METHOD FOR OPERATING AN APPARATUS FOR ADDITIVELY MANUFACTURING OF THREE-DIMENSIONAL OBJECTS

Abstract

Method for operating at least one apparatus (1) for additively manufacturing of three-dimensional objects (2-5) by means of successive layerwise selective irradiation and consolidation of layers (6) of a build material which can be consolidated by means of an energy beam (12), wherein at least one object (2-5) is being built by successively irradiating layers (6) of the object (2-5) in a build plane (13), wherein at least one part (16-31) of at least one layer (6) of the object (2-5) is assigned to be irradiated by a first energy beam (12) and at least one other part (16-31) of at least one layer (6) of the object (2-5) is assigned to be irradiated by another energy beam (12), wherein the parts (16-31) of layers (6) are assigned to be irradiated by one of the at least two energy beams (12) based on a Huffman coding.

Claims

1. Method for operating at least one apparatus (1) for additively manufacturing of three-dimensional objects (2-5) by means of successive layerwise selective irradiation and consolidation of layers (6) of a build material which can be consolidated by means of an energy beam (12), wherein at least one object (2-5) is being built by successively irradiating layers (6) of the object (2-5) in a build plane (13), wherein at least one part (16-31) of at least one layer (6) of the object (2-5) is assigned to be irradiated by a first energy beam (12) and at least one other part (16-31) of at least one layer (6) of the object (2-5) is assigned to be irradiated by another energy beam (12), characterized in that the parts (16-31) of layers (6) are assigned to be irradiated by one of the at least two energy beams (12) based on a Huffman coding.

2. Method according to claim 1, characterized in that a Huffman tree (14) is generated, wherein at least two parts (16-31) of layers (6) to be irradiated are sorted in different nodes and/or sub-trees (32-43) of the Huffman tree (14) dependent on a determined, in particular an estimated or a calculated, writing time required to irradiate the respective parts (16-31).

3. Method according to claim 1, characterized in that the Huffman tree (14) is generated by: determining a writing time for at least two parts (16-31) of layers (6) of the at least one object (2-5) sorting the parts (16-31) of layers (6) to be irradiated in the Huffman tree (14) dependent on the determined writing time, wherein each part (16-31) of a layer (6) to be irradiated forms a leaf (15) in the Huffman tree (14), wherein each leaf (15) is connected to a root of the Huffman tree (14) via at least one node grouping the nodes and/or leaves (15) to sub-trees (32-43), wherein each two nodes comprising the leaves (15) with the lowest writing times are grouped to a sub-tree (32-43) grouping the nodes and/or leaves (15) to sub-trees (32-43) until only one tree remains

4. Method according to claim 1, characterized in that the Huffman tree (14) is divided into sub-trees (32-43), in particular at nodes of the same layers, wherein the number of sub-trees (32-43) equals the number of energy beams (12).

5. Method according to claim 1, characterized in that the respective parts (16-31) of a layer (6) of a first object (2-5) and at least one other object (2-5) are irradiated solely by the assigned energy beam (12).

6. Method according to claim 5, characterized in that all parts (16-31) of the first object (2-5) are entirely assigned to be irradiated with the first energy beam (12) and all parts (16-31) of the at least one other object (2-5) are entirely assigned to be irradiated with the at least one other energy beam (12).

7. Method according to claim 1, characterized by a plurality of objects (2-5) to be built during a manufacturing process, wherein single parts (16-31) or entire objects (2-5) are assigned to be irradiated with an energy beam (12) in that a total manufacturing time is minimized.

8. Method according to claim 7, characterized in that a manufacturing time of the parts (16-31) of the layers (6) or the objects (2-5) is determined, whereby the assignment of parts (16-31) or objects (2-5) to the respective energy beams (12) is performed in that the total manufacturing time is minimized.

9. Method according to claim 1, characterized in that the assignment of parts (16-31) or objects (2-5) to the respective energy beams (12) is optimized using at least one algorithm, in particular a local search algorithm.

10. Method according to claim 1, characterized in that a part (16-31) of an object (2-5) is assigned to be irradiated with an energy beam (12) capable of irradiating the respective part (16-31).

11. Method for assigning at least two parts (16-31) of at least one layer (6) of at least one three-dimensional object (2-5) to be additively manufactured by means of successive layerwise selective irradiation and consolidation of the layers (6) of a build material which can be consolidated by means of an energy beam (12), wherein at least one object (2-5) is being built by successively irradiating layers (6) of the object (2-5) in a build plane (13), wherein at least one part (16-31) of at least one layer (6) of the object (2-5) is assigned to be irradiated by a first energy beam (12) and at least one other part (16-31) of at least one layer (6) of the object (2-5) is assigned to be irradiated by another energy beam (12), characterized in that the parts (16-31) of layers (6) are assigned to be irradiated by one of the at least two energy beams (12) based on a Huffman coding.

12. Method for assigning at least two parts (16-31) of at least one layer (6) of at least one three-dimensional object (2-5) to be additively manufactured by means of successive layerwise selective irradiation and consolidation of the layers (6) of a build material which can be consolidated by means of an energy beam (12), wherein at least one object (2-5) is being built by successively irradiating layers (6) of the object (2-5) in a build plane (13), wherein at least one part (16-31) of at least one layer (6) of the object (2-5) is assigned to be irradiated by a first energy beam (12) and at least one other part (16-31) of at least one layer (6) of the object (2-5) is assigned to be irradiated by another energy beam (12), characterized in that the parts (16-31) of layers (6) are assigned to be irradiated by one of the at least two energy beams (12) based on a Huffman coding, characterized in that the method is performed in connection with a method for operating at least one apparatus (1) for additively manufacturing three-dimensional objects (2-5) according to claim 1.

13. Apparatus (1) for additively manufacturing three-dimensional objects (2-5) by means of successive layerwise selective irradiation and consolidation of layers (6) of a build material which can be consolidated by means of an energy beam (12), comprising at least one beam generating unit (8-11) configured to generate at least two energy beams (12) or at least two beam generating units (8-11) each configured to generate at least one energy beam (12), for manufacturing at least one object (2-5) by successively irradiating layers (6) of the object (2-5) in a build plane (13), wherein at least one part (16-31) of at least one layer (6) of the object (2-5) is assigned to be irradiated by a first energy beam (12) and at least one other part (16-31) of at least one layer (6) of the object (2-5) is assigned to be irradiated by another energy beam (12), characterized by a control unit (44) configured to assign the parts (16-31) to the at least two energy beams (12) based on a Huffman coding.

14. Apparatus (1) according to claim 13, characterized in that the apparatus (1) is configured to perform a method for operating at least one apparatus (1) for additively manufacturing of three-dimensional objects (2-5) by means of successive layerwise selective irradiation and consolidation of layers (6) of a build material which can be consolidated by means of an energy beam (12), wherein at least one object (2-5) is being built by successively irradiating layers (6) of the object (2-5) in a build plane (13), wherein at least one part (16-31) of at least one layer (6) of the object (2-5) is assigned to be irradiated by a first energy beam (12) and at least one other part (16-31) of at least one layer (6) of the object (2-5) is assigned to be irradiated by another energy beam (12), characterized in that the parts (16-31) of layers (6) are assigned to be irradiated by one of the at least two energy beams (12) based on a Huffman coding.

Description

[0033] Exemplary embodiments of the invention are described with reference to the Fig. The Fig. are schematic diagrams, wherein

[0034] FIG. 1 shows an inventive apparatus; and

[0035] FIG. 2 shows a hierarchic tree as result of the inventive method.

[0036] FIG. 1 shows an apparatus 1 for additively manufacturing of three-dimensional objects 2-5 by means of successive layerwise selective irradiation and consolidation of layers 6 of a build material.

[0037] The apparatus 1 further comprises an irradiation device 7 comprising four beam generating units 8-11 that, for example, comprise beam sources adapted to generate energy beams 12, e.g. electron beams or laser beams, such as laser diodes and corresponding beam guiding units (not shown) adapted to guide the generated energy beams 12 onto a build plane 13 and along a beam path (not shown) extending in the build plane 13.

[0038] The irradiation device 7 is controlled by a control unit 44 in that the control unit 44 is adapted to control the single beam generating units 8-11 and the corresponding beam guiding units. Each of the beam generating units 8-11 is adapted to generate at least one energy beam 12, wherein it is also possible that each of the beam generating units 8-11 is adapted to generate more than one energy beam 12 simultaneously. The control unit 44 further is adapted to assign at least one part of a layer 6 of one of the objects 2-5 to one of the beam generating units 8-11. In other words the control unit 44 defines which layer 6 of which object 2-5 or which part thereof is irradiated using an energy beam 12 generated by one of the beam generating units 8-11. The section of the objects 2-5 that has not yet been manufactured in the manufacturing process is depicted in FIG. 1 as a dashed line.

[0039] The assignment the control unit 44 performs is based on a Huffman coding in that, in particular in advance to or during the manufacturing process, the objects 2-5 are divided into parts of the layers 6, wherein the layers 6 are sub-divided into the respective parts. The assignment of the workload of the single beam generating units 8-11 is performed with regard to the finding of a global minimum of the total manufacturing time. To avoid an uneven distribution of the writing time of the objects 2-5 over the beam generating units 8-11 the control unit 44 performs the assignment of the parts of the layers 6 based on a Huffman coding. The objects 2-5 may differ from each other, in particular regarding their shape and/or their cross-sections and/or their dimensions, wherein the corresponding parts of the layers 6 of the objects 2-5 require different writing times.

[0040] The assignment of parts 16-31 (FIG. 2) of the layers 6 to the different beam generating units 8-11, the Huffman Coding forms the basis for, is described in detail with respect to FIG. 2. For the sake of convenience, the total number of parts 16-31 is only sixteen. Of course, the number of layers 6 of each of the objects 2-5 would exceed the number of sixteen, accordingly would the number of parts 16-31.

[0041] FIG. 2 shows an exemplary Huffman tree 14. The leaves 15 represent the sixteen parts 16-31 of layers 6 of the objects 2-5. Since the diameter or the cross-section, respectively, of each object 2-5 may differ, or may vary in build direction (essentially perpendicular to the build plane 13), the different layers 6 and the different objects 2-5 require different writing times. Hence, assigning one object 2-5 to one beam generating unit 8-11 would result in an uneven distribution of writing times over the beam generating units 8-11. The writing times according to this exemplary embodiment, as depicted in FIG. 2, are to be understood as exemplary and depend, as described before, on various parameters of the respective part 16-31 of the layer 6 of one of the objects 2-5.

[0042] In other words, the layers 6 of all objects 2-5 are sub-divided into the parts 16-31 to be independently assigned to one of the energy beams 12 generated by one of the beam generating units 8-11. The control unit 44 therefore, estimates or calculates the writing time required for each of the parts 16-31 and the Huffman tree 14 is generated.

[0043] To generate the Huffman tree 14 the parts 16-31 have to be sorted into sub-trees, wherein each two parts 16-31 with the lowest determined writing times are grouped into one node/are contained in one sub-tree. For example, the parts 16 to 21 each require a writing time of 1 second, the parts 22-26 each require a writing time of 2 seconds, the part 27 requires a writing time of 4 seconds, the part 28 requires a writing time of 3 seconds, the part 29 requires a writing time of 5 seconds, the part 30 requires a writing time of 4 seconds and the part 31 requires a writing time of 9 seconds. This results in a total writing time of 41 seconds that needs to be distributed over the four beam generating units 8-11.

[0044] Thus, grouping the nodes 16-21 results in sub-trees 32, 33 and 34 each of the nodes connecting the sub-trees 32, 33 and 34 therefore, contains parts 16-21 with the resulting writing time of 2 seconds. Further, the part 22 is grouped with the sub-tree 32 resulting in the sub-tree 35. Accordingly, the parts 23 and 24 as well as the part 25 and the sub-tree 33 are grouped resulting in the sub-trees 36, 37. The sub-trees 35, 36 each comprise parts requiring a manufacturing time of 4 seconds, since for example the sub-tree 35 contains the sub-tree 32 with a writing time of 2 seconds and the part 22 with a writing time of 2 seconds.

[0045] Further, the sub-tree 34 is grouped with the part 26 to form the sub-tree 38 and the parts 28, 27 are grouped to the sub-tree 39. The sub-tree 40 is built by grouping the sub-tree 35 with the part 29 and the sub-tree 41 is formed by grouping the sub-tree 37 with the sub-tree 36. The sub-tree 42 results by combining the sub-tree 38 and part 30, wherein the sub-tree 43 is built combining the sub-tree 39 with the part 31.

[0046] Subsequently, the total manufacturing time of 41 seconds is distributed over the four beam generating units 8-11 by dividing the Huffman tree 14 in the third layer which comprises the sub-trees 40-43. Hence, the generated Huffman tree 14 is separated into sub-trees that are assigned to the beam generating units 8-11. For example, the sub-tree 40 is assigned to the beam generating unit 8 with a total writing time of 9 seconds, the sub-tree 41 is assigned to the beam generating unit 9 with a total writing time of 8 seconds, the sub-tree 42 is assigned to the beam generating unit 10 with a total writing time of 8 seconds and the sub-tree 43 is assigned to the beam generating unit 11 with a total writing time of 16 seconds.

[0047] Thus, the total manufacturing time of 41 seconds is essentially equally distributed over the beam generating units 8-11, resulting in the manufacturing process to complete in 16 seconds. The resulting distribution may further be improved by using an algorithm, such as a local search algorithm.

[0048] Using local search, the original part 28 with a writing time of 3 seconds, now part of the sub-tree 39 which is part of the sub-tree 43 with a combined writing time of 16 seconds, may be moved to sub-tree 41 with a combined writing time of 8 seconds, resulting in an improved workload distribution. This move of part 28 (depicted via a dashed line) results in sub-tree 41 to complete in 11 seconds and sub-tree 43 to complete in 13 seconds. With the remaining writing times of 9 seconds for sub-tree 40 and 8 seconds for sub-tree 42, the manufacturing process can be completed in 13 seconds using beam generating units 8-11 concurrently.

[0049] This local search algorithm can be repeated, as long as new improvements to the workload distribution are found that reduce the maximum of the manufacturing times across all beam generating units 8-11.