Exposure strategy within cross sections

Abstract

A method for providing control data for an additive manufacturing device (1) involves: a first step (S1) of accessing model data of a number of partial cross sections of the object to be manufactured, each of which comprises a subarea of an object cross section and a portion of the periphery of this object cross section, a second step (S2) of creating a data model of the number of partial cross sections, wherein the data model specifies a scanning of the locations of the number of partial cross sections with a number of beams (22) along a plurality of trajectories (54) in the layer plane (7), wherein at least one of the partial cross sections has a set sequence for scanning the trajectories such that first a starting trajectory is scanned, wherein at least one point of the starting trajectory is at such a distance from the periphery of the object cross section that at least one further trajectory lies between the at least one point and the periphery, and a third step (S3), in which control data for generating a set of control data are provided.

Description

[0001] Exposure strategy within cross sections

[0002] The present invention relates to a method and a device for providing control data for an additive manufacturing device, a correspondingly adapted method and a correspondingly adapted device for controlling an energy input device of an additive manufacturing device, a correspondingly adapted additive manufacturing method and a correspondingly adapted additive manufacturing device and a correspondingly adapted computer program.

[0003] Additive manufacturing devices and associated methods to which the invention relates are generally characterized in that objects are produced in them by solidifying a formless building material (e.g. a metal or plastic powder) layer by layer. The solidification can be brought about, for example, by supplying thermal energy to the building material by irradiating it with electromagnetic radiation or particle radiation (e.g. laser sintering (SLS or DMLS) or laser melting or electron beam melting). For example, in laser sintering or laser melting, a laser beam is moved over those points in a layer of the building material which correspond to the cross-section of the object to be produced in this layer, so that the building material is solidified at these points. After the building material has been melted or solidified at one point by the supply of thermal energy.sintered, after cooling the build-up material is no longer in a formless state, but as a solid.

[0004] After all areas of an object's cross-section that require solidification have been scanned, a new layer of the build-up material is applied and also solidified at the locations corresponding to the object's cross-section in this layer. The inventors were able to observe undesirable height differences (fluctuations in layer thickness) of the solidified build-up material at the locations of a layer corresponding to the object's cross-section, particularly when using metal-containing build-up materials. Such inhomogeneities complicate the production of high-precision objects and impair the manufacturing process.The object of the invention is therefore to provide a method and a device for generating control data for an additive manufacturing device, a correspondingly adapted method and a correspondingly adapted device for controlling an energy input device of an additive manufacturing device, a correspondingly adapted additive manufacturing method and a correspondingly adapted additive manufacturing device and a correspondingly adapted computer program, by means of which objects with improved detail resolution can be obtained through a more reliable additive manufacturing process.

[0005] The object is achieved by a method for providing control data according to claim 1, a corresponding device according to claim 12, a correspondingly adapted method for controlling an energy input device according to claim 13, a correspondingly adapted additive manufacturing method according to claim 14, a correspondingly adapted device for controlling an energy input device according to claim 15, a correspondingly adapted additive manufacturing device according to claim 16 and a correspondingly adapted computer program according to claim 17.

[0006] Further developments of the invention are claimed in the dependent claims. In particular, a device according to the invention can also be further developed by 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. A computer-aided method according to the invention for providing control data for an additive manufacturing device for producing a three-dimensional object by means of the same, wherein the additive manufacturing device is designed such thatthat objects are produced by means of the additive manufacturing device by applying a build-up material layer upon layer and solidifying the build-up material in a layer plane by supplying radiation energy to those locations in each layer that are assigned to an object cross-section in this layer, comprises: a first step (S1) of accessing computer-based model data of a number of partial cross-sections of the object to be produced, each of which comprises a partial area of ​​an object cross-section and a portion of the edge of this object cross-section, a second step (S2) of generating a data model of the number of partial cross-sections, wherein in the data model a scanning of the locations of the number of partial cross-sections with a number of rays along a plurality of trajectories in the layer plane is specified,wherein in at least one of the number of partial cross-sections, an order of scanning of the trajectories is determined such that a starting trajectory is scanned first, wherein at least one point of the starting trajectory is spaced from the edge of the object cross-section in the layer plane such that at least one further trajectory lies between the at least one point and the edge, preferably at least two further trajectories lie between the at least one point and the edge, and a third step (S3) in which control data corresponding to the data model generated in the second step (S2) are provided for generating a control data set for producing the object by means of the additive manufacturing device.

[0007] The method can in particular be carried out entirely by a computer, which carries out all method steps independently without operator intervention. 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 a formless building material in the form of electromagnetic radiation or particle radiation. The working plane (also referred to as the building plane) is a plane in which the upper side of the layer to which the energy is supplied lies and is also referred to here as the layer plane. The radiation energy can be generated, for example, by a laser or an electron beam source, although a plurality of radiation sources and / or beams can also be used. The radiation supplied to the building material heats it and thereby causes a sintering or melting process.In particular, the present invention relates to laser sintering, laser melting, and electron beam melting devices, as well as the associated methods. Although the invention can be applied both in connection with plastic-based building material and in connection with metal-based building material, an application of the invention in connection with additive manufacturing methods and devices in which a metallic or at least metal-containing building material is used, for example a metal powder or metal alloy powder, is of particular advantage. In particular, the invention can also be applied in connection with a combination of a metal-based building material and a plastic-based building material, wherein a combination consists of a mixture between a metal-based and a plastic-based building material, wherein optionally also further components can be included.For example, a building material can be in powder form and, in particular, the powder granules can consist of a metal-containing core and a plastic-containing coating (or vice versa).

[0008] It should be noted at this point that using an additive manufacturing device according to the invention, not only one object but also several objects can be manufactured simultaneously. Whenever the present application refers to the production of one object, it is understood that the respective description is equally applicable to additive manufacturing methods and devices in which several objects are produced simultaneously. The term "beam" is not intended to imply that the diameter of the beam must be very small. Rather, the beam impact area on the build material (in the build plane or layer plane) can also have a larger diameter, particularly if the radiation impacts the build material at an angle or if a larger beam impact area is deliberately created upon impact with the build material through beam shaping.

[0009] A beam trajectory specified in a data model defines a path a beam follows in the build plane when the beam is directed onto the build material. The data model thus specifies the locations (locations to be solidified) at which a beam should impinge on the build plane and the chronological order in which the locations in the build plane should be scanned. In the context of the invention, a trajectory is defined as a path having a predefined directional course that can be described by a single, concrete mathematical function. If the direction of the path changes, for example, due to a change in the sign of the curve (i.e., a reversal of direction), this is a new trajectory that can be distinguished from the previously mathematically described trajectory by the different function.Along the trajectory, the beam can be directed at the build material, but there may also be locations along the trajectory where the beam is switched off or paused. In other words, the radiation source does not necessarily have to be permanently activated while a scanner moves along the trajectory.

[0010] When scanning the areas of a layer to be solidified, a distinction is sometimes made between an inner region and an edge region (often an edge line whose width roughly corresponds to the diameter of the beam impact area on the build material in the build plane perpendicular to the direction of movement of the beam) of an object cross-section. The inner region is solidified by moving the beam along trajectories that are usually essentially parallel to one another. The area is hatched, so to speak, which is why the individual trajectories are also referred to as "hatch lines." In particular, in this application, the term "trajectory" is often used synonymously with "hatch line" or scan line, even if, strictly speaking, a trajectory refers to a line (of zero width) specified in the control data, and a "hatch line" orScan line refers to a track in the build plane (with a width other than zero, which roughly corresponds to the diameter of the beam impact surface on the build material in the build plane perpendicular to the direction of movement of the beam). In order to account for the non-zero widths of the melt tracks in the build plane, the trajectories or hatch lines are spaced apart from one another in the data model, thus enabling a uniform, gapless energy input into the build material when scanning the same. Within the scope of the invention, it is preferred that the hatch lines be designed as straight lines.

[0011] The edge region (also referred to as the contour region) of an object cross-section is typically solidified by moving a beam along the course of the edge region. The trajectories to which this application relates, in contrast, are lines traversed when scanning an interior region of an object cross-section. Scanning an edge region of the object cross-section can occur either before or after scanning the interior region, or, particularly if a different beam than the one used for scanning the interior region is used for scanning the edge region, can occur with a temporal overlap with the scanning of the interior region.

[0012] The computer-based model data accessed in the first step contains a geometric description of the (partial cross-section of the) object, i.e., in particular, a three-dimensional CAD model. However, other geometric description options are also possible, e.g., a description using a parameter set and a design specification. In this context, it is only important that the model data describe the geometric shape of at least one partial cross-section of an object to be manufactured, to which a layer of the construction material, preferably exactly one layer, is assigned.

[0013] Even if the second step is to create a data model of a

[0014] partial cross-section, it is understood that a data model can also be generated which relates to a plurality of partial cross-sections, i.e. for at least one, preferably a plurality, particularly preferably all of these partial cross-sections, an inventive scanning of locations of the partial cross-section with a number of rays along a plurality of trajectories in the layer plane is specified. The prerequisite for this is that the corresponding computer-based model data of these partial cross-sections is accessed in the first step. The invention thereby comprises data models in which the number of partial cross-sections is assigned to the same building material layer. In particular, however, data models can also be generated which relate to a plurality of partial cross-sections which are assigned to different building material layers. If necessary, a data model of the entire object can also be generated.

[0015] A partial cross-section of an object is defined here as a partial region (partial area) of a cross-section of an object to which a layer of the build material is assigned during additive manufacturing. This partial region is additionally characterized in that it comprises a section of the edge of an object cross-section, i.e., borders on locations in the layer plane outside the object cross-section that are not to be solidified. In a preferred embodiment of the invention, a partial cross-section according to the invention is at least predominantly separated from the remaining regions of the entire object cross-section by build material that is not to be solidified. This means that the edge of a region of a build material layer assigned to the partial cross-section borders on build material that is not to be solidified with at least 50%, preferably with at least 75%, even more preferably with at least 95% of its length, particularly preferably with 100% of its length.If a partial cross-section does not border with its entire edge on areas in the layer plane that are not to be consolidated, the shape and position of the partial cross-sections in the layer plane can either be specified by an operator of the process, for example, by modifying the computer-based model data, or defined fully automatically. With automatic definition of the shape and position of the partial cross-sections, for example, a partial area of ​​an object cross-section that differs from the remaining areas of the entire object cross-section by at least one geometric property (e.g., its geometric shape and / or the orientation of its geometric shape in the layer plane) can be defined as a partial cross-section.In particular, a partial cross-section can also comprise the entire cross-section of an object to be manufactured, but only if the entire cross-section does not break down into separate sub-areas (sub-areas) (i.e. if it is path-connected in the mathematical sense).

[0016] It should also be noted that a partial cross-section according to the invention can only be a surface with a minimum extent in any direction in the layer plane. The minimum extent is preferably at least three times, more preferably at least five times, the distance between adjacent trajectories traversed to solidify the partial cross-section.

[0017] Furthermore, it should be noted that the invention is advantageous regardless of the way in which partial cross-sections are defined within a (path-connected) object cross-section.

[0018] A start trajectory is defined here as the trajectory that is traversed first in time when scanning a partial cross-section.

[0019] In the present case, a distance of the starting trajectory from the edge of the partial cross-section in the layer plane is defined such that at least one further trajectory lies between the starting trajectory and the edge at least at one point of the starting trajectory, preferably at least two further trajectories lie between the starting trajectory and the edge. Furthermore, the distance of a point of the starting trajectory from the edge is preferably determined in a direction perpendicular to the path of the starting trajectory through the point. In particular, the point can be the starting point of the starting trajectory, i.e., the point of the starting trajectory that specifies the location in the build plane to which the beam is first directed when scanning the starting trajectory. The starting point then corresponds to a two-dimensional area in the build plane or layer plane that is essentially as large as the area of ​​incidence of the beam on the build plane.Preferably, at least 25% of the points of the starting trajectory to which the starting point preferably belongs, further preferably at least 50% of the points of the starting trajectory, even more preferably at least 75% of the points of the starting trajectory to which the starting point preferably belongs, even more preferably at all points of the starting trajectory, there is at least one further trajectory between the starting trajectory and the edge, preferably at least two further trajectories.

[0020] The control data set can be viewed as the totality of all control data specified for controlling the manufacturing process in an additive manufacturing device. The control data relating to an individual layer is usually referred to as a layer data set. In the present application, it is assumed in particular that a layer data set contains a data model of locations of an object cross-section or partial object cross-section that are to be solidified in a layer by means of one or more beams during the manufacturing process. In addition, 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 or partial object cross-section are to be solidified by specifying scan lines or trajectories along which the beam is to be moved, a chronological sequence of the scanning of a plurality of scan lines orTrajectories or, for example, the layer thickness or irradiation parameter values, such as the diameter or the travel speed of a beam impinging on the build material, etc.

[0021] The provision of control data according to the invention allows for more uniform thicknesses of the solidified build material layers in a layer-by-layer additive manufacturing process. This allows for the production of objects with more precise dimensions perpendicular to the layer planes (usually referred to as the z-direction). It also prevents interference with the layer deposition caused by protrusions protruding upward from an already solidified layer, which could potentially collide with a coating element. The inventors explain the achieved improvements as follows:

[0022] Wherever a beam hits the build material, a molten pool forms. As the beam moves along a trajectory, this molten pool moves within the build material, generating a molten track which, once solidified, represents a solidification path consisting of solidified build material. Due to the surface tension that forms on the surface of the molten pool, unsolidified build material from the area near the molten pool is drawn into the molten pool itself. In addition, molten (not yet solidified) build material is pulled from the molten track in the direction of the first point of impact of the beam, as long as a molten pool continues to form there. When the beam first hits an applied layer of build material, more build material is available to the molten pool, allowing the build material to be transported to the impact position orinto the first melt track (when the beam is moved along a trajectory in the build plane) is greater than the build material transport into the other positions. This leads to an increase in the molten material and, as a result, to a thickening, in particular of the first solidification track in the z-direction (in the following, the terms “build material accumulation” and “superelevation” are also used to describe the increase in the molten material and the thickening of a solidification track in the z-direction). The subsequent solidification tracks are thickened (raised) to a lesser extent, since there is less unsolidified build material to the side of the corresponding melt tracks. In the subsequent solidification tracks (or in positions that are further away from the first impact point of the beam orThis results in a build material shortage because build material was transported from these solidification paths (positions) to the first impact point of the beam or into the first solidification path. If the starting trajectory in the following layers, which in turn is spaced from the edge of the corresponding object (partial) cross-section, lies at a different location in the build plane than in the previous layer(s), then an overshoot in previous layers can be compensated more efficiently.Preferably, in the second step (S2), a data model of at least one partial cross-section in a first building material layer and at least one partial cross-section in an overlying second building material layer is generated, and a starting trajectory is selected for the partial cross-section in the second building material layer, which at most partially, preferably not at all, overlaps with the starting trajectory for the partial cross-section of the first building material layer.

[0023] An overlap can occur when the two starting trajectories intersect in the build plane. Alternatively, an overlap can occur when the two starting trajectories are at least partially congruent in the build plane or parallel to each other and slightly offset from each other in the build plane. An overlap can also occur if the starting trajectories are slightly offset in the build plane, since it must be taken into account that the trajectories correspond to tracks in the build material with a width other than zero. Assuming that the distance between the trajectories specified for a build material layer corresponds to the track width in the build material, then an overlap already exists if the offset of the starting trajectories is less than the average distance between the trajectories in one of the two build material layers, in particular the first build material layer.Since a constant value is usually specified for the distance between the trajectories within a build-up material layer, the mean distance usually corresponds to the specified constant distance.

[0024] If the starting trajectory in the second build material layer overlaps the starting trajectory in the first build material layer without a lateral offset, there should preferably be an overlap of at most half the length of the starting trajectory in the first build material layer, more preferably an overlap of at most 1 / 10, and particularly preferably an overlap of at most 1 / 100 of the length of the starting trajectory in the first build material layer. Since each starting trajectory corresponds to a track in the build material layer with a width corresponding to the trajectory spacing, one can also briefly say that the values ​​given above for the maximum covered length of the starting trajectory in the first build material layer correspond to the values ​​for the maximum covered area of ​​the starting trajectory in the first build material layer.If there is a lateral offset of the two starting trajectories, the covered area of ​​the starting trajectory in the first build material layer can be calculated using the following equation: covered area = covered length x (trajectory distance - offset).

[0025] It was assumed that the offset has a value between zero and the trajectory spacing. Thus, even in the presence of an offset of the starting trajectories and generally for any course of the starting trajectories, it can be stated that preferably an overlap of a maximum of half the area of ​​the starting trajectory in the first build material layer should be present, more preferably an overlap of a maximum of 1 / 10, and particularly preferably an overlap of a maximum of 1 / 100 of the area of ​​the starting trajectory in the first build material layer.

[0026] Preferably, the starting point of the starting trajectory in the second build material layer is laterally offset from the starting point of the starting trajectory in the first build material layer in the build plane by an amount that is greater than the average distance between the trajectories in the first build material layer, preferably greater than twice the average distance between the trajectories in the first build material layer, and even more preferably greater than three times the average distance between the trajectories in the first build material layer. Typically, a distance between the trajectories is specified for a build material layer, so that the average distance between the trajectories simply corresponds to the distance specified for the build material layer.

[0027] In this procedure, a data model of a plurality of partial cross-sections is created, which are assigned to different building material layers.

[0028] Since an over-emphasis occurs in the solidified build material layer in the area of ​​the starting trajectory, the over-emphasis can accumulate at the points in the build plane where the areas of the starting trajectories in different build material layers overlap – even a few layers are sufficient here. As a result, the sum of the over-emphasis in an upper layer could be so large that, when applying another build material layer, a coating element used for this purpose could collide with an over-emphasis. This would lead to the abort of the build process and possibly even damage to the coating element.

[0029] By ensuring that the starting trajectory in a second build material layer does not completely overlap with the starting trajectory in a first layer, an increase in the camber resulting from the first build material layer can be prevented or reduced in the second build material layer. Compensating for the cambers, for example, in a first and a second layer, can further prevent impairment of the manufacturing process or even interruption of the process.

[0030] More preferably, the launch trajectories in more than two consecutive build-up material layers overlap at most partially, and even more preferably not at all. This results in an even more efficient avoidance of large overshoots.

[0031] Further preferably, the starting trajectory in the partial cross-section of the second building material layer is selected such that it has a different distance from the edge of the object cross-section in the layer plane than the starting trajectory in the partial cross-section of the first building material layer, wherein the other distance is characterized by a different number of further trajectories lying between the starting trajectory or a point thereof and the edge.

[0032] Especially when the position and orientation of the partial cross-sections in the first and second build material layers are very similar, this procedure can ensure that a starting trajectory in a first build material layer and a starting trajectory in a second build material layer are offset in the build plane. This minimizes or completely prevents an overlap of the starting trajectories. Preferably, the procedure described above is used for the starting trajectories in more than two consecutive build material layers, whereby a distance relative to another build material layer following the first build material layer can also be modified.

[0033] Further preferably, the trajectories in the second building material layer are rotated relative to the trajectories in the first building material layer by an angle that is different from 0°, 90° and 270°.

[0034] The preferred angles serve to efficiently reduce an increase in the superelevations by changing a build material accumulation and a build material deficiency in a build material layer located above the first build material layer compared to the first build material layer (or another build material layer following the first build material layer) by rotating the trajectories.

[0035] The preferred angles are particularly applicable in the case where the first and second build material layers lie directly on top of one another. If possible, a rotation angle can also be selected that ensures that the starting trajectory in the second build material layer does not overlap the starting trajectory in the first build material layer. In general, a rotation angle should preferably be selected that, when a rotation by this angle occurs from layer to layer, only overlaps the starting trajectory in an overlying build material layer with the starting trajectory of the first build material layer after the largest possible number of layers.

[0036] It should be noted that the above angle specifications apply regardless of the direction in which the rotation takes place, although preferably the direction of rotation is always the same.

[0037] Further preferably, the trajectories in the second construction material layer are rotated relative to the trajectories in the first construction material layer by an angle that is greater than 90° and / or less than 270°. Even more preferably, the angle is greater than 120° or less than 120°, preferably greater than 100° and less than 140°.

[0038] The value of 120° is excluded because a rotation of 120° from layer to layer in the layer after the second build material layer would again have the same orientation of the trajectories in the build plane as in the first build material layer, which is generally undesirable.

[0039] For the preferred angular range, particularly homogeneous thicknesses of the solidified layer regions could be achieved. In particular, within this angular range, it is possible to ensure that the trajectories in the successive build-up material layers are as heterogeneous as possible, i.e., run in as many different directions as possible. By ensuring sufficient heterogeneity of the trajectories in the successive build-up material layers, it is often possible to ensure that the starting trajectory in a subsequent build-up material layer overlaps with the trajectory of a previous build-up material layer only after the largest possible number of layers. This makes it possible to efficiently compensate for the elevations in this angular range by rotating the trajectories, resulting in an accumulation of build-up material and a lack of build-up material in the build plane at locations other than those in the first build-up material layer.

[0040] Particularly preferred values ​​for the angle are 105°, 115°, 125°, 130°, 135° or 140°.

[0041] Preferably, the starting trajectory is selected from the plurality of trajectories to be scanned in the partial cross-section using a random generator.

[0042] It is often the case that the shape of a (partial) cross-section and its position in the build plane change only slightly (and possibly not at all) from one build material layer to the next. In these cases in particular, the addition of superimposed regions of the start trajectories can be avoided by varying the distance between the start trajectory and the edge in the individual layers. This applies in particular to cases in which the trajectories in the second build material layer run essentially parallel to the trajectories in the first build material layer. The use of the random principle is intended to ensure that there is no overlap of start trajectories of superimposed build material layers or that there is only a small number of overlaps of start trajectories of superimposed build material layers.

[0043] Preferably, the trajectories in a second build material layer have the same shape and orientation to each other as the trajectories in a first build material layer.

[0044] In this case, it is easier to choose a starting trajectory in the second build material layer such that this starting trajectory has as little overlap as possible with the starting trajectory in the first build material layer.

[0045] Preferably, individual or all subsections of at least two trajectories, particularly preferably of all trajectories, are parallel to one another in a partial cross-section. The parallelism of the trajectories in a partial cross-section, in particular in each partial cross-section of the number of partial cross-sections, facilitates the selection of the starting trajectory, since in this case it is easy to check whether further trajectories lie between the intended starting trajectory and the edge of the object cross-section. It should be emphasized that parallel trajectories or subsections thereof do not necessarily have to be straight. Rather, parallelism can also exist in curved curves, in particular in closed line courses of the trajectories.

[0046] Preferably, a partial cross-section is solidified segment by segment, with each segment corresponding to a partial area of ​​the partial cross-section, and each segment being solidified by scanning along a plurality of trajectories in the layer plane. A segment is a partial area of ​​a partial cross-section, so that during segment-by-segment solidification, the region of a building material layer corresponding to the partial cross-section is solidified partial area by partial area. The segments preferably have the same shape and orientation in the layer plane or construction plane. Particularly preferably, the segments are rectangular, and in particular square.Further preferably, the shape and orientation in the construction plane of the trajectories is the same in all segments, particularly preferably also the direction in which the trajectories are scanned one after the other in a segment (the trajectory sequence direction), so that the position of the trajectory to be scanned first relative to the area of ​​the segment is the same for all segments.

[0047] When solidifying the area of ​​a build material layer corresponding to the partial cross-section in segments, the distance of the starting trajectory from the edge of the object's cross-section can be achieved by appropriately selecting the segment to be solidified first in the partial cross-section. This is particularly true if the position of the trajectory to be scanned first relative to the area of ​​the segment is the same in all segments and the shape and orientation of the segments in the build plane are the same.

[0048] Preferably, the trajectories within a segment run parallel to each other.

[0049] Further preferably, the segments have a rectangular shape and the trajectories in the segments enclose an angle between 5° and 175°, preferably between 45° and 135°, particularly preferably between 85° and 95°, with an edge of the segment.

[0050] This approach preferably uses rectilinear, particularly parallel, trajectories in the individual segments. The angles mentioned refer to an angle formed by a starting or ending section of the trajectory—the beginning and ending are determined by the direction in which the trajectory is traversed—with an edge of the segment. The angle is preferably substantially 90°, in particular exactly 90°.Even more preferably, a trajectory lying in one of the segments is defined as a starting trajectory, wherein the starting trajectory is defined such that it is scanned in a direction pointing away from a boundary of the segment to an adjacent neighboring segment, and wherein the first of the trajectories to be scanned in the adjacent neighboring segment is defined such that it is scanned starting at a location adjacent to the starting trajectory in a direction pointing away from the boundary.

[0051] The boundary between two segments is considered the region in the plane where the two segments adjoin each other. This is preferably a boundary line or edge line. The reason why the boundary can also be considered a region is that there may be embodiments in which the trajectories of one segment extend somewhat into the other segment or begin or end at a certain distance from the other segment. However, the resulting "overlap" or the resulting remaining distance to the other segment is generally less than the width of the track corresponding to the trajectories in the build material layer, in other words, less than the distance between the adjacent trajectories in a segment.

[0052] In this context, a location adjacent to the starting trajectory is in particular a location in the neighboring segment whose distance to the starting point of the starting trajectory is smaller than the width of the track in the building material layer corresponding to the trajectories or smaller than the distance between neighboring trajectories in the segment in which the starting trajectory lies.

[0053] If a trajectory is scanned in a direction pointing away from the boundary, this is immediately obvious for trajectories perpendicular to the boundary. If the trajectories enclose an angle other than 90° with the boundary, then when scanning away from the boundary, at least one directional component of the movement is present that points away from the boundary. The inventors explain the advantage of this approach by the fact that scanning the starting trajectory in the area of ​​the neighboring segment adjacent to the starting trajectory creates a lack of buildup material.If this area is scanned first in the neighboring segment, then this lack of build-up material is compensated for by the fact that, during the solidification of this area, the build-up material adjacent to this area that has not yet solidified is solidified in addition to the unsolidified build-up material already present in this area, or by the fact that adjacent, already solidified build-up material is melted / melted again and drawn into this area.

[0054] Furthermore, it is preferable for all trajectories in both the segment containing the starting trajectory and the adjacent segment to be sampled in the same direction. This means that the starting points of all trajectories are preferably located at or near the boundary between the two segments. This approach can take into account the fact that an overshoot tends to occur at the beginning of a trajectory.

[0055] A device according to the invention for providing control data for an additive manufacturing device for producing a three-dimensional object by means of the same, wherein the additive manufacturing device is designed such that objects are produced by means of the additive manufacturing device by applying a building material layer upon layer and solidifying the building material in a layer plane by supplying radiant energy to those locations in each layer that are associated with the cross-section of the object in this layer, comprises: an access unit designed to access computer-based model data of a number of partial cross-sections of the object to be produced, each of which comprises a partial area of ​​an object cross-section and a portion of the edge of this object cross-section, a data model generation unit designed to generate a data model of the number of partial cross-sections,wherein the data model specifies a scanning of the locations of the number of partial cross-sections with a number of rays along a plurality of trajectories in the layer plane, wherein the data model generation unit is designed to define an order of scanning of the trajectories in at least one of the number of partial cross-sections such that a start trajectory is scanned first, wherein at least one point of the start trajectory is spaced from the edge of the object cross-section in the layer plane such that at least one further trajectory lies between the at least one point and the edge, preferably at least two further trajectories lie between the at least one point and the edge, and a control data provision unit which is designedTo provide control data according to a data model generated by the data model generation unit for generating a control data set for the production of the object by means of the additive manufacturing device.

[0056] The provision of the data model generated by the data model generation unit 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 produced in the additive manufacturing device during a manufacturing process.

[0057] In a method according to the invention for controlling an energy input device 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 in a layer plane by supplying radiant energy to those locations in each layer that are associated with the cross-section of the object in this layer, wherein the additive manufacturing device for supplying radiant energy has an energy input device that is designed to solidify a number of partial cross-sections of the object to be produced, each of which comprises a partial area of ​​an object cross-section and a portion of the edge of this object cross-section,To scan the locations of the number of partial cross-sections with a number of rays along a plurality of trajectories in the slice plane, an order of scanning of the trajectories is defined for at least one of the number of partial cross-sections such that a starting trajectory is scanned first, wherein at least one point of the starting trajectory is spaced from the edge of the object cross-section in the slice plane such that at least one further trajectory lies between the at least one point and the edge, preferably at least two further trajectories lie between the at least one point and the edge.

[0058] To scan the build material along trajectories, the energy input device can, in particular, comprise a number of beam deflection devices (e.g., galvanometer scanners) by means of which light from a radiation source (e.g., a laser) is directed to the desired locations in the build plane. The beam deflection devices also control the speed of movement of the beam(s) across the build plane. The method for controlling the energy input device can, in particular, be implemented by processing a control data set generated using the control data provided by a method according to the invention for providing control data.

[0059] In an additive manufacturing method according to the invention for producing a three-dimensional object by means of an additive manufacturing device, a method according to the invention for controlling an energy input device of an additive manufacturing device is carried out.

[0060] Preferably, these are manufacturing processes in which a metal-based

[0061] A build-up material is used, i.e. a build-up material in which the metal content exceeds 50 percent by weight, e.g. a metal powder or metal alloy powder such as steel powder or powder containing chromium, titanium, tungsten, cobalt, nickel, copper or aluminum, whereby the list of the elements mentioned is not intended to be exhaustive. In particular, however, a combination of a metal-based build-up material and a plastic-based build-up material can also be used, whereby the combination consists of a mixture of a metal-based and a plastic-based build-up material, whereby further components can optionally also be included. For example, a build-up material can be in powder form and in particular the powder granules can consist of a metal-containing core and a plastic-containing coating (or vice versa).The additive manufacturing process is preferably a laser sintering process or a laser melting process.

[0062] A device according to the invention for controlling an energy input device of an additive manufacturing device for producing a three-dimensional object by means of the same, wherein the objects are produced by means of the additive manufacturing device by applying a building material layer upon layer and solidifying the building material in a layer plane by supplying radiant energy to those locations in each layer that are associated with the cross-section of the object in this layer, wherein the additive manufacturing device for supplying radiant energy has an energy input device that is designed to solidify a number of partial cross-sections, each of which comprises a partial area of ​​an object cross-section and a portion of the edge of this object cross-section, by scanning the locations of the number of partial cross-sections with a number of beams along a plurality of trajectories in the layer plane,has a scanning control unit which is designed to specify a sequence of scanning the trajectories for at least one of the number of partial cross-sections such that a starting trajectory is scanned first, wherein at least one point of the starting trajectory is spaced from the edge of the object cross-section in the slice plane such that at least one further trajectory lies between the at least one point and the edge, preferably at least two further trajectories lie between the at least one point and the edge.

[0063] The control device of an energy input device is capable of implementing the method described above for controlling an energy input device. The individual components of the device, in particular the scanning control unit, or the entire control device can be implemented solely by software, solely by hardware, or by a mixture of hardware and software. Interfaces do not necessarily have to be designed as hardware components, but can also be implemented as software modules. Likewise, interfaces can consist of both hardware and software components, for example in the form of a standard hardware interface that is specifically configured by software for the specific application. Furthermore, several interfaces can also be combined into a common interface, for example an input-output interface.

[0064] In particular, the control device can be a unit within a control unit that controls a manufacturing process in an additive manufacturing device. Nevertheless, it should be emphasized that the control device can equally well be present outside the control unit and can exchange signals with the additive manufacturing device, in particular with the energy input device, via a network. In particular, if the control device is implemented solely by software, the control device can be in the form of a computer program. Such a computer program for a manufacturing process is then preferably executed by the additive manufacturing device in its control unit.

[0065] An additive manufacturing device according to the invention for producing a three-dimensional object by means of the same comprises a device according to the invention for controlling an energy input device of an additive manufacturing device. The additive manufacturing device is preferably designed for producing objects from a metal-based construction material in which the metal content exceeds 50 percent by weight, e.g., a metal powder or metal alloy powder such as steel powder or powders containing chromium, titanium, tungsten, cobalt, nickel, copper, or aluminum, whereby the list of the elements mentioned is not intended to be exhaustive.In particular, the additive manufacturing device can be designed for producing objects from a combination of a metal-based build material and a plastic-based build material, wherein the combination consists of a mixture of a metal-based and a plastic-based build material, optionally also containing additional components. For example, a build material can be powdered, and in particular, the powder granules can consist of a metal-containing core and a plastic-containing coating (or vice versa). The additive manufacturing device is preferably a laser sintering device or laser melting device.

[0066] A computer program according to the invention comprises a sequence of instructions by means of which, when executed, a computer-aided method according to the invention for providing control data for an additive manufacturing device and / or a method according to the invention for controlling an energy input device of an additive manufacturing device or an additive manufacturing method according to the invention for producing a three-dimensional object by means of an additive manufacturing device is implemented.

[0067] A computer program implementing a method according to the invention for providing control data can be executed on a computer or data processor that is completely independent of the additive manufacturing device, in particular, cannot exchange data with it. Execution of the computer program's commands by a data processor integrated into the additive manufacturing device or interacting with it is naturally advantageous. Implementing the method according to the invention 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).

[0068] A computer program implementing a method according to the invention for controlling an energy input device or an additive manufacturing method according to the invention is preferably executed on a data processor that is integrated into the additive manufacturing device or interacts with it. The term "interaction" mentioned several times above is intended to mean that the data processor can exchange data with the additive manufacturing device, e.g., via a wireless network or data lines.

[0069] Fig. 1 shows a schematic, partially sectioned view of an exemplary device for additively manufacturing a three-dimensional object according to the invention.

[0070] Fig. 2a to 2c serve to explain the term "partial cross-section" used in the application.

[0071] Fig. 3 shows schematically an example of an inventive procedure for determining the starting trajectory.

[0072] Fig. 4 schematically shows another example of an inventive procedure for determining the starting trajectory.

[0073] Fig. 5a to 5c serve to explain the possibilities of defining a distance between the starting trajectory and the edge of an object cross-section.

[0074] Figs. 6a to 6c illustrate the procedure for determining the starting trajectories in multiple layers. Fig. 7 schematically shows the sequence of a method according to the invention for providing control data.

[0075] Fig. 8 shows schematically the structure of a device according to the invention for providing control data.

[0076] Fig. 9a and 9b show another example of the procedure for determining the starting trajectories in several layers.

[0077] Fig. 10a and 10b show variants of the procedure according to Figure 4.

[0078] The term "partial cross-section" used in the present application will first be explained in more detail with reference to Figs. 2a, 2b, and 2c. Fig. 2a shows an exemplary object 200 to be manufactured by additive manufacturing. Fig. 2b shows an entire cross-section 280 through the object 200 in a plane A shown in Fig. 2a. In additive manufacturing, a layer of the build material is assigned to the cross-section 280, and accordingly, plane A is selected to be parallel to the layer of the build material. As can be seen in Fig. 2b, the entire cross-section 280 comprises eight mutually delimited sub-regions 281, 282, 283, 284, 285, 286, 287, 288. Each of these sub-regions can be regarded as a partial cross-section that is completely delimited from the other regions of the entire cross-section 280. Fig.Fig. 2c shows an exemplary object 210, which is also to be manufactured by additive manufacturing, together with an overall cross-section 290 through the object 210 in a plane B. As in the case of the object cross-section 280, a layer of the build material is assigned to the cross-section 290 during additive manufacturing, and accordingly, the plane B is selected to be parallel to the layer of the build material. As can be seen in Fig. 2c, four sub-regions 291, 292, 293, and 294 differ from one another in their geometric properties in the overall cross-section 290. Sub-region 291 is essentially rectangular, with the exception of two semicircular bulges at the edge. Sub-region 292 is an arc.The partial region 293 is a reflection of the partial region 292 about a horizontal line in the plane of the drawing and has the same shape and the same area as the partial region 292. However, the partial region 293 differs from the partial region 292 because the partial region 293 has a different sign of curvature in the plane B. In addition, each of the partial regions 291, 292, 293, 294, which together form the object cross-section 290, borders on building material that is not to be consolidated. According to the invention, only the partial region 291 is considered a partial cross-section, since it is the only one of the partial regions in which the minimum extent is greater than five times the distance between the trajectories in the partial region. To illustrate this fact, exemplary trajectories in each of the partial regions are shown in Fig. 2c.In sub-area 291, a multitude of concentric trajectories can be seen, while in each of the sub-areas 292, 293 and 294 there is only a single trajectory (the trajectories 2992, 2993, 2994).

[0079] 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.

[0080] 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. The upper opening of the build container 5 defines a work plane 7 (also called the build plane), 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.

[0081] Arranged within the build container 5 is a support 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 support 10 and fastened to the support 10, or it can be formed integrally with the support 10. Depending on the powder used and the process, a build platform 12 can be attached to the base plate 11 as a build 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 build base. In Fig. 1, the object 2 to be formed in the container 5 on the build platform 12 is shown below the work plane 7 in an intermediate state with several solidified layers, surrounded by unsolidified build material 13.

[0082] The laser sintering or melting device 1 further contains 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.

[0083] The exemplary additive manufacturing device 1 further includes an energy input device 20 with a laser 21 that generates a laser beam 22, which is deflected by a beam emitter 23, for example one or more galvanometer mirrors with associated drive, and focused onto the work 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. Although not shown in Fig. 1, an additive manufacturing device can have two or more beam emitters 23. This allows a manufacturing process to be completed in a shorter time, since the build material can then be scanned and solidified at different locations simultaneously with multiple beams.

[0084] The specific structure of a laser sintering or melting device shown in Fig. 1 is only exemplary for the present invention and can of course also be modified, in particular when using a different energy input device than the one shown.

[0085] 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.

[0086] 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 energy input device 20, in particular the beam emitters 23 and optionally also the laser 21 and / or the focusing device 24, to solidify the respective layer at the locations corresponding to the respective object by scanning these locations with the laser. In this application, a unit 39 within the control device 29 responsible for controlling the energy input device 20 is referred to as the control device 39 of the energy input device.Nevertheless, it should be emphasized that a control device 39 of the energy input device can also be present outside the control device 29 in the same way (also in the form of a computer program), provided that it is ensured that the control device 39 of the energy input device can sufficiently interact with the control device 29 for the additive production of objects, i.e. in particular can exchange signals with the control device 29.

[0087] In the additive manufacturing device just described by way of example, a manufacturing process proceeds in such a way that the control unit 29 or the actuation device 39 of the energy input device processes a control data set. 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, for each point in time during the solidification process, to which point on the working plane 7 radiation is to be directed. Fig. 8 shows a device 100 for providing control data for an additive manufacturing device. This device contains a data access unit 101, a data model generation unit 102, and a control data provision unit 103. The functioning of the device 100 for providing control data is described by way of example with reference to Fig. 7.

[0088] In the device 100 shown in Fig. 8 for providing control data for an additive manufacturing device, the data access unit 101 first accesses computer-based model data of the object. In the method sequence shown in Fig. 7, this data access step is the first step S1. The computer-based model data contain a geometric description of the object, in particular a three-dimensional CAD model, although there are also other possibilities for the geometric description, e.g. a description by means of a parameter set and a design specification. In this context, it is only important that the model data describe the geometric shape of at least one partial cross-section of an object to be manufactured, to which a layer of the building material is assigned.In other words, the data access unit 101 can also access the entire model data (the complete CAD model) of the object to be manufactured (or the objects to be manufactured if there are several objects to be manufactured in parallel in the additive manufacturing device).

[0089] The data access step (the first step S1) may also include forwarding the model data to a data model generation unit 102 described below, but the data model generation unit 102 may also retrieve these data from the data access unit 101 or read them from a memory (not shown in Fig. 8) in which they are stored.

[0090] In the second step S2 shown in Fig. 7, the data model generation unit 102 now specifies a data model in which a solidification of the locations of the associated building material layer corresponding to the at least one partial cross-section is defined in a temporal sequence that corresponds to the movement of a beam along trajectories over the building material. In particular, the temporal sequence in which the trajectories are traversed one after the other is specified.

[0091] After at least one data model has been generated in the second step S2 in Fig. 7, control data for generating a control data record is subsequently provided by the control data provision unit 103 shown in Fig. 8 (in Fig. 7, this is step S3). In this case, either the data model generated in the second step S2 can be provided as control information (control data) or the data model can be reformatted into a control data record for better integration.

[0092] Below, examples of the procedure in the second step S2 are described for different (partial) cross-sections and line courses of the trajectories.

[0093] The schematic Figure 3 shows an exemplary partial cross-section 30, which is identical to the entire cross-section of an object and has an elliptical outer edge 31 for the build-up material not to be solidified, as well as a likewise elliptical inner edge 32 for the build-up material not to be solidified. Due to the curved edges, to solidify the area between the two edges, it is advisable to move the beam not along straight trajectories, but along curved trajectories, which are designated by reference numerals 301 to 309 in Fig. 3. Since the trajectories in the example have a shape adapted to the shape of the edges 31 and 32, the number of trajectories required to scan the area of ​​the cross-section is fewer than would be the case if straight trajectories were selected.

[0094] The inventive procedure is characterized in that, when scanning the building material, the first scan is not along a trajectory 303 or 309 (the edge trajectories) closest in time to one of the edges 31, 32, but along a trajectory spaced from the edges. In Fig. 3, the trajectory 301, along which the first scan is performed (the start trajectory), is shown with a solid line to distinguish it from the other trajectories. As can be seen in the figure, the two trajectories 302 and 303, which are scanned after the start trajectory 301, lie between the start trajectory 301 and the edge 31. The reference numerals in Fig. 3 are selected such that trajectories with a higher reference numeral are traversed after trajectories with a lower reference numeral.

[0095] Of course, according to the invention, a trajectory other than trajectory 301 could also be selected as the starting trajectory in Fig. 3, for example, trajectory 307. It is only important that the starting trajectory is not the trajectory closest to the edge. Although in the most general approach of the invention it would be sufficient if at least one point of the starting trajectory, in particular the starting point, was spaced from the edge, in the present case a starting trajectory can be defined in which all points are spaced from the edge.

[0096] Fig. 4 shows a further example of the procedure in the second step S2. The exemplary partial cross-section 40, which in the example corresponds to the entire cross-section of an object to be produced by additive manufacturing, has a rectangular shape. Unlike Fig. 3, the build material in the region of a build material layer assigned to this cross-section is not scanned using trajectories that traverse the entire cross-section. Rather, the scanning is carried out segment by segment, by defining segments that each correspond to a partial area of ​​the cross-section. Fig. 4 shows the rectangular segments 401, 402, 403, 404, and 405 as an example. As illustrated by segment 401, the area of ​​each segment is scanned along trajectories 91, 92, 93, 94, and 95. As is often the case, the sequence in which the trajectories are scanned within the individual segments is chosen to be the same in all segments.4, the trajectories in each of the segments are scanned from top to bottom (in the image plane). This is illustrated in Fig. 4 in that the trajectory to be scanned first in each of the segments is shown with a solid line, while the trajectories following in time are shown with dashed lines. With reference to segment 401, trajectory 91 is scanned first, followed by trajectory 92, then trajectory 93, then trajectory 94, and then trajectory 95. Although in Fig. 4 the trajectories within a segment are perpendicular to the edge of the segment, i.e., they form a 90° angle with the edge of the segment, the trajectories can also form a different angle with the edge of the segment, for example, a 45° angle, although an angle of essentially 90° or exactly 90° is preferred.

[0097] If segment-by-segment scanning is selected for scanning the region of a building material layer corresponding to a (partial) cross-section, then a procedure according to the invention can be implemented such that, within the cross-section, a segment is scanned first in which the trajectory scanned first in time in the segment is spaced from the edge of the cross-section. This trajectory is thus the starting trajectory when scanning the (partial) cross-section. In the example of Fig. 4, segment 401 is scanned first, followed by segments 402, 403, 404, and 405 in the order of the reference numbering. Alternatively, segments 402 and 403 could of course also be scanned first, but not segments 404 and 405, in which the trajectory to be scanned first in time lies adjacent to edge 41.To indicate that the trajectory 91 to be scanned first in segment 401 is the starting trajectory for the cross-section 40, the trajectory 91 is shown with a thicker line.

[0098] Fig. 10a and 10b show an embodiment of how the trajectories to be scanned in two adjacent segments can be advantageously defined in order to avoid excessive increases in the thickness of the solidified layer that occur during the solidification of an object cross-section.

[0099] Fig. 10a shows a top view of a cross-section 1000 of an object to be produced by additive manufacturing, which has, for example, a circular shape with an outer edge 1100. As in the example of Fig. 4, the scanning of the build material is carried out segment by segment in the example of Fig. 10a. As in Fig. 4, for the sake of clarity, only some of the segments are shown that are to be scanned in order to bring about solidification of the build material corresponding to the cross-section 1000. As in Fig. 4, the two segments 1001 and 1002 shown in Fig. 10a have a rectangular shape, with the trajectories along which the area of ​​each segment is scanned being illustrated by arrows.In each segment, the trajectory to be scanned first in this segment is shown with a solid line. In segment 1001, this is trajectory 1021, and in segment 1002, this is trajectory 1020. The subsequent trajectories are shown with dashed lines. Since in the example of Fig. 10a, segment 1002 is the first to be solidified in the object cross-section, trajectory 1020 is the starting trajectory for cross-section 1000 and is shown with a thicker line for identification.

[0100] In the procedure according to Fig. 10a, it can be seen that in segment 1001, the trajectory 1021 whose starting point 1021a is in the immediate vicinity of the starting point 1020a of the starting trajectory 1020 is scanned first. Furthermore, the trajectory 1021 in segment 1001 is traversed in the opposite direction to the starting trajectory. This procedure can ensure that material accumulated at the starting point of the starting trajectory is at least partially removed with the scanning of the first trajectory in the neighboring segment, thereby reducing layer elevation.

[0101] Fig. 10b shows a modification of the procedure according to Fig. 10a, where the same reference numerals also indicate the same features. In the procedure according to Fig. 10b, all trajectories in a segment 1001, 1002 are scanned in the same direction. Furthermore, all trajectories start at the boundary 1012 between the two segments 1001 and 1002. In this way, layer elevations that tend to occur at the beginning of the trajectories in the first scanned segment 1002 can be at least partially eliminated.

[0102] Possible definitions of a distance of a starting trajectory from the edge of a partial cross-section are explained below with reference to Figs. 5a to 5c. Figs. 5a to 5c each show a partial cross-section 50, which, for the sake of simplicity, is identical to the entire cross-section of the object, is square by way of example, and has an edge 51. Fig. 5a shows four trajectories 501, 502, 503, 504 in the partial cross-section 50, of which trajectory 501 is defined as the starting trajectory and is therefore shown with a thicker line. The figure shows three subsections 510, 511, and 512 of the starting trajectory 501. As can be seen, two further trajectories 502 and 503 lie between the partial section 510 and the edge 51 of the object cross-section 50 in a direction perpendicular to the course of the partial section 510.Furthermore, three further trajectories 502, 503 and 504 lie between the partial section 511 and the edge 51 of the object cross-section 50 in a direction perpendicular to the course of the partial section 511. Finally, a further trajectory 502 lies between the partial section 512 and the edge 51 of the object cross-section 50 in a direction perpendicular to the course of the partial section 512. Thus, according to the invention, the trajectory 501 can be defined as the starting trajectory, since there is at least one partial section of the trajectory 501 in which at least one further trajectory lies between the starting trajectory and the edge.

[0103] While the preferred case was explained with reference to Fig. 5a, in which the distance of the subsections or points of the starting trajectory from the edge was determined in a direction perpendicular to the course of the subsections or the starting trajectory through the points, determining the distance in this way is not absolutely necessary, as will be explained with reference to Figs. 5b and 5c. Fig. 5b shows a starting trajectory 505 and two further trajectories 555 and 556. The trajectories 555 and 556 lie between the starting point 550 of the starting trajectory 505 and the edge 51 of the object cross-section 50. In particular, the trajectories 555 and 556 lie in a direction parallel to the course of the starting trajectory (more precisely in a course direction of the initial section of the starting trajectory) between the starting point 550 of the starting trajectory 505 and the edge 51 of the object cross-section 50. While in the example of Fig.While in Fig. 5a the distance between linear subsections of the starting trajectory and the edge was determined, here the distance of a single point of the starting trajectory, here the starting point, to the edge is determined. In Fig. 5b, according to the invention, trajectory 505 can be defined as the starting trajectory, since then at least one further trajectory lies between at least one point, here the starting point, of the starting trajectory and the edge. As shown in Fig. 5b, trajectories 555 and 556 are neither parallel nor perpendicular to each other. Furthermore, trajectories 555 and 556 are neither parallel nor perpendicular to starting trajectory 505. Fig. 5c shows a starting trajectory 506, a circular arc-shaped section 560 of starting trajectory 506, and trajectories 565 and 566. Trajectories 565 and 566 lie between section 560 of starting trajectory 506 and edge 51 of object cross-section 50.In particular, trajectories 565 and 566 lie in a radial direction of subsection 560 of the starting trajectory, relative to the circular arc shape, between subsection 560 of starting trajectory 506 and edge 51 of object cross-section 50. According to the invention, trajectory 506 can thus be defined as the starting trajectory, since there is at least one point, here even a plurality of points (subsection 560), for which at least one further trajectory lies between the starting trajectory and the edge. As shown in Fig. 5c, trajectories 565 and 566 are neither parallel nor perpendicular to each other. Furthermore, trajectories 565 and 566 are neither parallel nor perpendicular to the (circular arc-shaped) course of subsection 560 of starting trajectory 506.

[0104] As should be illustrated by Figures 5a, 5b, and 5c, the direction in which the additional trajectories lie between the edge and the starting trajectory relative to the direction of the starting trajectory is irrelevant for the implementation of the present invention. The directions of the additional trajectories that lie between a point or subsection of the starting trajectory and the edge are also irrelevant for the implementation of the invention.

[0105] Even if the inventive procedure can improve the uniformity of the thickness of the solidified layer, the greatest thickness in the solidified building material layer within a partial cross-section generally still occurs in the region of the starting trajectory. Since an object to be manufactured generally has many superimposed object cross-sections (corresponding to many superimposed building material layers), adding up the excessive thicknesses in the individual layers can lead to an undesirably large variation in the overall height (extension in the z-direction) of the object. In particular, the variation in height can be so large even during the manufacturing process that it leads to a collision of a coating element with projections of solidified building material protruding upwards from an already solidified layer. Such undesirable behavior can be prevented by means of the method described below with reference to Fig.6a to 6c.

[0106] Fig. 6a shows a top view of a cross-section 60 of an object to be produced by additive manufacturing, which has, for example, a circular shape with an outer edge 61. As in the example of Fig. 4, the scanning of the build material takes place segment by segment in the example of Fig. 6a. As in Fig. 4, for the sake of clarity, only some of the segments are shown that are to be scanned in order to bring about solidification of the build material corresponding to the cross-section 60. As in Fig. 4, the two segments 601 and 602 shown in Fig. 6a have a rectangular shape, with the trajectories along which the area of ​​each segment is scanned being illustrated by arrows.In each segment, the trajectory to be scanned first in this segment is shown with a solid line. In segment 601, this is trajectory 691, and in segment 602, this is trajectory 692. The subsequent trajectories are shown with dashed lines. Since segment 601 is solidified first in the example of Fig. 6a, trajectory 691 is the starting trajectory for cross-section 60 and is shown with a thicker line for identification.

[0107] Fig. 6b shows a plan view of another cross-section 60' through the same object to which Fig. 6a refers. The cross-section 60' refers to a position in the z-direction that is higher than the position to which the cross-section 60 in Fig. 6a refers. In other words, with respect to the orientation of the object in space during its manufacture, the cross-section 60' of Fig. 6b is at a greater height than the cross-section 60 of Fig. 6a. The cross-section 60' is thus assigned a build-up material layer that, during manufacture, lies above the build-up material layer assigned to the cross-section 60 of Fig. 6a.

[0108] For simplicity, cross-section 60' in Fig. 6b has the same shape and size as cross-section 60 in Fig. 6a, and segments 60T and 602' in Fig. 6b have the same shape and size as segments 601 and 602 in Fig. 6a. However, it can be seen that segments 60T and 602' are rotated 25° clockwise relative to the segments in Fig. 6a. Other possible angles of rotation include, for example, 45°, 65°, 85°, 105°, 115°, 125°, 135°, 155°, and 175°. This also applies accordingly to the trajectories in segments 601' and 602', e.g., trajectory 691', which is the first to be consolidated in segment 601', and trajectory 692', which is the first to be consolidated in segment 602'. In Fig. 6b, trajectory 692' is the starting trajectory.

[0109] Fig. 6c shows a top view of the cross sections 60 and 60' of Figures 6a and 6b together with the segments and trajectories shown in Figs. 6a and 6b. The overlay shows that the trajectory 69T, which is the first to be scanned in time in segment 60T of cross section 60', overlaps the starting trajectory 691 of cross section 60. If the segment 60T in cross section 60' were to be solidified first, the trajectory 69T would become the starting trajectory of cross section 60'. At the point where the starting trajectories 691 and 69T overlap, the layer thickness increases would then add up. Depending on the application, adding the layer thickness increases in a small area (in the hypothetical example, the starting trajectories 691 and 69T intersect at only one point) may be acceptable. However, for some applications, the presence of an overlap of the starting trajectories may be disadvantageous or even impossible.This may be undesirable, particularly if layers 60 and 60' are only separated by a small number of additional layers (e.g., fewer than 64 layers, preferably fewer than 32, particularly preferably fewer than 16 layers). Therefore, the example of Fig. 6 provides that in cross-section 60', segment 602' is solidified first, whereby trajectory 692' becomes the starting trajectory for cross-section 60', as also shown in Fig. 6b.

[0110] Fig. 9a and 9b show a further exemplary procedure. Fig. 9a is very similar to Fig. 6a and shows a top view of a cross-section 90 of an object to be produced by additive manufacturing, which object has, for example, a circular shape with an outer edge 91. As in the example of Fig. 6a, the scanning of the build material is carried out segment by segment in the example of Fig. 9a. As in Fig. 6a, for the sake of clarity, only some of the segments are shown that are to be scanned in order to bring about solidification of the build material corresponding to the cross-section 90. As in Fig. 6a, the two segments 901 and 902 shown in Fig. 9a have a rectangular shape, whereby the trajectories along which the area of ​​each segment is scanned are again illustrated by arrows.In each segment, the trajectory to be scanned first in time is shown with a solid line. In segment 901, this is trajectory 991, and in segment 902, this is trajectory 992. The subsequent trajectories are shown in dashed lines. Since segment 901 is solidified first in the example of Fig. 9a, trajectory 991 is the starting trajectory for cross-section 90 and is shown with a thicker line for identification.

[0111] Fig. 9b shows a plan view of another cross-section 90' through the object of Fig. 9a. The cross-section 90' refers to a position in the z-direction that is higher than the position to which the cross-section 90 in Fig. 9a refers. In other words, with respect to the orientation of the object in space during production, the cross-section 90' of Fig. 9b is at a greater height than the cross-section 90 of Fig. 9a. The cross-section 90' is thus assigned a build-up material layer that, during production, lies above the build-up material layer assigned to the cross-section 90 of Fig. 9a.

[0112] For the sake of simplicity, in this example, cross-section 90' in Fig. 9b has the same shape and size as cross-section 90 in Fig. 9a, and segments 90T and 902' in Fig. 9b have the same shape and size as segments 901 and 902 in Fig. 9a. In addition, segments 90T and 902' and the trajectories therein also have the same position and orientation in the build plane or layer plane as segments 901 and 902 and the trajectories therein in Fig. 9a. However, when solidifying cross-section 90', trajectory 90T is not selected as the starting trajectory (and thus segment 90T is selected as the starting segment), but trajectory 902' (and thus segment 902' is selected as the starting segment). This is because if trajectory 99T were selected as the starting trajectory, it would completely overlap starting trajectory 991 during the consolidation of the underlying cross-section 90, causing the layer elevations to add up. As an alternative to the method shown in Fig.Using the procedure shown in Figure 9b, an overlap of the starting trajectories could also be avoided or reduced by spatially offsetting segments 901' and 902' and / or the trajectories contained therein relative to segments 901 and 902 and / or the trajectories contained therein in the layer plane or construction plane (without rotation). Depending on the extent of the offset, the (now spatially offset) trajectory 99T could then be the starting trajectory.

[0113] Finally, it is also possible to select the starting trajectory from the trajectories in a layer, especially a second layer following a first layer, using a random generator. This approach can be chosen in particular if the segment and / or trajectory patterns in the successive layers are identical and / or have the same orientation in the build plane.

[0114] Especially when partial cross-sections in superimposed build-up material layers are scanned segment by segment, a change in the orientation of the trajectories in the layer plane or build-up plane (a rotation) can sometimes ensure that the starting trajectories in the different build-up material layers do not overlap (do not lie on top of each other at any point), even though the scanning sequence of the segments in the different layers is the same.

[0115] In general, it is advantageous if the position and orientation of the trajectories in the plane differ in different layers, as this counteracts the formation of anisotropic properties or preferred directions in the manufactured object. Therefore, if the orientation of the trajectories in superimposed building material layers is the same, then the trajectories in these layers should preferably not lie directly on top of each other, but rather be horizontally offset from each other, especially in a direction perpendicular to the direction of the trajectories.

[0116] A simple way to prevent anisotropies is to change the orientation of the trajectories in the subsequent layer, or at least in the layer after that. Assuming that the shape of the trajectories does not change from layer to layer, a change in the orientation of the trajectories corresponds to a rotation in the build plane or layer plane. Preferably, the angle of rotation should not be an integer part of 360°, and especially preferably should not have a common factor of 360° other than one. This prevents the orientation of the trajectories from repeating in different build material layers.

Claims

Patent claims 1. A computer-assisted method for providing control data for an additive manufacturing device (1) for producing a three-dimensional object (2) by means of the same, wherein the additive manufacturing device is designed such that objects are produced by means of the additive manufacturing device by applying a build-up material layer upon layer and solidifying the build-up material in a layer plane (7) by supplying radiant energy to those locations in each layer that are associated with an object cross-section in this layer, wherein the method for providing control data comprises: a first step (S1) of accessing computer-based model data of a number of partial cross-sections of the object to be produced, each of which comprises a partial area of ​​an object cross-section and a portion of the edge of this object cross-section, a second step (S2) of generating a data model of the number of partial cross-sections,wherein the data model specifies scanning of the locations of the number of partial cross-sections with a number of rays (22) along a plurality of trajectories (54) in the layer plane (7), wherein in at least one of the number of partial cross-sections, an order of scanning of the trajectories is defined such that a starting trajectory is scanned first, wherein at least one point of the starting trajectory is spaced from the edge of the object cross-section in the layer plane such that at least one further trajectory lies between the at least one point and the edge, preferably at least two further trajectories lie between the at least one point and the edge, and a third step (S3) in which control data corresponding to the data model generated in the second step (S2) are provided for generating a control data set for producing the object by means of the additive manufacturing device.

2. The method according to claim 1, wherein in the second step (S2) a data model of at least one partial cross-section in a first building material layer and at least one partial cross-section in an overlying second building material layer is generated and a starting trajectory is selected for the partial cross-section in the second building material layer which at most partially, preferably not at all, overlaps with the starting trajectory for the partial cross-section of the first building material layer.

3. The method according to claim 2, wherein the starting trajectory in the partial cross-section of the second building material layer is selected such that it has a different distance from the edge of the object cross-section in the layer plane than the starting trajectory in the partial cross-section of the first building material layer, wherein the different distance is characterized in that a different number of further trajectories lies between the starting trajectory or a point thereof and the edge.

4. The method according to claim 2 or 3, wherein the trajectories in the second building material layer are rotated relative to the trajectories in the first building material layer by an angle different from 0°, 90° and 270°.

5. The method according to claim 4, wherein the trajectories in the second building material layer are rotated by an angle greater than 90° and / or less than 270° relative to the trajectories in the first building material layer.

6. The method according to claim 5, wherein the angle is greater than 120° or less than 120°, preferably greater than 100° and less than 140°.

7. Method according to one of the preceding claims, wherein the starting trajectory is selected from the plurality of trajectories to be scanned in the partial cross-section using a random generator.

8. Method according to one of the preceding claims, wherein the trajectories in a second building material layer have the same shape and orientation to one another as the trajectories in a first building material layer.

9. Method according to one of the preceding claims, wherein a partial cross-section is solidified segment by segment, wherein a segment corresponds to a partial area of ​​the partial cross-section and each segment is solidified by scanning along a plurality of trajectories in the layer plane (7).

10. The method according to claim 9, wherein the segments have a rectangular shape and the trajectories in the segments enclose an angle between 5° and 175°, preferably between 45° and 135°, particularly preferably between 85° and 95°, with an edge of the segment.

11. The method according to claim 10, wherein a trajectory lying in one of the segments is defined as the starting trajectory, wherein the starting trajectory is defined such that it is scanned in a direction pointing away from a boundary of the segment to an adjacent neighboring segment, and wherein the first of the trajectories to be scanned in the adjacent neighboring segment is defined such that it is scanned starting at a location adjacent to the starting trajectory in a direction pointing away from the boundary.

12. Device for providing control data for an additive manufacturing device (1) for producing a three-dimensional object (2) by means of the same, wherein the additive manufacturing device is designed such that objects are produced by means of the additive manufacturing device by applying a building material layer upon layer and solidifying the building material in a layer plane (7) by supplying radiant energy to those locations in each layer which are assigned to the cross-section of the object in this layer, wherein the device for providing control data comprises: an access unit configured to access computer-based model data of a number of partial cross-sections of the object to be produced, each of which comprises a partial area of ​​an object cross-section and a portion of the edge of this object cross-section, a data model generation unit configured to generate a data model of the number of partial cross-sections, wherein the data model specifies scanning of the locations of the number of partial cross-sections with a number of rays (22) along a plurality of trajectories (54) in the layer plane (7), wherein the data model generation unit is configured to specify an order of scanning of the trajectories in at least one of the number of partial cross-sections such that a starting trajectory is scanned first, wherein at least one point of the starting trajectory is spaced from the edge of the object cross-section in the layer plane in such a way thatthat at least one further trajectory lies between the at least one point and the edge, preferably at least two further trajectories lie between the at least one point and the edge, and a control data provision unit which is designed to provide control data corresponding to a data model generated by the data model generation unit for the generation of a control data set for the production of the object by means of the additive manufacturing device.

13. Method for controlling an energy input device of an additive manufacturing device (1) for producing a three-dimensional object (2) 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 in a layer plane (7) by supplying radiant energy to those locations in each layer which are assigned to the cross-section of the object in this layer, wherein the additive manufacturing device for supplying radiant energy has an energy input device which is designed to solidify a number of partial cross-sections of the object to be produced, each of which forms a partial area of ​​an object cross-section as well as a portion of the edge of this object cross-section comprises scanning the locations of the number of partial cross-sections with a number of beams (22) along a plurality of trajectories (54) in the slice plane (7), wherein in the method, for at least one of the number of partial cross-sections, an order of scanning of the trajectories is defined such that a start trajectory is scanned first, wherein at least one point of the start trajectory is spaced from the edge of the object cross-section in the slice plane such that at least one further trajectory lies between the at least one point and the edge, preferably at least two further trajectories lie between the at least one point and the edge.

14. Additive manufacturing method for producing a three-dimensional object (2) by means of an additive manufacturing device, wherein a method according to claim 13 is carried out in the additive manufacturing method.

15. A device for controlling an energy input device of an additive manufacturing device (1) for producing a three-dimensional object (2) by means of the same, wherein the objects are produced by means of the additive manufacturing device by applying a building material layer upon layer and solidifying the building material in a layer plane (7) by supplying radiant energy to those locations in each layer that are associated with the cross-section of the object in this layer, wherein the additive manufacturing device for supplying radiant energy has an energy input device that is designed to solidify a number of partial cross-sections, each of which comprises a partial area of ​​an object cross-section and a portion of the edge of this object cross-section, by scanning the locations of the number of partial cross-sections with a number of beams (22) along a plurality of trajectories (54) in the layer plane (7),the device comprises a scanning control unit which is designed to specify a sequence of scanning of the trajectories for at least one of the number of partial cross-sections such that a starting trajectory is scanned first, wherein at least one point of the starting trajectory is from the edge of the object cross-section in, the layer plane is spaced such that at least one further trajectory lies between the at least one point and the edge, preferably at least two further trajectories lie between the at least one point and the edge.

16. Additive manufacturing device for producing a three-dimensional object (2) by means of the same, wherein the additive manufacturing device comprises a device according to claim 15.

17. A computer program comprising a sequence of instructions which, when executed, implements a method according to any one of claims 1 to 11 and / or a method according to any one of claims 13 or 14.

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