EP3818463A1

EP3818463A1 - Improved method for manufacturing a workpiece by additive manufacturing

Info

Publication number: EP3818463A1
Application number: EP19753141.1A
Authority: EP
Inventors: Sébastien Vincent François DREANO; Tiphaine DE TINGUY; Michel Daniel Régis SERS
Original assignee: Safran Aircraft Engines SAS
Current assignee: Safran Aircraft Engines SAS
Priority date: 2018-07-02
Filing date: 2019-07-02
Publication date: 2021-05-12
Also published as: US20210187615A1; CN112334903A; US11511349B2; FR3083159A1; FR3083159B1; WO2020008137A1; CN112334903B

Abstract

A method for manufacturing a workpiece by additive manufacturing, the workpiece (1) to be manufactured comprising at least one portion to be held forming an angle of less than 60° with respect to a direction of construction of the workpiece to be manufactured, the portion to be held having a first lateral surface (1a) and a second lateral surface (1b) opposite each other, the method comprising the following steps: providing a digital model of the workpiece (1) to be manufactured, adding to the digital model at least one holding element (10, 20) positioned to one side of the portion to be held, so as to be in contact with said first lateral surface (1a) or with said second lateral surface (1b).

Description

Improved part manufacturing process by additive manufacturing

FIELD OF THE INVENTION

The present disclosure relates to a part manufacturing process by additive manufacturing making it possible to maintain certain surfaces of the part liable to deform during manufacture, and in particular the surfaces influencing the aerodynamics of the final part.

Such an additive manufacturing process is particularly suitable for manufacturing complex parts provided with sensitive surfaces, intended in particular for the aeronautical field.

STATE OF THE PRIOR ART

It is now known, in the aeronautical field in particular, to use additive manufacturing methods for the production of certain parts whose geometry is fine or complex.

A classic example of additive manufacturing is the manufacturing by melting or sintering of powder particles by means of a high energy beam. Among these high energy beams, mention may be made in particular of the laser beam and the electron beam.

By "selective laser melting", in English "Selective Laser Melting" (SLM), also known as the "Laser Beam Melting" (LBM) process, is meant a process the main characteristics of which are recalled below. next, with reference to FIG 1 illustrating a conventional device for manufacturing a part by selective melting or selective sintering of powder beds by means of a laser beam.

Is deposited, for example using a spreading tool 200 (for example a roller), a first layer 100a of powder of a material on a construction plate 210 (it may be a '' a plate alone or surmounted by a solid support, a part of another part or a support grid used to facilitate the construction of certain parts).

This powder is transferred from a feed tank 220 during a forward movement of the roller 200 then it is scraped, and possibly slightly compacted, during one (or more) movement (s) of return from the roller 200. The powder is composed of particles 110. The excess powder is recovered in a recycling container 230 located adjacent to the construction container 240 in which the construction plate 210 moves vertically.

We also use a laser beam generator 300 310, and a control system 320 capable of directing this beam 310 on any region of the construction plate 210 so as to scan any region of a layer powder previously deposited. The shaping of the laser beam 310 and the variation of its diameter on the focal plane are done respectively by means of a beam dilator or focusing system 330 and a “Beam Expander” 340, the assembly constituting the system optical.

Next, one carries a region of this first layer 100a of powder, by scanning with a laser beam 310, at a temperature above the melting temperature of this powder.

This type of additive manufacturing process can use any high energy beam in place of the laser beam 310, and in particular an electron beam, as long as this beam is sufficiently energetic to melt the powder particles and part of the material on which the particles rest.

This scanning of the beam is carried out for example by a galvanometric head forming part of a control system 320. For example this control system comprises at least one adjustable mirror 350 on which the laser beam 310 is reflected before reaching a layer of powder, each point of the surface of which is always located at the same height with respect to the focusing lens, contained in the focusing system 340, the angular position of this mirror being controlled by a galvanometric head so that the beam laser scans at least one region of the first layer of powder, and thus follows a preset workpiece profile. To do this, the galvanometric head is controlled according to the information contained in the database of the computer tool used for the computer-aided design and manufacture of the part to be manufactured.

Thus, the powder particles 110 of this region of the first layer 100a are melted and form a first element 120a in one piece, integral with the construction plate 210. At this stage, it is also possible to sweep with the laser beam multiple regions independent of this first layer to form, after melting and solidification of the material, several first elements 120a separated from each other.

The construction plate 210 is lowered by a height corresponding to the thickness of the first layer of powder 100a (20 to 100 μm and in general from 30 to 50 μm).

Then depositing a second layer 100b of powder on the first layer 100a and on this first element in one piece or consolidated 120a, then heating by exposure to the laser beam 310 a region of the second layer 10b which is located partially or completely above this first element in one piece or consolidated 120a in the case illustrated in FIG 1, so that the powder particles of this region of the second layer 100b are melted with at least one part of the element 120a and form a second element in one piece or consolidated 120b, the assembly of these two elements 120a and 120b forming, in the case illustrated in FIG 1, a block in one piece.

Such an additive manufacturing technique therefore provides excellent control of the geometry of the part to be manufactured and makes it possible to produce parts having great complexity.

However, during the production of parts with complex geometry, certain parts of the part are momentarily found in strong overhang, or even without any other maintenance than the volume of non-solidified powder located below, and therefore present a risk of collapse in the manufacturing tank. This is particularly the case of the parts of the part which are substantially parallel to the production plate. In such a case, it is then necessary to manufacture supports at the same time as the part in order to maintain these parts during the manufacturing phase.

However, when the manufacturing is completed, and during the removal of these supports, residues remain at the interface between the supports and the part. Consequently, the part obtained comprises zones whose surface condition is not homogeneous. This non-homogeneous surface state, when it concerns sensitive areas of the room (for example areas in contact with an air flow), can disturb the flow of the fluid and thus alter the aerodynamic properties and therefore the performance of the machine concerned.

To avoid this problem, one solution is to orient the part so as to limit the use of supports, for example by arranging the largest surface in a substantially vertical manner.

However, when making parts with a slender geometry, that is to say long and thin parts in which one dimension is much greater than another dimension, for example a blade, certain surfaces tend to get deforming during manufacture, by buckling under the effect of the stresses resulting from the cooling and the solidification of the molten zone. This deformation can give rise to form deviations of the order of 4 mm on the aerodynamic profiles, which can alter the aerodynamic properties of the latter. To limit these deformations, and limit the need for supports, it is also possible to arrange the part, for example the blade, by positioning the largest dimension vertically, that is to say by positioning the leading edge and the trailing edge vertically. However, this arrangement greatly increases the manufacturing time.

There is therefore a real need for a part manufacturing process by additive manufacturing, making it possible to maintain certain particularly sensitive surfaces of the part and in particular the surfaces influencing the aerodynamics of the final part, while limiting the presence of residues on these surfaces during the manufacture of the part.

PRESENTATION OF THE INVENTION

The present disclosure relates to a method of manufacturing a part by additive manufacturing, the part to be manufactured comprising at least one portion to be maintained forming an angle less than 45 ° relative to a direction of construction of the part to be manufactured, the portion to be maintained having a first lateral surface and a second lateral surface opposite one another, the method comprising the following steps:

supply of a digital model of the part to be manufactured, addition to the digital model of at least one holding element positioned on one side of the portion to be maintained, so as to be in contact with said first lateral surface or said second surface lateral. In certain embodiments, the digital model comprises at least two holding elements, a first holding element being positioned on a first side of the portion to be held, so as to be in contact with said first lateral surface and a second holding element being positioned on a second side of the portion to be held so as to be in contact with said second lateral surface.

In the present description, by “direction of construction”, we understand direction in which the part is constructed, that is to say in which the powder layers, or manufacturing layers, are stacked one on the other. other. For example, when the part is manufactured on a construction plate, the construction direction corresponds to a direction orthogonal to said construction plate. By construction plane is then meant a plane orthogonal to the direction of construction and substantially parallel to the construction plate. In addition, by “in contact”, it is understood that the holding element is directly in contact with the lateral surface, or with a clearance less than 0.1 mm.

Preferably, a main direction of the workpiece forms a lower angle 30 ° relative to the direction of construction. In a case where the part to be manufactured would be a plate, for example, the plate having two lateral surfaces opposite to each other would be arranged so as to form an angle less than 30 ° relative to the direction of construction, c that is to say with respect to the direction orthogonal to the construction plate. In other words, the plate would be arranged substantially vertically, or sub-vertically, with respect to the construction plate.

The addition to the digital model of at least two holding elements makes it possible to construct these holding elements by additive manufacturing, at the same time as the part to be manufactured. The two holding elements are arranged on either side of the portion to be maintained and in contact with the latter, so as to take the latter in sandwich. In other words, while a lower portion of the workpiece is supported either by a support element or directly by the construction plate, the holding elements allow to maintain the lateral surfaces of the portion to be maintained of the part to be manufactured.

The presence of these holding elements makes it possible to avoid deformation of the part during manufacture, by buckling under the effect of the constraints of cooling and the solidification of the molten zone. It is thus possible to precisely position the retaining elements against the part, according to the modes of deformation thereof. In the case of an aeronautical part, these holding elements thus make it possible to limit the modification of the aerodynamic properties of this part.

In some embodiments, the contact between the first holding member and the first side surface, and the contact between the second holding member and the second side surface, are linear contacts.

By "linear contact" is meant a contact along a straight or curved line in a given plane, the line being continuous or discontinuous. In other words, the linear contact can be in the form of a succession of point contacts, insofar as these point contacts are aligned on the same line. The presence of these linear contacts between the holding elements and the lateral surfaces makes it possible to limit the contact surface between the holding elements and the lateral surfaces. Thus, when the manufacture of the part is finished, it is possible to easily detach the retaining elements from these lateral surfaces, by limiting the presence of residues thereon, caused by these elements. The final part obtained thus has a homogeneous surface condition. It is therefore possible to dispense with a manual polishing step for these surfaces after obtaining the final part.

In some embodiments, the first and second holding elements are opposite one with respect to the other.

By "vis-à-vis one with respect to the other", it is understood that the first and second holding elements are arranged on each side of the portion to be maintained, but are understood one and the other in the same plane, said plane being substantially perpendicular to the portion to be maintained and parallel to the direction of construction. This arrangement improves the maintenance of the portion to be maintained during manufacture, further limiting its deformation, by constraining its shape on a given section.

In some embodiments, a contact end of at least one holding element, in contact with the corresponding lateral surface of the portion to be held, has a thinned shape.

By "thinned shape", it is understood that in a transverse plane of the holding element, the transverse plane being perpendicular to the direction of construction, the contact end is thinner, that is to say thinner than the rest of the holding element. For example, the contact end can be rounded. By "rounded", it is understood that the contact end is rounded in the transverse plane of the holding element. This thinned shape, for example rounded, makes it possible to further limit the contact surface between the holding element and the surface. corresponding side of the portion to be maintained. This further limits the presence of residue after removal of the holding member. In addition, this rounded shape facilitates the manual removal operation of the holding element.

In certain embodiments, at least one retaining element has a plurality of teeth aligned with respect to each other, said retaining element being positioned so that the teeth are in contact with the corresponding lateral surface of the portion to maintain.

According to this configuration, the contact between the holding element and the corresponding lateral surface of the portion to be maintained is a discontinuous linear contact. In a plane parallel to the direction of construction and perpendicular to the lateral surfaces, the plurality of teeth of the holding element can for example take the form of saw teeth. Furthermore, when the contact ends of the teeth of the retaining element, in contact with the corresponding lateral surface of the portion to be maintained, are rounded, said contact is in the form of a succession of contact points aligned with relative to each other along a line. This configuration makes it possible to further limit the contact surface between the holding element and the lateral surface. corresponding portion to maintain, and thus further limit the residue present after removal of the holding element.

In some embodiments, the teeth of at least one holding element are aligned with respect to each other in a direction forming part of a plane comprising the direction of construction of the part to be manufactured.

In other words, the teeth can be aligned along a straight line, but can also be aligned along a curved line, the latter being part of a plane comprising the direction of construction, that is to say perpendicular to the building plate. This configuration makes it possible to limit the deformation of the part to be produced more effectively.

In some embodiments, at least one holding element has, in the direction of construction of the workpiece, a decreasing section.

The section of the holding element considered is a cross section, that is to say a section perpendicular to the direction of construction. According to this configuration, the cross section of the holding element decreases as one moves away from the construction plate along the construction direction. In other words, a portion of the holding element closer to the building plate is more massive than a portion of the holding element more distant from the building plate. Given the fact that the part to be produced tends to deform under the effect of the cooling stresses accumulated throughout the manufacture and of successive layers, the need to maintain the latter is more important towards the bottom of the part, c that is to say close to the construction plate, thus requiring a sufficiently rigid holding element to limit deformation in this area. Conversely, the rigidity of the retaining element may be lower in areas further from the construction plate. Adapting the section of the holding element as a function of the deformation stresses exerted by the portion to be maintained according to the height of the latter makes it possible to limit the amount of material used to manufacture the holding element. This configuration thus makes it possible to limit the costs of manufacturing the part and its retaining elements, as well as the manufacturing time. In some embodiments, the contact line between at least one holding element and the corresponding lateral surface extends over the entire height of the portion to be maintained.

The height of the portion to be maintained is considered according to the direction of construction, that is to say the direction perpendicular to the construction plate. This configuration makes it possible to improve the maintenance of the portion to be maintained, and to more effectively limit the deformation thereof.

In certain embodiments, the digital model comprises a plurality of first holding elements in contact with the first lateral surface of the portion to be maintained, and a plurality of second holding elements in contact with the second lateral surface of the portion to maintain.

These holding elements can be distributed uniformly on each lateral surface of the portion, but can also be distributed in a non-uniform manner, as required. For example, the number of elements in contact with one or the other of the lateral surfaces may be greater in the areas of these surfaces where the part presents a greater risk of deformation, and vice versa. This configuration makes it possible to optimize the maintenance of the portion to be maintained, as a function of the modes of deformation thereof.

In certain embodiments, each first holding element of the plurality of first holding elements in contact with the first lateral surface of the portion to be maintained, is positioned opposite one of the second elements. maintaining the plurality of second holding elements in contact with the second lateral surface of the portion to be maintained.

By "vis-à-vis", it is understood that the holding elements are arranged two by two of each of the portion to be maintained, being included one and the other in the same plane, said plane being substantially perpendicular to the portion to be maintained and parallel to the direction of construction. This arrangement improves the maintenance of the portion to be maintained during manufacturing by fixing the shape of the latter on given sections.

In some embodiments, each first holding element of the plurality of first holding elements in contact with the first lateral surface of the portion to be held, is positioned in staggered rows with respect to the second holding elements of the plurality of second holding elements in contact with the second lateral surface of the portion to be held.

By "staggered", it is understood that the first holding elements are not opposite one of the second holding elements. In other words, the first and second holding elements are offset from each other in a longitudinal direction, parallel to the construction plane. This arrangement makes it possible to optimize the position of the holding elements as a function of the buckling of the part.

In some embodiments, at least one tooth of at least one holding element has a face having an angle between 30 ° and 70 °, preferably between 40 ° and 60 ° ₇ relative to the direction of construction.

In some embodiments, at least 50% of the teeth of at least one holding element, preferably at least 80% of the teeth, more preferably all the teeth, have a face having an angle between 30 ° and 70 °, preferably between 40 ° and 60 °.

The angles of inclination of these surfaces make it possible to avoid the installation of supports thereon. Indeed, it is known that from a construction angle of approximately 30 ° relative to the construction plate, the layer of the part being manufactured has sufficient grip on the solidified part of the layer of lower manufacturing in order to be able to remain in position during the production of the part, without the need for additional holding means. It is therefore not necessary to install supports on said surface. Thus, by orienting the model so that these surfaces have these angles of inclination, the teeth of the holding element are not likely to collapse under their own weight during manufacture, the establishment of supports are thus not necessary.

In some embodiments, at least one holding element comprises a shell part entirely enveloping the first lateral surface of the portion to be maintained and / or the second lateral surface of the portion to be maintained, so that a clearance exists between the shell part and the lateral surface (s), the shell part having supports in contact with the surface (s) (s) lateral (s), the contact being linear.

The shell has an internal surface whose shape matches that of the corresponding lateral surface of the portion to be maintained, these two surfaces being opposite one another and being separated by a clearance between 0.1 and 0.5 mm. It is known to use a shell of this type, having a smooth surface, to limit the overall deformations of the part. However, the shell according to the present description also has supports on its internal surface comprising, for example, a plurality of teeth in contact with the corresponding lateral surface, in the same way as the retaining elements. The presence of this shell comprising these supports makes it possible to further limit the deformations of the part during manufacture, including in the areas of the portion to be maintained not maintained by the supports. In the case of parts exhibiting strong buckling zones, this shell thus makes it possible to avoid having holding elements over the entire length of the part.

In some embodiments, the shell part has a plurality of orifices.

The orifices make it possible to more easily recover the powder and to recycle the unused powder at the end of manufacture.

In some embodiments, the portion to be maintained of the part to be produced has a slender face.

By "slender" is meant a part of which at least one dimension is at least 10 times, preferably at least 50 times greater than another dimension. For example, a flat plate may have a length and a width much greater than its thickness.

In certain embodiments, the part to be manufactured is an aeronautical part, in particular of a turbomachine, and the lateral surfaces of the portion to be maintained are surfaces intended to be in contact with a flow of a working fluid.

The surfaces intended to be in contact with a flow of a working fluid may be surfaces delimiting a vein flow of the working fluid in a turbomachine for example. The presence of the holding elements therefore makes it possible to limit the deformation of these surfaces during manufacture, and thus to limit the risks of degrading the performance of the turbomachine.

In some embodiments, the part to be manufactured is a turbomachine blade, the first lateral surface being the lower surface of the blade, the second lateral surface being the upper surface of the blade.

According to this configuration, the surface to be maintained, comprising the lower surface and the upper surface, is oriented so that the angle which it forms with respect to the direction of construction, as a function of the curvature of the 'lower surface and upper surface, remains below 45 °. Furthermore, considering that the main direction of the blade is the rope of the latter, the rope forms an angle less than 30 ° relative to the direction of construction. During manufacturing, the leading edge of the blade can rest either on a support or directly on the construction plate, the construction of the blade therefore starting with its leading edge, and going layer by layer up to 'at its trailing edge, depending on the direction of construction. In this case, the holding elements, and more specifically the linear contacts between the latter and the blade, follow the curvature of the lower surface and the upper surface. The use of these holding elements to maintain the lower surface and upper surface of the blade during the manufacture thereof makes it possible to limit a deformation, causing the modification of the curvature thereof, and therefore a modification of its aerodynamic properties. In addition, these retaining elements allow, after their removal, to limit the presence of residues on the lower surface and upper surface of the blade. It is therefore possible to dispense with a manual polishing step for these surfaces after obtaining the final blade.

In certain embodiments, the method further comprises:

a step of producing the part to be manufactured layer by layer using an additive manufacturing technique based on the digital model, and

a step of removing the holding elements. In some embodiments, the method further comprises, after the removal of the holding elements, an automated polishing step of the surface to be saved from the part thus obtained.

Although the holding elements described in the previous embodiments make it possible to limit the presence of residues after the removal of the latter, the automated polishing step of the surface to be saved from the part obtained makes it possible to further improve the homogeneity of said surface.

This presentation also relates to a blank comprising:

a part having at least one portion to be held forming an angle less than 45 ° with respect to a direction of construction of the part, the portion to be held having a first lateral surface and a second lateral surface opposite to each other, and

at least two holding elements, a first holding element being positioned on a first side of the portion to be held, so as to be in contact with said first lateral surface and a second holding element being positioned on a side of the portion to be maintained so as to be in contact with said second lateral surface.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention and its advantages will be better understood on reading the detailed description given below of different embodiments of the invention given by way of nonlimiting examples. This description refers to the pages of attached figures, on which:

- Figure 1 shows an overview of an additive manufacturing device by selective melting of powder beds;

- Figure 2a shows a perspective view of a digital model of a part to be manufactured, and Figure 2b shows a cross section along A-A of the part of Figure 2a;

- Figure 3a shows the cross section of Figure 2b, comprising holding elements according to the present description, and Figure 3b shows a sectional view of Figure 3a along line B-B;

- Figure 4 shows a perspective view of a holding element according to the present description; - Figure 5 shows a cross section of an upper portion of the part to be manufactured.

- Figure 6 shows a sectional view of the workpiece and a shell.

DETAILED DESCRIPTION OF EXAMPLES OF EMBODIMENT

In the following description, the height of the workpiece is considered in the vertical direction Z, corresponding to the direction of construction. Consequently, the terms “upper”, “lower” and their deviations are considered in this direction Z. Furthermore, a longitudinal direction of the workpiece is considered in a horizontal direction X, perpendicular to the vertical direction Z. In addition , the thickness of the part to be manufactured is considered in a direction Y, perpendicular to the direction x and to the direction Z.

Furthermore, for the sake of simplicity, it will be understood in the following description that any reference to the blade or to the holding elements in fact refers to the digital model of the part to be manufactured, the digital model comprising said blade and said holding elements.

2a shows a perspective view of a model 1 of a part to be manufactured on a construction plate P, by a part manufacturing process by additive manufacturing. The construction direction, corresponding to the vertical axis Z, is perpendicular to the construction plane, corresponding to the upper surface of the construction plate P. In this embodiment, the workpiece 1 is a turbine engine blade. The blade 1 has a lower surface la and an upper surface lb. The lower surface la and the upper surface lb are lateral surfaces of the portion to be maintained during the manufacture of the blade 1 by additive manufacturing.

In fact, during the manufacture of the blade 1 by additive manufacturing, the lower surface la and the upper surface lb of the blade 1 extend substantially in the vertical direction Z, a lower end of the blade 1, for example the trailing edge, being supported by at least one support 2, or resting directly on the construction plate P. More precisely, the model of the blade 1 is oriented so that the chord of the blade forms an angle preferably less than 30 ° relative to the direction of construction, that is to say the vertical direction Z. 3a shows a lower portion of the cross section of Figure 2b, in which the holding elements 10 and 20 are arranged on either side of the blade 1. The holding element 10 is a holding upper surfaces allowing the upper surface 1b of the blade 1 to be maintained during manufacture, and the holding element 20 is a lower surface support making it possible to maintain the lower surface 1a of the blade 1 during manufacture. In this embodiment, each holding element 10, 20 is supported by the construction plate P, and is in contact with the blade 1 along a contact line extending over the entire height of the latter, c that is to say from the leading edge to the trailing edge thereof. Alternatively, the holding elements 10, 20 may be in contact with the blade 1 only over a portion of the height thereof. In addition, the holding elements 10 and 20 are arranged so that they are aligned with each other along the thickness direction Y (cf. FIG. 3b). In other words, the contact line between the lower surface retaining element 20 and the lower surface la, and the contact line between the upper surface retaining element 10 and the upper surface 1b, are both included in the YZ plan.

Figure 4 shows a perspective view of an upper retaining element 10 according to the present description. The retaining element 10 extends mainly along the direction of construction, following the shape, or more precisely the curvature, of the upper surface 1b of the blade 1. The retaining element 10 comprises a structural portion 10a, and a contact portion 10b. One end of the contact portion 10b is provided to be in contact with the upper surface 1b of the blade 1. The contact portion 10b has a convergent shape from the structural portion 10a to the end in contact with the extrados lb. The structural portion 10a is the portion of the retaining element making it possible to limit the deformations thereof. In other words, the structural portion 10a makes it possible to give the retaining element 10 sufficient rigidity to resist deformations of the blade 1.

The right part of Figure 4 has cross sections of the holding member 10 perpendicular to the direction of construction, on a lower portion and an upper portion of the latter. The structural portion 10a and the contact portion 10b have a width, that is to say a dimension in the longitudinal direction X, substantially constant, and small compared to their dimension in the vertical direction Z. On the other hand, the thickness, that is to say the dimension in the direction Y, of the structural portion 10a, decreases along the direction of construction, from the lower end to the upper end of the holding element 10. In other words, the total cross section of the holding element 10 decreases along the direction of construction. Indeed, the need to maintain the latter is greater in the lower portions, that is to say close to the construction plate, requiring that the holding element 10 is more rigid to limit deformation in this area. Conversely, the rigidity of the holding element 10 may be lower in the upper portions of the blade 1.

In addition, the end of the contact portion 10b, in contact with the upper surface 1b, comprises a plurality of teeth 12. Each holding element can comprise between three to ten teeth 12 per cm along the line according to which the teeth 12 are aligned. The teeth 12 are aligned with respect to each other in a plane perpendicular to the longitudinal axis X, so that a discontinuous linear contact, in the form of a succession of contacts punctual, or established between the upper surface lb and the holding element 10, over the entire height of the upper surface. In a cross section perpendicular to the longitudinal axis X, corresponding to the view of Figures 3a and 5, the teeth 12 have the shape of saw teeth. More specifically, each tooth 12 has a bearing face 12a, the bearing face 12a having, in this section, an angle b between 30 ° and 70 °, preferably between 40 ° and 60 °, more preferably equal to 45 ° , in relation to the horizontal, that is to say in relation to the construction plane. This angle avoids the installation of supports thereon.

Furthermore, along a cross section perpendicular to the axis Z, corresponding to the view of Figure 3b, each tooth 12 has a rounded end 14. Thus, the linear contact between the upper surface lb and the element of holding 10 is in the form of a succession of contact points aligned with each other over the entire height of the blade 1. This rounded shape makes it possible to limit the contact surface between the holding element 10 and the extrados 1b, and thus limit the residue present after removal of the holding element 10.

Although not described in detail, the lower surface holding elements 20 have the same structural characteristics as the upper surface holding element 10, except that the curvature of the lower surface holding element 20 follows the curvature of the lower surface. The end of the contact portions in contact with the lower surface 1a, comprises in particular a plurality of teeth 22.

Furthermore, Figures 3a and 3b show sections of the blade 1 in which a single upper support element 10 and a single lower support element 20 are visible. However, the digital model may include two or more upper surface holding elements 10 along the longitudinal direction X, and two, or more, lower surface holding elements 20 along the longitudinal direction X. The number of elements holding on each side of the blade, as well as their positions, are determined according to needs, that is to say according to the portions of the blade most likely to deform during manufacture.

6 shows a sectional view of the part to be manufactured according to another embodiment in which, instead of the holding elements 10, 20, a shell 30 is arranged on either side of the part to manufacture. The shell 30 includes supports 32 having the same characteristics as the holding elements 10, 20, in particular a plurality of aligned teeth and in contact with the lateral surfaces la, lb of the portion to be maintained. The shell also has intermediate portions 34 between two adjacent supports 32. The intermediate portions 34 have a surface whose shape matches that of the corresponding lateral surface 1a, 1b of the portion to be maintained, these two surfaces being opposite one another. The intermediate portions 34 are not in contact with the lateral surfaces of the portion to be maintained, but have a clearance J of between 0.1 and 0.5 mm with them. The intermediate portions 34 also include orifices 36. The orifices 36 make it possible to be able to recover the powder more easily and to recycle the powder not used at the end of manufacture. Although the present invention has been described with reference to specific exemplary embodiments, it is obvious that modifications and changes can be made to these examples without departing from the general scope of the invention as defined by the revendications. In particular, individual features of the different illustrated / mentioned embodiments can be combined in additional embodiments. Therefore, the description and the drawings should be considered in an illustrative rather than restrictive sense.

It is also obvious that all the characteristics described with reference to a method can be transposed, alone or in combination, to a device, and conversely, all the characteristics described with reference to a device can be transposed, alone or in combination, to a method.

Claims

1. Method for preparing a digital model for the manufacture of a part by additive manufacturing, the part to be manufactured (1) comprising at least one portion to be maintained forming an angle less than 45 ° relative to a direction of construction of the part to be manufactured, the portion to be maintained having a first lateral surface (la) and a second lateral surface (lb) opposite one another, the method comprising the following steps:

providing a digital model of the workpiece (1), adding to the digital model at least one holding member (10, 20) having a plurality of teeth (12) aligned with each other, and being positioned on one side of the portion to be held so that the teeth (12) are in contact with said first lateral surface (la) or with said second lateral surface (lb).

2. Method according to claim 1, in which the holding element (10, 20) is a first holding element (20) positioned on a first side of the portion to be held, so as to be in contact with said first lateral surface (la), and the digital model comprises at least a second holding element (10) positioned on a second side of the portion to be held so as to be in contact with said second lateral surface (lb).

3. Method according to claim 2, wherein the contact between the first holding element (20) and the first lateral surface (la), and the contact between the second holding element (10) and the second lateral surface (lb) , are linear contacts.

4. Method according to claim 2 or 3, wherein the first and second holding elements (10, 20) are vis-à-vis each other.

5. Method according to any one of claims 1 to 4, in which a contact end of at least one holding element (10, 20), in contact with the corresponding lateral surface (la, lb) of the portion to be maintained, has a thinned shape.

6. Method according to any one of claims 1 to 5, in which at least one tooth (12) of at least one holding element (10, 20) has a face having an angle between 30 ° and 70 °, preferably between 40 ° and 60 °, relative to the direction of construction.

7. Method according to any one of claims 1 to 6, wherein at least one holding element (10, 20) has, in the direction of construction of the workpiece (1), a decreasing section.

8. Method according to any one of claims 2 to 7, in which the digital model comprises a plurality of first holding elements (20) in contact with the first lateral surface (la) of the portion to be held, and a plurality of second holding elements (10) in contact with the second lateral surface (lb) of the portion to be maintained.

9. The method of claim 8, wherein each first holding element (20) of the plurality of first holding elements (20) in contact with the first lateral surface (la) of the portion to be maintained, is positioned vis-à-vis with respect to one of the second holding elements of the plurality of second holding elements (10) in contact with the second lateral surface (lb) of the portion to be held.

10. Method according to any one of claims 1 to 9, in which the part to be manufactured (1) is an aeronautical part, in particular of a turbomachine, and in which the lateral surfaces of the portion to be maintained are surfaces intended to be in contact with a flow of a working fluid.

11. Method according to any one of claims 1 to 10, in which the workpiece (1) is a turbine engine blade, the first lateral surface (la) being the lower surface of the blade, the second lateral surface (lb ) being the upper surface of the blade.

12. A method of manufacturing a part by additive manufacturing comprising the preparation of a digital model obtained using a method according to any one of claims l to 11, and the manufacture of the part by additive manufacturing.

13. Draft comprising:

a part (1) having at least one portion to be held forming an angle less than 45 ° with respect to a direction of construction of the part (1), the portion to be held having a first lateral surface (la) and a second lateral surface (lb) opposite one another, and at least two holding elements (10, 20), a first holding element (20) comprising a plurality of teeth (12) aligned with each other, and being positioned on a first side of the portion to be held, so that the teeth (12) are in contact with said first lateral surface (la), and a second holding element (20) comprising a plurality of teeth ( 12) aligned with each other, and being positioned on one side of the portion to be held so that the teeth (12) are in contact with said second lateral surface (lb).