WO2020244832A1

WO2020244832A1 - Method for determining an irradiation pattern, method for selective irradiation and controller for additive manufacturing

Info

Publication number: WO2020244832A1
Application number: PCT/EP2020/059543
Authority: WO
Inventors: Jan Pascal Bogner
Original assignee: Siemens Aktiengesellschaft
Priority date: 2019-06-05
Filing date: 2020-04-03
Publication date: 2020-12-10
Also published as: DE102019208202A1

Abstract

The invention relates to a method for determining an irradiation pattern (10) for a material layer (L) for powder-bed-based additive manufacturing. The method comprises determining a surface vector (1, 2, 3) for the irradiation pattern (10) for programming a first beam unit (S1), and determining a contour vector (A, B, C, D, E, F, G, H) for the irradiation pattern (10) for programming a second beam unit (S2), wherein the contour vector (A, B, C) directly adjoins the surface vector (1, 2, 3) and the irradiation of the surface vector (1, 2, 3) coincides in time with the irradiation of the contour vector (A, B, C). The invention further relates to a corresponding method for selective irradiation, a corresponding additive manufacturing process, a corresponding controller, and a computer program product.

Description

description

Method for defining an irradiation pattern, method for selective irradiation and control for additive manufacturing

The present invention relates to a method for setting or defining an irradiation pattern for or for a material layer for powder-bed-based additive manufacturing. Furthermore, the present invention relates to a corresponding method for selective irradiation, a corresponding additive manufacturing method, preferably selective laser melting or electron beam melting, and a controller which is set up to control beam units or irradiation devices according to the defined irradiation pattern. Furthermore, a computer program product is specified which comprises commands for defining the irradiation pattern mentioned.

Due to its potential to disrupt industry, generative or additive manufacturing is also becoming increasingly interesting for the series production of components made of high-performance materials, such as turbine blades or other components in the hot gas path of gas turbines.

Additive manufacturing processes include, for example, powder bed processes such as selective laser melting (SLM) or laser sintering (SLS), or electron beam melting (EBM). Other additive processes are, for example, “Directed Energy Deposition (DED)” - Process, in particular laser deposition welding, electron beam or plasma powder welding, wire welding, metallic powder injection molding, so-called "sheet lamination" process, or spraying process (VPS LPPS, GDCS).

Additive manufacturing processes have already proven to be particularly advantageous for complex or complicated or filigree components, for example labyrinth-like structures, Proven cooling structures and / or lightweight structures. In particular, additive manufacturing is advantageous due to a particularly short chain of process steps, since a manufacturing or manufacturing step of a component can largely take place on the basis of a corresponding CAD file and the selection of appropriate manufacturing parameters.

Geometrically complex shapes or designs are increasingly predestining parts or components made of high-performance alloys or superalloys for additive manufacturing routes due to suitable production batch sizes. Nevertheless, there are restrictions with regard to the at least for powder bed-based processes ("PBF" for "powder bed fusion") achievable surface roughness, which, at least for internal areas of a component, can hardly be reworked or improved at all. The dimensional accuracy of the additively manufactured components is often inferior to conventionally manufactured parts. This applies in particular to overhanging areas of components that can hardly be built from the powder bed with sufficient accuracy and structural quality. This is due, on the one hand, to the difficulty of dissipating heat from the powder bed if only thermal, quasi-insulating powder is arranged underneath an overhang and no structure that sufficiently dissipates the heat. Furthermore, surrounding powder particles are drawn into the weld pool during the solidification of the corresponding overhanging area and the surface quality is drastically impaired as a result.

The size of a melt pool in selective melting processes depends on a number of irradiation or manufacturing parameters. Usually, however, the weld pool is two to three times as wide as a common energy or laser beam diameter and about three to five times as deep as a conventional process layer thickness, which can be between 20 and 40 μm, for example. Experiments have shown that a particularly controlled input of energy during the selective irradiation or during the solidification of a, in particular powdery, base material for the component to be built can be achieved by a pulsed irradiation operation, for example a pulsed laser. This is due to the weld pool, which is basically reduced in size for pulsed operation, during the (selective) welding process. As a result, both the surface quality and the dimensional accuracy of a component, the geometry of which for additive manufacturing is mostly specified by a CAD file, can be significantly improved. However, this takes place at the expense of a greatly increased process time for the construction, since the pulsed irradiation operation - compared to continuous irradiation in continuous wave operation - is significantly slower. The process time is one of the main drivers for the costs of additive processes, especially in industrialized manufacturing.

A method for selective laser melting, containing an edge area irradiation of a material layer with a pulsed laser and a corresponding irradiation device is known, for example, from EP 3 022 008 Bl. It describes that in particular the quality of the edge area of the structure to be built is improved by the pulsed laser irradiation leaves. However, the process time for irradiating the edge area is disadvantageous, which basically has to be carried out after the surface irradiation (so-called "hatching").

It is therefore an object of the present invention to provide means with which a good compromise can be found between the necessary process time and the structure or surface quality of the component to be built. What is more, means are specified with which the contour or edge area irradiation of a component can be significantly improved without impairing the process time of a component. which is built without corresponding improvements.

This problem is solved by the subject matter of the independent patent claims. Advantageous refinements are the subject of the dependent claims.

One aspect of the present invention relates to a method for establishing or defining an irradiation pattern of a material layer, in particular for powder-bed-based additive manufacturing. The material layer preferably denotes a layer made of a base material for a component to be built accordingly, such as a powder, a liquid or a pasty material.

The method includes defining an area vector for the irradiation pattern for programming a first beam unit. The first beam unit preferably comprises a beam source or source of an energy beam for the selective solidification of the material layer and a corresponding device or optics for guiding or controlling the corresponding energy beam. The first beam unit is preferably set up to irradiate the material layer along surface vectors in continuous wave operation.

In the present case, the term "surface vector" preferably denotes a vector or a main direction along which an energy beam emanating from the first beam unit, in particular a laser beam, is guided or scanned over the material layer by means of a corresponding selective irradiation or additive manufacturing can be a "hatch vector" along which large areas of the material layer are rasterized across the board. This vector can also designate a main or carrier direction for surface irradiation, which is modulated with further "sub-vectors". The method further comprises defining a contour vector for the irradiation pattern for programming a second beam unit. The second beam unit preferably comprises a beam source or source of an energy beam for the selective solidification of the material layer and a corresponding device or optics for guiding or controlling the corresponding energy beam. The second beam unit is preferably set up to irradiate the material layer along contour vectors in pulsed mode (“pulsed wave operation”).

The term "contour vector" in this case preferably denotes a vector or a trajectory along which an energy beam emanating from the second beam unit, in particular a special laser beam, is guided or scanned over the material layer by means of a corresponding selective irradiation or additive manufacturing.

In the present context, the term “programming” is intended to mean that data from the specified irradiation pattern or data or information from the available surface or contour vectors - for example in the form of or in the context of a CAM process (“Computer-Aided Manufacturing”) - are sent to a

Control or to the corresponding jet unit itself or directly transferred or read.

In the method described, the contour vector directly adjoins the area vector. In this sense, the designated area vector is a near-contour area vector.

Furthermore, in the context of the method described, the area vector is irradiated in such a way that it coincides with the irradiation of the contour vector. In other words, the irradiation of the surface vector takes place at least partially simultaneously with the irradiation of the contour vector, or vice versa. Due to this at least partial temporal overlap of two different types of irradiation (continuous and pulsed) and the use of two different beam units, for example a laser unit for continuous surface irradiation and a laser unit for pulsed contour irradiation, the process time of additive manufacturing processes can advantageously be reduced and at the same time a particularly advantageous edge structure or contour of the building to be built part can be achieved. The idea of irradiating the surface and the contour of the material layer at the same time is by no means trivial, but requires the use of different types of irradiation, including the provision and programming of the necessary hardware or beam units. A multi-laser or multi-beam system is therefore a prerequisite for additive manufacturing.

In order to continue to be able to adequately control an energy input into the material layer during the irradiation or during the manufacture of the construction, it is required that the described irradiation of the contour along the o of the contour vectors and the area irradiation along the or the area vectors both in terms of time also to be carried out spatially sufficiently parallel or simultaneously in order not to damage the structure, which is built up in layers and selectively from the material layer, by excessive energy input. The person skilled in the art is aware that both insufficient energy input and excessive energy input equally impair the structural result of the component and can lead to structural pores, cracks and / or chemical disproportionations. The energy to be introduced into the material layer by irradiation must therefore be precisely controlled.

In one embodiment, the method described is a CAM method. In one embodiment, one, two, three or more contour vectors are defined for each area vector, which directly enclose this (near-con) area vector - viewed in a plan view of the irradiation pattern. As a result of this configuration, the corresponding contour areas of the radiation pattern that adjoin a specific surface vector can advantageously be irradiated simultaneously and also spatially closely correlated. As a result, the heat input into the layer can advantageously be precisely controlled, which is particularly important in the case of the additive construction of components made of high-performance alloys. In particular, the emergence of hot cracks or corresponding crack centers as well as the tension of the entire structure can be prevented in a practical and advantageous manner.

In one embodiment, four, five, six or more contour vectors are defined for each area vector, which directly enclose this (near-contour) area vector. The advantages described for the previous embodiment also apply or analogously to this embodiment.

In one embodiment, at least ten, at least 20, at least 50 or more contour vectors are defined for each area vector, which directly enclose this (near-contour) area vector. The advantages described for the previous embodiment also apply or analogously to this embodiment.

In one embodiment, the area vector for the area-wide irradiation of the material layer is defined in such a way that it has a, for example meander-like or strip-like, modulation or superstructure of sub-vectors. This configuration can in particular be provided in order to irradiate large surface areas of the material layer.

In one embodiment, all contour vectors of a contiguous irradiation area of the irradiation pattern are ters set such that they are aligned along the same circumferential direction of the irradiation area. In other words, according to this embodiment, all of the contour vectors are preferably aligned along the same circumferential direction, which advantageously affects the structural result of the grain structure and the defect density of the solidified

Layer affects. The alignment of the contour vectors along one and the same circumferential direction also offers an economic or process-economical advantage, since areas are closed off with a contour immediately after the surface vectors have been exposed. This reduces the total waiting time between exposures, especially since the pulsed exposure or irradiation is often carried out at lower scanning speeds than is the case with continuous irradiation.

In one embodiment, a plurality of area vectors are set parallel to one another for the irradiation pattern.

In one embodiment, a plurality of contour vectors are defined for the irradiation pattern, which include said area vectors.

Another aspect of the present invention relates to a method for selective irradiation in additive manufacturing, comprising the irradiation of a material layer for the production of the corresponding component, the material layer being irradiated according to the described method for defining the irradiation pattern and the first beam unit Irradiation of area vectors of the irradiation pattern with an energy beam, in particular laser, causes continuous line operation, and the second beam unit causes the loading of contour vectors of the irradiation pattern with an energy beam, in particular laser, in pulsed operation.

The pulsed operation can be, for example, operation with laser or electron beam pulses in short pulse (milliseconds to nanoseconds) or ultra-short pulse range (picoseconds to femtoseconds) act.

A further aspect of the present invention relates to an additive manufacturing method, comprising the described method for selective irradiation, a geometry of the component being defined by a CAD file (CAD: “Computer-Aided Design”) prior to the selective irradiation.

Another aspect of the present invention relates to a controller which is set up to control the first beam unit and the second beam unit for selectively irradiating the material layer according to the specified irradiation pattern described.

Another aspect of the present invention relates to a computer program product, comprising instructions which, when a corresponding program is executed by a computer, cause the computer to execute the method for determining the irradiation pattern, as described.

A computer program product such as a computer program means, for example as a (volatile or non-volatile) storage medium, e.g. a memory card, a USB stick, a CD-ROM or DVD, or also in the form of a downloadable file from a server in a network can be provided or included. The provision can also take place, for example, in a wireless communication network by transmitting a corresponding file with the computer program product or the computer program means. A computer program product can include program code, machine code, G-code and / or executable program instructions in general.

Refinements, features and / or advantages that in the present case relate to the method for establishing the irradiation pattern, the method for selective irradiation or the additive Manufacturing processes can also relate to the controller or the computer program product, and vice versa.

Further features, properties and advantages of the present invention are explained in more detail below using exemplary embodiments with reference to the present figures.

All the features described so far and below are advantageous both individually and in combination with one another. It is understood that other embodiments can be used and structural or logical changes can be made without departing from the scope of protection of the present invention. The following description is therefore not to be interpreted in a restrictive sense.

The term "and / or" as used herein, when used in a series of two or more elements,

means that any of the listed items can be used alone, or any combination of two or more of the listed items can be used.

FIG. 1 shows a schematic, simplified sectional view of material layers during an additive manufacturing process.

Figure 2 indicates on the basis of a simplified schematic

Representation of an irradiation pattern of a material layer in the additive manufacturing of a component.

Figure 3 indicates using a simplified schematic

Representation of area vectors and contour vectors for an irradiation pattern according to the present invention.

In the exemplary embodiments and figures, elements that are the same or have the same effect can each be given the same reference numerals. be provided. The elements shown and their size relationships to one another are fundamentally not to be regarded as true to scale; rather, individual elements can be shown exaggeratedly thick or with large dimensions for better illustration and / or for better understanding.

FIG. 1 indicates, in a simplified and only qualitative manner, influences of a melt pool on material layers as they occur in the context of powder-bed-based additive manufacturing processes. In particular, individual layers L of a base material for the additive structure of a component (not shown explicitly) are indicated by horizontal lines. The layers L can consist of a powder P or some other base material for the component, or they can already be shown in the solidified state. A layer thickness d of the layers L shown can, as shown only by way of example, be 40 μm, or else more or less.

In the right part of the illustration in FIG. 1, a melt pool W _C w is also shown, as it is generated, for example, in selective melting processes by a laser or energy beam in continuous operation (see FIG. 3). The molten bath W _C w extends from a surface of the material layers L, which is not further identified, over at least four layer thicknesses d, ie more than 160 μm, into the interior of the structure or powder layer.

The weld pool W _{PW is} shown on the left. Such a weld pool is generated, for example, in selective melting processes by a laser or energy beam in pulsed operation or pulsed operation (see FIG. 3). The weld pool W _PW extends from the surface of the material layers L over only one or two layer thicknesses into the interior of the layer stack.

Based on these size ratios of the melt pools in the un ferent modes of irradiation relative to the The selected layer thickness shows what influence the irradiation can have on, for example, overhanging areas of the structures to be built up. This is further illustrated in the left part of FIG. 1 in that a dashed circle indicates a cavity in the stack of layers.

On the far left, the layered course of the melt pools with continuous wave irradiation (CW) along a surrounding overhanging area is indicated. The continuous irradiation in continuous wave operation can be carried out by a first jet unit S1. It can be seen in each case that the

Melt baths naturally protrude very far into a region of the cavity and thereby strongly falsify the specified structure of the component or the geometry of the cavity relative to a specified geometry.

Further to the right, the layer-by-layer course of the melt pools with pulsed irradiation (PW) is indicated. The pulsed radiation can be carried out by a second beam unit S2 different from the first beam unit S1. It can be seen that the weld pools, which are approximately in the range of the layer thickness d, provide a reasonably good image of overhanging structures by means of additive manufacturing.

FIG. 2 shows, on the basis of a schematic perspective view, a conventional irradiation pattern, as it is possible to choose for selective melting processes (SLM, SLS or EBM). In particular, three surface irradiation vectors or surface vectors 1, 2 and 3 are identified. These area vectors 1, 2 and 3 are aligned parallel to one another and extend over the area of the corresponding material layer L. The area vectors 1, 2, 3 are energized as part of the irradiation of the material layer L with an energy beam emanating from a beam unit S. , preferably gridded first in order to consolidate the surface of the L layer. This can also be done on the basis of further, example, meander-like or strip-like modulations or Partial vectors v take place in order to achieve large areas of the material layer L with a laser beam.

Only then is a contour of the material layer L, compare in particular contour vector X, which surrounds the surface of the material layer on the circumferential side, be irradiated.

In contrast to this, FIG. 3 now shows a radiation strategy according to the invention for the radiation or selective consolidation of one or each material layer L.

According to the present invention, the irradiation pattern 10 is preferably defined according to the invention in such a way that area vectors 1, 2, 3 are defined for the irradiation pattern 10 for programming the first beam unit S1. Furthermore, contour vectors A, B, C, D, E, F, G, H for the irradiation pattern 10 for programming the second

Jet unit S2 set. According to the invention, however, this is done in such a way that those contour vectors which directly adjoin a (near-contour) surface vector are irradiated at least largely simultaneously with this.

In particular, the first area vector 1 - in the situation shown in FIG. 3 - is defined in such a way that it can be irradiated at the same time as the irradiation of the contour vectors A, B and / or C, which directly adjoin the first area vector. As a result, the inventive advantages can be achieved in terms of optimizing the process time and improving the structure and surface properties, such as the dimensional accuracy of difficult-to-produce areas of the component to be produced, in particular of cavities and / or edge areas.

Analogous to this description, the irradiation pattern 10 is preferably defined in such a way that the second area vector 2 can be irradiated simultaneously with the contour vectors E and D. Here, too, the second surface vector 2 represents a con The vector for the contour vectors D and E, which limit the second area vector 2, is close to the turn.

The proposed irradiation pattern 10 is further defined by the method according to the invention so that the third area vector 3 and the contour vectors F, G and H bordering it are irradiated simultaneously with the third area vector 3 in a later irradiation for the additive manufacture of the component can.

The term "simultaneously" or "simultaneously" is intended to mean that the irradiation of the account vectors, as described, which framed the entered area vector, preferably takes place in a time interval in which an irradiation of the area vector is provided anyway, around no process time to lose.

A computer program or data set is preferably created by the present inventive definition of the irradiation pattern, which is transferred, for example, as a CAM data set to a controller 100 and then one or more corresponding irradiation devices or beam units (compare beam units S1 and S2) according to the fixed can control laid irradiation pattern 10 in order to achieve advantageous structural results in the additive manufacturing of the corresponding component.

In particular, for example, by means of selective irradiation of the entire material layer L with the beam unit S1, the area vector 1 shown on the left is irradiated in continuous line operation and at the same time the account vectors A, B and C in pulsed operation. Analogously to this, according to the invention, the second area vector 2 is preferably continuously irradiated and, at the same time, the contour vectors D and E in pulsed operation. The same applies to the third surface vector 3, which is also preferably continuously and simultaneously the contour vectors F, G and H are irradiated in pulsed operation. According to the invention, contour irradiation for a given irradiation area or a given irradiation pattern is no longer carried out after a corresponding area irradiation of the area, but in sections simultaneously with the area irradiation, as shown.

If a beam unit or additive manufacturing system is programmed with the irradiation pattern 10 defined as described above or a corresponding CAM file is read, for example into a corresponding controller, the left front area (compare the area around the first surface vector 1 in FIG 3) a corresponding layer L according to the irradiation pattern 10 are irradiated and solidified ver. A central area of the layer L (compare the area around the second area vector 2 in FIG. 3) is then preferably irradiated. Then a right rear area of the layer L (compare the area around the third area vector 3 in FIG. 3) is irradiated.

In contrast to what is shown in FIG. 3, according to the invention, one, two, three or more, for example four, five, six or more, in particular ten, 20, 50 or more contour vectors can alternatively or additionally be defined for each near-contour area vector an irradiation pattern 10 is considered to enclose the area vectors immediately. How many contour vectors are precisely defined or specified around a given area vector depends on the individual geometry of the component to be produced.

For a person skilled in the art, it is clear in the present case that for the proposed irradiation strategy not only the geometric irradiation pattern, as described, is adapted, but an adaptation to the irradiation pattern 10 also for further irradiation parameters, such as a scan or exposure Radiation speed, laser power, a track or strip spacing and / or strip width or other parameters, such as material parameters, is adjusted. The component to be produced additively is preferably a component that is used in the hot gas path of a flow machine, for example a gas turbine. In particular, the component can be a blade or guide vane, a segment or ring segment, a burner part or a burner tip, a frame, a shield, a heat shield, a nozzle, seal, a filter, a mouth or lance, a resonator, punch or denote a swirler, or a corresponding transition, insert, or a corresponding retrofit part.

The invention is not restricted to these by the description based on the exemplary embodiments, but rather encompasses any new feature and any combination of features. In particular, this includes any combination of features in the claims, even if this feature or this combination is not itself explicitly specified in the claims or exemplary embodiments.

Claims

1. A method for defining an irradiation pattern (10) of a material layer (L) for powder-bed-based additive manufacturing, comprising the following steps:

Defining an area vector (1,2,3) for the irradiation pattern (10) for programming a first beam unit (S1),

Defining a contour vector (A, B, C, D, E, F, G, H) for the irradiation pattern (10) for programming a second beam unit (S2), the contour vector (A, B, C) being directly linked to the area vector (1,2,3) and the irradiation of the area vector (1,2,3) coincides with the irradiation of the contour vector (A, B, C).

2. The method of claim 1 which is a CAM method.

3. The method according to claim 1 or 2, wherein per surface vector (1,2,3) one, two, three or more contour vectors (A, B, C) are defined, which the surface vector (1,2,3) in Auf view of the irradiation pattern (10) immediately enclose.

4. The method according to any one of the preceding claims, where in the area vector (1,2,3) for area-wide irradiation of the material layer (L) is set such that it has a, for example meander- or strip-like, modulation or superstructure of partial vectors (v ) having.

5. The method according to any one of the preceding claims, where in all contour vectors (A, B, C, D, E, F, G, H) of a coherent irradiation area of the irradiation pattern (10) are set such that they are along the same circumferential direction of the Irradiation area are aligned.

6. The method according to any one of the preceding claims, where for the irradiation pattern (10) a plurality of areas surface vectors (1,2,3) are set parallel to each other, and a plurality of contour vectors (A, B, C) which include these area vectors (1,2,3).

7. A method for selective irradiation in additive manufacturing, comprising irradiating a material layer (L) for the production of a component, the material layer (L) being irradiated according to the irradiation pattern (10) defined according to one of the preceding claims, and the first Beam unit (Sl) causes the irradiation of area vectors (1,2,3) of the irradiation pattern (10) with an energy beam, in particular laser, in continuous wave operation (CW), and the second beam unit (S2) irradiates contour vectors (A, B , C) the irradiation pattern (10) with an energy beam, in particular laser, acts in pulsed operation (PW) be.

8. Additive manufacturing method comprising the method for selective irradiation according to claim 7, wherein a geometry of the component is defined by a CAD file before the selective irradiation.

9. Controller (100) which is set up to control a first beam unit (S1) and a second beam unit (S2) for selective irradiation of a material layer (L) according to the irradiation pattern (10) defined according to one of the preceding claims.

10. Computer program product, comprising instructions which, when a corresponding program is executed by a computer, cause the latter to carry out the method according to one of claims 1 to 6.