidified during production, preferably of the entire region of a building material layer to be solidified, which corresponds to a cross-section of an object section. In the device shown in Fig. 7 In the process sequence shown, this is the first step S1.

[0103] In the Fig. 7 In the second step S2 shown, the data model generation unit 102 now specifies in at least one data model of the at least one object section a solidification of locations of a building material layer in a temporal sequence that corresponds to the movement of a beam along a solidification path over the building material. The procedure is described with reference to Fig. 2 explained.

[0104] Fig. 2 shows a partial area 53 of the object cross-section, which in the example is strip-shaped and is scanned by moving the beam solidification path by solidification path. For the sake of clarity, Fig. 2 only the two solidification paths 64 and 65 are shown. Below these two solidification paths, there are further solidification paths which are not shown. Based on the directions of the arrows in the solidification paths, which are intended to illustrate the direction of movement of the radiation exposure area of ​​the beam, and based on the presence of the reversal area 55, it can be seen that the solidification path 64 is traversed temporally before the solidification path 65. For the solidification path 64, the starting point and the end point are designated by the reference numerals 64A and 64E, respectively. For the solidification path 65, the starting point and the end point are designated by the reference numerals 65A and 65E, respectively. For the solidification path 64, in Fig. 2 For the sake of simplicity, it is assumed in the left-hand area that the radiation power Φ impinging on the building material per unit area (more precisely, a reference value thereof) does not change over time. In contrast, in the dashed section 642 of the solidification path 64, it is specified that the reference value for the radiation power Φ impinging on the building material per unit area decreases on average during the movement of the radiation exposure region along the section 642.

[0105] Fig. 3b shows a schematic representation of the course of a reference value for the radiation power Φ incident on the building material per unit area during the movement of the radiation exposure area along the solidification path 64. In order to achieve a better assignment to the Fig. 2 shown consolidation path 64 is possible, the course of the reference value for the radiation power Φ incident on the building material per unit area in Fig. 3b in the consolidation path section 642 is also shown in dashed lines. It can be seen that in the consolidation path section 642, the reference value for the radiation power Φ incident on the building material per unit area decreases linearly towards the end 64E of the consolidation path. In the example of the Fig. 3b The reference value for the radiation power Φ incident on the build-up material per unit area at the end 64E of the consolidation path 64 is only approximately 20% of the reference value for the radiation power incident on the build-up material per unit area at other points along the consolidation path. Thus, the change in the radiation power per unit area when starting the reversal process of the direction of movement in the reversal area 55 takes place in Fig. 2 less abrupt. As a result, the component homogeneity improves at this point.

[0106] After the end 64E of the solidification path has been reached, i.e., at the start of the reversal of the direction of movement, the radiation output per unit area is generally reduced to a value close to zero, e.g., by blocking or interrupting the radiation or switching off the radiation source. However, if the radiation output per unit area is reduced sufficiently, it is also possible to maintain the energy supply in the reversal region 55, provided the energy supply is sufficiently low to prevent solidification of the build material in the reversal region. Therefore, the temperature of the build material in the reversal region should not rise above the liquidus temperature or melting temperature or a specific temperature threshold of a phase transition (depending on the type of solidification to be achieved).

[0107] Even if in some cases, e.g., when using metallic or metal-containing powder as the build-up material, it is possible to maintain the speed of movement of the radiation impact zone while reducing the radiation power incident per unit area on the build-up material towards the end of the solidification path, the aim is generally to simultaneously change the speed of movement of the radiation impact zone of the beam bundle while changing the radiation power incident per unit area on the build-up material. In other words, the speed of movement of the radiation impact zone of the beam bundle is preferably reduced at the same time as, or in temporal overlap with, the reduction of the radiation power incident per unit area on the build-up material. This situation is again schematically illustrated in Fig. 3a Again, for reasons of better comparability with Fig. 2 the course of the speed in the solidification path section 642 is shown in dashed lines.

[0108] The homogeneity of the object can be improved not only at the end but also at the beginning of the solidification path. Fig. 2 This is illustrated by the solidification path 65. The solidification path 65 has, on the one hand, a solidification path section 652, in which the reference value for the radiation power incident on the building material per unit area is reduced towards the end 65E of the solidification path. On the other hand, it has a section 651, in which the radiation power incident on the building material per unit area is increased when scanning the solidification path. The situation is schematically shown in Fig. 4b It can be seen that the reference value for the radiation power incident on the building material per unit area increases linearly from the beginning 65A of the solidification path, starting from a starting value, until a maximum value is reached, which is maintained in order to be linearly reduced again in the solidification path section 652 towards the end 65E of the solidification path 65. As already mentioned in connection with Fig. 3a und 3b As explained, in addition to varying the reference value for the radiation power impinging on the building material per unit area, the speed can also be varied. This ensures a uniform energy input per unit area even while increasing the reference value for the radiation power impinging on the building material per unit area in the solidification path section 651 by simultaneously increasing the speed. Preferably, the speed and / or the reference value for the radiation power impinging on the building material per unit area at the starting point 65A of the solidification path 65 are equal to the speed or the reference value for the radiation power impinging on the building material per unit area at the end point 64E of the preceding solidification path 64.

[0109] After the second step S2 in Fig. 7 At least one data model has been created, are then processed by the Fig. 8 The control data provision unit 103 shown provides control data for generating a control data set. In this case, either the at least one data model generated in the second step S2 can be provided as control information (control data) or the data model is reformatted into a control data set for better integration. The described procedure can be applied to all solidification paths within a strip-shaped or square partial area. Furthermore, the procedure can also be generalized such that the described procedure is always followed when, when scanning the build-up material layer, the beam is moved from one location (the end point of a solidification path) to another location (the starting point of another solidification path) without solidification of the build-up material taking place.

[0110] The period of time specified for reducing or increasing the radiation power impinging on the build-up material per unit area is, to a first approximation, not subject to any restrictions. The respective period of time at the beginning of a solidification path and / or at the end of a solidification path correlates, via the movement speed v of the beam, with the length of sections 651 or 652, 642 at the beginning and end of the solidification path, in which the reference value for the radiation power impinging on the build-up material per unit area is varied. For short solidification paths, the corresponding periods (and sections) must be selected to be correspondingly short, generally so short that the intended radiation power impinging on the build-up material per unit area can still be achieved at some point along the solidification path.Nevertheless, in the case of very short solidification paths, the time periods at the beginning and end of the solidification path can also be selected such that in the middle section of the solidification path, i.e. in the middle section relative to the direction in which the solidification path is scanned, the radiant power incident on the build-up material per unit area is lower than in the case of longer solidification paths. Under certain circumstances, the increase in the reference value for the radiant power incident on the build-up material per unit area along the solidification path can directly transition into a decrease in the reference value for the radiant power incident on the build-up material per unit area. For example, the reference value for the radiant power incident on the build-up material per unit area along the solidification path can have an almost sinusoidal curve (only the first half-wave of the sine). Such a procedure is shown schematically in . Fig. 9 , in which reference symbols A and E indicate the beginning and end of a solidification path, respectively. Of course, the speed can be varied analogously, e.g., proportionally to the radiation power per unit area, in order to ensure the most homogeneous energy input possible during irradiation of the solidification path. This allows, for example, a substantially constant energy input per unit area to be achieved, or fluctuations in the energy input per unit area can be limited, e.g., to below 15%, preferably below 5%.

[0111] As already indicated in the last paragraph, the speed and the reference value for the radiation power impinging on the build material per unit area within the section of the solidification path adjacent to the end point and within the section of the solidification path adjacent to the starting point do not necessarily have to be changed linearly. How the speed and the radiation power impinging on the build material per unit area change along the solidification path also depends essentially on the number of energy input devices used in the additive manufacturing device or the device for controlling this number of energy input devices. Fig. 5 shows that it is quite possible that, while lowering the reference value for the radiant power incident on the build-up material per unit area, there may even be a local increase in the reference value for the radiant power incident on the build-up material per unit area (see, for example, section 501 on the consolidation track). However, a decrease in the reference value for the radiant power incident on the build-up material per unit area should be specified towards the end point E, resulting in a reference value for the radiant power incident on the build-up material per unit area Φ at the end point E that is lower than a reference value for a region of the consolidation track that is far away from the end point E. Fig. 6 shows that even stepwise changes in the radiation power incident on the construction material per unit area are possible. Fig. 5 und 6The procedure described can also be applied to speed in the same way. This corresponds to the operation of many control devices that emit control signals in a timed manner, e.g., at fixed, short time intervals, which can have a corresponding effect on the radiation power per unit area emitted by the radiation source and / or the movement speed of the radiation exposure zone.

[0112] Although the figures only ever refer to the case where, in the reversal regions 55, the beam bundle is moved along an arcuate path to the starting point of the subsequent solidification path, alternatively, the beam bundle can also be moved from the end point of one solidification path to the starting point of the subsequent solidification path on a substantially straight path or an exactly straight path, in particular if the movement speed of the radiation exposure region has already been reduced to a very low value before reaching the end point.

[0113] Finally, it should be mentioned that a device 100 according to the invention for providing control data for an additive manufacturing device can be implemented not only solely by software components, but also solely by hardware components or combinations of hardware and software. In particular, interfaces mentioned in the present application do not necessarily have to be designed as hardware components, but can also be implemented as software modules, for example, if the input or output data can be taken over by other components already implemented on the same device, or only need to be transferred to another component via software. Likewise, the interfaces could consist of hardware and software components, such as a standard hardware interface that is specifically configured by software for the specific application.In addition, several interfaces can also be combined into a common interface, for example an input-output interface.

Claims

1. A computer-aided method for providing control data to an additive manufacturing device for manufacturing a three-dimensional object, wherein the object is manufactured by means of the additive manufacturing device by applying a building material layer by layer and by solidifying the building material by supplying radiation energy to locations in each layer assigned to the cross-section of the object in that layer by scanning these locations with at least one beam bundle according to a set of energy introduction parameter values along a number of solidification paths, wherein a solidification path extends between a starting point and an end point, and wherein at the most as much energy is introduced outside of the solidification path that the building material is heated but no solidification is caused, the method for providing control data comprising: a first step (S1) of accessing computer-based model data of at least a portion of the object to be manufactured, a second step (S2) of generating at least one data model of a region of a building material layer to be selectively solidified for manufacturing said at least one object portion, wherein the data model specifies solidification of the building material by moving at least one beam bundle along at least one solidification path (64, 65), wherein a set of energy introduction parameter values is specified for the end point (64E, 65E) of the at least one solidification path (64, 65), said set of energy introduction parameter values causing a reference value for the radiation power per unit area in the radiation impact area of the beam bundle on the building material which is lower than the reference value for the radiation power per unit area at other locations of the solidification path (64, 65), and a third step (S3) in which control data corresponding to the at least one data model generated in the second step (S2) are provided for generating a control data set for the additive manufacturing device.

2. Method according to claim 1, wherein the reference value for the radiation power per unit area in the radiation impact area on the building material at the end point (64E, 65E) of a solidification path (64, 65) is less than or equal to 50%, preferably less than or equal to 20%, even more preferably less than or equal to 10%, even more preferably less than or equal to 5%, still more preferably maximally 3%, still more preferably maximally 2% of the reference value for the radiation power per unit area at the other locations of the solidification path.

3. Method according to claim 1, wherein the energy introduction parameter values in the radiation impact area at the end point (64E, 65E) of a solidification path (64, 65) are determined in such a way that a heat conduction welding process takes place when the radiation acts on the building material, wherein a deep penetration welding process takes place at at least one other location of the solidification path (64, 65) when the radiation acts on the building material.

4. Method according to claim 3, in which the energy introduction parameter values in the radiation impact area within a section (642, 652) of the solidification path (64, 65) adjacent to the end point (64E, 65E) are determined in such a way that a heat conduction welding process takes place when the radiation acts on the building material, wherein preferably a maximum extension of the section corresponds to at most twenty times the maximum extension of the radiation impact area, more preferably at most ten times, still more preferably at most five times, particularly preferably at most twice the maximum extension of the radiation impact area.

5. Method according to one of the preceding claims, wherein for the end point (64E, 65E) and / or a section (642, 652) of the at least one solidification path (64, 65) adjoining the end point, a greater or equal maximum extension of the radiation impact area perpendicular to the direction of movement of the beam bundle than at the other locations of the solidification path (64, 65), 65) is specified and / or a different distribution of radiation intensity per unit area within the radiation impact area, in particular a larger value of the ratio of the radiation power per unit area at the edge of the radiation impact area to the radiation power per unit area in the middle of the radiation impact area is specified than at the other locations of the solidification path.

6. Method according to one of the preceding claims, wherein at the end point (64E, 65E) and / or within a section (642, 652) of the at least one solidification path (64, 65) adjacent to the end point the beam bundle performs a periodic or irregular movement in the working plane having an amplitude which is less than five times, preferably less than three times, particularly preferably less than twice a maximum extension of the radiation impact area in the working plane.

7. Method according to one of the preceding claims, wherein the energy introduction parameter values of the beam bundle are specified for a period immediately after the beam is directed to the end point (64E, 65E) of the solidification path (64, 65), so that a reference value for the radiation power per unit area in the radiation impact area of the beam bundle on the building material is less than or equal to 50%, preferably less than or equal to 20%, even more preferably less than or equal to 10%, even more preferably less than or equal to 5% of the reference value for the radiation power per unit area at the end point (64E, 65E).

8. Method according to one of the preceding claims, wherein the energy introduction parameter values are specified in such a way that within the section of the solidification path (642, 652) adjacent to the end point (64E, 65E) the reference value for the radiation power per unit area decreases in the radiation impact area of the beam bundle.

9. Method according to one of the preceding claims, wherein the beam bundle is directed onto the solidification path so that the speed of movement of the radiation impact area of the beam bundle in the working plane within a section (641, 651) adjacent to a starting point (64A, 65A) of the solidification path increases by at least 10%, more preferably by at least 100%, even more preferably by at least 1000% and / or decreases within the section (642, 652) of the solidification path adjacent to the end point (64E, 65E) by at least 20%, more preferably by at least 50%, even more preferably by at least 80%.

10. Method according to one of the preceding claims, wherein the speed of movement of the radiation impact area of the beam bundle in the working plane within a section (641, 651) of the solidification path adjacent to a starting point (64A, 65A) and / or within the section (642, 652) adjacent to the end point (64E, 65E), of the solidification path is varied together with the reference value for the radiation power per unit area in the radiation impact area in such a way that at least at one location the percentage change in the reference value for the radiation power per unit area per unit time is greater than the percentage change in the speed of the movement per unit time.

11. Additive manufacturing method for the manufacturing of a three-dimensional object, wherein the object is manufactured by means of an additive manufacturing device by applying a building material layer by layer and by solidifying the building material by supplying radiation energy to locations in each layer assigned to the cross-section of the object in that layer by scanning said locations with at least one beam bundle according to a set of energy introduction parameter values along a number of solidification paths, wherein a solidification path extends between a starting point and an end point, and wherein at the most as much energy is introduced outside of the solidification path that the building material is heated but no solidification is caused, wherein the process of the additive manufacturing method is controlled by a control data set generated using a method according to one of claims 1 to 10.

12. Device for providing control data for an additive manufacturing device for manufacturing a three-dimensional object, wherein the object is manufactured by means of the additive manufacturing device by applying a building material layer by layer and by solidifying the building material by supplying radiation energy to locations in each layer assigned to the cross-section of the object in that layer by scanning these locations with at least one beam bundle according to a set of energy introduction parameter values along a number of solidification paths, wherein a solidification path extends between a starting point and an end point, and wherein at the most as much energy is introduced outside of the solidification path that the building material is heated but no solidification is caused, wherein the device for providing control data comprises: a data access unit (101) adapted to access computer-based model data of at least a portion of the object to be manufactured, a data model generating unit (102) adapted to generate at least one data model of a region of a building material layer to be selectively solidified for manufacturing the at least one object portion, wherein solidification of the building material by moving at least one beam bundle along at least one solidification path is specified in the data model, wherein, when directing the at least one beam bundle onto the end point (64E, 65E) of the at least one solidification path (64, 65), a set of energy introduction parameter values is specified which causes a reference value for the radiation power per unit area in the radiation impact area of the beam bundle on the building material which is lower than the reference value for the radiation power per unit area at other locations of the solidification path (64, 65), and a control data providing unit (103) adapted to provide control data corresponding to the at least one data model generated by the data model generating unit (102) for generating a control data set for the additive manufacturing device.

13. Device for computer-aided control of a number of energy introduction devices of an additive manufacturing device for manufacturing a three-dimensional object by means thereof, wherein the object is manufactured by means of the additive manufacturing device by applying a building material layer by layer and by solidifying the building material by supplying radiation energy to locations in each layer assigned to the cross-section of the object in that layer by scanning those locations with at least one beam bundle according to a set of energy introduction parameters along a number of solidification paths, wherein a solidification path extends between a starting point and an end point, and wherein at the most as much energy is introduced outside of the solidification path that the building material is heated but no solidification is caused, characterized in that the device is adapted to solidify the building material by moving at least one beam bundle along at least one solidification path so that a set of energy introduction parameter values is specified for the end point (64E, 65E) of the at least one solidification path (64, 65), which causes a reference value for the radiation power per unit area in the radiation impact area of the beam bundle on the building material which is lower than the reference value for the radiation power per unit area at other locations of the solidification path (64, 65).

14. Additive manufacturing device for manufacturing a three-dimensional object, in which additive manufacturing device the object is manufactured by applying a building material layer by layer and by solidifying the building material by supplying radiation energy to locations in each layer assigned to the cross-section of the object in that layer by scanning these locations with at least one beam bundle according to a set of energy introduction parameters along a number of solidification paths, the additive manufacturing device comprising: a layer application device (16) adapted to apply a layer of building material to an already existing, preferably already selectively solidified, building material layer, an energy introduction device (20) adapted to supply radiation energy to locations assigned to the cross-section of the object in a layer by scanning said locations with at least one beam bundle (22) according to a set of energy introduction parameter values along a number of solidification paths, wherein a solidification path extends between a starting point and an end point, and wherein at the most as much energy is introduced outside of the solidification path that the building material is heated but no solidification is caused, wherein the additive manufacturing device comprises a device according to claim 13 and / or is connected to a device according to claim 13 in terms of signal technology.

15. Computer program, comprising program code means for executing all the steps of a method according to one of claims 1 to 10 when the computer program is executed by means of a data processor, in particular a data processor cooperating with an additive manufacturing device.