Patent ID: 12202205

DETAILED DESCRIPTION

In the schematic, three-dimensional view,FIG.1shows an option of a basic structure for realizing a device for additive manufacturing of a workpiece (“AM machine”). A (developing) workpiece10still in the process of being manufactured is held so as to be movable in a rotatory manner on a rotary plate device12; as a depositing nozzle, a schematically shown print head14applies a starting material for producing workpiece body10layer by layer in a generally known manner along a vertical direction in the drawing layer ofFIG.1.

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 source16,18(irradiation source) directs a focused X-ray beam—a three-dimensionally split beam path20is schematically shown—at workpiece10and irradiates workpiece10with the ionizing X-rays. As shown by beam path20, the irradiation from source16leads to a radiography of the workpiece up to a detector unit (detector means)22which is disposed on the opposite side along the beam path in relation to workpiece10, 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 workpiece10in the present case, and supplies it to electronic evaluation means (not shown in detail) for further electronic processing and image editing. Additionally (not shown inFIG.1), workpiece measurement means16,18,22are adjustable in height along the vertical (reference planes ofFIG.1), the radiography thus being performable at different levels of the workpiece.

The combination of the three-dimensional/additive manufacturing device and the three-dimensional measurement device shown schematically inFIG.1is enclosed by a housing (enclosure)24which is configured to shield the environment from the ionizing radiation of radiation source16(for which end, housing24has suitable lead plates or similar shielding means, for example); additionally, housing shell24, which defines or realizes the recognizable building space for workpiece10to 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.

Compared to the exemplary embodiment ofFIG.1, the schematic view ofFIG.2shows 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)30in the process of being manufactured is supported by a fixed base unit32; furthermore, assemblies34,36illustrate an alternative AM machine in the form of a material application of the starting material which solidifies the material and in which component30is pulled out of a liquid material phase.

Developing workpiece30is 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 source40which is fixed to a support38mounted so as to be rotatable and to which detector means, in the present example in the form of an X-ray line detector42, are assigned on the opposite side in relation to workpiece30.

Therefore, the fan-like beam path (reference sign44) is initially two-dimensional compared to the exemplary embodiment ofFIG.1, whose beam path20is additionally split in the vertical direction. In the exemplary embodiment ofFIG.2, the assembly composed of irradiation source40and detector42also 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 means34,36, in particular depending on the type of the workpiece to be built.

Compared to the exemplary embodiment ofFIG.1, in which a single shot of detector22(or a plurality of shots if workpiece support12rotates) 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 means34,36at a vertical distance which ensures the solidification, in the exemplary embodiment ofFIG.2.

What both technologies have in common is that a measurement of (in particular developing and not yet completed) workpiece10or30allows 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).

The schematic block diagram ofFIG.3illustrates the control, measurement and detection technology which controls the embodiments ofFIG.1,FIG.2(andFIG.8to be explained below) or which enables the operation according to the invention: On the left side of schematically shown housing24, 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 components50which allow the additive application of the material and by workpiece positioning52. Said units (i.e., for example,14and12forFIG.1;34forFIG.2) are controlled by a manufacturing means control unit (“AM controller”)54which communicates, via an interface control unit56referred to as “master controller”, with the noncontact 2D/3D measurement device (“workpiece measurement means”)58which is integrated according to the invention. More precisely, measurement components62(i.e., for example, realized by the pair of source16and detector22inFIG.1, alternatively40and42ofFIG.2) of a measurement data detection unit60of workpiece measurement means58enable the noncontact measurement of the developing or completed workpiece by irradiation (which is also radiography if X-rays are used), and wherein a positioning system64is provided, for example in the case of workpiece measurement means ofFIG.2, which can be moved in a rotational manner

The overview block diagram ofFIG.3shows that a temporal synchronization of the measurement data acquisition and the additive manufacturing process is performed first in the form of synchronization means66which connect control units54,60, 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.

According to another embodiment of the invention, a correction module70realized in unit56is assigned to a measurement data processing unit68of workpiece measurement means58, wherein correction module70can 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 unit54) in the form of correction parameters.

More precisely, correction unit (correction module)70realizes 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 unit72and current measurement data of measurement data processing unit68. This comparison leads to a generation of correction parameter data which, when they are returned to control unit54, 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 unit54, 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.

Details of this functionality are explained below on the basis of the flow sequence diagram ofFIGS.4,5and on the basis of the tolerance diagrams ofFIG.6,FIG.7.

FIG.4(in combination with the detailed illustration of the 2D/3D measurement inFIG.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. InFIG.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 ofFIG.1) or two-dimensional, line-by-line measurement (in the manner of the exemplary embodiment ofFIG.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.

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 ofFIGS.4to7).

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 inFIG.5, in addition explanation inFIG.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.

By analogy with the geometry deviation described above (left side ofFIG.5in conjunction withFIG.6), different actions are similarly triggered depending on the measured size of the material inhomogeneities (e.g. density) (right branch ofFIG.5in conjunction withFIG.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).

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 ofFIG.4after the evaluation step would have to be amended by (or replaced with) a corresponding (quality) classification step.

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.

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.

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 ofFIG.8.

In a central, cell-like housing24for determining a cell-like building space for a workpiece10to be manufactured on a rotatable support12and by means of additive manufacturing means14by analogy with the exemplary embodiment ofFIG.1, workpiece10is provided with a line pattern by irradiation of an external outer wall80on one side by means of a first laser triangulation unit82and with another line irradiation of an internal outer wall84on the other side by means of a second laser triangulation unit86(both irradiations being optically detected, in a manner known per se, in the form of a known, predefined angle using units82or86and 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).

In contrast to the computer tomographic methods described on the basis ofFIGS.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.

Furthermore, cross tables88,90, which can be electronically controlled, allow a desired or required displacement or tilting by means of their respective slides, which support triangulation means82or86, in order to cover the internal and external walls of workpiece10(which is hollow-cylindrical in the present case). During the measurement, workpiece10is usually still being built by additive manufacturing means14, and rotary plate12ensures a suitable rotational positioning of the workpiece for the measurement and building.

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

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 inFIG.1,FIG.2. Such a solution has the advantage that no movement axes are required and that housing24does 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).

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.

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.

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.