METHOD FOR MANUFACTURED RAW PARTS IN CERAMIC AND / OR METALLIC MATERIALS BY ADDITIVE PROCESSES

Abstract

------ METHOD FOR MANUFACTURING RAW PARTS IN CERAMIC AND / OR METALLIC MATERIAL BY THE ADDITIVE PROCESSES TECHNIQUE According to the invention, before producing the first layer: the build platform is covered with a support sheet suitable for being pressed against it, forming a rigid and fixed surface for receiving successive layers, capable of retaining the successive layers formed on it; and said support sheet is pressed against said build platform by suction; the raw part is formed by the additive processes technique; and once the raw part is thus formed, the suction is removed in order to detach said support sheet from said platform, on which the raw part rests, along with the portion of the photocurable composition that has not been cured; said portion of the uncured photocurable composition is removed;and the said raw part is detached from the said support sheet, characterized in that the support sheet is a polymer sheet having a thickness of 0.05 to 5 mm and a flatness of less than 70% of the thickness of a layer, said support sheet being deformable to allow, once the suction is removed, the raw part to be detached from it by applying a stress on said sheet so as to deform it in order to release the raw part. Figure to be published with the abbreviation: Figure 1;

Description

Title of the invention: METHOD FOR MANUFACTURED RAW PARTS IN CERAMIC AND / OR METALLIC MATERIAL BY ADDITIVE PROCESSES

[0001] The present invention relates to a method of manufacturing, by the technique of additive processes, a raw part in at least one material chosen from ceramic materials and metallic materials.

[0002] The additive manufacturing process, also known as stereolithography, generally comprises the following steps for obtaining these raw parts: - a computer-aided design (CAD) model of the part to be manufactured is created, the dimensions of which are slightly larger than those of the actual part to allow for shrinkage of the ceramic or metallic material during the manufacturing process; and - The part is manufactured using additive manufacturing processes, a technique according to which: - a first layer of a photocurable composition is formed on a rigid support, comprising at least one ceramic or metallic material, at least one photocurable monomer and / or oligomer, at least one photoinitiator and, where applicable, at least one plasticizer and / or at least one solvent and / or at least one dispersant; - the first layer of the photocurable composition is hardened by irradiation (by laser scanning of the free surface of said layer or by diode projection system) according to a pattern defined from the model for said layer, forming a first stage; - a second layer of the photocurable composition is formed on the first stage; - the second layer of the photocurable composition is hardened by irradiation according to a pattern defined for said layer, forming a second stage, this irradiation being carried out in the same way as for the first layer; - Optionally, the above steps are repeated to obtain the piece in its raw state.

[0003] Next, as indicated above, to obtain the finished part, the raw part is cleaned to remove the unhardened composition; the raw part is unbound cleaned; and the piece is sintered in its raw, cleaned and unbound state to obtain the finished piece.

[0004] In a paste-like manufacturing process, the photocurable composition is in the form of a paste whose viscosity can vary, in particular, from 1 Pa·s to infinity at zero shear rate. The rigid support is a work platform that supports the different layers of the part being built, as well as the paste. Each layer is generally formed by lowering the work platform and spreading a predetermined thickness of paste. A supply of paste is stored in reservoirs that are automatically emptied of a predetermined quantity of paste for each layer using a piston. This creates a bead of paste to be spread onto the upper layer of the part being manufactured, which has been previously lowered by the work platform.Each layer is generally spread by scraping with a scraper blade that sweeps across the working surface of the work platform, for example by moving forward in a straight horizontal direction.

[0005] Another manufacturing process by pasty / creamy means is described in patent application FR3116461 which uses an applicator system with a suspension reservoir supplied by an external tank, the stacking of layers taking place in a tray which fills with suspension at each layer formation.

[0006] In liquid manufacturing, the photocurable composition is in the form of a low viscosity suspension. - In a first embodiment using the liquid method, the rigid support is a platform that is lowered into a bath of the photocurable suspension to be coated with a layer of said suspension, which is then cured by irradiation as described above. On this first layer, each of the other layers is then successively formed by lowering the platform step by step into the bath such that the upper layer of the part being formed is lowered below the free surface of the photocurable suspension to form the layer in question, which is then irradiated. - In a second embodiment using the liquid method, the photocurable suspension is contained in a transparent-bottomed reservoir for irradiation, and the part is held on a rigid support, which is a platform raised incrementally. Thus, a base layer is first cured, then the platform is raised one increment to allow the suspension to form a new layer, which is then cured, the operation being repeated for each layer. - In a third embodiment using the liquid route, the photocurable suspension is spread in a layer on a transparent film to The film is irradiated, allowing it to unwind horizontally. The part is formed on a rigid platform that descends to contact the layer, which is then cured by irradiation through the film. A new segment of film coated with a new photocurable layer is then unwound, and the process is repeated until the part is complete.

[0007] It is important that there be a good bond between the construction surface, in other words the rigid working platform (upper face of the working platform in the case respectively of the pasty process and the first aforementioned embodiment in liquid process, and lower face of the platform in the case of the second and third aforementioned embodiments in liquid process), and the part which is built by stacking the layers.

[0008] A support is therefore placed between the rigid working platform and the part under construction.

[0009] The choice of the substrate for building the part is crucial both for printing the part and for its recovery. The substrate must meet several conflicting constraints: • adhere sufficiently to the rigid working platform to ensure the stability of the parts; • have sufficient flatness to allow the printing of thin layers; • be easily detachable from the rigid working platform after printing; and • facilitate the removal of the raw part so as not to damage them after printing.

[0010] Currently, the printing of ceramic parts by stereolithography takes place on a magnetic support placed on the build platform and held in place by magnetism. While this system allows for very good adhesion to the work platform, it does not allow for compliance with the three other constraints stated above for thin-walled parts, typically less than 1 mm thick, or for parts built in thin layers, typically 25 to 30 µm thick.

[0011] The flatness of the magnetic supports is on the order of 50 µm, which is insufficient for thin-layer construction with a thickness of 25 to 30 µm. Furthermore, a lack of flatness results in irregular adhesion to the support depending on the position of the parts on the platform.

[0012] Furthermore, the rigidity of the magnetic supports and their roughness make it difficult to detach the support from the platform and to detach the parts from the support. Thin-walled parts are at high risk of damage during the detachment phase, rendering them unusable.

[0013] The difficulty of removing thin-walled parts also forces a reduction in the number of parts that can be printed at the same time on the same printer, which reduces their productivity.

[0014] To solve this problem, the Applicant Company sought a solution enabling the construction of thin film parts as well as thin wall parts while ensuring detachment of the parts without damage and allowing optimal filling of the construction platform.

[0015] To this end, the present invention relates to a method for manufacturing, using additive manufacturing techniques, a raw part in at least one material chosen from ceramic and metallic materials,

[0016] a process in which layers based on a photocurable composition comprising said ceramic and metallic materials in powder form and an organic part comprising at least one photocurable monomer and / or oligomer and at least one photoinitiator are successively cured by irradiation according to a pattern defined for each layer, the first layer being formed on a build platform, and each subsequent layer being formed and then cured in contact with the preceding layer,

[0017] method according to which: - before applying the first coat: • The construction platform is covered with a support sheet capable of withstanding stress against it, forming a rigid and fixed surface for receiving successive layers and retaining the successive layers formed; and • the said support sheet is pressed against the said construction platform by suction; - the raw piece is formed using additive manufacturing processes; and - Once the raw piece has been formed in this way, the suction is removed in order to detach of said platform said support sheet on which is placed the raw piece with the part of the photocurable composition which has not been cured; - the said uncured portion of photocurable composition is removed; and - the said raw piece is detached from the said support sheet,

[0018] characterized by the fact that the support sheet is a polymer sheet having a thickness of 0.05 to 5 mm and a flatness of less than 70% of the thickness of a layer, preferably less than 40% of the thickness of a layer, said support sheet being deformable to allow, once the suction is removed, the raw part to be detached from it by applying a stress on said sheet so as to deform it in order to release the raw part.

[0019] The flatness of the support sheet can be defined as the difference in height between the lowest point of the sheet and its highest point, when the sheet is placed on a vertical support.

[0020] For example, in the case of constructing a part using layers with a thickness between 25 and 30 µm, the flatness of the support sheet must be less than 17.5 µm, preferably less than 10 µm. It may have, for example, a flatness of 8 µm.

[0021] The support sheet may have a Young's modulus of 2.5 to 80 GPa, preferably from 2.5 to 15 GPa.

[0022] The support sheet can be a biaxially oriented poly(ethylene terephthalate) sheet, a polyetherimide sheet, a polyamide sheet or a polyolefin sheet.

[0023] A semi-liquid, photocurable composition can be used, which is spread layer by layer on the construction platform, the layers being irradiated from above,

[0024] or a photocurable composition in suspension can be used,

[0025] the platform being lowered step by step into the suspension to form the successive layers irradiated from above, or

[0026] the platform being positioned at a distance corresponding to the thickness of a layer from the bottom of a transparent-bottomed photocurable composition tank for irradiation and raised at each layer formation, the layers being irradiated from below each time; or

[0027] the platform coming into contact with a suspension layer applied to a segment of a transparent film which is unrolled horizontally to present a new segment at each layer formation, the layers being irradiated from below each time.

[0028] By photocurable composition of semi-liquid consistency, we mean a suspension having a viscosity between 0.5 and 100 Pa.s for a range of shear gradients between 5 and 50 s1.

[0029] A perforated or porous flat plate made of a rigid material, such as ceramic, metallic or plastic, can be used as a construction platform. The free face of this plate is covered by the support sheet and the opposite face is connected to a vacuum pump or vacuum generator. The pump or generator is put into operation to press the support sheet onto the free face of the platform, forming the rigid and fixed surface for receiving successive layers of photocurable composition, and is put into operation to detach the support sheet from the platform.

[0030] In particular, a perforated plate can be used, the perforations of which are in particular in the form of holes and slots connected to the vacuum pump or vacuum generator, arranged to ensure, when the latter is in operation, the coating of the support sheet.

[0031] A construction platform can be used, in particular made of metal or plastic, of flat shape, the bottom of which has perforations connected to a vacuum pump and which receives a grid, in particular made of metal, the support sheet being applied to the free edge of the receptacle and to the grid, said vacuum pump being put into operation to press said support sheet onto the free edge of the receptacle and onto the grid, forming the rigid and fixed surface for receiving successive layers of photocurable composition, and put out of operation to detach said support sheet from said platform.

[0032] A vacuum of 13.33 Pa - 10 10 Pa (0.133 mbar-10 12mbar) can be generated.

[0033] The present invention also relates to a manufacturing machine by the additive process technique for raw parts in a material selected from ceramic and metallic materials, according to which layers based on a photocurable composition comprising said ceramic and metallic material(s) in powder form and an organic part comprising at least one photocurable monomer and / or oligomer and at least one photoinitiator are successively cured by irradiation according to a pattern defined for each layer, the first layer being formed on a build platform, and each subsequent layer being formed and then cured on the preceding layer,

[0034] the machine comprising suction means against said construction platform of a support sheet intended to cover it before the first layer is made, forming a receiving surface for successive layers, capable of retaining on it the successive layers formed, said suction means being capable of being deactivated to detach from said platform said support sheet on which is located the raw part with the part of the photocurable composition which has not been cured,

[0035] the construction platform being a flat, grooved plate made of a rigid material, such as ceramic, metal or plastic, the free face of which is covered by the support sheet and which is connected, on its opposite face, to the suction means,

[0036] said machine also comprising means for irradiating successive layers,

[0037] characterized by the fact that the construction platform has a roughness Ra of 0.4 to 3.2 pm and a parallelism of 0.002 to 0.1% of the width of the construction platform.

[0038] To better illustrate the object of the present invention, a particular embodiment thereof will be described below, by way of indication and not limitation, with reference to the attached drawing.

[0039] On this drawing:

[0040] Fig. 1 is a perspective view of the build platform and support sheet equipping a stereolithography machine.

[0041] Fig. 2 is a schematic view of the steps for introducing a detachment aid sheet between the construction platform and the support sheet.

[0042] The stereolithography machine is a conventional prior art machine, of which only the platform will be described in more detail below. Figure 1 shows the construction platform 1 used in the present invention. A conventional laser irradiation means 2 is used for irradiating successive layers.

[0043] This platform 1 has a plurality of grooves 3. A support sheet 4 is placed on it, said support sheet being a sheet of poly(ethylene terephthalate) with biaxially oriented orientation.

[0044] The support sheet 4 has a thickness of 190 pm with a flatness of 8 pm, as well as a Young's modulus of 4.5 GPa.

[0045] It is possible to construct a plurality of parts 5 on the support sheet 4.

[0046] Before the parts are built, the support sheet 4 is placed on the build platform 1, and the air between the platform 1 and the support sheet 4 is drawn out through the grooves 3 using a closed-loop venturi vacuum generation system. Thus, during the building of the parts 5, the support sheet 4 is held firmly on the platform 1, ensuring the stability of the parts 5.

[0047] Once the parts 5 are built, the vacuum is stopped, which makes it easy to peel the support sheet 4 off the platform 1.

[0048] In the case of building a part in a so-called top-down system, where the parts being built are illuminated from above and the build platform is lowered as the parts are built, it is possible to use a detachment aid sheet to further facilitate the detachment of the support sheet from the build platform. This is illustrated in [Fig. 2].

[0049] We use a detachment aid sheet 6 which is a sheet made of poly(vinyl chloride) and which has a Young's modulus of 4.2 GPa and a thickness of 4 mm greater than that of the support sheet 3.

[0050] Initially, after stopping the vacuum, the detachment aid sheet 6 is placed near the construction platform 1 on which the support sheet 4 is placed and on which the parts 5 have been constructed.

[0051] We begin by slightly detaching the support sheet 4 from the construction platform 1 in order to place the edge of the detachment aid sheet 6 between platform 1 and support sheet 4. Then the detachment aid sheet 6 is gradually slid between support sheet 4 and construction platform 1 as shown in the central drawing of [Fig.2].

[0052] Once the detachment aid sheet 6 is fully inserted between the support sheet 4 and the construction platform 1, the assembly consisting of parts 5, support sheet 3 and detachment aid sheet 6 can be lifted.

[0053] It is thus easier to detach the support sheet 4 from the platform 1. The greater thickness of the detachment aid sheet 6 also makes it easier to handle the assembly formed by the constructed parts 5, the support sheet 4 and the detachment aid sheet 6 in order to more easily remove the parts 5.

Claims

1. Demands - A method for manufacturing, using additive manufacturing techniques, a raw part made of at least one material selected from ceramic and metallic materials, a method in which layers based on a photocurable composition comprising said ceramic and metallic material(s) in powder form and an organic part comprising at least one photocurable monomer and / or oligomer and at least one photoinitiator are successively hardened by irradiation according to a pattern defined for each layer, the first layer being formed on a build platform, and each subsequent layer being formed and then hardened in contact with the preceding layer, a method in which: - before applying the first coat: • The construction platform is covered with a support sheet capable of withstanding stress against it, forming a rigid and fixed surface for receiving successive layers and retaining the successive layers formed; and • the said support sheet is pressed against the said construction platform by suction; - the raw piece is formed using additive manufacturing processes; and - once the raw part has thus formed, the suction is removed in order to detach from said platform said support sheet on which the raw part is located with the part of the photocurable composition which has not been hardened; - the said uncured portion of photocurable composition is removed; and - the said raw part is detached from the said support sheet, the said support sheet being deformable to allow, once the suction is removed, the raw part to be detached from it by applying a constraint to the said sheet so as to deform it in order to free the raw part, characterized by the fact that the support sheet is a polymer sheet with a thickness of 0.05 to 5 mm and a flatness of less than 70% of the thickness of a layer, preferably less than 40% of the thickness of a layer, and that the construction platform has a roughness Ra of 0.4 to 3.2 pm.

2. - Method according to claim 1, characterized in that the support sheet has a Young's modulus of 2.5 to 80 GPa, preferably of 2.5 to 15 GPa.

3. - Method according to claim 1, characterized in that the support sheet is a biaxially oriented poly(ethylene terephthalate) sheet, a polyetherimide sheet, a polyamide sheet or a polyolefin sheet.

4. - A method according to any one of claims 1 to 3, characterized in that a semi-liquid photocurable composition is used, which is spread layer by layer on the building platform, the layers being irradiated from above, or a suspended photocurable composition is used, the platform being lowered step by step into the suspension to form successive layers irradiated from above, or the platform being positioned at a distance corresponding to the thickness of a layer from the bottom of a transparent-bottomed photocurable composition tank for irradiation and raised at each layer formation, the layers being irradiated from below each time;or the platform coming into contact with a suspension layer at each layer formation on a segment of a transparent film which is unrolled horizontally to present a new segment at each layer formation, the layers being irradiated from below each time.;

5. - A method according to any one of claims 1 to 4, characterized in that a perforated or porous flat plate made of a rigid material, such as ceramic, metal, or plastic, is used as a building platform, the free face of which is covered by the support sheet and which is connected, on its opposite face, to a vacuum pump or vacuum generator, which is put into operation to press the support sheet onto the free face of the platform, forming the rigid and fixed surface for receiving the layers successive photocurable composition, and put out of service to detach said support sheet from said platform.

6. - Method according to claim 5, characterized in that a perforated plate is used, the perforations of which are in the form of holes and slots connected to the vacuum pump or vacuum generator, arranged to ensure, when the latter is running, the coating of the support sheet.

7. - A method according to any one of claims 1 to 6, characterized in that a flat-shaped receptacle, in particular made of metal or plastic, is used as a construction platform, the bottom of which has perforations connected to a vacuum pump and which receives a grid, in particular made of metal, the support sheet being applied to the free edge of the receptacle and to the grid, said vacuum pump being put into operation to press said support sheet onto the free edge of the receptacle and onto the grid, forming the rigid and fixed surface for receiving successive layers of photocurable composition, and put out of operation to detach said support sheet from said platform.

8. - Method according to any one of claims 1 to 7, characterized in that the construction platform has a parallelism of 0.002 to 0.1% of the width of the construction platform.

9. - Method according to any one of claims 1 to 7, characterized in that a vacuum of 13.33 Pa - 10 10 Pa (0.133 mbar-10 12mbar) is generated.

10. - A machine for manufacturing, by additive manufacturing processes, raw parts from a material selected from ceramic and metallic materials, wherein layers based on a photocurable composition comprising said ceramic and / or metallic materials in powder form and an organic part comprising at least one photocurable monomer and / or oligomer and at least one photoinitiator are successively cured by irradiation according to a pattern defined for each layer, the first layer being formed on a build platform (1), and each subsequent layer being formed and then cured on the preceding layer, the machine comprising means for suctioning against said build platform (1) a support sheet (4) intended for the covering before the first layer is applied, forming a receiving surface for successive layers, capable of retaining the successive layers formed, said suction means being capable of being deactivated to detach from said platform (1) said support sheet (4) on which the raw part (5) is located with the part of the photocurable composition which has not been cured, the construction platform (1) being a flat grooved plate made of a rigid material, such as ceramic, metal or plastic, the free face of which is covered by the support sheet (4) and which is connected, by its opposite face, to the suction means, said support sheet (4) being deformable to allow, once the suction is removed, the raw part (5) to be detached from it by applying a stress on said sheet (4) so ​​as to deform it in order to release the raw part, said machine also comprising means (2) for irradiating successive layers, characterized by the fact that the construction platform (1) has a roughness Ra of 0.4 to 3.2 pm and a parallelism of 0.002 to 0.1% of the width of the construction platform (1); and the support sheet (4) is a polymer sheet having a thickness of 0.05 to 5 mm and a flatness of less than 70% of the thickness of a layer, preferably less than 40% of the thickness of a layer.

Images