Apparatus and Method for Producing a Three-Dimensional Shaped Object

Abstract

The invention relates to an apparatus and to a method for producing a three-dimensional shaped object by means of material application in layers S.sub.n (n=1 to N), which has at least a material dispensing device, a drive device, a print substrate, a control device having a data memory, and a material removal device. In order to be able to recognize and eliminate defects in a layer S.sub.n, which can still occur later, i.e., after completion of this layer S.sub.n, it is proposed, according to the invention, to provide a monitoring device. Furthermore, a downstream evaluation device determines a layer S.sub.x in which the at least one defect was detected. Thereupon an error signal is generated and passed on to the control device. The material removal device completely removes the material of a partial region of the shaped object, from the layer S.sub.N that was last printed, down to the first of the defective layers S.sub.x. Building up the three-dimensional shaped object begins anew at the layer S.sub.x−1.

Claims

1. An apparatus for producing a three-dimensional shaped object by means of material application in layers S.sub.n where n=1 to N, having: at least one material dispensing device for applying material that can be solidified physically or chemically to a print substrate or to a solidified layer S.sub.n of the shaped object situated on it; a drive device for positioning the print substrate and the at least one material dispensing device relative to one another; a control device having a data memory, for storing image data of the three-dimensional shaped object, wherein the control device stands in a control connection with the drive device and the at least one material dispensing device; a monitoring device for checking the layers S.sub.n of the three-dimensional shaped object, wherein the monitoring device is followed by an evaluation device; a material removal device, wherein the evaluation device and the material removal device stand in a control connection with the control device, and the material dispensing device is followed by a leveling device for leveling the layer S.sub.n that has been applied, in each instance, wherein the evaluation device is configured for determining a layer S.sub.n where n=x, in which layer at least one defect was detected by the monitoring device, for checking the layers S.sub.n where n=x+1, x+2 . . . that follow the defective layer S.sub.x for a defective geometry change of the shaped object, which change exceeds a predetermined dimension, for generating an error signal for the layer S.sub.x in the case of a defective geometry change of the subsequent layers S.sub.n where n=x+1, x+2 . . . , and for passing the generated error signal for this first one of the defective layers S.sub.x on to the control device; that the material removal device is structured for removing the material of a partial region of the three-dimensional shaped objects, from the layer S.sub.N last printed down to the first of the defective layers S.sub.x, for which an error signal was generated, wherein the material removal device is configured in such a manner that during removal of the material, complete layers S.sub.n can be removed.

2. The apparatus according to claim 1, wherein the partial region of the three-dimensional shaped objects comprises, from the last layer S.sub.N that was printed, down to the defective layer S.sub.x, at least one preferably complete layer S.sub.n, in particular between two and four preferably complete layers S.sub.n, preferably more than four preferably complete layers S.sub.n.

3. The apparatus according to claim 1, wherein the material removal device is configured for chip-removing machining, in particular by means of milling, grinding, preferably polishing and/or scraping.

4. The apparatus according to claim 1, wherein the material removal device is configured in such a manner that during removal of the material, the thickness of one layer S.sub.n or the thickness of at least two layers S.sub.n can be removed, preferably completely.

5. The apparatus according to claim 1, wherein the monitoring device is configured as an optical monitoring device, in particular a CCD camera, a CCD camera in combination with a laser beam, an optical or mechanical scanning device, a device that measures layer thickness or a measuring laser.

6. The apparatus according to claim 1, wherein the material dispensing device is configured in such a manner that it can be brought into a parked position, at which a service station for checking a function problem of the material dispensing device and for correcting the possible function problem is arranged.

7. The apparatus according to claim 1, wherein the print substrate is mounted so as to rotate about an axis of rotation, relative to the at least one material dispensing device.

8. The apparatus according to claim 1, wherein the drive device is configured for positioning the material dispensing device relative to the print substrate, which is in a fixed position in the vertical direction, or for positioning the print substrate relative to the material dispensing device, which is fixed in place in the vertical direction.

9. The apparatus according to claim 1, wherein the material removal device has a material removal tool for chip-removing machining of the shaped object, wherein the material removal tool spans the print substrate in at least one expanse, in such a manner that the material removal device completely removes the layers S.sub.N to S.sub.x.

10. The apparatus according to claim 9, wherein the material removal device and print substrate can be moved relative to one another by a certain height, wherein the height is predetermined by the evaluation device in accordance with the partial region of the defective layers S.sub.N to S.sub.x of the shaped object that is to be removed, and that the material removal tool removes the complete layers S.sub.N to S.sub.x in one work step.

11. The apparatus according to claim 9, wherein the material removal tool of the material removal device has a longitudinal expanse along an axis, can rotate about its axis, and is configured to be cylindrical or conical.

12. A method for producing a three-dimensional shaped object by means of material application in layers S.sub.n where n=1 to N, having the following steps: applying material that can be solidified physically or chemically to a print substrate in layers S.sub.n; checking the three-dimensional shaped object with regard to at least one existing defect; leveling each layer S.sub.n that is applied, in each instance; determining a layer S.sub.x of the three-dimensional shaped object, in which layer the at least one defect was detected; checking the subsequent layers S.sub.n, where n=x+1, x+2 . . . , for defective geometry changes of the shaped object, wherein an error signal is generated for this first one of the defective layers S.sub.x and passed on to a control device if a defective geometry change of the subsequent layers S.sub.n where n=x+1, x+2 . . . was detected, which change exceeds a predetermined dimension; the material application in layer S.sub.N is stopped in accordance with the error signal; in the image data of the shaped object, a slicer indicator is set to the first defective layer S.sub.x; a partial region of the three-dimensional shaped object is removed from the last layer S.sub.N that was printed, down to the defective layer S.sub.x for which an error signal was generated, wherein the layers S.sub.N to layer S.sub.x are completely removed, and afterward the layers that were previously removed, and possible further layers are applied and checked, layer by layer, until completion of the shaped object.

13. The method according to claim 12, wherein the partial region of the three-dimensional shaped objects, of the last layer S.sub.N that was printed, down to the defective layer S.sub.x, comprises at least one preferably complete layer S.sub.n, in particular between two and four preferably complete layers S.sub.n, preferably more than four preferably complete layers S.sub.n.

14. The method according to claim 12, wherein the layers S.sub.n are removed by chip cutting, in particular by means of milling, preferably polishing, grinding and/or scraping.

15. The method according to claim 12, wherein during removal of the material, the thickness of one layer S.sub.n or the thickness of at least two layers S.sub.n is removed, preferably completely.

16. The method according to claim 12, wherein the print substrate is rotated about an axis of rotation.

17. The method according to claim 12, wherein a material dispensing device is positioned relative to the print substrate, which is fixed in place in the vertical direction, or the print substrate is positioned relative to the material dispensing device, which is fixed in place in the vertical direction, by means of a drive device.

18. The method according to claim 12, wherein an object indicator follows the slicer indicator until the first defective layer S.sub.x has been reached.

19. The method according to claim 12, wherein the layers are applied to the print substrate or to the solidified layer of the shaped object that is situated on it by means of a material dispensing device, and that between the generation of the error signal and the subsequent application of a new layer S.sub.n, the material dispensing device is checked for a function problem, and—if a function problem is detected during this process—it is corrected.

20. The method according to claim 12, wherein the layers S.sub.N to layer S.sub.x are completely removed in one work cycle.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0046] Further details, characteristics, and advantages of the present invention will become evident from the following description of the exemplary embodiments of an apparatus for producing a three-dimensional shaped object, making reference to the drawings.

[0047] The figures show:

[0048] FIG. 1 a schematic representation of the apparatus in an arrangement according to a first exemplary embodiment,

[0049] FIG. 2 a side view of a shaped object and of a related image data model in the printing process,

[0050] FIG. 3 a side view of the shaped object and of the related image data model after defect detection,

[0051] FIG. 4 a side view of the shaped object and of the related image data model at the beginning of the dismantling process of a first exemplary embodiment,

[0052] FIG. 5 to

[0053] FIG. 8 a side view of the shaped object and of the related image data model of the first exemplary embodiment during the dismantling process,

[0054] FIG. 9 a side view of the shaped object and of the related image data model of the first exemplary embodiment after the dismantling process,

[0055] FIG. 10 a side view of the shaped object and of the related image data model of the first exemplary embodiment at the beginning of the new printing process,

[0056] FIG. 11 a side view of the shaped object and of the related image data model of the first exemplary embodiment after completion of the new printing process,

[0057] FIG. 12 a schematic representation of the apparatus in an arrangement according to a second exemplary embodiment,

[0058] FIG. 13 a side view of the shaped object and of the related image data model at the beginning of the dismantling process of the second exemplary embodiment,

[0059] FIG. 14 a side view of the shaped object and of the related image data model of the second exemplary embodiment after the dismantling process,

[0060] FIG. 15 a side view of the shaped object and of the related image data model of the second exemplary embodiment at the beginning of the new printing process,

[0061] FIG. 16 a side view of the shaped object and of the related image data model of the second exemplary embodiment after completion of the new printing process,

[0062] FIG. 17 a perspective side view of the material removal device with a cylindrical material removal tool,

[0063] FIG. 18 a perspective side view of the material removal device with a conical material removal tool, and

[0064] FIG. 19 a top view of the material removal device according to FIG. 18.

DESCRIPTION OF THE INVENTION

[0065] In the following, the invention will be described in detail in the form of exemplary embodiments, using the aforementioned figures. In all the figures, the same technical elements are identified with the same reference symbols.

[0066] FIG. 1 shows an apparatus 100 according to the invention in an arrangement according to a first exemplary embodiment. The apparatus 100 serves to produce a three-dimensional shaped object 200 and to remove a partial region T of the shaped object 200, which has a defective layer S.sub.x. The three-dimensional shaped object 200 is applied in layers S.sub.n. For this purpose, the apparatus 100 has a material dispensing device 300 for applying the material in layers S.sub.n. The first layer S.sub.n where n=1 is applied to a print substrate 400. The material dispensing device 300 is followed by a leveling device 310 which prevents a material excess from forming on the applied layer S.sub.n. Furthermore, the apparatus 100 has a material removal device 700 for removing a partial region T of the applied material from the uppermost layer S.sub.N down to a defective layer S.sub.x, where x: {1, . . . , N}. In the following we will speak of the first layer S.sub.n applied to the print substrate 400, where n=1, as the lowermost layer. The last layer S.sub.N applied is referred to as the uppermost layer. The uppermost layer S.sub.N can be the last layer with which the three-dimensional shaped object 200 was completed, or any desired layer before completion of the shaped object 200, at which the printing process is interrupted due to defect detection. Both the material dispensing device 300 and the material removal device 700 are controlled by a control device 500. The control device 500 has a data memory 510, in which image data 210, as shown in the following figures, of the three-dimensional shaped object 200 to be produced have been stored. Furthermore, the control device 500 controls a drive device 410 that positions the print substrate 400 and the material dispensing device 300 relative to one another. In this first exemplary embodiment, the drive device 410 positions the print substrate 400 relative to the material dispensing device 300, which is configured to be fixed in place in the vertical direction. This takes place in such a manner that during the layer-by-layer material application in layers S.sub.n, the print substrate 400 is moved downward in the vertical direction, and during layer-by-layer material removal of the layers S.sub.N to x, the print substrate 400 is moved upward in the vertical direction, in the direction of the material removal device 700, which is also configured to be fixed in place in the vertical direction in this exemplary embodiment. The movement direction of the print substrate 400, which is brought about by means of the drive device 410, is symbolized with vertical double arrows.

[0067] Furthermore, the apparatus 100 of the first exemplary embodiment shown in FIG. 1 has a monitoring device 600, which is followed by an evaluation device 610. The monitoring device 600 checks the three-dimensional shaped object 200 for possible defects that have occurred.

[0068] In order to detect and correct a damaged, i.e., defective layer S.sub.x, which might occur during the printing processes, in or on the three-dimensional shaped object 200, the three-dimensional shaped object 200 is checked by the monitoring device 600. For example, the defect is recognized by means of a comparison of the shaped object 200, which was formed from multiple layers S.sub.n to N, with the predetermined image data of the three-dimensional shaped object 200, which are stored in the data memory 510. The evaluation device 610 arranged between the monitoring device 600 and the control device 500 evaluates the detected defect and assigns a layer S.sub.x where x: {1, . . . , N} to the defect found by the monitoring device 600. The evaluation device 610 checks the subsequent layers S.sub.n where (n=x+1, n=x+2, etc.) for a defective geometry change of the shaped object 200, which change exceeds a predetermined dimension, and thereupon generates an error signal. The error signal generated for this first one of the defective layers S.sub.x is passed on to the control device 500. The printing process is stopped by the control device 500, because a defect has occurred in a layer S.sub.n, which defect has effects on the subsequent layers, and a dismantling process for removing the material of a partial region T of the previously printed three-dimensional shaped object 200 is initiated. This dismantling process is described in FIGS. 3 to 8.

[0069] In the case of alternative embodiments, the monitoring device 600 and the evaluation device 610 can be replaced by inspection personnel. Other than that, the apparatus 100 according to the invention functions as in the case of the first and second exemplary embodiment. The inspection personnel or monitoring personnel detect the defect on the basis of their technical knowledge, and enter the data for this first one of the defective layers S.sub.x by way of an input terminal, so that the control device 500 processes the data that have been input further, as described above. In this regard, the inspection personnel can undertake entry of the depth of the material to be removed also by means of thickness information (displacement path for the milling device in the Z axis) in millimeters, and the control device (500) calculates how many layers fit into the indicated millimeter entry, and sets the slicer indicator Z.sub.S to the calculated position of the layer S.sub.x.

[0070] FIG. 2, on the left side, shows the three-dimensional shaped object 200, and, on the right side, shows the corresponding image data 210 of the shaped object 200. Schematically, an object indicator Z.sub.o and a slicer indicator Z.sub.S are shown. The slicer indicator Z.sub.S detects the layer data of a layer S.sub.n that is to be printed in accordance with the image data 210. The object indicator Z.sub.o, which corresponds to the corresponding layer S.sub.n on the printer side, follows the slicer indicator Z.sub.S, so as to control, i.e., position the material dispensing device 300 accordingly. In this way, the layers S.sub.n of the shaped object 200 are printed in accordance with the image data 210. Once a layer S.sub.n−1 has been completely printed, the slicer indicator Z.sub.S jumps to the next layer S.sub.n to be printed, and the object indicator Z.sub.o follows, so that the layer S.sub.n is applied to the layer S.sub.n−1. This process is continued until the three-dimensional shaped object has been completed, or a defect is detected by the monitoring device 600 or the inspection personnel.

[0071] FIG. 2 shows a defect-free printing process, in which the three-dimensional shaped object 200 was printed without defects and all the layers S.sub.n where n=1 to n=N were built up correctly. To apply the material, the print substrate 400 according to the first exemplary embodiment was moved vertically. This representation and the representations of the shaped object 200 as well as of the image data 210 in the following figures apply analogously for the second exemplary embodiment and for the alternative embodiments of the apparatus 100 as described above.

[0072] Starting from FIG. 3, it is assumed that the monitoring device 600 or the monitoring/inspection personnel has detected a defect that has effects on the subsequent layers. The corresponding layer S.sub.n is assigned to this defect by means of the evaluation device 610. As an example, let us assume that the defect is situated in the layer S.sub.n−1 of the printed shaped object 200. The printing process is stopped. The slicer indicator Z.sub.S of the image data 210 is set to the first one of the defective layers S.sub.x, here to the layer S.sub.n−1 that was chosen as an example.

[0073] As soon as the printing process is stopped because a defect occurred in a layer S.sub.n, the material dispensing device 300 is moved to a parked position and releases the working position for the material removal device 700. In this way, a dismantling process for removing the material of a partial region T of the previously printed three-dimensional shaped object 200 is initiated.

[0074] While the material dispensing device 300 is in the parked position, it is checked by the service device for any functional problems. The service that is performed by the service device eliminates the problem, so that after removal of the defective layers, in other words after the dismantling process as described in the following, the material dispensing device 300 can apply the material layer by layer, without problems. This dismantling process will be described using FIGS. 4 to 8.

[0075] In FIG. 4, the material removal device 700 is already in the working position, so as to remove the material of the corresponding partial region T. In this example, the partial region T comprises the layers n to n−1. The object indicator Z.sub.o contains the data of the corresponding layer that is being removed and follows the slicer indicator Z.sub.S. Likewise, depending on the properties of the material removal device 700, one or more layers S.sub.n can be removed in a layer-by-layer working pass of the dismantling process. As an example, removal of one layer S.sub.n, in each instance, is shown in this and in the following figures.

[0076] According to FIG. 5, the object indicator Z.sub.o continues to follow the slicer indicator Z.sub.S, which stands on the defective layer n−1 until it is removed. FIG. 5 shows the dismantling process for the layer N−1, since the layer N has already been removed. For this purpose, the print substrate 400 was moved, by the drive device 410, to the height of the material removal device 700, in other words, in this example, vertically upward by one layer thickness of the printed shaped object 200, since here one layer thickness, in each instance, is being removed as an example. Analogous to FIG. 5, in FIG. 6 the print substrate 400 is moved further vertically upward by the drive device 410, so that the next layer S.sub.n+1 of the shaped object 200 can be removed by the material removal device 700. The broken-line layers S.sub.N and S.sub.N-1 of the image data 210 on the right side of the figure indicate that these layers S have already been removed.

[0077] The dismantling process is continued in accordance with the process described above, so as to remove the layers, individual ones or multiple ones. This is shown schematically in FIG. 7 for the layer n and in FIG. 8 for the layer x=n−1. Only when the object indicator Z.sub.o and the slicer indicator Z.sub.S stand on the same layer, here n−1, is the material removal device 700 stopped once again. In this way, it is guaranteed that all the layers down to the detected defective layer S.sub.x with x=n−1 were completely removed, and the dismantling process is terminated.

[0078] The material removal device 700 is moved to a parked position, and the material dispensing device 300 is moved to the working position, as shown in FIG. 9 for the first exemplary embodiment. Since the shaped object 200 was defective, the printing process now has to be started over again, so as to produce a defect-free shaped object 200.

[0079] FIG. 10 illustrates the printing process using the first exemplary embodiment. As can be seen in the representation of the three-dimensional shaped object 200 on the left, in each instance, the previously first one of the defective layers S.sub.x with x=n−1 was re-applied by the material dispensing device 300 and leveled, in other words smoothed by the leveling device 310. In this process, the material removal device 700 was raised or moved aside. The material application process is continued until the shaped object 200 has been printed entirely without defects. The material application continues until the object indicator Z.sub.O has reached the position of the slicer indicator Z.sub.S.

[0080] FIG. 11 shows the shaped object 200 after renewed application of the layers n=x to N, in other words at the end of the new printing process. The print substrate 400 has been moved into the starting position again by the drive device 410, and the uppermost layer N has been completely applied. The material removal device 700 is in the parked position. If a defect has been detected before final completion of the shaped object, then the printing process can be continued (after removal of damaged layers) until the shaped object has been entirely completed. During this process, the removed layers are re-applied.

[0081] FIG. 12 shows a second exemplary embodiment for positioning the print substrate 400 and material dispensing device 300 relative to one another. In contrast to the exemplary embodiment according to FIG. 1, the drive device 410 in FIG. 12 is arranged on the material dispensing device 300, so as to move it vertically, and the print substrate 400 is configured fixed in place in the vertical direction. The direction of the movement of the material dispensing device 300, which is brought about by the drive device 410, is symbolized with vertical double arrows. In this exemplary embodiment the material dispensing device 300 is moved vertically upward by the drive device 410 during application of the material in layers S.sub.n onto the print substrate 400, so as to produce the three-dimensional shaped object 200. During material removal, the drive device 410 moves the material removal device 700 downward in the vertical direction, in the direction of the print substrate 400, as will still be described in greater detail in FIG. 13. Regardless of the alternative placement of the drive device 410 as shown in this figure, the apparatus 100 functions in precisely the same manner as described with reference to FIG. 1.

[0082] In FIG. 13, the beginning of the dismantling process is shown for the second exemplary embodiment. In the case of the second exemplary embodiment, it is also assumed that a defect was detected in the layer n−1, which defect has effects on the subsequent layers, and therefore the dismantling process is initiated. As has already been mentioned, the material removal device 700 is moved vertically downward relative to the print substrate 400, which is configured fixed in place in the vertical direction. The arrow indicates the direction in which the drive device 410 moves the material removal device 700, layer by layer. Regardless of the alternative placement of the drive device 410 as shown in this figure, the dismantling process functions in precisely the same manner as described above with reference to FIGS. 5 to 9 of the first exemplary embodiment.

[0083] FIG. 14 shows how the material removal device 700 is in a parked position, since the material removal by means of the dismantling process has been concluded. The material dispensing device 300 is moved to the working position. Since the shaped object 200 was defective, the printing process now has to be started over again, so as to produce a defect-free shaped object 200. This material application begins in the layer n−1, at which the slicer indicator Z.sub.S and also the object indicator Z.sub.O are standing. As described above, the material application takes place by means of the material dispensing device 300; the leveling device 310 that follows the material dispensing device 300 prevents a material excess, and the shaped object 200 is newly built up. FIG. 15 illustrates the printing process, proceeding from the layer n−1, which was already completely built up anew in this view. The material dispensing device 300 is already standing at the next layer n, at which the slicer indicator Z.sub.S in the image data and, accordingly, the object indicator Z.sub.O are set.

[0084] As can already be seen in the representation of the three-dimensional shaped object 200 on the left, in each instance, the previously defective layer S.sub.x where x=n−1 is newly applied by the material dispensing device 300. The material application process is continued until the shaped object 200 is printed completely without defects; this is shown in FIG. 16. Analogous to FIG. 11 of the first exemplary embodiment, in this second exemplary embodiment the material dispensing device 300 has been moved back to the starting position again by the drive device 410, and the uppermost layer N has been completely applied. The material removal device 700 is in the parked position. The shaped object has been completed after defect-free material application. If the determination of a defect still took place before complete completion of the shaped object, then the printing process can be continued (after removal of damaged layers) until the shaped object has been completely completed. During this process, the removed layers are applied once again.

[0085] The material removal device 700 has a material removal tool that is suitable for full-area or complete removal of layers S.sub.x of the shaped object 200. For this purpose, the material removal tool extends over the printing width of the shaped object to be printed, in other words it spans the print substrate in terms of its printed width.

[0086] In FIGS. 17 to 19, exemplary embodiments of the material removal device 700 are shown in their perspective view, so as to illustrate that the material removal device 700 removes the material of one or more layers completely, in one work cycle.

[0087] FIG. 17 shows an embodiment of the material removal tool of the material removal device 700 in a longitudinal expanse along an axis 710. Only as an example, a milling machine is shown here. The material removal device 700 with its material removal tool can also be configured as further usual chip-cutting tools, without rotating about the axis 710. This holds true, in particular, for material removal tools that work in a planar manner, for example grinding, eroding or polishing material removal tools. The elongated material removal tool shown is suitable for a Cartesian system, since the material removal takes place uniformly over the full area, with a slight excess length beyond the width or the length of the print substrate 400, also called printing width, onto which the shaped object is applied. During the removal of the material, the elongated material removal tool of the material removal device 700 rotates about its axis 710. Since the dismantling process takes place independent of the type of defect, the local place of occurrence in a layer, and the size or dimension of a defect, the material is removed over the full surface area. To increase the speed, the layer can be removed not just over the full area, in other words completely, but rather—as has already been described in the other figures—multiple layers are also removed in this one working cycle of the material removal. Therefore, not only the productivity but also the quality of the three-dimensional shaped object 200 to be produced can increase, since the repair is not carried out in a minimalist manner but rather over a large surface area.

[0088] In FIG. 18, the elongated material removal tool of the material removal device 700 is shown in a conical embodiment, and also mounted so as to rotate about its axis 710. The elongated material removal tool is used for chip-removing machining in a polar printing system. As an example in this figure, as well, the material removal tool is shown so as to rotate, as it is used for milling away the defective layers. The material removal tool can also be configured to be fixed in place for chip-removing material removal along its axis 710.

[0089] FIG. 19 shows, in a top view, the material removal device 700 for the exemplary embodiment according to FIG. 18. In this representation it can be seen how the material removal device 700 extends over the entire width of the region to be printed, analogous to the Cartesian system according to FIG. 17. In FIG. 19, a ring-shaped printed field of a rotating print substrate 400 is shown as the printed region. The material removal device 700 extends laterally, in each instance, beyond the imprintable region, so as to undertake material removal in one work pass, over the full area. The print substrate 400 has rotation symmetry to an axis of rotation 420.

REFERENCE SYMBOL LIST

[0090] 100 apparatus [0091] 200 shaped object [0092] 210 image data of the shaped object [0093] 300 material dispensing device [0094] 310 leveling device [0095] 400 print substrate [0096] 410 drive device [0097] 420 axis of rotation [0098] 500 control device [0099] 510 data memory [0100] 600 monitoring device [0101] 610 evaluation device [0102] 700 material removal device [0103] 710 axis [0104] 800 service station [0105] T partial region [0106] S layer [0107] n n: {1 to N} where n=whole positive number [0108] N last layer that was printed [0109] x defective layerx: {1, . . . , N} [0110] Z.sub.o object pointer [0111] Z.sub.S slicer pointer