DEVICE AND METHOD FOR THE ADDITIVE MANUFACTURE OF A WORKPIECE

Abstract

A device for additive manufacturing of a workpiece (10; 30) having a cell-like building space (24) for the workpiece to be built, preferably layer by layer, and an additive manufacturing unit (14; 34, 36) provided on or in the building space, wherein a workpiece measurement apparatus (16, 18, 20; 40, 42; 82, 86) is provided on or in the building space such that the workpiece measurement apparatus that provides the workpiece with irradiation from an irradiation source has a detector unit (22; 42) configured to detect an irradiation image of the workpiece provided with the irradiation on and/or through an outer wall of the workpiece, and/or to detect a nuclear spin image of the workpiece provided with the magnetic field excitation, and to generate workpiece measurement data from the irradiation image or the nuclear spin image.

Claims

1. A device for additive manufacturing of a workpiece (10; 30) having a cell-like building space (24) for the workpiece to be built, and additive manufacturing means (14; 34, 36) provided on or in the building space, wherein workpiece measurement means (16, 18, 20; 40, 42; 82, 86) are provided and realized on or in the building space in such a manner that the workpiece measurement means providing the developing or completed workpiece with irradiation from an irradiation source (16; 40) and/or a nuclear spin magnetic field excitation have detector means (22; 42), which are configured to detect an irradiation image of the workpiece provided with the irradiation on and/or through an outer wall of the workpiece and/or to detect a nuclear spin image of the workpiece provided with the magnetic field excitation and to generate workpiece measurement data from the irradiation image or the nuclear spin image.

2. The device according to claim 1, wherein the irradiation source is configured to generate X-rays and/or ionizing radiation at least partially penetrating the workpiece and the detector means are configured to detect the irradiation image which is or can be generated by the radiography and are disposed relative to the workpiece and to the irradiation source.

3. The device according to claim 1, wherein the irradiation source (82, 86) is configured to project an image pattern which has dots, lines and/or stripes and/or which is in the visible spectral range onto the workpiece outer wall (80, 84) and wherein the detector means (82, 86) configured to optically detect the image pattern are disposed in order to perform an optical measurement method in a predefined angle relation to the irradiation source which allows triangulation.

4. The device according to claim 1, wherein the additive manufacturing means have manufacturing process control means (54) for controlling the building of the workpiece and wherein manufacturing correction means (70) are assigned to and/or connected upstream of the manufacturing process control means in such a manner that the building can be changed or ended in response to a correction signal of the manufacturing correction means, wherein the workpiece measurement data generated by the detector means or reconstruction data generated therefrom can be processed by the manufacturing correction means.

5. The device according to claim 4, wherein measurement specification means (72) and comparison means are assigned to the manufacturing correction means (70) in such a manner that the manufacturing correction means can realize a data comparison of the generated workpiece measurement data with measurement specification data for the developing and/or completed workpiece and have tolerance and/or threshold means by means of which a workpiece complying with the specifications, a correctable developing workpiece and/or a reject workpiece can be determined.

6. The device according to claim 1, wherein the detector means and/or the irradiation source are directed at the outer wall in such a manner that only one outer wall section of a finished contour and/or made of solid or solidified layer material is irradiated or detected during the building of a workpiece built layer by layer, wherein the irradiated and/or detected outer wall section has a distance from a layer material of the wall in the melted state.

7. The device according to claim 1, wherein the irradiation source and the detector means are provided and configured to be movable in relation to a support (12; 32) of the built workpiece or workpiece to be built in the building space, in a fixed relative position to one another.

8. The device according to claim 7, wherein a single-line or multiline line detector (42) of the detector means is assigned to the irradiation source (40) realized as an X-ray source in such a manner that a detector height of the line detector is smaller than a height of the built workpiece.

9. A method for additive manufacturing of a workpiece, claim 1, wherein additive manufacturing means being provided on or in a cell-like building space for the workpiece to be built, comprising the following steps: providing the developing workpiece with irradiation from an irradiation source and/or providing the workpiece with a nuclear spin magnetic field excitation; detecting an irradiation image of the irradiation and/or of a nuclear spin image of the magnetic field excitation by detector means; generating workpiece measurement data from the irradiation image and/or from the nuclear spin image; comparing the workpiece measurement data with workpiece specification data and influencing the building process by the additive manufacturing means in response to comparison data of the comparison.

10. The method according to claim 9, wherein the sequence of the method steps is repeated continuously and/or periodically repeated, during the building of a workpiece.

11. The method according to claim 9, further comprising the step of ending the building process before completion of the workpiece in response to comparison data outside a predefined tolerance and/or threshold value.

12. The method according to claim 9, further comprising the step of classifying a completed workpiece in response to the comparison data in the form of a classification of the workpiece into predefined quality classes.

13. The method according to claim 9, further comprising the step of generating the workpiece specification data from workpiece measurement data of a model workpiece measured by means of the detector means.

14. The method according to claim 13, wherein the workpiece specification data are generated as contour data in a machine-specific format of the additive manufacturing means directly from projection output data of the detector means realized as an X-ray detector without intermediate data conversion into an interpolated intermediate format.

15. The device according to claim 1, wherein the workpiece measurement data is selected from the group consisting of 3-dimensional workpiece contour data, workpiece homogeneity, density data and combinations thereof.

16. The device according to claim 4, wherein the manufacturing correction means (70) are assigned to and/or connected upstream of the manufacturing process control means in such a manner that the building can be geometrically changed.

17. The device according to claim 7, wherein the irradiation source and the detector means are provided and configured to be movable in relation to a support (12, 32) of the built workpiece or workpiece to to be built in the building space along a spiral and/or circular path around a longitudinal axis of the workpiece and/or of the direction in which the workpiece is built.

18. The method according to claim 14, wherein the interpolated intermediate format is STL format and/or three-dimensional voxel format.

Description

[0027] Further advantages, features and details of the invention are apparent from the following description of preferred exemplary embodiments of the invention and from the drawings; in the drawings,

[0028] FIG. 1 shows a schematic view of the device for additive manufacturing of a workpiece according to a first exemplary embodiment of the invention;

[0029] FIG. 2 shows a schematic view of the device for additive manufacturing of a workpiece according to a second exemplary embodiment of the invention, illustrated analogously to FIG. 1;

[0030] FIG. 3 shows a schematic block diagram describing the essential functional components in the exemplary embodiments of FIG. 1, FIG. 2;

[0031] FIG. 4 to

[0032] FIG. 7 show a sequence flow diagram and detailed and tolerance views illustrating an operating sequence during the additive manufacturing of a workpiece when the exemplary embodiments of FIG. 1, FIG. 2 are operated and illustrating an embodiment of the method according to the invention; and

[0033] FIG. 8 shows a schematic view illustrating a third exemplary embodiment of the device for additive manufacturing of a workpiece.

[0034] In the schematic, three-dimensional view, FIG. 1 shows an option of a basic structure for realizing a device for additive manufacturing of a workpiece (“AM machine”). A (developing) workpiece 10 still in the process of being manufactured is held so as to be movable in a rotatory manner on a rotary plate device 12; as a depositing nozzle, a schematically shown print head 14 applies a starting material for producing workpiece body 10 layer by layer in a generally known manner along a vertical direction in the drawing layer of FIG. 1.

[0035] According to the principle of the present invention, a three-dimensional measurement device for the workpiece is assigned to the additive manufacturing device (additive manufacturing means) in such an integrative manner that an X-ray source 16, 18 (irradiation source) directs a focused X-ray beam—a three-dimensionally split beam path 20 is schematically shown—at workpiece 10 and irradiates workpiece 10 with the ionizing X-rays. As shown by beam path 20, the irradiation from source 16 leads to a radiography of the workpiece up to a detector unit (detector means) 22 which is disposed on the opposite side along the beam path in relation to workpiece 10, and which, in the present case realized as an X-ray surface detector, electronically detects the irradiation image, i.e., the image of the radiography of workpiece 10 in the present case, and supplies it to electronic evaluation means (not shown in detail) for further electronic processing and image editing. Additionally (not shown in FIG. 1), workpiece measurement means 16, 18, 22 are adjustable in height along the vertical (reference planes of FIG. 1), the radiography thus being performable at different levels of the workpiece.

[0036] The combination of the three-dimensional/additive manufacturing device and the three-dimensional measurement device shown schematically in FIG. 1 is enclosed by a housing (enclosure) 24 which is configured to shield the environment from the ionizing radiation of radiation source 16 (for which end, housing 24 has suitable lead plates or similar shielding means, for example); additionally, housing shell 24, which defines or realizes the recognizable building space for workpiece 10 to be built layer by layer in its housing interior, provides the option of performing the additive manufacturing process in protective atmosphere or under similar predefined conditions, wherein a possible thermal shielding from the environment can additionally also be ensured.

[0037] Compared to the exemplary embodiment of FIG. 1, the schematic view of FIG. 2 shows another realization of the invention (the present principle of the invention not being limited to the shown exemplary embodiments; in particular, the variants which are apparent from the exemplary embodiments can be combined and realized in any combination): In the present case, the component (workpiece) 30 in the process of being manufactured is supported by a fixed base unit 32; furthermore, assemblies 34, 36 illustrate an alternative AM machine in the form of a material application of the starting material which solidifies the material and in which component 30 is pulled out of a liquid material phase.

[0038] Developing workpiece 30 is measured within the meaning of the workpiece measurement means according to the invention already during the building (and potentially also after the completion) by an assembly composed of an X-ray source 40 which is fixed to a support 38 mounted so as to be rotatable and to which detector means, in the present example in the form of an X-ray line detector 42, are assigned on the opposite side in relation to workpiece 30.

[0039] Therefore, the fan-like beam path (reference sign 44) is initially two-dimensional compared to the exemplary embodiment of FIG. 1, whose beam path 20 is additionally split in the vertical direction. In the exemplary embodiment of FIG. 2, the assembly composed of irradiation source 40 and detector 42 also rotates about the workpiece which is supported in a stationary manner; this means different requirements for the type and realization of the (three-dimensional) additive manufacturing means 34, 36, in particular depending on the type of the workpiece to be built.

[0040] Compared to the exemplary embodiment of FIG. 1, in which a single shot of detector 22 (or a plurality of shots if workpiece support 12 rotates) without vertical displacement can lead to a predefined partial or complete image of the workpiece (in the current manufacturing state)—additionally or alternatively supplemented by a vertical displacement—, the measurement according to the invention would take place layer by layer without vertical tracking in the immediate building space and in the assembly context, following the building in layers by solidifying manufacturing means 34, 36 at a vertical distance which ensures the solidification, in the exemplary embodiment of FIG. 2.

[0041] What both technologies have in common is that a measurement of (in particular developing and not yet completed) workpiece 10 or 30 allows an intervention in the building process during this process on the basis of the obtained measurement data by a correction or by a decision to cancel the process (if tolerances which are no longer sufficient and correctable are detected).

[0042] The schematic block diagram of FIG. 3 illustrates the control, measurement and detection technology which controls the embodiments of FIG. 1, FIG. 2 (and FIG. 8 to be explained below) or which enables the operation according to the invention: On the left side of schematically shown housing 24, the additive manufacturing means (“AM machine”) are shown in the form of functional components which allow the (otherwise known) manufacturing of the workpiece in layers by means of their hardware components 50 which allow the additive application of the material and by workpiece positioning 52. Said units (i.e., for example, 14 and 12 for FIG. 1; 34 for FIG. 2) are controlled by a manufacturing means control unit (“AM controller”) 54 which communicates, via an interface control unit 56 referred to as “master controller”, with the noncontact 2D/3D measurement device (“workpiece measurement means”) 58 which is integrated according to the invention. More precisely, measurement components 62 (i.e., for example, realized by the pair of source 16 and detector 22 in FIG. 1, alternatively 40 and 42 of FIG. 2) of a measurement data detection unit 60 of workpiece measurement means 58 enable the noncontact measurement of the developing or completed workpiece by irradiation (which is also radiography if X-rays are used), and wherein a positioning system 64 is provided, for example in the case of workpiece measurement means of FIG. 2, which can be moved in a rotational manner.

[0043] The overview block diagram of FIG. 3 shows that a temporal synchronization of the measurement data acquisition and the additive manufacturing process is performed first in the form of synchronization means 66 which connect control units 54, 60, for example in order to specify the time of the irradiation and the measurement and the orientation or positioning of the measurement, preferably outside a recently applied (and potentially not yet solidified) material layer, by such a synchronization functionality.

[0044] According to another embodiment of the invention, a correction module 70 realized in unit 56 is assigned to a measurement data processing unit 68 of workpiece measurement means 58, wherein correction module 70 can use results of the workpiece measurement according to the invention (or the data generated therefrom) in a manner to be explained below to influence the additive manufacturing process (controlled by control unit 54) in the form of correction parameters.

[0045] More precisely, correction unit (correction module) 70 realizes a comparison between measurement specification data (for example in the form of standard, tolerance and/or electronic drawing data) which are provided or supplied by a schematically shown data specification unit 72 and current measurement data of measurement data processing unit 68. This comparison leads to a generation of correction parameter data which, when they are returned to control unit 54, change the additive manufacturing process in such a manner that subsequently applied layers can potentially get the workpiece to be built into an acceptable tolerance range or that possible identified deviations can be corrected as long as they are within an acceptable tolerance range. An advantageous embodiment of the functionality of the correction module provides that an additive manufacturing process is cancelled—before the workpiece to be built layer by layer is completed—in the form of a control of control unit 54, in particular if the comparison described above shows that tolerance limits applying to an acceptable or good part cannot (can no longer) be achieved with the current measurement data.

[0046] Details of this functionality are explained below on the basis of the flow sequence diagram of FIGS. 4, 5 and on the basis of the tolerance diagrams of FIG. 6, FIG. 7.

[0047] FIG. 4 (in combination with the detailed illustration of the 2D/3D measurement in FIG. 5) does not only show the operation of the device described above, but also, in particular, the functionality of the combined manufacturing and measurement method according to the invention. In FIG. 4, the workpiece (component) is built in an additive manner in the form of two nested loops until it is completed (“completed?”). A three-dimensional measurement (for example in the manner of the exemplary embodiment of FIG. 1) or two-dimensional, line-by-line measurement (in the manner of the exemplary embodiment of FIG. 2) for identifying errors and/or deviations is performed within said manufacturing loop, the result of the measurement determining whether it is a good part having no need for correction (“OK”), whether, if a tolerance limit is exceeded and the part can no longer be corrected, the manufacturing is to be cancelled and an error report (“NOK”) is to be outputted, or whether, if a need for correction and an option for correction can be recognized (“OK but correction is required”), the measurement and correction loop returns to the manufacturing process including a calculation of correction values which influence the (further) additive manufacturing accordingly.

[0048] By the preferred radiography according to the embodiment, the measurement according to the invention by means of the workpiece measurement means in particular also detects the material distribution or the density of the (completely or partially built) workpiece, in particular the described X-ray tomography method generating information on the density distribution and on the geometry, with the possibility of identifying and detecting material errors or deviations from the target geometry (see process described above on the basis of FIGS. 4 to 7).

[0049] Depending on the size of the geometry deviation or a deviation from a target surface quality, the different actions described above can be triggered (left branch in FIG. 5, in addition explanation in FIG. 6): There is an area (1) which has small deviations from the nominal dimension and for which no correction is required within the margin of tolerance. At the edges of the margin of tolerance, areas (2), the dimensions are still within the tolerance, but the larger deviations compared to area (1) provide information for the initiation of correction measures to avoid values outside the tolerance. The size and length of area (2) depends inter alia on the distance of the manufacturing plane from the measurement plane. Depending on the specific realization, it may also be necessary to define area (2) with a distance from the tolerance limits. Furthermore, the analysis of the progression of the deviations over time allows the identification of trends and sometimes the timely detection and correction of a drift of manufacturing parameters. If the dimensions in area (3) are outside the tolerance, the manufacturing process has to be cancelled as described above. However, this is advantageous in any case because of the material and manufacturing time saved.

[0050] By analogy with the geometry deviation described above (left side of FIG. 5 in conjunction with FIG. 6), different actions are similarly triggered depending on the measured size of the material inhomogeneities (e.g. density) (right branch of FIG. 5 in conjunction with FIG. 7): There is an area (4) which has small inhomogeneities and for which no correction is required within the margin of tolerance for the material homogeneities. At the edges of the margin of tolerance (area (5)), the material inhomogeneities are still within the tolerance, but the greater material inhomogeneities compared to area (4) provide information for the initiation of correction measures to avoid values outside the tolerance. The size and length of area (5) depends inter alia on the distance of the manufacturing plane from the measurement plane. Depending on the specific realization, it may be required to define area (5) with a distance from the tolerance limit. The analysis of the progression of the material inhomogeneity over time again allows the identification of trends and sometimes the timely detection and correction of a drift of manufacturing parameters. If the material inhomogeneities in area (6) are outside the tolerance, the manufacturing process has to be cancelled. This, too, is advantageous because material and manufacturing time can be saved in relation to a completion of the complete workpiece (which is no longer reasonable).

[0051] Another variant of the method is characterized in that, depending on the size of the identified errors and/or the geometry deviations, components of different quality levels are classified and are accordingly used for different applications; in this respect, the sequence diagram of FIG. 4 after the evaluation step would have to be amended by (or replaced with) a corresponding (quality) classification step.

[0052] This shows that the present invention realizes and combines several advantages for the manufacturing of additively manufactured workpieces. Because of the timely detection of material inhomogeneities during the manufacturing, the manufacturing process can be corrected and the manufacturing (3D printing) quality can thus be improved. Reject is significantly reduced or completely avoided. Because of the timely detection of deviations from the contour or the geometry or the dimensional accuracy or the surface quality during the manufacturing, the manufacturing process can likewise be corrected and the dimensional accuracy and the quality of the produced parts can thus be improved. If errors or deviations outside a specified permissible tolerance occur, the manufacturing process can be cancelled immediately, which has corresponding advantages with respect to the saving of material and manufacturing time.

[0053] In addition to these advantages, the present invention provides the option of obtaining a completely or partially tested component—depending on the requirement and specification—directly following the completion of the manufacturing process. This in particular creates an important element for a realization of a so-called industry 4.0 approach for additively manufactured components (AM components), and a test subsequent to the manufacturing would no longer be necessary, in particular for safety-related components which require a 100% manufacturing test.

[0054] According to another embodiment of the invention, the geometry of the additively manufactured workpiece is measured by means of non-ionizing radiation, as it is explained on the basis of the exemplary embodiment of FIG. 8.

[0055] In a central, cell-like housing 24 for determining a cell-like building space for a workpiece 10 to be manufactured on a rotatable support 12 and by means of additive manufacturing means 14 by analogy with the exemplary embodiment of FIG. 1, workpiece 10 is provided with a line pattern by irradiation of an external outer wall 80 on one side by means of a first laser triangulation unit 82 and with another line irradiation of an internal outer wall 84 on the other side by means of a second laser triangulation unit 86 (both irradiations being optically detected, in a manner known per se, in the form of a known, predefined angle using units 82 or 86 and a surface measurement, in particular also a determination of surface deviations, being performed on the basis of a triangulation of the projected and recorded pattern).

[0056] In contrast to the computer tomographic methods described on the basis of FIGS. 1, 2, the irradiation source and detector means are therefore not located on opposite sides, but on the same side of the workpiece; they are, however, disposed at the angle described above.

[0057] Furthermore, cross tables 88, 90, which can be electronically controlled, allow a desired or required displacement or tilting by means of their respective slides, which support triangulation means 82 or 86, in order to cover the internal and external walls of workpiece 10 (which is hollow-cylindrical in the present case). During the measurement, workpiece 10 is usually still being built by additive manufacturing means 14, and rotary plate 12 ensures a suitable rotational positioning of the workpiece for the measurement and building.

[0058] An integration into the manufacturing process takes place corresponding to the sequence described above (in relation to the geometry deviation, i.e., left branch of FIG. 5).

[0059] Another embodiment of the invention (not shown in the figures) which is particularly suitable for organic materials for the additive manufacturing of the workpiece (e.g. polymers) provides that a magnetic resonance imaging device is provided instead of the X-ray tomographic workpiece measurement means realized in FIG. 1, FIG. 2. Such a solution has the advantage that no movement axes are required and that housing 24 does not have to be provided with special radiation protection measures (such as lead plates for shielding the X-rays) (however, precautions for shielding the strong magnetic fields related to the magnetic resonance imaging may be required).

[0060] CAD data, on the basis of which the described specification data (and therefrom correction data, if applicable) are advantageously generated via the known standard format STL, for example, are usually used as a data source for the additive manufacturing according to the invention. Nevertheless, in particular scanned data of existing model components (model workpieces) can also be used as a data source. For instance, in another embodiment of the invention, the master data (specification data) of the model workpiece could be generated (recorded) by means of the existing workpiece measurement data in a first step and the master data can then be converted into STL data which are supplied to the additive manufacturing means.

[0061] Alternatively, the conversion of the data along the process chain from the detector means to the control format of the 3D printer (additive manufacturing means) can be performed directly and without intermediate data format. In this process, the printer data are generated as contour data in a machine-specific format (e.g. in the so-called G-code) directly from projection output data of the detector means realized as an X-ray detector without intermediate data conversion into an interpolated intermediate format, for example the described STL format and/or another three-dimensional voxel format.

[0062] The present invention is not limited to the described exemplary embodiments (product and method); other embodiments and combinations of the described principles according to the invention are also conceivable and possible, in particular depending on a respective manufacturing, material and measurement context.