Method of optimizing a powder-bed-based additive manufacturing process and related system

Abstract

A method of optimising a powder-bed-based additive manufacturing process of a component by: (i), providing a multi-domain (CAD1, CAD2) component design where each domain corresponds to a different par

Description

The present invention relates to a method of optimizing the powder-bed-based additive manufacturing process of components, particularly for components with a multi-domain design. Preferably, said method is intended for quality assurance, more particularly ensuring sufficient solid connection between different domains or sections of the structure to be established out of a powder bed by local energy irradiation. The term component, article, or object may pertain to any component susceptible to be produced by 3D-printing or additive manufacturing. Preferably a high-performance component, such as a component applied in the energy sector, power generation, in the aviation or the automotive industry. Additive manufacturing (AM) or 3D-printing techniques comprise e.g. powder-bed-fusion methods, such as selective laser melting (SLM) or laser powder bed fusion (LPBF), selective laser sintering (SLS) and electron beam melting (EBM). Additive manufacturing, particularly powder-bed methods have proven to be useful and advantageous in the fabrication of prototypes or complex components, such as components with filigree structure or functionally cooled components. Further, the additive manufacture stands out for its short chain of process steps which in turn enables material economization and a particularly low lead time. Further additive manufacturing approaches relate to „Directed Energy Deposition (DED)", such as laser cladding, electron beam or plasma welding, metal inkjet molding (MIM), so-called sheet lamination methods, or even thermal spraying (VPS, LPPS) methods. Related machine hardware or setups for such methods usually comprise a manufacturing or build platform on which the component is built layer-by-layer after the feeding of a layer of base material which may then be melted, e. g. by an energy beam, such as a laser, and subsequently solidified. The layer thickness is determined by a recoater that moves, e. g., automatically, over the powder bed and removes excess material from a manufacturing plane or build space. Typical layer thicknesses amount to between 20 pm and 40 pm, for instance. During the manufacture, said energy beam scans over the surface and melts the powder on selected areas which may be predetermined by a CAD-file (cf. Computer-Aided-Design) according to the geometry of the component. Said scanning or irradiation is preferably carried out in a computer-assisted way, such as Computer-Aided-Manufacturing (CAM) instructions, which may be present in the form of a dataset. Said dataset or CAM-file may be or refer to a computer program or computer program product. In the industrial application of AM, such as in the development of ever more complex component design, like filigree heat exchanger or adsorber structures, lattices, or the like, there is the demand to assign multiple process parameters to different areas of the same model. In other words, parameters that are required for bulk, casing or shell material structures are usually not suitable or applicable for more complex, fine-structured functional elements of the related design. Heat exchangers exhibit - as an example - a relatively new application field for additive manufacturing. Its unique production capabilities allow the monolithic manufacturing of very detailed and complex channels or structures embedded in solid casings, for instance. The combination of bulky casings and finely structured elements requires dealing with a still increased design complexity in AM and related vector-pathing algorithms and strategies . Currently, specific segments or areas within a part cannot be produced with the required or intended quality and accuracy as state-of-the-art assignment of scan strategy and process parameters lack sufficient functionalities. Especially the structural connection or link between the aforementioned segments is often an issue, even more so as when the application of multiple parameter sets is required. This present invention provides a means and a solution to these technical problems already from a vector-pathing and scanning-strategy viewpoint. To this effect, the presented method may also be a computer-implemented method. It is evident that the mentioned issue can be generally tackled, e. g., by using a "higher than necessary" energy input to ensure that all connection points, to where different segments touch, fuse together. This does, however, go with further drawbacks and adverse solidification of powder due to an excessive energy input and related problems with dissipation of heat out of the build-up. A skilled person is aware of the fact that an excessive energy input may likewise have detrimental effects on a structural result than an insufficient one. It is hence an object of the present invention to provide means, that address the above problems in an improved way, particularly in a way that accounts for the complexity of the process as a whole and does not introduce further issues, be it in the data handling, vector-pathing, or the additive manufacturing process itself. The mentioned object is achieved by the subject-matters of the independent claims. Advantageous embodiments are subjectmatter of the dependent claims. An aspect of the present invention relates to a method of optimizing the powder bed additive manufacturing process of components with a multi-domain design. The term "multidomain" may relate in connection with the above to domains with different complexity, structural resolution, finesse and / or subtlety. The method comprises providing a component design, such as by a CAD-file or the like, either as a single file domain, or as segmented files corresponding to the different domains or sections . The method further comprises assigning irradiation or process parameters for the layerwise additive manufacture of the component to each domain, such as manually or from a database, for instance. The method further comprises assigning or deriving an estimated melt pool dimension to a related process parameter set. Preferably the melt pool dimension, be it laterally or transversally, is preferably assigned to each of the related process parameters. The term "process parameter" shall presently be understood in a broad sense, even indicating the related mode of operation, such as, e. g., a pulsed wave (pw) mode or continuous wave (cw) mode of irradiation. The method further comprises assigning a melt pool overlap to scan or irradiation vectors of the different domains, wherein the assign melt pool dimension is projected around the related irradiation vectors and an irradiation vector of a first domain is extended into a second domain corresponding to the assigned overlap, when said irradiation vectors of different type are intended to form a structural connection within a given layer. A "different type" may presently mean a different section, segment or domain which faces the related other type in any given layer. In other words, the melt pool overlap shall be assigned whenever there's an unwanted melt pool gap or insufficient structural link in the AA-process. As an advantage of the inventive functionality, novel settings, features and workflows are presented that allow for a largely defect-free connection or fusing of two different domain segments. In other words, a practical "melt pool gap filling" is provided - that is then realizing a structural connection only at the relevant and intended links in a given layer to be additively produced. The presented solution does preferably not provide a global assignment of melt pool overlap's but only at the intended locations. In this way, the solution accounts for very practical problems of an AM operator in that it provides a tailor-made melt pool or structural connection check and thereby enabling sufficient structural connection in the build-up. Finally, the design scope of AM-components can be significantly expanded and wastage of capacity, both in material and processing time, be drastically reduced. In an embodiment the irradiation vectors implement the process parameters for the additive manufacture of the component. In an embodiment, the melt pool overlap is assigned to an absolute length or a relative value, such as a relative value in percent. In an embodiment the melt pool overlap is assigned to a relative value of one hundred percent. Alternatively, the melt pool overlap may be assigned to any other relative value, such as 80%, 90%, or the like. In an embodiment the melt pool dimensions are assigned to each process parameter or process parameter set. In an embodiment a multi-domain design means a design with a plurality of segments or sections which require to be implemented with different process parameters. 5 In an embodiment a different type of irradiation vector(s) means any vector generated with a different process parameter set, from a different segment, or with a different designation, e. g., be it a hatching vector or contour vector, for instance. 10 In an embodiment a process parameter means an irradiation parameter and / or a mode of irradiation, like a pulsed or continuous mode of irradiation. 15 In an embodiment the melt pool dimension denotes a longitudinal and / or a transversal melt pool width. A further aspect of the present invention relates to a method of additive manufacturing employing the method as described 20 above. A further aspect of the present invention relates to a system, such as for optimizing the additive manufacturing of the object as described above. The system may, hence, form a 25 functional part of an additive manufacturing machine, like a 3D printer. The system comprises a build processor or similar means configured to communicate data of an additive manufacturing 30 process to an additive manufacturing machine and preferably back from the machine to the processor, wherein the build processor is configured to project an estimated melt pool dimension around the related irradiation vector. The build processor is also configured to provide process instructions 35 for an extension of the irradiation vector corresponding to the assigned overlap. Also, the system may comprise a communication module configured to obtain data, such as CAD data of an additive manufacturing process of the object to and from the related manufacturing machine. The system may further comprise a projection module configured to project an estimated melt pool dimension around the related irradiation vector. The system may still further comprise an instruction generation module configured to provide process instructions for an extension of the irradiation vector to the assigned overlap. A further aspect of the present invention relates to a computer program product comprising executable program instructions which product is configured, when executed, to perform the following steps, such as to cause the mentioned system to carry out the providing or importing a multi-domain component design for powder-bed-based additive manufacturing, either as a single file, or as segmented files corresponding to different domains. The computer program product further comprises assigning process parameters for the layerwise additive manufacture of the component to each domain. The computer program product further comprises assigning an estimated melt pool dimension to a related process parameter. The computer program product further comprises assigning a melt pool overlap, to irradiation vectors of the different domains, respectively, wherein the assigned melt pool dimension is projected around the related irradiation vectors and an irradiation vector of a first domain is extended into a second domain corresponding to the assigned overlap, when said irradiation vectors of different type are intended to form a solid structural connection within a given layer. A further aspect of the present invention relates to a computer-readable medium, such as stored thereon the mentioned computer program product, comprising executable program instructions which medium is configured, when executed, to perform the step of providing a multi-domain component design for powder-bed-based additive manufacturing, 5 either as a single file, or as segmented files corresponding to different domains, The computer-readable medium further comprises assigning process parameters for the layerwise additive manufacture of 10 the component to each domain. The computer-readable medium further comprises assigning an estimated melt pool dimension to a related process parameter, 15 The computer-readable medium further comprises assigning a melt pool overlap, to irradiation vectors of the different domains, respectively, wherein the assigned melt pool dimension is projected around the related irradiation vectors and an irradiation vector of a first domain is extended into 20 a second domain corresponding to the assigned overlap, when said irradiation vectors of different type are intended to form a solid structural connection within a given layer. A computer program product as referred to herein may relate 25 to a computer program or media constituting or being stored on a computer-readable storage medium (be it volatile and non-volatile) like a memory card, a USB stick, a CD-ROM, a DVD or a file downloaded or downloadable from a server or network. Such product may be provided by a wireless 30 communication network or via transfer of the corresponding information by the given computer program, computer program product, or the like. A computer program product may be, include or be included by a (non-transitory) computer-readable storage medium storing applications, programs, 35 program modules, scripts, source code, program code, object code, byte code, compiled code, interpreted code, machine code, executable instructions, and / or the like. Advantages and embodiments relating to the described method and / or the described system are valid or pertain likewise to the computer program product and / or the medium, or vice versa . Further, features and advantageous embodiments become apparent from the following description of the exemplary embodiment in connection with the Figures. Figure 1 indicates part of an AM component design in a top view image, also indicating irradiation vectors for its additive manufacture. Figure 2 shows a similar situation as in Figure 1, however indicating further details, like the melt pool dimensions corresponding to the indicated irradiation vectors. Figure 3 shows a similar situation as in Figure 1, however indicating further details, like an adapted beam offset. Figure 4 indicates by way of a plurality of simple sketches, an assessment of a melt pool overlap according to the present invention. Figure 5 indicates in a simplified flow chart inter alia inventive method steps . Like elements, elements of the same kind and identically acting elements may be provided with the same reference numerals in the Figures. The Figures are not necessarily depicted true to scale and may be scaled up or down to allow for a better understanding of the illustrated principles. Rather, the described Figures are to be construed in a broad sense and as a qualitative base which allows a person skilled in the art to apply the presented teaching in a versatile way. The term „and / or" as used herein shall mean that each of the listed elements may be taken alone or in conjunction with two or more of further listed elements. Figure 1 indicates a sectional or top view of an additively manufactured structure or parts of an additively manufactured article, such as during its buildup by powder bed based additive methods, like selective laser melting or electron beam melting. The component 1 as referred to herein may particularly relate to a part or an article of complex shape, such as with filigree portions of structures. Preferably, said component is or is part of a heat exchanger or adsorber structure, such as made of a high-performance material, like a material of great strength and / or thermal resistivity or conductivity. Particularly, said part may constitute a part of a steam or gas turbine component, such as a blade, vane, shroud, shield, or the like. Alternatively, said component may relate to another or similar component. It is shown on the left in Figure 1 that a rigid wall of the component 1 is indicated by a section or segment Di. On the right-hand side of Figure 1, a filigree section D2 of the component 1 is shown. Due to the different design complexity of D2 and D2, the component may form our multi-domain design object which may require to manufacture the overall design with different sets of process parameters, therefore irradiation vectors for the different sections. Both sections D2 and D2 may be part of the same component design, as indicated by the CAD. Alternatively, it is also possible to provide two separate design files or a design segmented into separate design, as indicated by numerals CAD-and CAD2 . Related CAD-files usually provide the required geometric information to additive manufacturing machines or 3D printers as to implement the design by a layerwise irradiation via AM. Related irradiation vectors Vi, and V2 are indicated in Figure 1 as well for each of the indicated subsections, Dlf D2. In Dlz forming a very simple rigid portion, like an outer wall of the component, parallel hatch vectors V2 are shown, whereas parts of the cross-like design of D2 are formed of single irradiation vector only, such as at the link 2 (cf. arrow in the middle of Fig. 1) between both segments. The link 2 may hence denote a collision point of both related sections . The overall component design shown may particularly be intended for a heat exchanger or absorber structure. To this effect, the right and filigree design D2 may be optimized for a maximum effective surface, permeability of fluids or the like. Accordingly, sub-design D2 may relate to a functional structure, whereas the sub-design D2 may relate to a mere outer shell. In the preparation of an additive manufacturing build job for those multi-domain structures, the problem arises that one part of a component can usually only be assigned to a single exposure or irradiation vector set. This is a conventionally known freedom limitation in the preparation of 3D printing. In other words, one part, object, or component can usually only be assigned to only one exposure set. That means that, e. g., all hatching vectors, contour vectors, or edge vectors have basically the same adjustments by default. In the current situation, however, an optimal or "best practice" parameter for the outer shell D2 may likely lead to overheating for the functional elements in D2 of a heatexchanger geometry. This applies the more so as the structural link 2 between the two domains D2 and D2 might be fairly weak and to be established by a single irradiation vector, for instance. Figure 2 shows a similar situation as in Figure 1, however, further indicating two melt pool courses according to estimated melt pool dimensions which are estimated to be generated by the irradiation vectors V2 and V2. The estimation of the dimension of the melt pool, that is in width and length may be predetermined, or any derived number, such as calculated from a related process parameter set for the given domains D2 and D2, respectively. The set irradiation vectors V2 and V2 are, according to this embodiment, intended to form the structural link and therefore a structural connection between the two domains D2 and D2 for the overall component design. Each area or segment, particularly, the domain of the outer shell Di and that one of the functional elements (cf. D2) may each relate to independent or separate (CAD-)files. In this way, parameters can be assigned individually, and the material properties can favorably be fine-tuned individually. Usually, scan paths are then offset from the part contour such that the actual melt pool width coincides with the intended part contour. This is sometimes called "part contour offset" or just "beam offset". The problem is however that - since both elements D2 and D2 have individual part contours in this scenario, this beam offset BOi might be conventionally applied to each file and there is regularly no overlap between the exposure paths of each subdomain. This would plainly result in an insufficient fusion, such as a so-called lack-of-fusion defect in the structure, at the link2 and the part may fail to comply with its standards. All currently and conventionally available solutions to extend the vector at the collision point from domain D2 into domain D2 would also extend vectors at other unintended locations, there is no standard way or automatism as to specifically identify the link section, where a vector extension is intrinsically needed for the structural cohesion of the component. As shown in greater detail in Figure 3, another rather cumbersome solution for the above-mentioned problem would be to manually define a beam offset B02, which is defined, however, with an opposite (algebraic) sign as compared to be a one shown above. In other words, for those vectors which are directly intended at the collision area (usually from the inner design or part section) this negative beam offset B02 is applied, such that it extends into the other part (usually the outer part section) for a better connection. By way of the following Figures, the inventive approach is outlined in further details, showing that the above-mentioned problems may indeed be solved in a far better way by the inventive solution. Particularly Figure 4 shows in greater detail (cf. also indication of Figure 3) that melt pool dimensions are estimated to a related process parameter set and then the melt pool overlap is further assigned to irradiation vectors of the different domains. Figure 4 shows actually six subfigures, i. e. three lower ones and three upper ones, wherein those on the left show an overlap O of the melt pool's MP equal to zero (of the exemplified different domains D2 and D2). It is apparent that the extension of the respective vector length is dependent on the melt pool dimensions of both parameter sets. The depictions in the middle show two embodiments of an overlap of equal to 100% percent, meaning here that the lateral melt pool width W1 coincides with the transversal melt pool width Wt of the opposing side, or vice versa, respectively. The depictions on the right in Figure 4 finally indicate an overlap of more than 100%. To this effect, a melt pool overlap O is assigned to a relative value of 100 %. Instead of a relative value, the vector extension can also be defined as an absolute length or value and even multiplied by a melt pool width factor, to ensure that a sufficient overlap is applied everywhere at the intended locations regardless of the set of parameters that "collide" or abut. The whole inventive process flow is finally indicated in Figure 5. The inventive method at issue is a method of optimizing a powder-bed-based additive manufacturing process of objects or components 1 with a multi-domain design CAD2, CAD2. As mentioned already, the multi-domain design CAD2, CAD2 means a design with a plurality of segments or sections D2, D2 which require to be implemented with different process parameters . As further mentioned above, the component 1 or its design may relate to any shape or structure, preferably however to filigree or segmented shape to which the merits of the present invention manifest most of its benefits. Preferably, said component is or is part of a heat exchanger structure, like comprising a lattice or cooling ribs with a complex course which provide for certain permeability or to be flown through by gases, for instance. Particularly, said part may constitute a part of a steam or gas turbine component, such as a blade, vane, shroud, shield, or the like. Alternatively, said component may relate to another or similar component. Under (i) the method comprises providing a component design CAD, either as a single file, or as segmented files corresponding to different domains D2, D2. Under (ii) the method comprises assigning process parameters P, v for the layerwise additive manufacture of the component 1 to each domain D2, D2. Reference numeral P may particularly relate to an intensity, power or power density put into the powder bed, whereas v may indicate scanning velocity. Alternatively, a process parameter shall mean any irradiation parameter and / or a mode of irradiation, like even a pulsed wave (pw) or continuous wave (cw) mode or irradiation. Actually the number of process parameters accordingly describing or characterizing a layer for a structurally complex component 1, may easily exceed the number of 100. The further quantities e.g. as well be understood as process parameters: Layer thickness, melt pool geometry, laser wavelength, hatching distance, i.e. distance of adjacent scanning lines, beam offset BO, melt pool dimension, geometry of beam spot, beam angle, type of purge gas, flow rate of purge gas, flow rate of possible exhaustion gas, states of gas valves, or a set ambient pressure. It is further apparent that the above-described irradiation vectors V2, V2 implement the process parameters P, v for the additive manufacture of the component, respectively. Under (iii) the method comprises assigning an estimated melt pool dimension W to a related process parameter. Preferably, melt pool dimensions W are assigned to each process parameter. Under (iv) the method comprises assigning a melt pool overlap O, to irradiation vectors Vi, V2 of the different domains D2, D2, respectively, wherein the assigned melt pool dimension W, is projected around the related irradiation vectors V2, V2 and an irradiation vector V2 of a first domain D2 is extended into a second domain D2 corresponding to the assigned overlap 0, when said irradiation vectors V2, V2 of different type are intended to form a solid structural connection within a given layer . The expression "different type" shall in the present context of irradiation vector mean any vector V generated with a different process parameter set P, v or from a different segment, domain D or purpose. Furthermore, i.e. under (v), the method comprises additively manufacturing the component 1 employing the method steps mentioned further above claims. The dashed contour around the square encircling the latter method step v) shall indicate that this method step is not necessarily essential to the present application. Instead, the merits of the present application may be imparted already by the (computer-implemented) method steps of (i) to (iv). Reference numeral 10 further indicates an apparatus or system for optimizing the additive manufacturing of the object like as part of an additive manufacturing machine or 3D printer, which is indicated by reference numeral 20. Expediently, there is further a functional link between the system 10 or its said modules and the additive manufacturing device 20 itself. For carrying out the essential method steps, the system 10 may comprise related computation modules and build job preparation capabilities like a build processor. The system 10 may particularly comprise a communication module configured to obtain data of an additive manufacturing process of the object, a control or projection module configured to project an estimated melt pool dimension W, Wi, Wt around the related irradiation vector, and an instruction generation module configured to provide process instructions corresponding to an extension of the irradiation vector corresponding to the assigned overlap. The proposed idea has advantageously the potential to be adaptable and adjustable to many different geometries, parameters, materials and combinations of each without the need manually adjust vector-pathing in the build job preparation, such as based on empirical data. Reference numerals CP shall presently indicate a computer program or computer program product, comprising executable program instructions which is configured, when executed, cause the system 10 to perform the inventive method steps (i) to (iv). Reference M shall presently indicate a computer readable medium, being likewise configured to execute the method steps, such as by comprising executable program instructions which when executed, perform the inventive method steps.

Claims

1. A method of optimizing a powder-bed-based additive manufacturing process of components (1) with a multi-domain design (CAD2, CAD2), comprising the following steps:- (i) providing a component design (CAD), either as a single file, or as segmented files corresponding to different domains (Di, D2),- (ii) assigning process parameters (P, v) for the layerwise additive manufacture of the component (1) to each domain (D2 D2) ,- (iii) assigning an estimated melt pool dimension (W) to a related process parameter- (iv) assigning a melt pool overlap (O), to irradiation vectors (V2, V2) of the different domains (D2, D2) , respectively, wherein the assigned melt pool dimension (W, Wi, Wt) is projected around the related irradiation vectors (Vi, V2) and an irradiation vector (V2) of a first domain (D2 is extended into a second domain (D2) corresponding to the assigned overlap (0), when said irradiation vectors (V2, V2) of different type are intended to form a solid structural connection within a given layer.

2. The method according to claim 1, wherein the irradiation vectors (V2, V2) implement the process parameters (P, v) for the additive manufacture of the component.

3. The method according to claim 1 or 2, wherein the melt pool overlap (0) is assigned to an absolute length or a relative value in percent.

4. The method according to one of the previous claims, wherein the melt pool overlap (0) is assigned to a relative value of 100 %.

5. The method according to one of the previous claims, wherein the melt pool dimensions (W) are assigned to each process parameter.

6. The method according to one of the previous claims, wherein a multi-domain design (CAD2, CAD2) means a design with a plurality of segments or sections (Di, D2) which require to be implemented with different process parameters.

7. The method according to one of the previous claims, wherein a different type of irradiation vector means any vector (V) generated with a different process parameter (P, v), or from a different segment (D) or with a different designation.

8. The method according to one of the previous claims, wherein a process parameter means an irradiation parameter and / or a mode of irradiation, like a pulsed (pw) or continuous (cw) mode or irradiation.

9. The method according to one of the previous claims, wherein the melt pool dimension (W) denotes a longitudinal (W2) and / or a transversal melt pool width (Wt) .

10. A method of additive manufacturing (v) employing the method according to one of the previous claims.

11. A system (10) comprising a build processor configured to communicate data of an additive manufacturing process to an additive manufacturing machine, wherein the build processor is configured to project an estimated melt pool dimension (W Wi, Wt) around the related irradiation vector, and configured to provide process instructions for an extension of the irradiation vector corresponding to the assigned overlap.

12. A computer program product (CP) comprising executable program instructions which is configured, when executed, to perform the steps of:- (i) providing a multi-domain component design for powder-bed-based additive manufacturing (CAD), either as a single file, or as segmented files corresponding to different domains (D2, D2),- (ii) assigning process parameters (P, v) for the layerwise additive manufacture of the component (1) to each domain (Di, D2) ,- (iii) assigning an estimated melt pool dimension (W) to a related process parameter,- (iv) assigning a melt pool overlap (0) to irradiation vectors (V2, V2) of the different domains (D2, D2 ) , respectively, wherein the assigned melt pool dimension (W, Wi, Wt) is projected around the related irradiation vectors (Vi, V2) and an irradiation vector (V2) of a first domain (D2) is extended into a second domain (D2) corresponding to the assigned overlap (0), when said irradiation vectors (V2, V2) of different type are intended to form a solid structural connection within a given layer.

13. A computer-readable medium (M) comprising executable program instructions which is configured, when executed,-perform the steps:- (i) providing a multi-domain component design for powderbed-based additive manufacturing (CAD), either as a single file, or as segmented files corresponding to different domains (D2, D2),- (ii) assigning process parameters (P, v) for the layerwise additive manufacture of the component (1) to each domain (D2, D2) ,- (iii) assigning an estimated melt pool dimension (W) to a related process parameter,- (iv) assigning a melt pool overlap (0) to irradiation vectors (V2, V2) of the different domains (D2, D2) , respectively, wherein the assigned melt pool dimension (W, Wi, Wt) is projected around the related irradiation vectors (Vi, V2) and an irradiation vector (V2) of a first domain (D2) is extended into a second domain (D2) corresponding to the assigned overlap (0), when said irradiation vectors (V2, V2) of different type are intended to form a solid structural connection within a given layer.21

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