APPARATUS FOR ADDITIVELY MANUFACTURING THREE-DIMENSIONAL OBJECTS

Abstract

Apparatus for additively manufacturing three-dimensional objects by means of successive layerwise selective irradiation and consolidation of layers of a build material which can be consolidated by means of an energy beam, which apparatus comprises an irradiation device adapted to guide an energy beam across a build plane, wherein a calibration device is provided comprising a positioning unit, a determination unit and a calibration unit, preferably arranged in a process chamber of the apparatus, that is adapted to at least partially reflect the energy beam, wherein the irradiation device is adapted to guide the energy beam to the calibration unit for generating a reflected part of the energy beam, wherein the positioning unit is adapted to position the irradiation device dependent on at least one parameter of the reflected part of the energy beam determined via the determination unit.

Claims

1. Apparatus (1) for additively manufacturing three-dimensional objects (2) by means of successive layerwise selective irradiation and consolidation of layers of a build material (3) which can be consolidated by means of an energy beam (5), which apparatus (1) comprises an irradiation device (6) adapted to guide an energy beam (5) across a build plane (4), characterized by a calibration device (7) comprising a positioning unit (8), a determination unit (9) and a calibration unit (10), preferably arranged in a process chamber of the apparatus (1), that is adapted to at least partially reflect the energy beam (5), wherein the irradiation device (6) is adapted to guide the energy beam (5) to the calibration unit (10) for generating a reflected part (12) of the energy beam (5), wherein the positioning unit (8) is adapted to position the irradiation device (6) dependent on at least one parameter of the reflected part (12) of the energy beam (5) determined via the determination unit (9).

2. Apparatus according to claim 1, characterized in that the irradiation device (6) is arranged on a calibration body (15) that is moveably coupled with the positioning unit (8).

3. Apparatus according to claim 1, characterized in that the positioning unit (8) is adapted to position the irradiation device (6) along at least one reference axis, preferably along a x- and y- and z-axis, and/or around at least one reference axis preferably around a x- and y- and z-axis.

4. Apparatus according to claim 1, characterized in that the calibration unit (10) is arranged in a reference plane, in particular in a process plane (11) of the apparatus (1).

5. Apparatus according to claim 1, characterized in that the calibration unit (10) is arranged in the process plane (11), in particular between two guiding rails of an application unit (14).

6. Apparatus according to claim 1, characterized in that the calibration unit (10) comprises at least one reflective region.

7. Apparatus according to claim 1, characterized in that the calibration unit (10) is built as or comprises a reflective prism.

8. Apparatus according to claim 1, characterized in that the calibration unit (10) is arranged in a reference position, in particular the top (13) of the calibration unit (10), wherein an energy beam (5) incident on the top (13) of the calibration unit (10) is reflected to a reference region (26) on a determination element of the determination unit (9) and an energy beam (5) incident on a flank (27) of the calibration unit (10) is incident in a region different from the reference region (26).

9. Apparatus according to claim 1, characterized in that the determination unit (9) comprises a beam splitter (18) adapted to split the reflected part (12) of the energy beam (5) in a first part (19) and a second part (20) and guide the first part (19) of the reflected part (12) of the energy beam (5) along a first beam path to a focal position determination unit (21) and the second part (20) along a second beam path to a position determination unit (22).

10. Apparatus according to claim 9, characterized in that the focal position determination unit (21) comprises a determination element (25), a focusing optical unit (23) and an aperture (24), wherein the focusing optical unit (23) is arranged in that a focal position of a properly calibrated energy beam (5) lies in the plane of the aperture (24).

11. Apparatus according to claim 9, characterized in that the position determination unit (22) comprises a position sensitive determination element, preferably a psd-sensor, in particular a quadrant photo diode or a CCD or CMOS.

12. Apparatus according to claim 1, characterized in that the calibration device (7) is adapted to generate calibration information based on the at least one parameter of the reflected part (12) of the energy beam (5), which calibration information relates to a calibration status of the irradiation device (6), in particular comprising a deviation from a nominal focal position and/or a nominal spatial position.

13. Apparatus according to claim 12, characterized in that the positioning unit (8) is adapted to position the irradiation device (6) based on the calibration information, preferably in a closed loop process, in particular during an application step.

14. Calibration device (7) for calibrating an irradiation device (6), in particular an irradiation device (6) of an apparatus (1) for additively manufacturing three-dimensional objects (2) by means of successive layerwise selective irradiation and consolidation of layers of a build material (3) which can be consolidated by means of an energy beam (5), in particular an apparatus (1) according to claim 1, which apparatus (1) comprises an irradiation device (6) adapted to guide an energy beam (5) across a build plane (4), characterized in that the calibration device (7) comprises a positioning unit (8), a determination unit (9) and a calibration unit (10), preferably arrangeable or arranged in a process chamber of the apparatus (1), that is adapted to at least partially reflect the energy beam (5), wherein the irradiation device (6) is adapted to guide the energy beam (5) to the calibration unit (10) for generating a reflected part (12) of the energy beam (5), wherein the positioning unit (8) is adapted to position the irradiation device (6) dependent on at least one parameter of the reflected part (12) of the energy beam (5) determined via the determination unit (9).

15. Method for operating an apparatus (1) for additively manufacturing three-dimensional objects (2) by means of successive layerwise selective irradiation and consolidation of layers of a build material (3) which can be consolidated by means of an energy beam (5), in particular an apparatus (1) for additively manufacturing three-dimensional objects (2) by means of successive layerwise selective irradiation and consolidation of layers of a build material (3) which can be consolidated by means of an energy beam (5), which apparatus (1) comprises an irradiation device (6) adapted to guide an energy beam (5) across a build plane (4), characterized by a calibration device (7) comprising a positioning unit (8), a determination unit (9) and a calibration unit (10), preferably arranged in a process chamber of the apparatus (1), that is adapted to at least partially reflect the energy beam (5), wherein the irradiation device (6) is adapted to guide the energy beam (5) to the calibration unit (10) for generating a reflected part (12) of the energy beam (5), wherein the positioning unit (8) is adapted to position the irradiation device (6) dependent on at least one parameter of the reflected part (12) of the energy beam (5) determined via the determination unit (9), characterized by guiding the energy beam (5) to a calibration unit (10), preferably arrangeable or arranged in a process chamber of the apparatus (1), for generating a reflected part (12) of the energy beam (5) guiding the reflected part (12) of the energy beam (5) to a determination unit (9) of a determination device, in particular a calibration device (7) according to claim 14, determining at least one parameter of the reflected part (12) of the energy beam (5) via the determination unit (9) positioning the irradiation device (6) via a positioning unit (8) dependent on the at least one determined parameter of the reflected part (12) of the energy beam (5).

Description

[0036] Exemplary embodiments of the invention are described with reference to the Fig. The Fig. are schematic diagrams, wherein

[0037] FIG. 1 shows an inventive apparatus; and

[0038] FIG. 2 shows a detailed view of the determination device of the apparatus from FIG. 1.

[0039] FIG. 1 shows an apparatus 1 for additively manufacturing three-dimensional objects 2 by means of successive layerwise selective irradiation and consolidation of layers of a build material 3. In this exemplary embodiment, build material 3 is arranged in a build plane 4 to be selectively irradiated via an energy beam 5, e.g. a laser beam, that is generated and guided via an irradiation device 6.

[0040] The apparatus 1 comprises a calibration device 7 comprising a positioning unit 8, a determination unit 9 and a calibration unit 10, which is built as reflective prism, for instance. Of course, the irradiation device 6 and the determination unit 9 are arranged outside a process chamber in which the additive manufacturing process is performed. Hence, the irradiation device 6 and the determination unit 9 are thermally decoupled from the environment inside the process chamber, e.g. high temperatures. It is further possible to actively cool the irradiation device 6 and the determination unit 9 via a cooling unit (not shown).

[0041] The calibration unit 10 is arranged in a process plane 11 of the apparatus 1 and is adapted to reflect a part 12 of the energy beam 5 towards the determination unit 9. Hence, the irradiation device 6 is adapted to guide the energy beam 5 (depicted as dashed line) to the calibration unit 10 from where it is reflected to the determination unit 9. It is possible to determine at least one parameter of the reflected part 12 of the energy beam 5 via the determination unit 9, e.g. a spatial position or a focal position of the reflected part 12 of the energy beam 5 and conclude on the corresponding parameter of the energy beam 5, e.g. a spatial position or focal position in the process plane 11.

[0042] The positioning unit 8 can be used to move/(re-) position the irradiation device 6 dependent on the at least one determined parameter of the reflected part 12 of the energy beam 5 that has been determined via the determination unit 9. In other words, the irradiation device 6 may be positioned dependent on the at least one parameter that has been determined via the determination unit 9. Thus, if a deviation in the positioning (spatial position, focal position) of the energy beam 5 occurs, the reflected part 12 of the energy beam 5 is reflected differently compared with a reflected part 12 of the energy beam 5 being incident on the calibration unit 10 in a reference position, e.g. on the top 13 of the calibration unit 10 (the tip of the reflective prism). Therefore, it is possible to derive based on the at least one parameter of the reflected part 12 of the energy beam 5 determined via the determination unit 9 whether the energy beam 5 is properly calibrated or whether a calibration of the irradiation device 6 is necessary.

[0043] Preferably, the determination process in which the at least one parameter of the reflected part 12 of the energy beam 5 is determined is performed during an application step in which an application unit 14 is used to apply build material 3 in the build plane 4. Of course, any arbitrary application unit may be used instead of a recoater. During the application process in which build material 3 is applied in the build plane 4, the energy beam 5 can be used to irradiate build material 3. Thus, performing the determination process during the application process is time efficient, as the energy beam 5 cannot be used to irradiate build material 3. Hence, an additional downtime of the apparatus 1 can be avoided, as the time in which the energy beam 5 cannot be used to irradiate build material 3 is used for determining the at least one parameter of the reflected part 12 of the energy beam 5.

[0044] It is possible to determine the at least one parameter of the reflected part 12 of the energy beam 5 for each application process step or for defined (selected) application process steps, e.g. every fifth application step. It is further possible to perform the determination process and/or the calibration process in a closed-loop process, wherein the positioning of the irradiation device 6 via the positioning unit 8 is performed dependent on the at least one parameter that has been determined via the determination unit 9. Thus, it is possible to verify whether the positioning of the irradiation device 6 causes the energy beam 5 to meet nominal parameters, e.g. a nominal spatial position and/or a nominal focal position.

[0045] In this exemplary embodiment, the irradiation device 6 is mounted to a calibration body 15, e.g. a metal plate that is movably coupled with the positioning unit 8, e.g. an actuator, preferably comprising one or more motors. The positioning unit 8 may be adapted to move/position the irradiation device 6 along the axis x, y and z and rotate the irradiation device 6 around the axis x, y and z, as indicated via the coordinate system 16.

[0046] FIG. 2 shows the determination unit 9 and the calibration unit 10 in detail. As depicted, a properly calibrated energy beam 5, e.g. an energy beam 5 generated and guided via a properly calibrated irradiation device 6, is incident on the top 13 of the calibration unit 10 (tip of the reflective prism). The part 12 of the energy beam 5 is therefore, reflected along the same beam path as the incoming energy beam 5. The reflected part 12 of the energy beam is reflected at a mirror element 17 and guided towards the determination unit 9, as described before. Instead of arranging the calibration unit 10, e.g. the reflective prism with the tip facing upwards, it is also possible to arrange the calibration unit 10 the other way around, i.e. inverse to the arrangement described above. Hence, the calibration unit 10 being built as or comprising a reflective prism may be arranged in that the base of the reflective prism faces upwards, e.g. faces the irradiation device 6.

[0047] The determination unit 9 comprises a beam splitter 18 that is adapted to split the reflected part 12 of the energy beam 5 into a first part 19 and a second part 20, wherein the first part 19 of the reflected part 12 of the energy beam 5 is guided along a first beam path to a focal position determination unit 21 and the second part 20 is guided along a second beam path to a position determination unit 22. The focal position determination unit 21 to which the first part 19 of the reflected part 12 is guided, is adapted to determine the focal position of the energy beam 5, in particular via the focal position of the reflected part 12 of the energy beam 5.

[0048] The focal position determination unit 21 comprises an optical unit 23, in particular a lens, an aperture 24 and a determination element 25, e.g. a photo diode. As can be derived from FIG. 2, the first part 19 of the reflected part 12 of the energy beam 5 can only entirely pass the aperture 24, if the focal position meets a nominal focal position. If the focal position of the energy beam 5 deviates from a nominal focal position, the focal position of the first part 19 of the reflected part 12 of the energy beam 5 will lie before or after the plane of the aperture 24 and therefore, a defined part of the first part 19 of the reflected part 12 of the energy beam 5 will be absorbed or reflected via the aperture 24. Thus, it is possible to determine the focal position of the first part 19 and conclude on whether the energy beam 5 is properly focused via a maximum detection procedure performed via the determination element 25.

[0049] The second part 20 of the reflected part 12 is guided to the position determination unit 22, which can be built as or comprise a position sensitive device, e.g. a camera. The position determination unit 22 comprises a reference region 26 to which the reflected part 12 of the energy beam 5, in particular the second part 20, is guided, if the energy beam 5 is properly calibrated. Besides, an energy beam 5 that is not properly calibrated or that is generated and guided via an irradiation device 6 that is not properly calibrated, respectively, is depicted via a dashed line with arrows. This energy beam 5 is not incident on the calibration unit 10 in the top 13 of the calibration unit 10 (tip of the reflective prism), but is incident on a flank 27 of the calibration unit 10 (flank of the reflective prism). Therefore, the reflected part 12 of this energy beam 5 is not reflected towards the mirror element 17 on the same beam path as the incoming energy beam 5. This deviation between the incoming energy beam 5 and the reflected part 12 causes the reflected part 12 to be incident on the position determination unit 22 in a region other than the reference region 26. Therefore, the determination unit 9 is adapted to determine that a deviation between the nominal spatial position and the actual spatial position of the energy beam 5 occurs. Thus, it is possible to control the positioning unit 8 in that the irradiation device 6 is moved accordingly, e.g. repositioned along at least one of the x, y and z-axis.

[0050] Of course, it is also possible that the energy beam 5 is not properly calibrated with respect to its focal position. In this case, the first part 19 of the reflected part 12 of the energy beam will be at least partially absorbed via the aperture 24 and therefore, the irradiation device 6 may be repositioned via the positioning unit 8 until the maximum intensity is found incident on the determination element 25 indicating a proper focal position.

[0051] Of course, the inventive method may be performed on the apparatus 1.