Powder bed fusion additive manufacturing with load balancing for multiple beams

Abstract

A method for manufacturing a workpiece includes melting a region (A) of a layer of a fusible material by projecting a corresponding number of n beam spots onto n sets of positions (L i ) on the surface region (A) of the layer using at least two beam sources with a number n, where n≥2, to irradiate the surface of the region (A) of the layer, and each beam source has a predefined melting rate (R i ) and a field of view (F i ), (I), and the indices of L i , R i and F i represent the corresponding beam sources, i.e., 0 < i ≤ n, and the set of all beam source indication indices is I = {1,..., n}. If first for the region (A) and at least for the first beam source, i.e., for at least the first index i = 1, the optimal melting time t o (i) is estimated, then it is operated more efficiently by allocating at least IS1 := A ∩ F1 to determine the intersection set (IS i ) of the surface region (A) and the field of view (F i ) for at least the first index i = 1. This enables comparing the size (|S i |) of this intersection set with the product of the optimal average melting time t o (i) and the melting rate Rt of the corresponding i-th beam source, and if the relation to·R i < |S i | holds, then the subtracted surface S i following (II) can be determined, where for each (III), k > i, α i ∈ {0.25, 0.2, 0.15, 0.1, 0.05, 0.025, 0.01, 0.005, 0}. Next, a set of positions L i := IS i - S i can be allocated, and then the i-th beam source can be used to melt the set of positions. #imgabs0##imgabs1##imgabs2#

Description

Technical Field

[0001] The present invention relates to a method and an apparatus for a powder bed fusion process, and a storage medium comprising instructions for executing the method. Background Art

[0002] There are a variety of additive manufacturing technologies, which are also known as 3D printing processes. One of these technologies is the so-called powder bed fusion process. In a very concise summary, the powder bed fusion process involves iteratively applying a powder layer to a support structure and selectively adhering the powder particles to another or previously adhered agglomerate by heating the corresponding particles using an electron beam, a laser beam or any other kind of radiation beam (hereinafter collectively referred to as a "beam"). Adhering the particles of the powder bed by scanning the surface of the powder bed with a beam is called melting, regardless of the physical or chemical process (melting, sintering, welding, radiation-induced chemical reaction, ...) that provides the result of the adhered particles. Vividly speaking, it can be said that a cross-sectional view of the product to be manufactured is written on each newly applied top layer by moving the beam spot over the surface of the topmost powder layer. By adding a new powder layer after each writing step, a so-called powder bed is formed. Embedded in the powder bed is the already processed part of the workpiece. Depending on the final product, sometimes additional auxiliary structures must be "written" into the powder layer, but in this article we do not focus on this aspect, and we consider these to be part of the workpiece. Once all layers have been written, the workpiece, potentially with its adhesion aiding structures, can be removed from the powder bed and, if necessary, subjected to further processing.The terms product and workpiece are used interchangeably in this field and are therefore also used interchangeably herein.

[0003] Powder bed fusion processes are very capable, but it is desirable to reduce the manufacturing time for a given workpiece. To this end, it has been suggested to use multiple beams that independently write a portion of each layer of the workpiece (i.e. a portion of a "cross-sectional view") onto each layer of the powder bed. In addition, particularly where the upward facing surface of the powder is increased to manufacture larger workpieces, multiple beam sources can be distributed at different locations above the powder bed to reduce defects due to beam expansion and parallax. However, this approach has limitations, for example, fumes produced by a first beam may interfere with another beam, which is detrimental to the quality of the product. Other problems are related to heat dissipation in the powder bed or beam spot distortion. Beam spot distortion describes the effect of increased elliptical distortion of the beam spot formed on the powder bed as a function of increased deviation of the angle of incidence from nearly normal incidence.

[0004] WO 2016 / 075026A proposes to optimize a multi-beam laser powder bed melting process by virtually separating the surface of the powder bed into a plurality of surface segments, wherein each beam irradiates and thus melts the powder particles in a single surface segment assigned to the beam. Once all beams have finished writing on a layer, i.e. when the next powder layer can be applied to the powder bed, the operating time of each beam source - also referred to as the "beam-on-time" of the different beam sources - is compared and the boundaries between the surface segments are adjusted to compensate for the differences in operating time. For example, if beam source No. 1 has a shorter beam-on-time than beam source No. 2, when writing layer No. 1, the boundaries between the surface segments associated with beam source No. 1 and beam source No. 2 are moved to increase the surface area of ​​the surface segment associated with beam source No. 1 and to reduce the surface segment associated with beam source No. 2. Thus, when melting the next layer (i.e. layer No. 1+1), the idle time of the beam sources is reduced. Alternatively, the areas of the surfaces actually illuminated may be compared, and based on this comparison, the boundaries between surface segments may be adjusted to compensate for differences in the surfaces actually illuminated.

[0005] WO 2020 / 178216 A suggests controlling the position of the beam spots of a multi-beam laser powder bed melting process so that at any point in time, any line connecting two beam spots is parallel to the flow direction of the inert gas flow above the powder bed.

[0006] DE 10 2013 205 724 A1 proposes to improve the powder bed process by coordinating the direction in which the beam of the beam source scans a portion of the powder bed with the inert gas flow direction. This coordination can be achieved by limiting the angle between the scanning direction and the inert gas flow direction to the interval [22.5°, 337.5°], preferably to the interval [90° and 270°].

[0007] DE 10 2018 203 233 A1 proposes to scan a cross-sectional view of a workpiece by at least two lasers in a powder bed process. Each laser is assigned an area of ​​the cross-sectional view, i.e. the respectively assigned area is scanned by the corresponding laser. The boundary between the two adjacent areas of the cross-sectional view is a sawtooth line, thereby increasing the strength of the manufactured workpiece.

[0008] WO 2016 / 110440 A1 also relates to a multi-beam powder bed process. Each beam has a field of view, and at least two of these fields of view overlap. In order to increase the scanning speed, it is recommended to position the cross-sectional view to be irradiated by the beam at least partially in a part of the powder bed in which the fields of view of at least two beams overlap. The cross-sectional view is scanned simultaneously by the beams, wherein the distance between the simultaneously irradiated spots is reduced over time until the irradiated spots of the beams at least partially overlap, preferably completely overlap. The beam intensity is reduced as the overlap increases to maintain a constant energy provided to each spot of the scanned cross-sectional view. Summary of the invention

[0009] It is therefore an object of the present invention to further improve the multi-beam powder bed fusion process with the aim of reducing the costs for producing workpieces.

[0010] The invention is based on the observation that prior art proposals for defining a boundary between two adjacent surface segments of the surface of the top layer of a powder bed are based on the beam-on time measured when writing the previous layer. This process iteratively seeks the optimal boundary position and thus results in a significant accumulation of idle time. This approach becomes increasingly less efficient the more the surface area to be irradiated in different surface segments changes from layer to layer.

[0011] The solution to this problem is described in the independent claim. The dependent claims relate to further developments of the invention.

[0012] The method for manufacturing a workpiece includes melting a region A (referred to as "region A") of a surface of a layer (referred to as "layer") of meltable material. In practice, the layer may be the current uppermost layer of a powder bed above a powder bed support of an additive manufacturing machine configured to use and / or implement a powder bed fusion process. Once region A of the top layer intended to be melted has been melted, the next layer may be applied to the powder bed, for example using a recoater. Initially, the uppermost layer may be the first layer of the powder bed subsequently deposited during the process.

[0013] As is already evident, the term "area" does not denote the entire surface of the layer, but only a portion thereof that should be melted. Thus, the symbol A denotes a region that can be represented as a vector A set of positions (points) - all in the plane defined by the surface of the layer, which should and during the process are illuminated by at least one beam spot emitted by the beam source. Therefore, the symbol |A| represents a value indicating the size of the surface of area A, that is, |A| is the surface area of ​​area A. Using the language of technicians, |A| is the norm, usually referred to as ||A||, and we omit the second set of vertical bars in this article only for simplicity.

[0014] The area A may be the entire area EA of the layer to be irradiated, but in another example, the area A may be only a part thereof, i.e. For example, those parts of the entire area EA to be irradiated, which parts define, for example, a part of the contour of the workpiece, can be subtracted from the entire area EA, thereby obtaining an "area A". For example, the subtracted contour parts can, for example, always be irradiated by the same beam source to increase the quality of the workpiece surface defined by the contour. Alternatively or additionally, the "entire area EA" can be divided into sub-areas, for example to improve fume management. As already stated, the "area A" can be a sub-area of ​​the 'entire area EA'. In general, it can be said that this area A can be at least a part of a cross-sectional view of a workpiece manufactured by applying a laser powder bed fusion process, wherein the cross-sectional plane corresponds to the position of the layer of meltable material to be irradiated.

[0015] Area A may comprise a plurality of sub-areas, which we refer to as sectors, to distinguish in words the sectors from the previously discussed 'sub-areas of the whole area to be irradiated'. The sectors may be spaced apart from each other, i.e. there may be gaps between adjacent sectors of area A. Furthermore, as has been apparent, for the present invention it is immaterial which layer area A is associated with. All that is required is that area A may be irradiated by a beam emitted by a beam source. When referring to area A on a particular layer, the symbol A may be used. l Therefore, A l will be the area on the first layer of the powder bed, A 2 The area that will be the subsequent layer of the powder bed, A l is the area on layer 1. If the superscript is omitted, this means that the position of area A in the layer sequence is irrelevant and can take any number.

[0016] The area A is usually determined by a so-called "slicer" on the basis of a CAD model of the workpiece to be manufactured. However, the invention is not limited to this example.

[0017] As is already evident from the wording of melting a surface area A of a layer of meltable material, the method comprises melting a portion of the meltable material of the layer as defined by the surface area A. To this end, at least two spots of at least two beams are projected by at least two beam sources onto a set of positions defining the surface area A. The method can be used in the case where there are only two beam sources, but in practice the number is higher. Typical values ​​are between 8 and 12, depending on the size of the layer, but the invention is not limited to this range. It is expected that future powder bed melting devices will have a higher number of beam sources. In this article, we use "n" to represent the total number of available beam sources. This number "n" of available beam sources may be different from the number of beam sources of the powder bed melting device. For example, if one or more beam sources have been assigned the task of melting a contour portion that is not part of the area A, these assigned beam sources cannot contribute to melting the area A, but melt the corresponding contour portion. Once the assigned contour portion has been melted, these beam sources can be used to melt sections of the area, and thus the number "n" can be increased. Another reason why the number "n" is smaller than the number of installed beam sources may be to reduce the thermal power that needs to be removed from the workpiece, or simply because a section of region A will be so small that position management will be difficult. For example, if a section is very small, it will be almost impossible to avoid melting that section without operating in the smoke plume created by melting the powder bed in another section. Therefore, in short, the number "n" represents the number of lasers that are assigned to collectively melt region A. As will become apparent below, in assigning the positions of region A to multiple groups of positions L i During the process of (1≤i≤n), this number can even change, and the plurality of groups of positions can then be melted by the corresponding i-th beam source. For example, if the size of the area of ​​a group of positions is found to be within a predetermined threshold T i This may happen if the following

[0018] Each of the n (n≥2) beam sources has a predefined field of view F i , where index i indicates the corresponding i-th beam source, for example, F 1 is the field of view of the first beam source, F 2 is the field of view of the second beam source, or more generally, F i is the field of view of the i-th beam source. Field of view F i is the surface portion of the layer that can be illuminated by the corresponding i-th beam emitted by the i-th beam source. In fact, each field of view F i The field of view F can be defined by the scanner optics of the i-th beam source. i The constraints in may be imposed by the pivot range of the scanner optics, the limitations of the (optional) focusing optics, and the limitations of acceptable beam distortion.i can be understood as the portion of the layer that can be reasonably melted using the corresponding i-th beam source. i can be represented as the set of vectors on the surface of the layer that can be irradiated and thus melted using the i-th source Therefore, |F i | is the size of the portion of the surface of the layer that can be irradiated by the corresponding i-th beam source. In addition, each beam source i has a predefined melting rate R i (positive real number), where the melting rate indicates the size of the surface field that can be melted by the i-th beam source per unit time. The melting rate R i is the surface area at each time, and can therefore be calculated, for example, as For example, when melting a surface, the beam spot usually travels along a first vector defining a first melting trajectory until a stop condition is reached. Then, the beam can be turned off and the beam source repositioned to a new starting point. Next, the beam is turned on again and the beam spot travel can, for example, travel parallel to the previously melted melting trajectory. Therefore, the melting rate R i The calculation of can take into account the time required to reposition the beam source. In fact, the melting rate R i can be considered as an average melting rate, which can be determined iteratively with increasing accuracy. i The melting rate R may vary between different beam sources and may also depend on the given material to be melted. At least for a given material, the melting rate R i Preferably, they are at least nearly identical, which means in In another example, the melting rate R i is the length (times the width) of the track scanned by the ith laser per unit time, without taking into account the time required to reposition the laser beam optics when starting a new track.

[0019] Melting the region A may include for a corresponding set of positions L i Use the i-th beam source to illuminate the position on the layer Different groups of L i , where the intersection of different groups of positions is preferably empty, i.e., preferably the relationship This basically means that every position in region A Only a single beam source is used to melt the region. Generally, it is preferred to use all beam sources of the powder bed melting device to melt the region, but this is not necessary and, in some cases, may not even be possible (as explained above). Of course, different groups of positions L ican be irradiated simultaneously. In practice, the trajectories of the projections of the beam spots of different beam sources can overlap, for example similar to the overlap of segments of a single beam trajectory, to ensure a given intensity and surface quality in those areas of the layer where the final workpiece should not have gaps. There have been suggestions to use overlapping sets of positions for melting, but in this context - although not excluded - this is not contemplated. It is contemplated that |L i ∩L j |≤β L Max({|Li|,|L j |}, where Preferably β L = 0. Therefore, in general, it is expected that the area A is divided into n groups of positions L i , where n indicates the number of beam sources that should be used. Preferably, n indicates the number of beam sources that have a field of view with non-zero overlap with area A, i.e., satisfying F i ∩A≠{}. In another example, n indicates the number of beam sources with a field of view overlapping with area A greater than a threshold T, that is, only beam sources satisfying |F i ∩A|≥T i Those beam sources.

[0020] Preferably, before melting the region A, an optimal melting time t is determined. o (i) (Step 1.1). There are many possibilities to estimate the optimal melting time t o (i) and in a preferred example, the area |A| can be obtained by dividing the melting rate R of all involved beam sources. i The optimum melting time is determined by the sum of In this case, all beam sources will require the same amount of time to bring their respective group positions L i Melt, that is, idle time is minimized. Other estimates can also be used. For example, one can use or in Preferably β t，i = 0. Generally, the optimal melting time t o Any suitable measure of (i), preferably t o (i) Selected to follow Therefore, the optimal melting time depends on the size of the surface area to be melted |A|. Following the convention of the superscript indicating the number of layers, the optimal melting time can also be indicated as Unless necessary, for simplicity we will omit the superscript and the indication of the associated beam source "(i)".

[0021] Equivalent to determining the optimal melting time t o(i) It is also possible or additionally possible to determine the corresponding melting area In a preferred example

[0022] In addition, the surface area A of the first beam source and the first field of view (F 1 ) of at least the first intersection set IS 1 , therefore, US 1 : =A∩F 1 (Step 1.2). This is equivalent to determining those vectors of the region A on the surface of the layer that can generally be irradiated by the first beam source and therefore undergo melting by the first beam source. Furthermore, the intersection set IS can be determined i , where IS i is the intersection set associated with the i-th beam source. In one example, IS i It can usually be defined as However, as will become apparent below, other definitions may also be used. In addition, it should be noted that the intersection set IS i , i ≥ 2 preferably when a set of positions L has been determined as explained below i-1 To simplify the form, L can be limited to 0 :={} or more generally define

[0023] In a further step, at least the first intersection set |IS 1 The size of | and the optimal melting time t o (i) and the corresponding melting rate R of the i-th beam source i The product of is compared (step 1.3), and if the relation t o (i) R i <|IS i | holds true, then it is determined that (1-α 1 )·(|IS 1 |-t o (i) R 1 )≤|S 1 |≤(1+α 1 )·(|IS 1 |-t o (i) R 1 ) and its equivalent At least one of The subtractive surface S 1 , where for each Observe this condition (step 1.3.1). 1 can be considered as an error margin (so α 1 =0 is preferred), and is defined in detail below.

[0024] Likewise, by replacing index 1 with index i, this step can be generalized to obtain the i-th subtrahend surface S associated with the i-th beam source i , that is, in summary, if the condition t o (i) R i <|IS i | holds true, then use for each All conditions must be followed and (1-α i )·(|IS i |-t o (i) R i )≤|S i |≤(1+α i )(|IS i |-t o (i) R i )(and / or ) Determine the i-th subtrahend surface S i , where α i ∈ {0.25, 0.2, 0.15, 0.1, 0.05, 0.025, 0.01, 0.005, 0}. α i Smaller values ​​of are preferred. In a particularly preferred example, α i =0. If α i =0, then about |S i The constraint condition of | is simplified to |S i |=|IS i |-t o (i) R i These about S i The constraints make it possible to determine L i =IS i -S i , and thus a set of positions L can be determined i , the group position L i can be expected at the preselected optimum melting time t o (i) is almost exactly melted by the i-th source. Therefore, if all group positions {L i} are determined iteratively, for example as explained above, then they are selected so that the time for melting the region is minimized. This minimization is due to the fact that the proposed i} is determined by β t，i and α i Within the given error tolerance, it can be expected that all beam sources require the same amount of time to bring their respective group positions L i Melting. Idleness of the beam source is minimized.

[0025] In this paper, we assume that the steps are repeated for each i≤n, starting with the lowest value of i=1, and then in each iteration, this value is increased by one, i.e. before each repetition of step 1.1 or 1.2, i:=i+1 is performed. Based on the following assumptions: Determine the subtrahend surface S in ascending order i , that is, for a specific i, the subtrahend surface S has been determined i Then i is incremented by one. This order is not essential, but if it is lifted, the condition "k>i" will read as "where i can take a value for which the subtraction surface S k The two expressions are equivalent, since by renumbering the beam sources, the subtrahend surface S can be determined. i , noting that the index i steadily increases by 1 after a particular subtrahend surface has been determined.

[0026] Of course, the method can be repeated for each layer and thus the time for manufacturing the workpiece is minimized.For a given powder bed fusion apparatus, the cost for manufacturing the workpiece is reduced.

[0027] To reiterate vividly, the subtractive surface S i Therefore, it is a subset of vectors of region A, which is selected so that for irradiation by a set of positions L i :=IS i -S I The expected time for a given surface is <t i >Equal to the optimal melting time t o (i), where the accuracy is given by α i , β t，i The choice of is given. Assume t o (i) R i <|IS i |For all i and α=0 and β t，i = 0 are all true, then That is, the total time t required to melt area A using n beam sources simultaneously tot Yes tot =Max(t o (i)) and is equal to a lower limit inherent to the device and the material to be melted. At this point, it should be recalled that in practical applications, a workpiece may have thousands of layers, and therefore a small saving in the area irradiated on each layer accumulates into a non-negligible cost saving.

[0028] Once S has been determined for a given i i , you can use L i :=IS i -S iDetermine the i-th group position L i (Step 1.3.2), and the method can continue using the i-th beam source to make the corresponding set of positions L i Melting (step 1.4). Preferably, at least steps 1.2 to 1.3.2 are repeated for each other beam source, i.e. for all remaining beam sources (1<i≤n), before proceeding to step 1.4. Preferably, at least two different L i , L j , (i≠j) perform step 1.4. Simultaneously illuminate their correspondingly assigned surfaces L i The more the number of beams, the better. Preferably, all n beam sources irradiate simultaneously.

[0029] If segment L i is below a given threshold, for example, the threshold T explained above. i Above, the section L i Can be set to zero (L i :={}), which is equivalent to reducing the number of beam sources to n-1, that is, if |L i |<T i , the i-th beam source can be removed from the pool of n beam sources.

[0030] The following situations may exist: area A and field of view F i The overlap between them is so small that the illumination corresponds to the set of interest IS i =A∩F i The time required is less than the optimal time t o (i), in this case, t o ·R i >|IS i | is correct. In this case, we can simply specify L i :=IS i , but in practice, it may be necessary to have L i The defined shape, or L i does not extend in a predetermined sector of region A. Therefore, more generally, in satisfying each Under the condition of i ,in In addition, at t o ·R i >|IS i |In the case of |S i | is preferably minimized. Once S i It has been determined that using L i :=IS i -S i To determine a set of positions L to be illuminated by the i-th beam sourcei , that is, the method can continue to step 1.4.

[0031] Condition "satisfy each "Written in simple language, for each vector (The vector is the subtrahend surface S i There is at least one field of view F k , so that the field of view F k Include this vector where index k is greater than index i. This condition ensures that the intersection set IS i Any point / position of the removed area A can be obtained by k is irradiated by at least one other beam source that has not yet been determined, the latter following k>i. Therefore, any position in the area A that can only be melted by a finite number of beam sources forming an index set X is assigned at the latest to a set of positions L having the highest index of said set X Max(X) .

[0032] The corresponding expected value of the time for the i-th beam source to illuminate the surface of the layer is read out in the other case <t i >=L i / R i In summary, it can be said that at t o ·R i ≥|IS i |, that is, in the “ELSE” case of step 1.3 (i.e., if (t o ·R i ≥|IS i |)), can be in the condition (1-α i )·(|IS i |-t o ·R i )≤|S i |≤(1+α i )·(|IS i |-t o ·R i ) is released and steps 1.3.1 and 1.3.2 are performed at the same time.

[0033] Preferably, especially at t o ·R i ≥|IS i | (but generally in any case), you can use something like In the subsequent iteration of step 1.1 (ie after setting i:=i+1) the corrected minimum time t is calculated o (i+1)—also called t′ oThis corrected minimum time can then be used in future executions of steps 1.3 to 1.3.2 and replaces the initially calculated or estimated optimal melting time. o This adjustment of (i) enhances uniform load distribution among a set of beam sources whose positions have not yet been determined, i.e. |L j The variation of |(i<j≤n) is reduced. This provides a further increase in the efficient use of the capabilities of the device and thus translates into a reduction in the manufacturing costs of the corresponding workpieces.

[0034] The procedure for calculating the corrected minimum time can be summarized by recalculating the (corrected) minimum optimal time at each iteration, i.e., in step 1.1, t o (i) It can be and Equivalent to If i = 0, the term And therefore Likewise, the preferred case is β t (i) = 0, and i indicates the i-th execution of the step. As already apparent, β as defined above t，i is used as an error tolerance, and t o (i) is chosen to be within the bounds given by the choice of “+” or “-” for “±”. In general, for each iteration β t，1 =β t (i) can be different, but for simplicity we will also write β t If the non-negligible α i The step of calculating the minimum time for correction is particularly useful if the influence of is accumulated. In short, both possibilities take into account the calculation of L i For each iteration, the optimal average melting time t o The actual expected melting time <t i >=|L i | / R i If not resolved, these differences can lead to n |Significantly larger than all other L j , (1≤j<n), and therefore, the significant idle time of beam sources 1 to n-1 reduces the efficiency of the additive manufacturing process. Therefore, the step of also recalculating the updated optimal average melting time further helps to reduce the operating cost per workpiece.

[0035] If segment L i is below a given threshold, for example, the threshold T as explained above. i Hereinafter, the section L i Can be set to zero (L i:={}), which is equivalent to reducing the number of beam sources to n-1, that is, if |L i |<T i , the i-th beam source can be removed from the pool of n beam sources. Of course, in this case, it is preferred to calculate the corresponding melting area The minimum time of the correction and / or the optimal size of the correction.

[0036] The threshold T can be defined individually for each i-th beam source i The threshold value may also be set manually for each beam source individually or for all or multiple beam sources, for example, based on the operator's experience. In a preferred example, the threshold value T i The melting area The optimal size of the settings section. For example in

[0037] Preferably, the method further comprises defining at least a first (preferably meandering) line B i，j , and also preferably, defining a second (preferably meandering) line B i，k , where the first (preferably meandering) line B i，j In the first direction extends (preferably meandering) upward, and a second (preferably meandering) line B i，k In the second direction The first (preferably meandering) line can be used to limit the subtractive surface S i In at least the first direction Similarly, a second (preferably meandering) line may be used to limit the subtrahend surface S i In at least the second direction Thus, at least one of the first (preferably meandering) line and the second (preferably meandering) line determines a subtrahend surface S i At least one of these first (preferably meandering) lines and second (preferably meandering) lines may be moved to reduce ΔS i , where ΔS i =|t o (i) R i -|IS i -S i ||. Further preferably, when in another S i Then determine S j (i.e., i<j), and if the i-th beam source and the j-th beam source are adjacent (or at least have overlapping fields of view), then B j，i =B i，j .

[0038] During this movement, the first (preferably meandering) line B i，j Preferably at least substantially orthogonal to the first direction The movement and / or the second (preferably meandering) line is preferably at least substantially orthogonal to the second direction Move to reduce ΔS i , preferably until condition 1.3.1 is satisfied. As is already evident, these two vectors are preferably linearly independent (condition 5), and particularly preferably, they are at least substantially orthogonal to each other, i.e. preferably The exception is that the vector The indices of are not associated with one beam source; they are only used to distinguish these vectors. However, the indices of the line gas are associated with two beam sources, namely the i-th beam source and the j-th beam source, and are used to determine all L i Afterwards, the (preferably meandering) line B i，j Separate multiple groups of positions L i and L j .

[0039] If line B i，j With compliance conditions The first endpoint And if and If this is not true, then line B i，j along Direction or Zigzag in direction.

[0040] So that in a set of positions L i Melting the meltable material at the position may include pivoting the i-th beam source while the i-th beam source projects the i-th beam spot, so that the i-th beam spot is along the vector In a preferred example, the zigzag line includes a plurality of lines perpendicular to or parallel to connected segments or by alternating order perpendicular to or parallel to The connected segments are composed of (step 6).

[0041] Particularly preferably, the method further comprises first performing steps 1.2 and 1.3 (and of course optionally all other steps) for the beam source having the field of view which overlaps the least with the fields of view of the other beam sources. Next, performing said steps for the beam source having the field of view which overlaps the other fields of view the second least, and so on. This helps to reduce the number of subtrahend surfaces S corresponding to the calculations i , because in this way, firstly, those parts of the area are assigned to a set of positions L that can only be illuminated by a single beam source in the worst case. i, which - if not taken into account - may lead to a situation where a single beam source runs much longer than other beam sources. Steps 1.2 and 1.3 (and of course optionally any of the other steps) are performed first for the beam source with the field of view that overlaps the least with the fields of view of the other beam sources, and so on, which can be obtained by sorting the indices of the beam sources so that the first (i=1) beam source has the field of view F with the least overlap 1 , and the second (i=2) beam source has the second least overlapping field of view F 2 , and so on. In other words, this means that preferably initially, but at the latest before step 1.2, the field of view F i The index is preferably sorted to follow the condition And repeat at least steps 1.2 and 1-3, while increasing the index value by one each time, until index i=n. Of course, for those F i ∩A=F of {} i , the sorting can be omitted, because it is obvious that the corresponding set of positions L i is empty, that is, L i ={}.

[0042] Additionally or alternatively, the method may include (also before step 1.2) performing a i The indexes are sorted to follow the condition And repeat steps 1.2 and 1.3 and optionally repeat at least one of steps 2.1 to 2.3, while increasing the value of the index by one each time. Similarly, one can arbitrarily choose a i ∩A = the position of the beam source indexed by {}. Again, this sorting step makes the subtrahend surface S i is easy to determine while keeping the error margin α small i , i.e. reducing the avoidable idle time of the beam source which would normally help to melt area A.

[0043] The method may further include, in determining the subtrahend surface S i Previously, a portion of area A, C i is assigned to a dedicated i-th beam source. In practice, the beam sources are calibrated to operate in the same coordinate system. However, this calibration is not perfect and may deteriorate during the manufacturing process. i When a priori assigned to a dedicated i-th beam source, the defect of the workpiece is in this part C i can be reduced, so Part C i In the field of view F iTypically, such an allocation increases the total manufacturing time because the load distribution between different beam sources deteriorates. In a preferred embodiment of the present invention, by determining the subtraction surface S in step 1.3.1 and / or step 2.1, for example i Consider the additional constraint S i ∩C i = {}, this degradation can be avoided. Following the additional constraint S i ∩C i ={} Ensure that part C i is a set of positions L determined later by the i-th beam source i subset, and in step 1.3.1 the load balancing constraint (1-α i )·(|IS i |-·t o ·R i )≤|S i |≤(1+α i )·(|IS i |-·t o ·R i ) is considered due to part C i The resulting set of positions L i Additional size.

[0044] In a preferred embodiment, when step 1.2 is repeated, the intersection set IS j (j≥2) is determined as This step provides a number of advantages: memory requirements are reduced and further determination of a suitable subtrahend surface S i The idea behind this improvement is that the positions L have been allocated to multiple groups of positions L in the previous execution i of at least one of steps 1.2 to 1.3.2 and / or steps 1.2 to 2.3. i , the field of view F of (i<j) i Those parts of need not be included in further consideration. When the condition ≥2 can be lifted, that is, IS j Can be limited to

[0045] During the melting process, i.e. during operation of the beam source, it is preferred to establish an inert gas flow above the top of the powder bed, so as to remove fumes and other residues from the field of view F. iPreferably, a flow in a flow direction parallel to the top surface of the layer is established, for example by arranging at least one inlet nozzle on a first side of the top layer and at least one outlet nozzle on an opposite side of the top layer, and by establishing an inert gas flow from the inlet nozzle to the outlet nozzle, thereby defining a main flow direction. In other words, the method may also include establishing a flow direction above the top of the powder bed The inert gas flow on represents the (preferably normalized) component parallel to the flow direction of the layer of meltable material, i.e. the flow direction Projection onto area A. For example, if the z-axis is perpendicular to the surface of the layer of meltable material (and therefore perpendicular to area A), then a Cartesian coordinate system is used: in Just set up is a normalization factor for , and can be omitted. Usually, d x d y and d z They are vectors The x-, y-, and z-components of

[0046] Parallel to the flow direction of the layer Preferably with limiting subtractive surface S i The zigzag line B i，j is associated with an extension of and defines the adjacent group position L i and L j The boundary between these two sets of positions L i and L j The boundary between i，j With first endpoint The first endpoint Follow the conditions This means that the first endpoint and boundary B i，j Any other point Any distance between exists only once. Therefore, B i，j Any sub-section in the direction of flow has a non-zero extension in the direction defined by the horizontal component of . In this case, the relationship and is preferably not implemented, so B i，j Not a straight line, but basically parallel to the flow direction The horizontal component is tortuous.

[0047] Alternatively, boundary B i，j Can be perpendicular to the flow direction In this case, the relationship in is followed, and the conditions Preferably not implemented.

[0048] These measures, referred to as conditions 13.1 and 13.2, are each greatly simplified to coordinate the movement of n beam spots over the layer so that at any moment, while the beam sources are operated simultaneously, no beam spot is below the smoke generated by another beam spot.

[0049] As stated above, the beam source can be pivoted when irradiating the surface so as to project a beam spot onto the layer. Thus, preferably, each beam spot is moved over the surface of the layer and so as to project a beam spot onto the layer at a corresponding set of positions L i Position in In other words, the meltable material at a set of positions L i Melting the meltable material at the region A comprises: pivoting the i-th beam source when the i-th beam source projects the i-th beam onto the region A, thereby moving the i-th beam spot. Preferably, the movement of the i-th beam spot can be performed by a flow direction of the inert gas flow. Vector of opposite components It can be said that the beam spot moves towards the gas inlet and the melting process is therefore less affected by the fumes previously generated by the beam spot. Subsequently, the beam source can be switched and repositioned to continue the process again by When moving in a limited direction, irradiate L i Thus, the quality of the workpiece to be manufactured is improved.

[0050] For example, if condition 13.1 applies to B i，j and B q，r Second, multiple sets of positions L i , L j , L q and L r Can be parallel to The zigzag line is divided into m parts L s，1 , L s，2 , ..., L s,m , (m≥2), and among them (the factor 0.15 can be replaced by any other value of {0.1, 0.05, 0.025, 0.1, 0.005}), where the parts with the same second index are parallelized The beam spots are aligned and only the portions with the same second index are irradiated simultaneously. This provides a very effective and simple measure to avoid that the smoke generated by any beam spot affects the melting of the meltable material by another beam spot. The increase in the number of portions makes it possible to increase the number of portions perpendicular to the vector The minimum distance between two beam spots measured. Parallel or perpendicular to A meander means that the line between the end point of the corresponding line and any other point of the line is parallel to or perpendicular to The distance measured is unique (condition 13.1 or 13.2 applies to the line, respectively).

[0051] Preferably, the region A is divided into a horizontal component at least substantially parallel to the inert gas flow. Preferably, during melting, only positions l in every two strips are extended. i are melted simultaneously. Therefore, between two beam spots is at least a distance corresponding to the width of the corresponding beam spot. By choosing the width of the strips, it is avoided that any beam spot melts at a location where the concentration of fumes generated by another beam spot is significant. Therefore, between two strips irradiated simultaneously, there are c-1 strips that are not irradiated, and their width is the minimum distance separating the two beam spots. It is already obvious that the boundaries of at least some of the strips are preferably given by meander lines as explained above.

[0052] Just to avoid any misunderstanding, we remember that usually this layer is the top layer of the powder bed. In addition, in this article, usually, "{}" represents an empty set. In this article, we also use the number "0" to indicate that a set is empty, that is, if a set V is empty, it can be represented as V = {} and V = 0.

[0053] In this context, "at least substantially perpendicular" or "at least substantially orthogonal" means that an angle of 90° is preferred, but deviations may be accepted, so that the angle may be within 90°±45°, 90°±30°, 90°±15°, 90°±10°, 90°±5°, 90°±2.5°, 90°±1° or 90°±0°. Similarly, "at least substantially parallel" allows deviations from a completely parallel alignment, i.e., angles within 0°±45°, 0°±30°, 0°±15°, 0°±10°, 0°±5°, 0°±2.5°, °±1° or 0°±0° may also be selected, wherein exactly parallel (±0°) is preferred. In addition, if the vector and vector are perpendicular or parallel respectively, then in the vector and vector Two meander lines that meander in a given direction are considered to be perpendicular or parallel. BRIEF DESCRIPTION OF THE DRAWINGS

[0054] The present invention will be described below by way of example and not by way of limitation of the general inventive concept with respect to examples of embodiments with reference to the accompanying drawings.

[0055] Figure 1 An additive manufacturing device is shown,

[0056] Figure 2 A top view of the upward facing surface of the powder bed is shown,

[0057] Figure 3 Shows Figure 2 Details of D 1 .

[0058] Figure 4 Shows Figure 2 Details of D 11 .

[0059] Figure 5 The method for determining multiple sets of positions L is shown. i Flowchart of the method.

[0060] exist Figure 1 , a first embodiment is shown. The additive manufacturing device 1 is shown in a cross-sectional view and has a process chamber 5, which is surrounded by side walls 7, a bottom 8 and a ceiling 9. In the bottom is an opening 81. Below the opening is a support 82 that is movably supported as indicated by the double-headed arrow 2. On top of the support is a powder bed 12 with a top layer having a surface 14. As outlined, a portion of a workpiece 6 can be embedded in the powder bed 12.

[0061] Figure 1 The surface 14 of the powder bed may be formed by n beam sources 20 i Projected beam spot 22 i Irradiation. A number n = 8 beam sources 20 are depicted. i , but this is only a preferred example, and any other number n≥2 may be selected. Figure 2 In the position irradiated by the i-th beam spot emitted by the i-th beam source, The powder particles of the powder bed 12 at are melted together. Figure 1 For simplicity, only a single beam spot 22 is indicated. i and a single location However, in practice, it is preferred to emit at least two beam spots 22 simultaneously, for example, at least three, at least four or at least five beam spots 22. i Preferably, all n beam sources 20 i At the same time, each position (i.e. 1≤i≤n) emits a beam spot 22 i . Beam source 22 i can be pivoted so that the beam spot 22 i moves over the surface 14, and each beam source 20 i A set of locations can be illuminated The index i indicates the corresponding beam source 20 of the n beam sources.i Once all groups of positions L i are all irradiated, then the area has been irradiated (see Figure 2 ). Thus, area A may be the top surface of the corresponding layer of workpiece 6 or at least a portion thereof. Once area A has been irradiated, the support may be made to lower the thickness of the powder layer and a new powder layer may be applied, for example using a so-called coater, advancing over opening 81. Subsequently, the beam source 20 may be used. i The next surface 14 of the new uppermost layer of the powder bed 12 is irradiated.

[0062] During melting of the surface 14 of the powder bed, fumes appear at the location of the surface These fumes can be removed from the process chamber by establishing an inert gas flow 3 above and on the surface 14 of the powder bed 12, which is indicated by the dashed arrows 3. The dashed arrows 3 each have a common projection on the bottom 8, indicated as a dashed arrow Therefore, the vector is the direction of the horizontal component of the inert gas flow 3 above and on the surface 14. In other words, the inert gas flow 3 has a component parallel to the upwardly facing surface of the support

[0063] A programmable electronic circuit 10, referred to as a controller 10, controls at least a plurality of beam sources 20. i Preferably, at least one of the inert gas flow 3 , the applicator, and the movement of the support 82 may also be controlled by the controller 10 .

[0064] Figure 2 A top view of the surface 14 of a layer of the powder bed 12 is shown. Each cross mark 20 1 Up to 20 14 A beam source 20 is shown on the surface 14 i (ie, n=14 in this example). Or in other words, the position of the cross mark 20 can be obtained by the projection of the beam source 20 onto the surface 14. Just to be able to refer to a specific beam source 20, we add a subscript to each cross mark, i.e. 20 1 and 20 4 , respectively indicate the cross-shaped marks representing the projections of the first beam source and the fourth beam source. i (1≤i≤n) indicates a cross sign representing the i-th beam source. Figure 1 It is stated that the present choice of n=14 is only an example. The only condition on the number n of beam sources is that n≥2.

[0065] Each beam source 20 i A specific portion F of the surface 14 may be illuminatedi These surfaces F 1 , ..., F 14 It is called the field of view F i . Figure 2 An example region A is also shown. Embodiments of the present invention enable portions of region A to be assigned to different beam sources and subsequently melt the powder in region A while operating a maximum number of beam sources simultaneously. Idle time of beam source 20 is reduced. Region A may be calculated based on a CAD model of workpiece 6, where "CAD" stands for "Computer Aided Design" and thus a CAD model is a description of the workpiece that enables the workpiece to be manufactured.

[0066] As already explained above, the beam sources are marked with an index or in any other suitable way, which makes it possible to distinguish two of them. In this paper, we assume that the first beam source 20 1 At the beginning, the i-th beam source 20 is determined in ascending order. i Multiple groups of positions L i This ascending order is not required, but simplifies the explanation and understanding of the invention.

[0067] Once the beam source 20 i The area A to be marked and illuminated has been determined, and the field of view F can be determined. i The intersection set IS with area A i , usually IS i =F i ∩A, such as Figure 5 Thus, the method may at least include determining IS 1 :=F 1 ∩A. In addition, the optimal melting time t can be determined o (1). This can occur when determining IS i The optimal melting time t o (i) can be considered to make the subsequently determined portion L of the region A i An estimate of the time required for melting. In other words, determine the size of the group of positions |L i |, so that it can be expected that the group position L i The optimum melting time t o (i) The i-th beam source 20 i Melt.

[0068] Preferably, the actual melting time t a (i) are all the same, and in this case the optimum melting time for the first source can be estimated as The value R i is the melting rate of the i-th source (see Figure 5 ). Usually, the melting rate R of the i-th source i is the size of the test surface T and the time t required to melt the test surface t The quotient of (i), i.e. Determine t o This example of (1) is not for t o (i) is the only valid choice. Typically, it is written as t o (i)(i.e. ) can be considered reasonable, usually can be considered as a reasonable range of tolerance, such as β t，i ∈B, where B = {0.25, 0.2, 0.15, 0.1, 0.05, 0.025, 0.0125, 0.01, 0.005, 0.001}. Preferably, β t，i A smaller value, particularly preferably β t，i =0.

[0069] If it has been determined that o (1), the method can proceed to determine the first subtraction surface S 1 (See Figure 5 ). The first subtrahend surface S 1 IS is the first intersection set 1 A subset of And as the name suggests, it was taken from IS 1 Subtract to determine the first set of positions L 1 When determining the first subtrahend surface S 1 When , only the first intersection set IS can be considered 1 Those points are also included in the other fields of view F k , (k≠1). In a more concise way, this can be expressed as Interpretation: for the subtrahend surface S 1 All points Field of view F k , so that these points is at least one field of view F k elements of , where k can take any integer value greater than 1. This condition ensures that the elements from the intersection set IS 1 The removed (subtracted) points can be illuminated by another beam source. In addition, adjust |S 1 | is as large as possible to reasonably meet the constraints (1-α 1 )·(|IS 1 |-t o (1) R 1 )≤|S 1 |≤(1+α1 )·(|IS 1 |-t o (1) R 1 ). This means |IS 1 |≥(1-α 1 )·t o (1) R 1 As explained above, Selected α 1 The smaller the better, that is, the particularly preferred α 1 = 0. Once S 1 It has been determined that the first set of positions L to be illuminated by the first beam source 1 It can be determined as L 1 :=IS 1 -S 1 .

[0070] There may be some cases where the constraints (1-α) cannot be satisfied. 1 )·(|IS 1 |-t o (1) R 1 )≤|S 1 |≤(1+α 1 )·(|IS 1 |-t o (1) R 1 ) because IS 1 The size is less than (1-α 1 )·t o (1) R 1 (See Figure 5 ). In this case, you can select S 1 :={}=0, but there may be other conditions to observe, which may require finding a non-zero subtraction surface S 1 This can be summarized as follows: If the constraint (1-α i )·(|IS i |-t o (i) R i )≤|S i |≤(1+α i )·(|IS i |-t o (1) R i ) cannot be satisfied because IS i (i.e. |IS i |) is smaller than (1-α i )·t o (i) R i In this case, you can select S i: = {} = 0, but there may be other conditions to observe, which may require or at least make it advantageous to find a non-zero subtracting surface. i An example is when the adjacent surface L i and L j The border between should have a predefined shape.

[0071] As explained above, it is preferred that the multiple groups of positions L i With a threshold value T i The size above, namely |L i |>T i If this condition cannot be met, then S i Can be set to IS i , that is, S i :=IS i , which is equivalent to removing the i-th beam source from the pool of available beam sources.

[0072] These steps can then be repeated for the next beam source, which in this example is the second beam source. Formally, this can be described as replacing index 1 with index 2 and by using t o (2) Replace t o (1) to repeat the steps (see Figure 5 ). Thus, this repetition provides a second set of positions L 2 In a more general way, we can say that once the i-th group of positions L i has been determined or at least can be determined because IS i and S i It is known that the method is repeated for all remaining beam sources, or in other words, i:=i+1 until i=n. In explicit language, this means that preferably for each i∈I a new optimal time t is determined. o (i) Preferably, the new optimal time takes into account the time required for the beam source with the lower index to be expected <t j >, (j<i) any deviation. For example More generally, and to allow for small deviations from the suggested optimum, the optimal time for the update can be determined to obey the constraint It is equivalent to Or in short If i = 0, the term And therefore Likewise, the preferred case is β t，i =0.

[0073] Next or similarly, in determining an updated optimal melting time t o (i) Before, using ISi :=F i ∩A determines the next intersection set.

[0074] Once IS i and t o (i) is determined, the method can proceed to determine the corresponding subtrahend surface S i steps, where S i Follow the conditions And if |IS i |≥t o (i) R i , S i Further follow (1-α i )·(|IS i |-t o (i) R i )≤|S i |≤(1-α i )·(|IS i |-t o (i) R i ), and α i ∈{0.25, 0.2, 0.15, 0.1, 0.05, 0.025, 0.01, 0.005, 0}.

[0075] Once IS i and S i is determined, the method can be performed to define L i :=IS i -S i , and increase i by one (i:=i+1, unless i=n), and repeat the process until n sets of positions L i , 1≤i≤n has been determined. Then, the controller can control the beam source 20 i so as to make their corresponding beam spots 22 i Project to the corresponding multiple sets of positions L i superior.

[0076] about Figure 3 Explain the method used to determine the subtrahend surface S i An example of . Figure 3 shows a graph with some additional information Figure 2 Details of D: Determine the subtrahend surface S i This may include determining at least a first meander line B i，j .exist Figure 3 In the example, there are two zigzag lines, the first zigzag line B 1，j Parallel to flow direction Extends, and the second zigzag line B 1,k Perpendicular to Parallel to (therefore ) extends. It can be seen that the first zigzag line has a first endpoint Line B i，j Along direction or in the direction The upper zigzag, because line B 1，j As the first endpoint And the zigzag line B 1，j Any point on With to the first endpoint The only distance, therefore, is the zigzag line B 1，j Follow the conditions Also in this example is the preferred choice. Orthogonal, zigzag line B 1，j The distance of the points is not unique, that is and In the preferred example described, the first zigzag line B 1，j has a melting vector that can be described as A multiple of a straight line segment, and further straight line segments extending at an angle, preferably orthogonal to the melting vector Therefore, the corresponding vector is indicated as Melt Vector is to make the group position L i The vector along which the i-th beam spot moves over the surface during melting.

[0077] exist Figure 3 In the example, there is a first zigzag line B 1，j Optional second meander line B that meanders orthogonally 1，k .therefore, Also in this example It is emphasized that this option is only an example and other options may also be used. Preferably, and are linearly independent (i.e. ).

[0078] When determining the subtrahend surface S 1 (More generally S i ), we can simply move the zigzag line B 1，j and B 1，k (More generally B i，j and B i，k In a preferred exemplary embodiment, the corresponding meander line B i，j and B i，kAt least substantially perpendicular (i.e., within 90°±45°, ±30°, ±15°, ±10°, ±5°, ±2.5°, ±1°, or ±0°) to their respective vectors and Move until S 1 (More generally S i ) is followed. In other words, line B i，j and B i，k The subtractive surface S can be defined i The inner boundary of the field of view F i The boundaries are provided by, or preferably by, IS i The outer boundary of the i-th beam source is provided by the terms “inner” and “outer”, where the terms “inner” and “outer” refer to the field of view F of the corresponding i-th beam source. i The position defined by the center of is denoted herein by “x” representing the corresponding projection of the i-th beam source.

[0079] exist Figure 3 In the example, determine the subtrahend surface S i Only two meander lines are needed. In this example, this is because area A is relative to the first field of view F. 1 The center of the i-th field of view F i center) position.

[0080] If area A is relative to the field of view F of the i-th beam source i If the geometry and / or position of the subtrahend surface is different, three or four of the meander lines may be required to determine the inner boundary of the subtrahend surface.

[0081] Figure 4 A corresponding example is shown in . Figure 4 Shows Figure 2 Another detail of the eleventh field of view of the eleventh beam source is located at the center of the projection. Again, the number 11 is only an example and can be generalized. When determining the eleventh subtrahend surface S 11 , the zigzag line can be used again, in which case it can be marked as B 11,j , B 11，k and B 11，i When S is determined 11 When the first group position L 1 and the second set of positions L 2 has been determined, and therefore the 11th intersection set IS 11 By B 1，j′ and B 2，j″ Restrictions. Figure 2 As can be seen in B 1，j′ and B 2，j″ The left part of the defined surface is not in the field of view F ior any other beam source except the 11th beam source. Therefore, for B 1，j′ and B 2，j″ Points between and to the left of the circle defining the boundary of F_13, cannot satisfy the equation about S 11 The constraints are Therefore, it involves S i The result is j′=j″=11, and B is obtained. 11,1 :=B 1，11 and B 11，2 :=B 2，11 Therefore, only a single meander line B 11，l The position of must be determined by moving it, e.g. at least substantially perpendicular to move, In this example follow exist Figure 4 In other words, the zigzag line B 11,l (Generally, B i,l ) is moved until the 11 (As S i Thus, in the example depicted, it is sufficient to determine the remaining conditions of IS 11 The contour and zigzag line B 11,5 , B 11,6 and B 11，l The dimensions of the enclosed surface are used to determine the |IS 11 -S 11 |(Generally, |IS i -S i |). If the size |IS 11 -S 11 |greater than (or less than) (1±α i )·t o (i) R i , then the zigzag line B 11,l Move slightly to the left (or right, respectively) until (1-α i )·(|IS i |-t o ·R i )≤|S i |≤(1+α i )·(|IS i |-t o ·R i ).

[0082] Next, the method can proceed to determine the next subtrahend surface S i+1 (In the given example, S 11+1 =S 12).

[0083] If the subtractive surface S is determined based on the contribution of the i-th beam source to the melting of the region A, i The example method can be particularly easily implemented if the order of the contributing capabilities is . The measure for this contribution capability can be considered as their corresponding field of view F i The size of the overlap with area A. Therefore, it can be directly seen that Figure 2 In the example, |F 1 ∩A|≤|F 2 ∩A|, or generally If |F i ∩A|=0, then L i ={}, and it does not matter in which step of the sequence this result is assigned or determined. Therefore, in a preferred example, the subtraction surface S is determined i And thus determine multiple sets of positions L i The order is preferably to represent the field of view F with the smallest overlap with area A. i The index of the beam source starts, and preferably the index is sorted so that |F i ∩A|=|IS i |as i increases. Just to avoid any misunderstanding, it is repeated that, of course, if |IS i |=0, at which point in the method is L executed i :={} does not matter, it can be at the beginning, at the end, or at any other point in time.

[0084] Reference Number List

[0085] 1 Additive manufacturing device

[0086] 2 Double-headed arrow indicating the movement of the support 82

[0087] 3 Inert gas flow

[0088] 5. Processing Chamber

[0089] 6 Workpiece (partially manufactured)

[0090] 7 Side wall of processing chamber 5

[0091] 8 Bottom of treatment chamber 5

[0092] 81 Bottom opening 8

[0093] 82 movably supported support member

[0094] 9 Ceiling of treatment chamber 5

[0095] 10 Programmable electronic circuits / controllers

[0096] 12 Meltable Materials

[0097] 14 Top surface of the meltable material

[0098] 20 i The i-th beam source / the projection of the i-th beam source

[0099] twenty two i The i-th beam source 20 i The i-th beam spot

[0100] F i Field of view of the i-th beam source

[0101] L i Waiting for the i-th beam source 20 i A set of melting positions

[0102] The horizontal component of the inert gas flow in the process chamber 5

[0103] At least substantially perpendicular to Vector

[0104] vector

[0105] vector

[0106] vector

[0107] vector

[0108] vector

[0109] vector

[0110] B i，j Zigzag line (i, j ≤ n, i ≠ j)

Claims

1. A method for manufacturing a workpiece, comprising: - melting a region A of a layer of fusible material by projecting n beam spots corresponding to at least two beam sources with a number n, n≥2, onto n sets of positions L of the region A of the layer to irradiate the surface of the region A of the layer, where i each beam source has a predefined melting rate R and a field of view F i , and the indices of L i , L j , R i and F i represent the corresponding beam sources, i.e., 0 < i ≤ n and 0 < j ≤ n, and the set of all beam source indication indices is I = {1,..., n}; characterized in that the method further comprises at least the following steps: 1.

1. Estimate the optimal melting time t for the region A, at least for the first beam source, i.e., at least for the first index i = 1, o (i) and / or the optimal size of the melted region 1.

2. Determine the intersection set IS i of the region A and the field of view F i , i.e., assign IS i := A ∩ F i ; 1.

3. Compare the size |IS i | of the intersection set with the product of the optimal melting time t o (i) and the melting rate R i of the corresponding i-th beam source and / or with the optimal size of the melted region , and if the relationship t o (i)·R i < |IS i | and / or holds, then 1.3.

1. Determine that (1 - α i )(|IS i | - t o (i)·R i ) ≤ |S i | ≤ (1 + α i )(|IS i | - t o (i)·R i ) and At least one of The subtractive surface S i , where for each Under the condition of i<k≤n, α i ∈{0.25, 0.2, 0.15, 0.1, 0.05, 0.025, 0.01, 0.005, 0}, and 1.3.

2. Allocate L i :=IS i -S i ,as well as 1.

4. After step 1.3.2., use the i-th beam source to make the position L of the group i The meltable material melts at the location.

2. The method according to claim 1, It is characterized in that If the relationship t in step 1.3 o (i) R i <|IS i | and / or If not, the method further comprises at least the following steps: 2.

1. For each Determine the subtrahend surface S under the condition i ,in as well as 2.

2. Assigning L i :=IS i -S i .

3. The method according to claim 2, It is characterized in that The method further comprises: 2.

3. Calculation of the corrected minimum average time of the melting area and / or correct the optimal size And then for the subsequent execution of step 1.2 and step 1.3, use t′ o Replace t o (i) and / or use |L opi′ |Replace in <t i > is limited to 4. The method according to claim 3, It is characterized in that The method further comprises: 3.

1. If and only if IS i = {}, set L i :={}, and / or 3.

2. If and only if IS i ≠{}, repeat at least one of step 1.1, step 1.2, step 1.3, step 2.1, step 2.2 and step 2.3 for all remaining i∈I.

5. The method according to any one of claims 1 to 4, It is characterized in that Step 1.3.1 also includes: 4.

1. Limiting parallel to the first direction At least the first meander line B i，j ; 4.

2. Using at least the first meander line B i，j To determine the subtrahend surface S i The first boundary of 4.

3. Reducing △S i The second direction Move the first zigzag line B upward i，j , where △S i =|t o (i) R i -|IS i -S i ||.

6. The method according to claim 5, It is characterized in that The first direction and the second direction are linearly independent of each other.

7. The method according to claim 5, It is characterized in that Zigzag Line B j，i is parallel to the first direction Zigzag lines.

8. The method according to claim 5, It is characterized in that Make the group position L i The melting of the meltable material at the position includes: when the i-th beam source projects the i-th beam spot, the i-th beam source is pivoted so that the i-th beam spot is along the melting vector The line moves in multiples of i，j , B i，k At least one of them is alternately perpendicular to and parallel to the melting vector The connecting section is composed of.

9. The method according to claim 2 or 3, It is characterized in that The method further comprises, in determining the subtrahend surface S i Before, a portion of the region A, C i Assigned to a dedicated i-th beam source, where the condition applies And the conditions S observed in step 1.3.1 and / or step 2.1 apply i ∩C i ={}.

10. The method according to any one of claims 1 to 4, It is characterized in that Before step 1.2, the field of view F i The index is sorted to follow the condition And repeat steps 1.2 and 1.3, while increasing the value of the index by 1 each time, except for the case where F is satisfied i ∩A={} except those index i.

11. The method according to claim 5, It is characterized in that Before step 1.2, the field of view F i The index is sorted to follow the condition And repeat steps 1.2 and 1.3, while increasing the value of the index by 1 each time, except for the case where IS is satisfied i = {} except those index i.

12. The method according to any one of claims 1 to 4, It is characterized in that The method comprises repeating step 1.2, wherein for at least one j≥2, the intersection set IS j Determined to be 13. The method according to claim 8, It is characterized in that The method also includes establishing a flow direction on top of the powder bed. The inert gas flow on represents the component of the layer of meltable material parallel to the flow direction.

14. The method according to claim 13, Features ， 13.

1. In B i，j Endpoint and B i,j Any other point Parallel to The measured distance is unique, i.e. or 13.

2. In B i，j Endpoint and B i,j Any other point Orthogonal to The measured distance is unique, i.e. in 15. The method according to claim 14, It is characterized in that The melting vector Having a flow direction of the inert gas flow Opposite weight.

16. The method according to claim 15, It is characterized in that There are at least two different zigzag lines B i，j , B q，r , respectively, are the adjacent group positions L i , L j and L q , L r The boundary between 0<q≤n and 0<r≤n, where the zigzag line B i，j The endpoints of the zigzag line B are q，r endpoint.

17. The method according to claim 16, It is characterized in that Either of the conditions 13.1 or 13.2 applies to B i，j and B q，r both.

18. The method according to claim 17, It is characterized in that Condition 13.1 applies to Bi, j and B q，r Both, and where L i , L j , L q and L r Each is parallel to The extended line is divided into m parts L s,1 , L s，2 , ..., L s,m , m ≥ 2, and among them The parts with the same second index are parallel to The two components are aligned and only the parts having the same second index are illuminated simultaneously.

19. The method according to any one of claims 1 to 4, It is characterized in that Using relationships and / or To determine the optimal melting time t. (i), where is the size of the area A, t o (0) = 0, and L 0 =0. 20 . A storage medium comprising a program, which, when executed, instructs a controller of an additive manufacturing device to execute the method according to claim 1 .

21. An additive manufacturing apparatus, comprising a support, a number n of beam sources, and a controller, wherein n ≥ 2, the beam sources are used to melt a meltable material, and the controller is configured to control the operation of the n beam sources, It is characterized in that The manufacturing device further includes the storage medium according to claim 20.

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