Additive manufacturing process

Abstract

TITLE: Additive Manufacturing Process A process for the additive manufacturing of a part (10) by melting and local solidification of successive layers of powder of a metallic manufacturing material, the process comprising: Fabrication of a support (20) configured to support at least a portion of said part (10); Fabrication of a protrusion (30) on a surface (11) of the part (10), said protrusion (30) being configured to connect the support (20) to said part (10), said protrusion (30) comprising a first junction surface (31) with said part (10) and a second junction surface (32) with said support (20), the support (20) comprising a breakable zone (23) defining a connection between said support (20) and the protrusion (30); Removal of said support (20) by breaking said breakable zone (23). Figure 3a

Description

Title of the invention: Additive manufacturing process technical field

[0001] The field of this disclosure is that of additive manufacturing, more specifically of a laser powder bed fusion process. Previous technique

[0002] A number of processes for shaping parts, which may be metallic or composed of a polymer, are known in the prior art. Some of these processes differ from so-called "conventional" methods involving material removal, such as machining. Such processes consist of the selective consolidation of powder layers to build up, layer by layer, a three-dimensional object.

[0003] More specifically, such a selective melting process can be described as follows: first, a digital production file is created using suitable software. This instruction file is typically generated by slicing the CAD model of an object into layers, generally of a given thickness. The production file includes all the instructions necessary to execute the process: in particular, the laser paths required to produce the object, layer by layer.

[0004] The equipment for implementing the process may include a build platform that serves as the base for manufacturing the object. A powder spreading device allows a layer of powder of the desired material to be spread onto the build platform, to a desired thickness. This device may be a roller or a scraper that moves in translation along an axis on either side of the powder bed.

[0005] Once the powder layer is deposited, one or more lasers selectively scan certain areas of the powder bed, corresponding to a slice of the object to be produced, according to the instruction file created beforehand. Indeed, the scanning pattern, as well as all the parameters of this laser scanning (such as the laser power, the scanning speed, the spacing between two laser passes, etc.), can be dictated to the equipment by the instruction file. The laser's passage over the powder bed raises the powder to a temperature above its melting point. A molten pool is thus created. It can also be provided that another heat source preheats the powder bed to a temperature slightly below its melting point, to accelerate the laser scanning.Upon cooling, at least to a temperature below its melting point, this bath solidifies and forms a bead of solid metal, defining a "slice" of the object to be created. At the end of the... By laser scanning a layer of powder, a 2-dimensional section of the desired object is obtained.

[0006] The powder spreading device then deposits a new layer of powder on top of the previous one. A new laser scan is performed to consolidate a new "slice" of the object.

[0007] Thus, iteratively, a 3-dimensional object is reconstituted by successive consolidation of 2-dimensional sections, or slices, one on top of the other.

[0008] Only a certain amount of powder is solidified by the laser as the process progresses, so the object is "embedded" in the remaining powder. This technique can therefore have the advantage of using the powder as a support for the creation of successive layers of the part, unlike, for example, the rapid prototyping process by fused deposition modeling (FDM), which requires specific supports for the overhanging parts of the part.

[0009] However, with regard to the production of metal parts by powder bed fusion, it may be necessary to create supports to enable the feasibility of the part. In particular, such supports are useful for parts of the part where the first fused layer does not rest on the build platform or on a previous layer. This is especially true for portions of the part that extend cantilevered from a main body of the part, and where the first layer, for example at a distal end of the portion, rests only on the powder bed and is distant from the main body of the part. The need for a support is increased when this cantilevered portion is connected to the main body of the part by a slope greater than approximately 45° relative to the horizontal build platform.

[0010] These supports can also serve as thermal bridges, connecting the part to the manufacturing platform. After the part is manufactured, these supports are removed, through an adjustment operation, before the part is mounted.

[0011] It is common for this fitting operation to be performed manually by an operator for certain parts. It is therefore particularly difficult for the operator to remove the support sections while maintaining a satisfactory surface finish and without removing too much material, which could locally weaken the part. Furthermore, the fitting operation may be inconsistent in terms of the quality of the result.

[0012] The solution in this disclosure therefore aims to mitigate at least in part the disadvantages of the prior art mentioned above, by making it easier and standardized to remove the media while avoiding the risks of generating non-quality. Summary

[0013] The objectives mentioned above are achieved in particular by an additive manufacturing process of a part by melting and local solidification of layers successive powdering of a metallic manufacturing material, the process comprising: - Creation of a support configured to support at least part of said part, - Fabrication of a protrusion on a nominal surface of the part, said protrusion being configured to link the support to said part, said protrusion comprising a first junction surface with said part and a second junction surface with said support, the support comprising a breakable area defining a link between said support and the protrusion, - Removal of said support by breaking said breakable area.

[0014] Thus, in a particularly effective manner, the solution avoids the risk of removing too much material when fitting the area where the support has been removed. Indeed, by adding a controlled amount of material as an excess thickness beyond the nominal surface by means of the protrusion, the repeatability of the fitting operation is ensured, and the risk of non-quality is eliminated. The material added by the protrusion ultimately allows the area to be fitted to be sufficiently separated from the nominal surface of the part, so that the operator has enough "margin" to avoid the risk of removing material beyond the nominal amount during a fitting operation. Thanks to the proposed solution, it is therefore possible to obtain a conforming and fitted part, with very little risk of non-quality and a satisfactory surface finish.

[0015] The features described in the following paragraphs may optionally be implemented independently of each other or in combination with each other:

[0016] According to examples, the height of said protrusion, before the removal of said support, is equal to a value H. The process comprises, after the removal of said support, an adjustment operation during which at least a part of said protrusion is removed, so that the final height HF of the protrusion, after the adjustment operation, complies with the formula H Final, the value of the factor k being between between 0.05 and 0.95.

[0017] Due to the non-zero and positive value of the factor k, it is understood that the fitting operation is carried out in such a way as to retain a residual portion of the protrusion as an excess thickness of the nominal surface of the part. Thus, any risk of reaching the nominal surface of the part during the fitting is avoided.

[0018] For example, the "height" of the protrusion may be defined as the measure of a segment formed by: the point of intersection of a line normal to the nominal surface with the nominal surface, and the point of intersection between this same line normal to the nominal surface and a distal surface of the protrusion.

[0019] According to examples, said first junction surface is larger than said second junction surface.

[0020] In this way, the protrusion is reinforced at its base, that is, at the junction between the protrusion and the part, and any risk of breakage occurring at the base of the protrusion during removal of the support is reduced. The base of the protrusion is thus less fragile than the breakable area.

[0021] According to examples, the protrusion comprises two curved, preferably concave, sides connecting the first junction surface to the second junction surface, so as to avoid stress concentrations at the base of the protrusion.

[0022] According to examples, the protrusion comprises two chamfers connecting the first junction surface to the second junction surface.

[0023] According to examples, the protrusion comprises a dimension e, measured transversely at the level of the second junction surface, and the support comprises a dimension E at the level of the breakable area, the dimension e of the protrusion respecting the following formula: e = q*E, in which the value of the factor q is between 1 and 2, preferably between 1 and 1.5, and even more preferably between 1.05 and 1.2.

[0024] According to examples, the protrusion includes a dimension e, measured transversely at the level of the second junction surface, greater than or equal to 0.5mm, preferably said dimension e is substantially constant over a length L of the protrusion.

[0025] According to examples, the protrusion, before removal of the support, comprises a Hinit height greater than or equal to 1mm. Brief description of the drawings

[0026] Other features, details and advantages will become apparent upon reading the detailed description below, and upon analysis of the accompanying drawings, on which:

[0027] [Fig.1] shows a schematic representation of a part and a support according to the prior art, the removal of the support resulting in a defect on the part.

[0028] [Fig.2] shows two schematic views A and B according to two different examples of arrangement of supports and protrusions according to the present disclosure.

[0029] [Fig. 3] shows a schematic view of a solution according to an example of the present disclosure. Views A, B, and C show three successive operations according to an example of the process according to the present disclosure.

[0030] [Fig.4] shows a detailed view of a protuberance according to an example in the present disclosure.

[0031] [Fig.5] shows a detailed view of an example of an embodiment of a breakable zone according to this disclosure.

[0032] [Fig.6] shows a schematic perspective view of a protuberance along a example of this disclosure.

[0033] [Fig.7] shows a schematic view of an additive manufacturing installation in which a part is made, as well as a detailed view of an area that may be provided with a support, according to an example of the process of this disclosure.

[0034] [Fig.8] shows a photograph of an example of a protuberance according to the present disclosure, after an adjustment operation.

[0035] [Fig.9] shows a breakable zone comprising a plurality of recesses, according to a example. Description of the implementation methods

[0036] The drawings and description below contain, essentially, elements of a definite nature. They may therefore not only serve to better explain this disclosure, but also contribute to its definition, if necessary.

[0037] In the various figures, the same reference numerals designate identical or similar elements. For the sake of brevity, only the elements that are useful for understanding the described embodiment are shown in the figures and are described in detail below.

[0038] In the following description, when reference is made to orientation qualifiers such as "horizontal", "vertical", etc., reference is made, unless otherwise specified, to the orientation of the figures or of an additive manufacturing installation in its normal position of use.

[0039] Reference is now made to [Fig. 1], which illustrates the prior art, the drawbacks of which we will now be able to appreciate. The figure shows a part 1, fitted with a support 2, the part 1 and its support being obtained by a known additive manufacturing process, by melting and local solidification of successive layers of powder. For example, the melting can be carried out, in a known manner, by scanning a laser beam which can be configured to locally heat the powder and thus "draw" the outline of the "slice" of the part to be produced. Solidification is achieved by cooling, for example by allowing the temperature to fall below the melting temperature of the powder after the laser has passed.

[0040] The support 2, directly attached to the part, causes a defect 3 when it is removed, taking with it some of the material belonging to the part 1. It is then necessary to carry out a fitting operation during which an additional part 4 of the part is removed, so as to obtain a homogeneous surface finish, for example along a fitting line 5. The nominal contour 6 of the part The specified shape is then modified, since the adjustment line 5 is recessed relative to the nominal contour 6, and the resulting part 1 is therefore non-conforming. Alternatively, without any part of part 1 being removed with the support 2, a portion of support 2 may remain attached to the part after its removal. Similarly, an adjustment operation is then necessary to remove this irregular excess material, which is often too small to be adjusted precisely. The operator performing the adjustment is then forced to remove some material, until the adjustment line 5 is recessed from the nominal contour 6 of the part 1, which is therefore non-conforming.

[0041] According to the present disclosure, examples of which are illustrated in [Fig.2] and [Fig.3], it is proposed to create a protrusion 30 between the support 20 and the part 10. The support can extend from a manufacturing platform 41 (see [Fig.2] b).It is also possible that the support 20 extends from another part of part 10, thus connecting a first part of part 10 and a second part of part 10, the second part of part 10 being supported by the first part of part 10 via the support 20 (see [Fig.2] a).

[0042] Part 10 has a so-called nominal surface 11, corresponding to the theoretical definition of part 10. During quality control of the manufactured part, its dimensions are typically compared to this nominal definition. The nominal surface 11 can typically be an external surface of the part, but can also be internal to the part. It could, for example, be an internal surface of a cavity in the part. The protrusion 30 is made so as to define a controlled and homogeneous addition of material on said nominal surface 11. Since the protrusion 30 is made by powder melting, it is typically made of the same material as the part 10, and / or of the same material as the support 20.

[0043] Said protrusion 30 defines a joining element between the support 20 and the part 10. The support 20 can be formed on such a protrusion 30. In other words, a first layer of said support 20 can be formed successively to a final layer of said protrusion 30, when the support extends from said protrusion 30. Conversely, such a protrusion 30 can also be formed on the support 20. Several protrusions 30 can be formed for a single support 20.

[0044] The protrusion 30 may include a first joining surface 31 with said part 10. Such a first joining surface 31 may correspond to the continuity of the nominal surface 11 of the part. The protrusion 30 may be made so as to form an addition of material on this joining surface 31. This surface 31 may then be defined as being common between the protrusion 30 and the part 10. The protrusion 30 may also include a second joining surface 32 with said support 20. In some examples, the first joining surface 31 has a area greater than said second junction surface 32. This results in the protrusion 30, at the level of the first junction surface 31, being wider than the protrusion 30 at the level of the second junction surface 32.

[0045] The support 20 may include a breakable zone 23 at the junction between the support 20 and the protrusion 30. Typically, the breakable zone 23 may be located on the support 20 at the second junction surface 32. The breakable zone 23 is generally more fragile than the adjacent parts of the support 20 or protrusion 30. The breakable zone 23 is designed so that sufficient stress on the support 20 and / or the part 10 causes localized rupture in this breakable zone 23. The breakable zone 23 may be dimensioned so that manual stress by an operator is sufficient to break the connection between the support 20 and the protrusion 30 at the breakable zone 23.

[0046] Such a breakable zone 23 can be made in different ways: the support 20 can, at its junction with the protrusion, form re-entrant angles 34 with the protrusion 30 so as to allow stress concentrations when the support 20 and / or the part is stressed 30. In this case, the breakable zone 23 corresponds to the section of the support 20 at these re-entrant angles 34. Such an example is particularly visible in [Fig.4].

[0047] The breakable zone 23 can also be achieved by a localized reduction 35 of the thickness of the material of the support 20, in the junction zone with the protrusion 30. Such an example is notably represented in [Fig.4].

[0048] According to other examples, the breakable zone 23 can include a plurality of recesses 231, arranged along the length of the junction between the support and the protrusion, the recesses 231 constituting a local reduction in the quantity of material and thus creating a zone of increased fragility, along which the break can be located during the withdrawal of the support.

[0049] The support 20 is thus removed from the part 10 by applying force, typically manually, to the part 10 and / or the support 20. It will be understood that the break is intentionally located at the breakable area 23, but it is not possible to guarantee that it is "clean," in the sense that small residual portions 21 of the support may still remain attached to the protrusion 30, and that small portions 36 of the protrusion 30 may be carried away by the removal of the support 20. However, the protrusion 30 can be dimensioned so that the parts that may be accidentally removed never reach the nominal surface 11 of the part. The remaining portions 21 of the support after the support is removed can be removed by a fitting operation. In particular, such a fitting operation may include a sanding operation, or any other known material removal operation.An example of an adjusted protrusion is shown in [Fig.8].

[0050] Reference is now made to view 2c of Figure 2. After the removal of said support 20, the process may include a fitting operation, the purpose of which is to standardize, by removing material, the surface finish of the part at the level of the breakable area 23. This fitting operation may include the removal of at least a portion of the protrusion 30. By way of example, the fitting operation may include the removal of 20% of the height of the protrusion. For example, if the protrusion 30 has a height equal to Hinit before the removal of the support 20, the fitting operation will be carried out so that the height of the protrusion, after this operation, is reduced by a factor k according to the following formula: HFilud = k*Hinit

[0051] The value of the factor k may vary between 0.05 and 0.95.

[0052] The "height" of the protrusion is understood to be the distance which separates the first joining surface 31 from the point of the protrusion furthest from this surface 31. Before the operation of removing the support 20, the height of the protrusion is equal to the first joining surface 31 corresponding to the nominal surface 11 of the part.

[0053] The adjustment operation can be performed in such a way that a residual portion 37 of the protrusion is retained. In this way, it is understood that, according to examples, the factor k as defined above is never equal to 0 and is always positive. Following the adjustment operation, the residual portion 37 of the protrusion may have dimensions that allow it to be visible to an operator performing the operation manually. According to examples, the residual portion may have a height HFjnal equal to 0.5 mm.

[0054] It is therefore understood that this residual part 37 remains after the adjustment operation, and that the part 10 produced thus retains this residual part 37 throughout its operational life. The area of ​​the part 10 on which the protrusion 30 is made is therefore chosen so that the permanent existence of this residual part 37 does not interfere with the operation of the part 10.

[0055] It can be advantageous, for example, for the protrusion 30 to have no breaks or discontinuities at its junction with the part 10. In this way, it is possible to avoid stress concentrations at the junction between the part 10 and the protrusion 30 during the removal of the support 20. Indeed, the breakable zone 23 is defined to locate the break at the junction between the support 20 and the protrusion 30; it is important to keep this break away from the junction between the protrusion 30 and the part 10 to avoid any risk of removing material beyond the nominal dimensions of the part 10. Thus, the breakable zone 23 can be fragile and, conversely, the junction between the part 10 and the protrusion 30 can be reinforced. To this end, the protrusion 30 may comprise two curved flanks 38, 39, typically concave, each connecting the first junction surface 31 to the second joining surface 32. In this way, like a fillet, each blank 38, 39 joins the nominal surface 11 of the part in a substantially "smooth" way, without defining an angle or break that could induce weaknesses at the base of the protrusion 30.

[0056] According to an example shown in [Fig.5], the protrusion 30 can extend straight and / or curved over the surface 11 of the part 10. The protrusion 30 can also be discontinuous (not shown), so that it has several distinct portions, each attached to the same support 20 in several distinct areas.

[0057] The protrusion 30 may include a dimension e measured transversely to the second junction surface 32, perpendicular to its elongation direction. For example, if the protrusion is straight and of length L, the dimension e may correspond to the width of the protrusion, measured transversely to its elongation direction. This dimension e can be equal to the dimension E of the support to which it is attached, the dimension E of the support corresponding to its thickness measured at the intersection with the second junction surface 32. Advantageously, the dimension e of the protrusion 30 is greater than the dimension E of the support 20. For example, the dimension e can be equal to 1.2 times the dimension E of the support 20. In general, it is possible for the dimension e to be determined according to the following formula: e = q*E, in which the coefficient q can vary between 1 and 2, more preferably between 1 and 1.5, more preferably between 1.05 and 1.2.

[0058] The dimension e of the protrusion 30 can be at least equal to 0.5 mm. In this way, it remains visible to the naked eye by an operator in charge of the adjustment operation.

[0059] According to examples, the dimension e of the protuberance is substantially constant over a length L of the protuberance 30.

[0060] The height Hinjt of the protrusion 30, before any removal operation of the support 20, can be at least 1 mm. In this way, the operator has sufficient extra thickness above the nominal dimension of the part 10 to be able to perform the adjustment operation without risking the removal of more material than permitted by the nominal specification.

[0061] Powder bed fusion processes generally involve polymer or metallic powders. The solution according to this disclosure is not limited to any one type of material, but is of particular interest with regard to metallic powders, for which the use of supports is more often required. In general, the process according to this disclosure can be applied to any material, provided that the part is fabricated using at least one support.

[0062] By way of example, the inventors have determined that the areas 22 requiring supports are primarily areas 22 located away from a main body of the part 10, typically situated at the lowest points of cantilevered portions, the first fused layer of which rests neither on a previous layer nor on the build platform 41, but on the powder bed 42. Such areas 22 are shown, in particular, in [Fig. 2] and [Fig. 7], by way of example. In principle, the need for support is all the greater as the slope connecting these areas 22 to the main body of the part increases. Indeed, a zero or shallow slope may still allow the cantilevered portion to be manufactured, depending on the material used and the dimensions of the part. It has thus been determined by the inventors that the need for support can be considered certain, according to usual cases, from a slope forming an angle a of approximately 45°.

Claims

Demands

1. A method for additive manufacturing a part (10) by melting and local solidification of successive layers of powder of a metallic manufacturing material, the method comprising: - Making a support (20) configured to support at least a part of said part (10), - Making a protrusion (30) on a nominal surface (11) of the part (10), said protrusion (30) being configured to link the support (20) to said part (10), said protrusion (30) comprising a first junction surface (31) with said part (10) and a second junction surface (32) with said support (20), the support (20) comprising a breakable zone (23) defining a link between said support (20) and the protrusion (30), - Removing said support (20) by breaking said breakable zone (23).

2. A manufacturing method according to the preceding claim, wherein the height of said protrusion (30), before the removal of said support (20), is equal to a value the method comprising, after the removal of said support (20), an adjustment operation during which at least a part of said protrusion (30) is removed, so that the height HFina} of the protrusion, after the adjustment operation, complies with the formula: HFinai = k*Hirüt, the value of the factor k being between 0.05 and 0.

95.

3. A method according to any one of claims 1 to 2, wherein said first joining surface (31) is larger than said second joining surface (32).

4. A method according to any one of claims 1 to 3, wherein the protrusion (30) comprises two curved blanks (38, 39), preferably concave, connecting the first joining surface (31) to the second joining surface (32).

5. A method according to any one of claims 1 to 4, wherein the protrusion (30) comprises two chamfers, connecting the first joining surface (31) to the second joining surface (32).

6. A method according to any one of claims 1 to 5, wherein the protrusion (30) comprises a dimension e, measured transversely at the level of the second junction surface (32),

7.

8. and the support (20) includes a dimension E at the level of the breakable zone (23), the dimension e of the protrusion (30) respecting the following formula: e = q*E, in which the value of the factor q is between 1 and 2, preferably between 1 and 1.5, again preferably between 1.05 and 1.

2. Method according to claims 1 to 6, wherein the protrusion (30) comprises a dimension e, measured transversely at the level of the second junction surface (32), greater than or equal to 0.5mm, preferably said dimension e is substantially constant over a length L of the protrusion (30). Method according to claims 1 to 7, wherein the protrusion (30) before removal of the support (20), comprises a Hinit height greater than or equal to 1mm.

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