Powder bed based additive manufacturing method

Abstract

The manufacturing method of the present invention comprises the following steps: extracting a sub-batch (18) from a batch (16) of powder, wherein the batch (16) has a ratio of X 0 a predetermined component; manufacturing a component (22) using powder bed-based additive manufacturing until all sub-batches (18) are used up; and then performing the following cycle n max second: recycling the powder and continuing the manufacturing until all the recycled powder is used up; determining the contact area S between the powder and the fused material in the part (22) n , n represents the number of cycles, and the cumulative mass of powder used since the beginning of the method M n and measuring a ratio X of a predetermined component in at least one component (22) or test piece (24) manufactured during the last cycle nmax , then determine the parameter R, such as formula (I); perform the following cycle at least once: recycle the powder, and continue manufacturing until at least all of the recycled powder has been used at least once, and then determine the cumulative powder contact area S n and quality M n , and use S n 、M n and R calculates the content X of the component in one of the parts (22) manufactured during the cycle n Formula (I) #imgabs0#

Description

Technical Field

[0001] The present invention relates to additive manufacturing of components, such as aerospace components, by powder bed fusion. Background Art

[0002] Laser powder bed fusion is a metal additive manufacturing method that involves fusing powder particles by means of a laser beam, producing a component layer by layer. This technique is also known as selective laser melting (SLM). It enables the production of components with geometries that cannot be produced using conventional methods. The laser beam can be replaced by an electron beam.

[0003] The method is carried out in a closed environment under inert gas. It can be described in four steps:

[0004] When the powder is stored in a supply tank, the piston raises the tank to a height of one layer thickness;

[0005] The layering component spreads a layer of powder of this thickness in the print tray. This is the powder bed;

[0006] If the layering is effective, the laser passes through the layer and creates the first part of the object by micro lines adjacent to each other, produced by the fusion of the powder particles located in its path. If the layer formed is not uniform, a second layering is performed to fill the gaps before the laser passes;

[0007] Finally, the print tray is lowered slightly (by a layer of powder) and the process is restarted. In this way, the particles fuse layer by layer until the finished part is obtained.

[0008] When the part is finished, the powder that has been installed but not used to produce the part is recovered. It can then be recycled to make new parts, which can be done several times in succession. In this way, significant powder savings are generated.

[0009] However, it has been observed that the chemical composition of the manufactured components changes during powder recycling. This concerns in particular their oxygen, nitrogen and hydrogen content.

[0010] However, the content of these elements in the component has an impact on the material's properties, especially the mechanical tensile and fatigue properties. It is therefore important to understand and even control these contents to ensure that the components are consistent with the basic composition of the raw materials and therefore how these components behave in operation.

[0011] To this end, the overall elemental chemical composition of the destroyed part or component, or of a test piece of close representative composition, can be analyzed to check its consistency with the basic composition. Therefore, a comprehensive chemical analysis is carried out for each manufacturing. However, this causes serious delays and hinders the delivery of components. The costs are high and often incompatible with the expected profitability. In addition, it involves destroying the component for analysis, or manufacturing a test piece, which causes additional fusion time and consumes powder, thus increasing costs. It is therefore a long and expensive analysis.

[0012] Of course, it is possible to define a maximum number of recycling operations, in other words to limit the number of uses of the unfused powder, ensuring that any changes in the chemical composition are not so great as to be unacceptable. This solution can be implemented after chemical analysis of several recycling operations to check that the limits of the basic composition of the raw material have not been exceeded, wherein the limits of the basic composition of the raw material are related to the type of machine and a given fixed output. However, this is expensive. Its implementation depends each time on the manufacturing equipment and the components produced. In addition, when the maximum number of powder recycling operations is reached, the powder must be completely discarded, which again leads to a loss of material. However, the maximum number of recycling operations is usually not very high, for example 5 times. Therefore, this solution leads to the discarding of powder, but this discarded powder may be potentially acceptable for the new manufacture of less demanding components. In addition, the chemical composition analysis to be carried out is still very large and therefore expensive overall.

[0013] An object of the present invention is to facilitate the conformity of manufactured parts with their desired properties by means of an inexpensive and powder-saving solution. Summary of the invention

[0014] To this end, the present invention relates to a manufacturing method comprising the following steps:

[0015] extracting a sub-batch from a batch of powder, said batch having a predetermined component in a content X0,

[0016] manufacturing a component by powder bed based additive manufacturing with the aid of the sub-batches until all of the sub-batches have been used; and then

[0017] Execute the following loop n max Second-rate:

[0018] recycling powder from said manufacturing, and continuing said manufacturing until all of the recycled powder has been used;

[0019] Determine: The contact area S between the powder and the fused material in the component, accumulated from the start of the method n, n represents the number of cycles; and the cumulative mass of powder used since the beginning of the method M n , the powder recycled in each cycle is counted as additional mass, and

[0020] Measuring the content X of said component in at least one of said parts manufactured during the last cycle or in a test piece manufactured during the last cycle nmax ,Then

[0021] Calculate the parameter R, for example:

[0022]

[0023] Execute the following loop at least once:

[0024] recycling the powder and continuing the manufacturing until at least all of the recycled powder has been used at least once, and then

[0025] Determine the contact area S of the powder n and quality M n ,and

[0026] Use S n 、M n and R calculates the content X of the component in one of the parts manufactured during the cycle n .

[0027] The invention thus makes it possible to estimate the content X in a component throughout the manufacturing cycle. n .

[0028] The theoretical principle of this method is that during the fusion of the component, in a given layer, the temperature of the powder close to the melt increases. This increase promotes a change in the content of certain elements in the powder, especially oxygen, nitrogen and hydrogen.

[0029] When manufacturing is achieved, the recirculation operation (through suction, sieving and mixing) homogenizes the distribution of the powder composition by diluting the powder close to the melt and whose composition has changed in the rest of the powder. This makes the overall change in the powder composition uniform.

[0030] Therefore, the change in composition can be experimentally related to the amount of powder heated by the melt. This amount can be related to the contact area between the powder and the fused part in each layer (i.e., the surface area of ​​the part, excluding the upper and lower surfaces). A law is proposed to relate these quantities and predict the chemical composition after each build and multiple builds.

[0031] The proposed method associated with this law enables predictive monitoring of chemical composition through the definition of the parameters of the law, knowledge of the initial composition of the powder, the robustness of the manufacturing process and the collection of simple manufacturing data.

[0032] The method of the invention enables the chemical composition of manufactured parts to be monitored quickly, even instantaneously, inexpensively, non-destructively and without risk to the consistency of the parts, and enables the powder to be reused as much as possible to limit the amount of discard, while facilitating the management of the powder, for example when mixing the powder during recycling operations.

[0033] When starting the method, the batch may be new.

[0034] The method is particularly useful when the component is oxygen, hydrogen or nitrogen, but the method can be practiced with other components as well.

[0035] The method may then include the following steps:

[0036] Determine the content X n whether the pre-determined conditions are met, and

[0037] The subsequent steps to be applied to the method are determined according to whether the content satisfies the condition.

[0038] In one embodiment, the method comprises the steps of:

[0039] extracting another sub-batch from the batch of powder;

[0040] preparing a mixture of said further sub-batch with said powder from said manufacturing; and

[0041] The preparation was repeated using the mixture.

[0042] This operation thus makes it possible to "update" the powder from manufacture with the powder from the batch in which the content of the components has been modified. At the end of mixing, the content of the mixture is equal to the weighted sum of the contents.

[0043] Alternatively, the powder can be renewed with powder that is not new and that has also been used for additive manufacturing itself, provided that a good estimate of its content is available. In fact, in such a mixture of subbatches of powders with different uses originating from the same initial batch, the final content is also the mass-weighted average of the chemical composition contents of the two subbatches.

[0044] Thus, powder that has not been recycled much, or even new powder, can be added to a sub-batch that has already undergone a number of recycling operations.

[0045] When the condition is not met, the above three steps related to the mixture can be performed.

[0046] Therefore, when it is determined that such renewal is necessary, mixing is performed, i.e., the powder is renewed.

[0047] Alternatively, these three steps can be performed without predetermining the content X n Whether the predetermined conditions are met.

[0048] Therefore, in this case, the renewal must be carried out anyway. For example, when all the powder has been used during the production, the renewal can be carried out systematically, for example in order to maintain a constant content of the components.

[0049] In one embodiment:

[0050] During at least some of said cycles, measuring the content X of said component in at least one of said parts during said cycle, in a test piece manufactured during said cycle, or in said powder used during said cycle n,mes ;

[0051] Determine the content X n,mes The standard deviation of

[0052] During at least some of said cycles, after said step of calculating R, said calculated content X is determined n Whether a predetermined condition related to the standard deviation is met.

[0053] These steps form a test that verifies the estimated content X n Is it still credible?

[0054] For example, determine whether:

[0055] |X n -X n,moy |=<2×σ

[0056] in:

[0057] X n,moy represents the content X of multiple cycles n the average value of

[0058] σ is the content X n,mes The standard deviation of .

[0059] The invention also relates to an apparatus for powder bed based additive manufacturing, comprising:

[0060] Device for powder bed based additive manufacturing, and

[0061] A control member is configured to control the execution of the method according to the present invention.

[0062] The invention also relates to a computer program comprising code instructions designed to control the execution of the method according to the invention when the computer program is used on a computer. The invention also relates to a data recording medium comprising the above program in recorded form. The invention also relates to a method for providing such a program over a telecommunications network for remote downloading or execution of the program. BRIEF DESCRIPTION OF THE DRAWINGS

[0063] Embodiments of the invention will now be described by way of non-limiting examples with the aid of the accompanying drawings, in which:

[0064] Figure 1 is a schematic diagram of the increase in powder temperature and the diffusion of oxygen in the powder;

[0065] Figure 2 is a graph showing the change in oxygen content as a function of the number of cycle operations;

[0066] Figure 3 is a schematic diagram of the increase in oxygen content in the powder after manufacturing;

[0067] Figure 4 is a schematic diagram of the chemical composition of oxygen of a sample from a powder batch after recycling;

[0068] Figure 5 is a schematic description of the parameters of the recycling law;

[0069] Figure 6 is a schematic depiction of the oxygen capturing regions of a powder and the regions where oxygen is not captured in the recirculation law;

[0070] Figure 7 is a schematic description of the parameters Sn, Pn and An; and

[0071] Figure 8 is a schematic diagram showing a device according to the present invention. DETAILED DESCRIPTION

[0072] The theoretical basis of the invention will now be described, followed by a progression of methods for carrying out the invention.

[0073] The following definitions are proposed:

[0074] Manufacturing or construction cycle: All the steps in producing a part or object, starting with spreading the first layer and ending with fusing the last layer;

[0075] manufacturing campaign: consists of all manufacturing cycles that use the same sub-batch of powder to manufacture a part or an article at a time; it also involves a cycle, thereby combining multiple manufacturing cycles together;

[0076] Recycling: An operation consisting of discharging powder from equipment, re-sieving, optionally roasting, reconditioning, and then reusing.

[0077] Here, description is made on the premise that manufacturing is performed by a laser beam, but the description is also applicable to an electron beam.

[0078] Reference Figure 1 , the method uses a metal alloy powder known per se. In addition to one or more metals, the particles 2 of the powder also include elements such as oxygen, nitrogen and hydrogen.

[0079] During the additive manufacturing of the component 22 by powder bed fusion, metal powder layers N, N-1, N-2, N-3, N-4, N-5 are stacked on top of each other. After positioning each layer, the laser beam passes through one or more powder layers to fuse some of the powder particles, thereby building the component 22. The part 4 fused in this way is Figure 1 More precisely, during the laser processing of each layer, several adjacent layers are re-fused simultaneously. In this figure, it is shown that the five upper layers have been re-fused, while the lowest layer, N-5, has not been re-fused.

[0080] Unfused powder particles 2 are located on the left. However, some of these particles are heated, especially those directly adjacent to the fused particles. Thus, the figure shows different degrees of heating of particles 2a, 2b, 2c, depending on their proximity to the fused portion 4, with the temperatures being indicated as high, medium and low, respectively, but not exceeding the melting temperature.

[0081] However, this heating changes some elements of the particles, in particular oxygen, nitrogen and hydrogen. This occurs by introducing additional elements into the powder from the atmosphere of the closed environment of manufacture. This addition is indicated in the figure by arrows 6. This atmosphere includes in particular air and moisture, which penetrate between the particles 2 of the powder and cause the above-mentioned changes when heated.

[0082] This change is visible during the continuous recycling operation of the powder and can change the chemical composition of the fused material (and therefore the part) to the point where it is unsatisfactory after multiple recycling operations of the powder. This can result in parts whose material has unsatisfactory properties (particularly tensile and fatigue properties) and must therefore be discarded.

[0083] Figure 2The variation of the oxygen content in a part as a function of the number of powder recycling operations is shown. In this example, it can be seen that an initial oxygen content of 0.015% in a part made with new powder, after 10 recycling operations, becomes increased to a content of more than 0.022%. This description mainly refers to oxygen; however, the invention is also applicable to nitrogen, hydrogen or any other element that changes during recycling operations.

[0084] The present invention is directed to monitoring changes in component chemical composition to ensure that they are consistent with expected performance.

[0085] A method is employed here that enables the chemical composition of powders and parts to be monitored, that is rapid, even instantaneous, low-cost, non-destructive, cheap to develop, that ensures the consistency of the parts without risk, that uses as much powder as possible in manufacturing, limits the amount discarded and facilitates the management of the powders, for example being able to mix the powders during recycling operations.

[0086] As mentioned above, the study of the general method of powder bed fusion has made it possible to propose the parameters that influence the variation of the chemical composition of the elements in the powder during a continuous recycling operation. It has been possible to identify the mechanism associated with this variation as the entrapment or evaporation of the elements due to local heating of the powder during manufacturing.

[0087] From this study, it has been determined that in each build, there are local variations in the composition of the non-fused powder as a function of the distance from the fusion zone, e.g. Figure 3 The figure illustrates the principle of increasing oxygen content in the powder after manufacturing.

[0088] Thus, it is observed that the particle 2a located in the region closest to the fused portion 4 has a relatively high oxygen content. In the next region, in other words, further to the left in the figure, the content decreases, moving to an average content in the particle 2b by comparison. In the other particles 2c located further to the left, the oxygen content is close to the oxygen content of the powder before the recycling.

[0089] Starting from this situation, at the end of the component manufacturing, the unfused powders are recovered and mixed according to a proven procedure that ensures a homogeneous mixture. Thus, particles 2a, 2b, 2c with different chemical compositions are mixed together to give Figure 4 , which shows the distribution of particles and their oxygen content in a powder sample during recycling.

[0090] This is the mixture used for the subsequent manufacture of new parts. During this manufacture, this mixture fuses in the areas of the part affected by the laser beam. The fusion of the particles produces a part whose oxygen content is equal to the average value of the oxygen content of the particles. Thus, a homogenization is produced in the melt, which makes the chemical composition equal to the average composition weighted by the mass of the fused powder particles.

[0091] The manufacturing apparatus 10 will be described in more detail below. The apparatus includes a manufacturing tray. A layer of powder for manufacturing each component is deposited on the manufacturing tray. The apparatus includes a production tank. Powder and spatter fall into the production tank during manufacturing. The apparatus includes a recovery tank. After each component is manufactured, unfused powder and spatter are poured into the recovery tank. Finally, the apparatus includes a screen. When appropriate, the contents of the recovery tank are recycled through the screen.

[0092] Set the following traceability numbers:

[0093] C n : the number of manufacturing movements n, n increases from the first use of the powder;

[0094] C' n,y : the number of the make or build cycle; and

[0095] R n : The number of times n of powder recycling operation;

[0096] Set the following variables for n:

[0097] H n : the cumulative height of each build cycle of manufacturing movement n (in meters);

[0098] P n : The contact perimeter between the powder and the fused material averaged by height in each build cycle of manufacturing motion n (in m);

[0099] S n : The contact surface area (in m) between the powder and the molten material accumulated in each build cycle of the manufacturing movement n 2 count);

[0100] VM n : Cumulative volume (in m) of the parts fused (built) from manufacturing campaign n 3 count);

[0101] VD n : The cumulative volume of powder deposited on the manufacturing tray or in the recovery tank for manufacturing movement n (in m 3 count);

[0102] A n: The area (cross section, in m) averaged by height on a plane (usually horizontal, XY) perpendicular to the building direction of the parts produced in each building cycle of the manufacturing movement n 2 count);

[0103] X n : Total average oxygen content (in mass %) of the recovered powders at the end of manufacturing movement n, after recycling and mixing;

[0104] ΔX 0->n : increase in oxygen content (in mass %) between the powder supplied and the end of manufacturing movement n (recycling operation n). X0 corresponds to recycling operation 0, in other words, to the initial situation without recycling;

[0105] ΔX n-1->n : the increase in oxygen content (in mass %) between the powder from recycling operation n-1 and the powder from recycling operation n;

[0106] M n : the accumulated mass of powder from each build cycle of manufacturing campaign n recovered after recycling (in g), including powder from production tanks and recovery tanks;

[0107] MM n : The mass (in g) of each fused part (fused material) from the manufacturing movement n;

[0108] MD n : the mass of powder deposited on the manufacturing tray or in the recovery tank during manufacturing movement n (in g);

[0109] MP n : The mass of powder and splashes recovered in the sieve during recycling (in g);

[0110] MC n : The mass of powder recovered at the end of manufacturing movement n after recycling (in g), which powder was heated during the fusion of the parts and trapped oxygen;

[0111] MF n : the mass of powder recovered at the end of manufacturing movement n after recycling (in g), which powder was not heated during part fusion and did not trap oxygen;

[0112] XC n : oxygen content (in mass %) of the powder recovered at the end of manufacturing movement n after recycling, which powder was heated during the fusion of the parts and trapped oxygen;

[0113] XF n: oxygen content (in mass %) of the powder recovered at the end of manufacturing movement n after recycling, which powder was not heated during the fusion of the parts and did not trap oxygen;

[0114] TR n : Makes the regeneration rate (in %) of movement n (if this rate is constant throughout the movement).

[0115] Set the following constants:

[0116] ΔX 机器 : the standard increase of oxygen per unit of heated powder in a specific machine (constant, in mass %), which is associated with a set of parameters and machine control program version;

[0117] AP: Area of ​​the manufactured pallet (cross section, in m 2 count);

[0118] PP: average percentage of powder and spatter that will be recovered by the screen during recycling (based on the volume of the fused part);

[0119] e: Powder thickness (in m) from the surface of the fused part that is heated and captures oxygen;

[0120] ρ p : Bulk density of the powder deposited on the manufacturing tray (in g / m 3 and

[0121] ρ m : Density of the fused material (in g / m 3 count).

[0122] The following diagram better illustrates the values ​​that were set to express the recirculation law. Thus:

[0123] Figure 5 is a schematic diagram showing the parameters of the recirculation law;

[0124] Figure 1 is a schematic diagram of oxygen-capturing regions and non-capturing regions of a powder in a recirculation law; and

[0125] Figure 7 is the parameter S n , P n and A n Schematic description of .

[0126] The above parameters have the following relationship.

[0127] The contact area is determined by averaging the contact perimeter by height and build height:

[0128] S n =Pn *H n

[0129] The volume of the fused part is determined by averaging the area by height and build height:

[0130] VM n =A n *H n

[0131] The volume of powder deposited depends on the area (cross-section) of the build tray, the regeneration rate, and the build height. For a constant regeneration rate throughout the motion n:

[0132] VD n =AP*TR n *H n

[0133] Therefore, the powder without captured oxygen has the oxygen content of the previous recycling operation:

[0134] XF n =X n-1

[0135] The oxygen content of the powder in the recycling operation n is equal to the mass weight of the oxygen content of the heated and unheated powders:

[0136]

[0137] Because XF n =X n-1

[0138] The increase in oxygen content between powder recycling operations n and n-1 is:

[0139] ΔX n-1→n =X n -X n-1

[0140] The increase in oxygen content between the supplied powder and the recirculation operation nmax is the sum of all increases from recirculation operation 0 to nmax:

[0141]

[0142] For a given machine (adjusted machine parameters, machine program, shielding gas), the average standard increase in oxygen per unit volume is constant and equal to the difference between the content of the powder before and after heating, and therefore equal to the difference between heated and unheated powder areas:

[0143] ΔX 机器 =XC n -XF n , because XFn =X n-1

[0144] <=>ΔX 机器 =XC n -X n-1

[0145] The total mass after recycling is the sum of the mass of heated and unheated powder recovered after recycling:

[0146] M n =MC n +MF n

[0147] The mass of the heated powder depends on the density of the packed powder, which is related to the thickness of the heated powder and the contact area (volume of the heated powder):

[0148] MC n =ρ p *e*Sn

[0149] The mass of powder for recycling operation n is equal to the mass of powder deposited minus the mass of powder that has been fused (and therefore not recycled, as it is incorporated into the part) minus the mass of powder lost during recycling (splash and large particles of powder discarded during sieving or in the ash pan):

[0150] M n =MD n -MM n -MP n

[0151] The quality of the built part depends on the volume of the part and the density of the fused materials:

[0152] MM n =ρ m *VMn

[0153] The mass of powder deposited in the machine depends on the volume of powder deposited and the density of the accumulated powder:

[0154] MD n =ρ p *VD

[0155] The mass of powder lost during the recycling operation is mainly in spatter, the percentage of which depends on the volume of the fused part:

[0156] MP n =ρ p *PP*VMn

[0157] These relationships can be used to derive a law that enables the prediction of the oxygen content X as a function of the manufacturingn Law (I) describes the change between manufactures n-1 and n, while law (II) describes the change after multiple manufactures based on the initial oxygen content X0, summed up to the total number of recycling operations n max :

[0158]

[0159] Where R = ρ p *e*ΔX 机器

[0160]

[0161] These laws make it possible to predict the variations in the oxygen composition of particles and components. They make it possible to implement the method of the invention, which will be done, for example, by means of Figure 8 Provide explanation.

[0162] The method is implemented by means of an apparatus for powder bed-based additive manufacturing 10, the apparatus comprising:

[0163] forming a machine for powder bed based additive manufacturing 12, and

[0164] Control means 14 configured to control the execution of the method.

[0165] The machine is conventional and will not be described in detail.

[0166] The component 14 comprises a computer associated with a program, the program comprising code instructions designed to control the execution of the method when the program is used on the computer. The program is recorded on a data recording medium. The program may be provided on an internal or external telecommunication network (such as the Internet) so that it can be downloaded to the machine or executed remotely.

[0167] It is assumed that the apparatus 12 is stable in terms of manufacturing parameters such as power, movement speed of the energy beam and protective atmosphere, etc. For the atmosphere, the parameters are, for example, moisture, oxygen, nitrogen and argon content of the protective gas or gas flow in the manufacturing enclosure.

[0168] Here, the steps of the method are as follows.

[0169] Start-up phase

[0170] A new batch 16 of metal powder having an initial oxygen content X0 is deposited. Information on this initial oxygen content appears in data communicated by the powder supplier, for example in a supply certificate. It is desirable to know X0 to a sufficient number of meaningful figures.

[0171] This initial phase aims to determine the constant R of formula (II) for the device and manufacturing parameters.

[0172] From this batch 16 of powder a sub-batch 18 is taken.

[0173] Using sub-batch 18, the machine manufactures part 22 by powder bed based additive manufacturing and does so until all sub-batches 18 are used. This means that all the powder of the sub-batches is fed into the machine. The unfused powder is recycled. This is the first movement.

[0174] Then, the next loop is executed, which is called the startup loop. max times, for example 10 times, this number is not limiting (it can be replaced by 5, 15, etc.). This cycle is a production movement.

[0175] 1) Powder from the previous manufacturing campaign is recycled. This powder is the powder that has not been consumed to form the part and can therefore be recovered after each manufacturing run.

[0176] 2) Continue making parts 22 until all the recycled powder has been used. During this step, a number of test pieces 24 are also made.

[0177] 3) During this cycle, determine the contact area S n and quality M n .

[0178] 4) According to the surface area S n and quality M n To calculate the content of component X n .

[0179] 5) Measure the oxygen content X in the test piece 24 n,mes This measurement is performed, for example, twice. An alternative consists in carrying out this measurement on one of the components 22, but this generally involves destroying this component. Alternatively or additionally, the measurement can be carried out on a sample of the powder used during the cycle.

[0180] The cycle ends here.

[0181] Therefore, the cycle is repeated n times. max times. This leads in particular to the production of n max Group component 22.

[0182] Therefore, there is a set of measured contents X n,mes , and these contents X can be calculated n,mes The mean and standard deviation of .

[0183] Measured content X n,mes In particular, the oxygen content X measured in the test piece 24 produced during the last cycle nmax .

[0184] The parameter R is then determined by formula (II). More precisely, once the data Xn, Sn and Mn are obtained, a graph according to the law of formula (II) can be drawn. According to the equation of the curve, after verifying that the calculated value of R is acceptable and verifying that Xn nmax After coordination with X0, the coefficient R is proven to be valid.

[0185] Thus, the startup phase ends.

[0186] Operational Phase

[0187] For the remainder of the method, R is then known and by using equation (I) one can predict or estimate the following for each of the manufacturing motions: n .

[0188] Therefore, several new production campaigns were carried out as follows.

[0189] The following cycle is called an operating cycle and is performed at least once. This cycle is also a production movement.

[0190] 1) Powder that was not consumed in the previous manufacturing campaign is recycled, and manufacturing continues until all recycled powder has been used at least once.

[0191] 2) Determine the cumulative contact area S of the powder n and quality M n .

[0192] 3) Use S n 、M n and R, calculate the oxygen content X of one of the components 22 manufactured during the cycle n This calculation is performed using formula (I). It involves a predicted or estimated content.

[0193] 4) Determine the content X n In this case, the calculated content X is determined. n Whether it meets the content X n,mes For example, determine whether:

[0194] |X n -X n,moy |=<2×σ(III)

[0195] in:

[0196] X n,moy Indicates the content of the previous movement X n the average value of

[0197] σ is the standard deviation.

[0198] In other words, using a law that predicts the chemical composition after each manufacture, a prediction graph is created. The predicted content is then checked for consistency with a margin of + / - 2 standard deviations above the mean suggested by the law.

[0199] 5) Depending on whether the content satisfies condition (III), the subsequent steps to be applied to the method are determined.

[0200] If condition (III) is met, the operating cycle ends and restarts from the beginning to carry out a new movement with the remaining powder (recycling of the remaining powder, manufacturing, etc.).

[0201] If the condition is not met, another sub-batch 20 is extracted from the batch 16 of powder. This other sub-batch 20 is mixed with the powder from the manufacturing. To do this, the following mixture law is used to obtain a mixture with an acceptable oxygen content, based on the content T0 of the new sub-batch 20 and the content X of the remaining powder n and their respective powder masses.

[0202] In fact, it is possible to determine the content X of a mixture of powders with different contents 混合物 Assume that the contents X1 and X2 of the two powder fractions to be mixed are known. Weigh these fractions so that their respective masses M1 and M2 are known. The mass of the mixture M 混合 is the sum of these two masses. The powders are mixed according to a procedure that ensures the homogeneity of the final mixture. The oxygen content in the mixture is calculated by the following weighted formula:

[0203]

[0204] A new operating cycle then begins with the powder mixture obtained in this way. The powder from the previous movement is thus renewed.

[0205] Thus, multiple operating cycles can be performed. Whenever necessary, the powder remaining after use at the end of the cycle is mixed with a new sub-batch from batch 16. This can continue until batch 16 is used up.

[0206] In another embodiment, the remaining powder is mixed with a new sub-batch at the end of each cycle so as to maintain a constant content at the beginning of each cycle. n The mixing step is performed when condition (III) is satisfied, or the mixing step is performed again even if the condition is satisfied.

[0207] Therefore, it can be seen that the prediction X nThis enables the used powder to be renewed with new powder in order to adjust its chemical composition and, when it is too close to the standard limits, to readjust it to within the standard chemical composition limits. Alternatively, it also allows continuous renewal in order to have a constant composition.

[0208] It is advantageous to carry out a back analysis of the powder sample every time a predetermined number of recycling operations have been carried out (for example every 10 recycling operations), but this number is not limiting. This makes it possible to measure the effective content X n to readjust the predictions of law (I). This is also a verification of the measured value X n The chance that the difference between the predicted mean and the predicted mean satisfies condition (III).

[0209] This process can continue until the powder from batch 16 is used up.

[0210] The method of the invention is inexpensive. In fact, the data of the law are collected during the start-up phase by standard manufacturing and some chemical analysis, and the cost of occasional back analysis is low compared to other methods. It does not increase the cycle time. This method is economical for powders and there should no longer be residual powder, especially if renewal is allowed. The invention does not require the production of parts dedicated to analysis.

[0211] The present invention can provide a method for industrial monitoring and prediction of chemical composition during manufacturing and can anticipate when there is a risk of deviation from the material's specification, which can affect the material's performance. The present invention enables monitoring of chemical composition during the continuous manufacturing of components, in particular aerospace components, by additive manufacturing based on metal powder beds (using laser LBM / SLM or electron beam EBM).

[0212] In another embodiment, during the operation phase, the content X n An estimate of can be used to determine, firstly, whether the powder can be recycled as is (i.e. without mixing) or whether it should be discarded. This is not the most powder-saving version of an embodiment of the invention. However, it can be seen that, with this alternative, the invention firstly enables a decision to be made on the subsequent steps of the method.

Claims

1. A powder bed based additive manufacturing method comprising the following steps: - extracting a sub-batch (18) from the batch (16) of powder, said batch having a predetermined component in a content X0, - manufacturing a component (22) by powder bed based additive manufacturing with the aid of said sub-batch until all said sub-batch (18) has been used; and then -Execute the following startup cycle n max Second-rate: -- recycling powder from said manufacturing and continuing said manufacturing until all of the recycled powder has been used; - Determination: the contact area S between the powder and the fused material in the component (22), accumulated from the beginning of the method n , n represents the number of cycles performed since the beginning of the method; and the cumulative mass of powder used since the beginning of the method M n , the powder recycled in each startup cycle is counted as additional mass, and - measuring the content X of said component in at least one of said components (22) produced during the last start-up cycle or in a test piece (24) produced during the last start-up cycle nmax ,Then - Calculate the parameter R as follows: - Perform the following operations at least once: - recycle the powder and continue the manufacturing until at least all of the recycled powder has been used at least once, and then - determining the contact area S between the powder and the fused material in the component (22), accumulated from the beginning of the method n , n represents the number of cycles performed since the beginning of the method; and the cumulative mass of powder used since the beginning of the method M n , the powder recycled in each operating cycle is counted as additional mass, and --Use S n 、M n and R calculates the content X of the component in one of the parts (22) manufactured during the operating cycle n , - Monitoring the chemical composition of said component (22).

2. The method according to the preceding claim, wherein: At the beginning of the process, the batch (16) is new.

3. The method according to claim 1, wherein: The components are oxygen, hydrogen or nitrogen.

4. The method according to claim 1, further comprising the steps of: Determine the content X n Whether the predetermined conditions are met; and According to the content X n Whether the predetermined condition is met determines the subsequent steps to be applied to the method.

5. The method according to claim 1, further comprising the steps of: extracting another sub-batch (20) from the batch of powder; preparing a mixture of said further sub-batch with powder from said manufacturing; and The preparation was repeated using the mixture.

6. The method according to claim 4, wherein: When the predetermined condition is not met, the following steps are performed: extracting another sub-batch (20) from the batch of powder; preparing a mixture of said further sub-batch with powder from said manufacturing; and The preparation was repeated using the mixture.

7. The method according to claim 1, further comprising the steps of: Determine the content X n Whether the predetermined conditions are met; and According to the content X n Whether the predetermined condition is met, determining the subsequent steps to be applied to the method, or The method performs the following steps without predetermining the content X n Whether the reservation conditions are met: extracting another sub-batch (20) from the batch of powder; preparing a mixture of said further sub-batch with powder from said manufacturing; and The preparation was repeated using the mixture.

8. The method according to claim 1, wherein: During at least some of the start-up cycles, measuring the content X of the component in at least one of the components (22) during the start-up cycle, in a test piece (24) manufactured during the start-up cycle, or in the powder used during the start-up cycle n,mes ; Determine the content X n,mes The standard deviation of and During at least some of said operating cycles after the step of calculating R, determining the calculated content X n Whether a predetermined condition related to the standard deviation is met.

9. The method according to claim 8, wherein: Determine whether: |X n -X n,moy |=<2×σ in: X n,moy The content X represents a number of operating cycles n the average value of σ is the content X n,mes The standard deviation of .

10. An apparatus (10) for powder bed based additive manufacturing, comprising: Apparatus (12) for powder bed based additive manufacturing, and A control member (14) is configured to control the execution of the method according to claim 1.

11. A computer program product comprising code instructions designed to control the execution of the method according to claim 1 when the computer program product is used on a computer.

12. A data recording medium comprising the computer program product according to claim 11 in recorded form.

13. Method for providing a computer program product according to claim 11 over a telecommunications network for remote downloading or execution of the computer program product.

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