Additive manufacturing method in a tunable constraint medium

Abstract

Additive manufacturing device and method, comprising the deposition of a suspended printing material within a printing tray (2) containing a stress medium (3) to form a three-dimensional object, this deposition of printing material being achieved by at least one step which is the injection of printing material through a nozzle (5) of a printing head (4), said nozzle (5) of the printing head (4) being immersed in the stress medium (3) and being able to move in three spatial dimensions in the stress medium (3), said method having at least one step of varying the level of the stress medium (3) in the printing tray (2).

Description

Technical Field

[0001] This invention relates to the field of additive manufacturing, also known as "three-dimensional printing" or "3D printing". More specifically, this invention relates to additive manufacturing in stress media. Background Technology

[0002] Among known additive manufacturing methods, some differ in that they involve depositing and shaping material within a print tray containing a stress medium, which performs the function of holding the printed material. In these methods, the printing material for forming a three-dimensional object is deposited through a print head that is movable in three spatial dimensions and has nozzles immersed in a stress medium formed by the material surrounding and containing the three-dimensional object during the forming process.

[0003] Patent application US2018057682 describes an additive manufacturing method that implements a stress medium. In this method, silicone-based ink is deposited in a liquid state in a stress medium composed of a gel. The interfacial surface tension between the silicone and the gel facilitates printing the silicone-based ink with the gel as a suspended phase, thereby enabling the printing of silicone parts.

[0004] In addition, patent application WO2020109745 also describes such an additive manufacturing method in which printing material is deposited in a particulate phase that acts as a stress medium.

[0005] These methods allow for the manufacture of parts using printing materials with flow properties that are not designed for or are not adequately designed for in traditional additive manufacturing methods. For example, acceptable printing materials for these methods include highly fluid silicone, which cannot be printed using conventional methods such as Fused Deposition Modeling (FDM), Liquid Phase Deposition Modeling (LDM), Multi-Nozzle Printing (MJP), Stereolithography (SLA), Selective Laser Melting (SLM), Selective Laser Sintering (SLS), Electron Beam Melting (EBM), and Binder Jetting. These methods are fundamentally different from additive manufacturing methods in stress media. Summary of the Invention

[0006] The purpose of this invention is to improve existing additive manufacturing apparatus and methods.

[0007] Therefore, the present invention relates to an additive manufacturing method comprising depositing suspended printing material within a printing tray containing a stress medium to form a three-dimensional object. This deposition of the printing material is achieved through at least one step, wherein the printing material is injected through a nozzle of a printhead immersed in the stress medium and movable in three spatial dimensions within the stress medium. The method includes at least one step of changing the height of the stress medium within the printing tray.

[0008] According to another subject matter, the present invention relates to an additive manufacturing apparatus having:

[0009] - Stress medium placed in the printing tray;

[0010] - A printhead designed for dispensing printing material has nozzles that are designed to move in three spatial dimensions in a stress medium;

[0011] - A device for changing the height of the stress medium in the printing tray.

[0012] The method and apparatus of this invention first achieve better 3D printing quality by adjusting the pressure exerted on the nozzle during printing.

[0013] Furthermore, this method opens up new perspectives for additive manufacturing in stress media. Therefore, these additive manufacturing methods in stress media can not only print parts using difficult-to-print materials (such as low-viscosity materials, materials with insufficient threshold stress, or materials with significant thixotropic behavior), but also adjust the physical properties of the printed parts.

[0014] In this specification and claims, the term "printing" is used to refer to the manufacture of a part by an additive manufacturing method, "printing material" refers to the material that is shaped in the method and constitutes all or part of the manufactured part, and "constraint material" refers to the material present in the printing tray that constitutes a stress medium and is therefore intended to surround and apply pressure to the part manufactured by the printing material.

[0015] The additive manufacturing method can influence the shape of the obtained part not only by controlling the printhead, but also by controlling the height of the stress medium.

[0016] For different parts printed based on the same 3D model, different parameters that are significantly related to the height variation of the stress medium in the printing tray will result in parts having the same shape but exhibiting different physical properties.

[0017] Therefore, by simply adjusting the method parameters, parts with different mechanical properties can be obtained from the same printing material. Thus, an additive manufacturing apparatus implementing this method would be able to be supplied with printing material from a single source, and the user would be able to select various physical properties required for the final part, achieved solely by adjusting machine parameters without changing the printing material supply. The mechanical properties of the part are, for example, physical properties that can be adjusted by the method.

[0018] Therefore, various parts with different mechanical properties can be obtained from the same printing material. Alternatively, identical parts with different mechanical properties can be obtained. Specifically, the method can change the mechanical properties of a portion of the part by controlling the height of the stress medium, so that different parts of the final part (although made of the same printing material) have different local characteristics suitable for the intended use of the part.

[0019] On the other hand, as an example of physical properties that can be adjusted by the method, the method ensures that all parts of the part have exactly the same mechanical properties by controlling the height of the stress medium (in this case), thereby obtaining a part that is very homogeneous in terms of mechanical properties.

[0020] The method described in this invention may have the following other features, either individually or in combination:

[0021] -The method includes a step of adjusting the stress applied to the printing material by the stress medium;

[0022] - In the step of changing the height of the stress medium in the printing tray, a layer of constraint material identical to the material constituting the stress medium in the printing tray is deposited on the surface of the stress medium;

[0023] - In the step of changing the height of the stress medium in the printing tray, a layer of constraint material different from the material constituting the stress medium in the printing tray is deposited on the surface of the stress medium;

[0024] - The deposition of a layer of confined material on a stress medium is achieved by diffusion across the entire surface of the stress medium;

[0025] - The deposition of a layer of constrained material on a stress medium is achieved via a movable diffusion head;

[0026] - In the step of changing the height of the stress medium in the print tray, the head support supporting the print head and the diffuser head moves toward the entire surface of the stress medium, the print head is deactivated and the diffuser head is activated;

[0027] - In the step of changing the height of the stress medium in the print tray, a layer of stress medium material is extracted from the print tray;

[0028] - The extraction of layers of stress medium material is achieved by suction across the entire surface of the stress medium;

[0029] - The suction is performed via a movable removal head;

[0030] - In the step of changing the height of the stress medium in the print tray, the head support supporting the print head and the removal head moves toward the entire surface of the stress medium, the print head is deactivated and the removal head is activated;

[0031] The method comprises the following sequential steps: printing a portion of a three-dimensional object; changing the height of the stress medium in the printing tray; and printing another portion of the three-dimensional object.

[0032] The method includes the following steps: a preliminary calibration step, in which a relationship between a predetermined physical property and a printing depth in a stress medium is determined; a step of selecting a printing depth corresponding to a predetermined value of the physical property; and a step of printing a part in a stress medium at a stress medium height corresponding to the selected printing depth.

[0033] - The stress medium has fluidity;

[0034] - The stress medium is composed of granular stress material;

[0035] - The stress medium is composed of gel;

[0036] - The printing material is a curable material.

[0037] The device described in this invention may have the following other features, either individually or in combination:

[0038] - A movable diffusion head, which is designed to deposit a layer of confinement material on the stress medium;

[0039] -The diffuser head has a control distribution device for controlling the distribution of the constrained material;

[0040] - A head support that supports the print head and diffuser head, which can move across the entire surface of the stress medium in a mode where the print head is deactivated and the diffuser head is activated.

[0041] - A constraint material reservoir that holds the same material as the stress medium constituting the printing tray, the reservoir supplying the diffuser head;

[0042] - A constraint material reservoir that holds a material different from the material constituting the stress medium in the printing tray, the reservoir supplying the diffuser head;

[0043] - A movable removal head designed to remove layers of stress-medium material;

[0044] -The removal head is connected to the suction device;

[0045] - A head support that supports the print head and the removal head, which is movable across the entire surface of the stress medium in a mode where the print head is deactivated and the removal head is activated.

[0046] - A reservoir of constrained material, with a removal head supplying the reservoir;

[0047] -The stress medium in the printing tray has fluidity;

[0048] - The stress medium in the printing tray is composed of granular stress material;

[0049] - The stress medium in the printing tray is composed of gel. Attached Figure Description

[0050] Referring to the accompanying drawings, other features and advantages of the invention will become apparent from the following non-limiting description, wherein:

[0051] - Figure 1 The additive manufacturing apparatus of the present invention is shown;

[0052] - Figure 2 It shows the use of Figure 1 The steps for the device to print the first part;

[0053] - Figure 3 It shows the use of Figure 1 Another step in the device printing the first part;

[0054] - Figure 4 It shows the use of Figure 1 Another step in the device printing the first part;

[0055] - Figure 5 It shows the use of Figure 1 The steps for the device to print the second part;

[0056] - Figure 6 It shows the use of Figure 1 Another step in the device printing the second part;

[0057] - Figure 7 It shows the use of Figure 1 Another step in the device printing the second part;

[0058] - Figure 8 The relationship between the elasticity of the printed part, the printing depth, and the constraining material is shown.

[0059] - Figure 9 It shows the use of Figure 1 The ball obtained by the device;

[0060] - Figure 10 It shows Figure 1 Details of the device used to change the height of the stress medium in the apparatus;

[0061] - Figure 11 It shows Figure 10 Variations of the device for changing the height of the stress medium. Detailed Implementation

[0062] Figure 1The additive manufacturing apparatus of the present invention is shown. The apparatus has a printing plate 1 on which a printing tray 2 holding a stress medium 3 is disposed. In practice, the printing plate 1 can be, for example, a one-square-meter aluminum plate, similar to the aluminum plate of the 3D printer sold by TOBECA under reference number 101015. The printing tray 2 can be, for example, a plastic box sold by LEROY-MERLIN under reference number 68993750, referred to as a multi-box. The apparatus also has a print head 4 equipped with nozzles 5. The term "nozzle" specifically refers to an outlet for dispensing printing material. Throughout the printing process, the nozzles 5 and a portion of the print head 4 are immersed in and move within the stress medium, thereby enabling the deposition of printing material. The print head 4 is supplied with printing material by a supply device 6, which is shown schematically only via a supply conduit. The supply device can be any known device used in 3D printing, such as a circuit equipped with a pump or pressure device to provide printing material in liquid form, a mechanical distributor to provide printing material in the form of molten continuous filaments or granules in the print head 4, etc. Regardless of the supply device 6 used, the printhead 4 is designed to dispense printing material in a sufficiently fluid manner through its nozzles 5 for printing. The printhead 4 may be, for example, a printhead sold by VISCOTEC under reference number vipro-HEAD3, and the nozzles 5 may be, for example, Optimum deposition needles sold by Nordson EFD.

[0063] The printing material is a curable material, meaning it cures after deposition in a stress medium. Printing materials can be, for example, molten materials dispensed by a heated printhead that solidify upon cooling, or crosslinkable polymers that can be crosslinked after chemical reactions, solvent evaporation, or exposure to, for example, UV light radiation. For instance, printing materials can be one-component (condensation) or two-component (addition) silicone.

[0064] The printing apparatus has a means of relative movement between the nozzle 5 and the tray 2 in three spatial directions. In this example, the print head 4 is mounted on a head support 7 connected to a slide 8, allowing the head support 7 to move in three orthogonal directions. As a variation, any other means capable of translating and / or rotating the print plate 1 and / or the head support 7 can be provided, as long as it is capable of moving the nozzle 5 within the stress medium 3 in three spatial directions. Notably, the print head 4 can be moved, for example, by a robotic arm with six axes, thereby angling the nozzle within the stress medium.

[0065] The stress medium 3 is fluid, meaning it is composed of a material conforming to the shape of its container. For example, the stress medium can be a particulate medium, a liquid or gel medium, or a foam. In this example, the stress medium 3 is a granular stress medium composed of a solid particulate phase and an interstitial gas phase. The particulate phase is a group of discrete solid components. Due to their pulverizability and non-adhesiveness, these discrete components spontaneously arrange themselves to conform to the shape of the tray 2, remaining close to each other under their own weight. The discrete components interact through contact areas between each adjacent discrete component and the surrounding discrete components. The granular stress medium has these discrete components and the interstitial gas phase between them. The mechanical behavior of the granular stress medium is affected only by changes in the contact points between the discrete components and not by the interstitial gas phase, which only affects the mechanical behavior of the granular stress medium to the extent that it can alter the contact areas between the discrete components.

[0066] As a variation, the invention can be implemented using any other stress medium, such as a gel. The advantage of a granular stress medium over a gel is that it is unaffected by buoyancy, ensuring that the geometry of the object does not change during printing or before removal from the stress medium.

[0067] Therefore, the stress medium 3, whether granular or non-granular, can be composed of various types of materials, including: silica, hollow microspheres, PMMA, sodium bicarbonate, sugar, sand, Pluronic F127 (gel), Carbopol, gelatin, etc., as long as they have fluidity. These different materials can also be mixed in various proportions. Furthermore, the printing device has a diffusion head 9 and a removal head 10, both designed to influence the height of the stress medium.

[0068] The diffuser head 9 is designed to discharge constraint material into the tray 2, thereby increasing the height of the stress medium 3. In this example, the stress medium 3 is, for example, a granular stress medium formed from solid polymer particles, and the diffuser head 9 is designed to diffuse a sufficient number of these polymer particles onto the surface of the stress medium 3. The head support 7 then moves the diffuser head 9. The diffuser head 9 has a diffusion start / stop mechanism and a mechanism for supplying polymer particles (not shown).

[0069] The removal head 10 functions in the opposite direction to the diffusion head 9, and is capable of removing polymer particles from the surface of the stress medium 3. In this example, the removal head 10 is connected to a suction device (not shown) or any suitable device to extract polymer particles from the surface of the stress medium 3, and then the head support 7 is controlled to move the removal head 10 across the entire surface of the stress medium.

[0070] The additive manufacturing apparatus features three operating modes that can be combined during the 3D printing of parts:

[0071] - Printing mode: In this mode, the head support 7 is controlled to immerse the nozzle 5 into the stress medium 3, and the movement of the head support 7 is controlled to place various printing material layers sequentially in the stress medium 3, thereby forming the part to be printed. During this printing mode, the diffuser head 9 and the removal head 10 are not activated. As a variation, the diffuser head 9 and / or the removal head 10 can be activated during the printing mode to add polymer particles to or remove polymer particles from the constraint medium during printing.

[0072] - Diffusion mode: In this mode, the control head support 7 sweeps across the entire surface of the stress medium 3, causing the polymer particles dispensed by the diffusion head 9 to be evenly distributed on the surface of the stress medium 3, thereby increasing the height of the stress medium 3 in the tray 2, that is, increasing the height of the surface of the stress medium 3. In this mode, the removal head 10, like the print head 4, is not activated, meaning that its nozzles 5 are not dispensed with printing material.

[0073] - Removal mode: In this mode, printhead 4 and diffuser 9 are not enabled, while removal head 10 is enabled. Head support 7 sweeps across the surface of stress medium 3, thereby uniformly picking up a layer of polymer particles, thus reducing the height of stress medium in tray 2.

[0074] Figures 2 to 4 The operational sequence of a 3D printing apparatus is shown, in which a three-dimensional part 11 is manufactured. In this simplified example, the thickness is increased, and the printed three-dimensional part 11 has a gantry-shaped profile that would be impossible to manufacture using fluid silicone 3D printing without a stress medium. Considering the buoyancy exerted by the gel, even a method of depositing fluid silicone in a stress medium composed of gel would not produce such a result, because the buoyancy exerted by the gel would cause the central portion 12 connecting the two transverse columns 13 to rise, or conversely, it would not be able to adequately support the printed silicone, thus weakening the central portion 12, or failing to achieve a precise connection between the central portion 12 and the two transverse columns 13. The stress medium 3, in this case a granular stress medium, allows the part to be manufactured by 3D printing, first printing the transverse columns 13, and then connecting them by the central portion 12 supporting the stress medium 3.

[0075] Figure 2The first step is illustrated, in which layers are deposited sequentially to print the transverse column 13, with the apparatus in printing mode. In this step, the height of the stress medium 3 in the tray 2 is N1, corresponding to the printing depth P1. The printing depth is the height of the stress medium 3 above the nozzle 5. In this example, the concept is simplified by showing the printing depth extending between the top of the transverse column and the surface of the stress medium 3. In this case, the depth P1 is predetermined and calibrated taking into account the pressure required to print the transverse column 13.

[0076] In the following steps, such as Figure 3 As shown, the device switches to diffusion mode. The diffusion head 9 discharges polymer particles of a certain thickness onto the stress medium 3. The head support 7 sweeps across the surface of the stress medium 3, which remains at the same height during this process, and then the nozzle 5 remains in the stress medium but is not activated. As a variation, the nozzle 5 can be withdrawn from the stress medium. Then, the stress medium 3 has a new height N2, which is higher than N1.

[0077] Once the horizontal column 13 is printed, according to Figure 4 The central portion 12 is then printed sequentially, with a printing depth P2 greater than the printing depth P1. In this step, the central portion 12 is kept properly straight and correctly connected to the two upper surfaces of the horizontal column 13.

[0078] In this example, the height of the stress medium 3 is increased, and the printing depth of the central portion 12 is greater than that of the transverse column 13. Therefore, there is pressure at the nozzle 5 that is adapted to the various parts of the part.

[0079] Figures 2 to 4 The simplified example aims to illustrate the basic mechanism of the increase in the height of the stress medium. Whenever it is necessary to change the hydrostatic pressure within a defined range corresponding to the printing thickness, a diffusion step can be performed to increase the height of the stress medium 3. The hydrostatic pressure can be changed multiple times as needed during part printing.

[0080] Figures 5 to 7 A 3D printing sequence is shown, in which the height of the stress medium 3 is reduced by removing the head 10.

[0081] In this simplified example, part 14 (see Figure 7 The pressure at nozzle 5 should be lower when printing the upper part 15 than when printing the lower part 16. This is because excessive pressure may cause deformation of some suspended parts.

[0082] according to Figure 5 First, print the lower part 16. The height of the stress medium 3 is N3, which corresponds to the printing depth P3.

[0083] Then, as Figure 6As shown, the 3D printer performs the removal step in removal mode. Print head 4 is not enabled (that is, the injection of printing material is interrupted), while removal head 10 applies suction to the surface of stress medium 3, removing some powder polymer and reducing the height of stress medium 3 to height N4, which is lower than height N3.

[0084] In subsequent printing steps, such as Figure 7 As shown, the upper part 15 of the printed part 14 has a printing depth P4 that is less than the printing thickness P3.

[0085] The height of the stress medium 3 in the control tray 2 can affect not only the geometric quality of the part manufacturing, but also the physical properties of the printed part, such as Young's modulus, fracture stress or fracture deformation, or thermal and / or sound insulation, as well as conductivity or dielectric constant.

[0086] For each pair of printing materials and constrained materials forming the stress medium 3, the effect of the height of the stress medium 3 on one or more physical properties can be determined. Figure 8 This was explained, and experimentally obtained curves were shown. For different stress materials constituting the stress medium, the variation of Young's modulus with the height of the stress medium 3 in tray 2 was determined. The inventors obtained these curves by conducting experiments with the same printing material (fluid silicone) at different printing depths in different granular stress media.

[0087] exist Figure 8 middle:

[0088] - Curve C1 corresponds to a stress medium composed of silicon dioxide;

[0089] - Curve C2 corresponds to a stress medium composed of sugar;

[0090] - Curve C3 corresponds to a stress medium composed of sand;

[0091] - Curve C4 corresponds to a stress medium composed of a mixture of sodium bicarbonate and silicon dioxide;

[0092] Curve C5 corresponds to a stress medium composed of powdered PMMA.

[0093] Figure 8 This indicates that, for certain stress media, changing the height in tray 2 has a significant impact on the Young's modulus of the finished part (e.g., sugar or sand as stress media). Therefore, the same part shape can have very different Young's moduli depending on the printing thickness performed in the stress medium when printing the part.

[0094] According to the present invention, a 3D printer operator can easily obtain such experimental patterns for any "stress medium material / printing material". Therefore, a preferred printing depth can be determined for a specific part, a specific stress medium, and a specific printing material. Similarly, variations in the stress medium height to be implemented can be determined to alter or maintain the mechanical properties of the printed part, such as Young's modulus.

[0095] Once such a diagram is created, it can be used to create a chart indicating the stress medium height to be performed for each print sequence of a part.

[0096] Therefore, the height of the stress medium 3 can be controlled so that a part with a certain height exhibits the same Young's modulus over its entire height. Thus, the height of the stress medium 3 can be changed to maintain the same pressure at the nozzle 5 of the print head 4.

[0097] Conversely, the height of stress medium 3 can be changed to make the Young's modulus of one part of the part different from that of the other parts. Figure 9 This situation is illustrated by showing a silicone ball 24 printed according to the present invention, which has a continuous material and thickness, a central portion Tc, a lower cover portion Ti, and an upper cover portion Ts. In this illustrative example, the central portion Tc is flexible (and therefore has a lower Young's modulus), while the two ball cover portions Ti and Ts are harder (they have higher Young's modulus).

[0098] The sphere will be printed in a stress medium, which will cause the Young's modulus of the part to be sensitive to the printing depth (e.g., sand, as shown by...). Figure 8 (Experimental data). In this regard, the method for obtaining ball 24 can have the following steps:

[0099] - The first step is to print the lower cover Ti at a first height in a stress medium. The first height corresponds to a fairly large printing depth (e.g., 5 cm) and is constant for each layer that makes up the lower cover Ti.

[0100] - Second step, removal step, under the action of removal head 10, the height of the stress medium in the tray is reduced to a second height; - Third step, printing the center part Tc, the printing depth is reduced (e.g. 1 cm), and is constant for each layer that constitutes the center part Tc.

[0101] - Fourth step, diffusion step, under the action of diffusion head 9, the height of the stress medium in the tray is raised to the third height; - Fifth step, printing the top cover Ts, through the increase of the stress medium height, its printing depth is equal to the printing depth of the bottom cover T1 (5 cm in this example), and is constant for each layer that makes up the top cover Tc.

[0102] Therefore, this method can adjust the mechanical properties of the part (Young's modulus in this case) by controlling the height of the stress medium in the tray without changing the material.

[0103] As a variation, different stress media can be deposited through the diffusion head 9 during the diffusion step, thereby achieving a change in Young's modulus (or any physical property that can vary depending on the printing depth) not only by changing the printing depth but also by changing the properties of the stress media.

[0104] In summary, the method of this invention can be implemented through a preliminary calibration step, which includes determining a graph that establishes a relationship between physical characteristics requiring adjustment (or conversely, ensuring constancy), print depth, and the properties of the stress medium. Based on this calibration step, a selection step determines the print depth corresponding to predetermined values ​​of the required physical properties for different portions of the part to be printed. Subsequent 3D printing steps can be implemented within the print depth range determined during the selection step by controlling the height of the stress medium.

[0105] Figure 10 The technical means that can be used for the diffusion head 9 and the removal head 10 are illustrated in more detail.

[0106] The 3D printing apparatus has a reservoir 17 that holds the same material constituting the stress medium 3. This reservoir 17 is connected to a hollow ring 20 via a conduit 18 equipped with an injection screw 19. The hollow ring 20 is positioned around the print head 4 and forms a diffusion head 9. The hollow ring 20 has a worm gear 21 for controlling the distribution of the stress medium from the hollow ring 20. During the diffusion step, the injection screw 19 is activated, the diffusion of the constraining material in the reservoir 17 is controlled by the worm gear 21, and the print head is controlled to move across the surface of the stress medium 3.

[0107] In itself, the removal head 10 is formed by a suction nozzle 22 connected to the suction device 23 for removing the controlled stress medium layer 3 and for conveying the drawn-in constrained material into the reservoir 17. The suction nozzle 22 may be telescopic, allowing it to be placed close to the surface of the stress medium 3 in the tray 2 for suction.

[0108] according to Figure 11 The device has the variation shown. Figure 10In addition to all the components shown, different types of stress materials can be added to the stress medium 3 via multiple reservoirs (two reservoirs 17 and 17' are shown in the example, which are connected to the diffuser head via pipes 18 and 18'). In this variation, the reservoir selector 25 can be connected to the suction device 23 to direct the suctioned constraint material to the reservoirs 17 and 17' containing the same constraint material. According to this variation, the diffuser head has means for selecting the constraint material to be deposited in the tray 2, while the removal head has means for selectively returning the suctioned constraint material to the correct reservoir.

[0109] Variations of the apparatus and method described herein may be implemented without departing from the scope of the invention. It is noteworthy that the method can be applied to any additive manufacturing method in which a nozzle dispensing material to be printed moves within a stress medium in three spatial dimensions, regardless of whether the stress medium is gelled or powdered, and regardless of whether the medium consists of a single material or a mixture of multiple different materials.

[0110] Besides Young's modulus, which is given as an example, any other physical property can be used as the subject of a chart to determine how that physical property of the finished part changes with the printing depth when the "printing material / stress medium material" pair is selected, such as fracture stress, thermal or sound insulation, conductivity, etc.

[0111] As just described, this invention can adjust various physical properties of printing materials. Therefore, many variations are conceivable:

[0112] Structural changes, such as improving grip conditions (handles, soles, orthotics, anatomical models, etc.);

[0113] Changes in optical performance (in some transparent devices, lenses, polarizing glass, etc.);

[0114] Changes in mechanical properties (bellows, springs, dampers, etc.);

[0115] Changes in acoustic performance (sound insulation components, sound inlets, etc.);

[0116] Changes in thermal properties (radiators, thermal insulators, etc.);

[0117] Changes in porosity, etc.

[0118] This invention makes these different variations possible, and the listed variations are not exhaustive. These variations, individually or in combination, can print objects with a wide range of applications, particularly in the health, aviation, automotive, railway, agri-food, sports, and luxury goods sectors.

Claims

1. An additive manufacturing method comprising depositing suspended printing material within a print tray (2) containing a stress medium (3) to form a three-dimensional object, the deposition of the printing material being achieved by at least one step of injecting the printing material through a nozzle (5) of a print head (4), the nozzle (5) of the print head (4) being immersed in the stress medium (3) and movable in three spatial dimensions within the stress medium (3), the method being characterized by having at least one step of changing the height of the stress medium (3) in the print tray (2), wherein the stress medium is a granular stress medium composed of a solid particulate phase and an interstitial gas phase, the solid particulate phase being a group of discrete solid components that interact through contact areas adjacent to each discrete component and the discrete components surrounding it.

2. The method according to claim 1, characterized in that... It has a step of adjusting the stress applied to the printing material by the stress medium.

3. The method according to claim 1, characterized in that... In the step of changing the height of the stress medium (3) in the printing tray (2), a layer of constraint material identical to the material constituting the stress medium (3) in the printing tray (2) is deposited on the surface of the stress medium (3).

4. The method according to claim 1, characterized in that... In the step of changing the height of the stress medium (3) in the printing tray (2), a constraint material different from the material constituting the stress medium (3) in the printing tray (2) is deposited on the surface of the stress medium (3).

5. The method according to any one of claims 3 and 4, characterized in that... The deposition of the confining material layer on the stress medium (3) is achieved by diffusion across the entire surface of the stress medium (3).

6. The method according to claim 4, characterized in that... The deposition of the confining material layer on the stress medium (3) is achieved by a movable diffusion head (9).

7. The method according to claim 6, characterized in that... In the step of changing the height of the stress medium (3) in the print tray (2), the head support (7) supporting the print head (4) and the diffuser head (9) moves toward the entire surface of the stress medium (3), the print head (4) is deactivated and the diffuser head (9) is activated.

8. The method according to claim 1, characterized in that... In the step of changing the height of the stress medium (3) in the printing tray (2), the material layer of the stress medium (3) is extracted from the printing tray (2).

9. The method according to claim 8, characterized in that... The material layer of the stress medium (3) is extracted by suction across the entire surface of the stress medium (3).

10. The method according to claim 9, characterized in that... The suction is performed by a movable removal head (10).

11. The method according to claim 10, characterized in that... In the step of changing the height of the stress medium (3) in the print tray (2), the head support (7) supporting the print head (4) and the removal head (10) moves toward the entire surface of the stress medium (3), the print head (4) is deactivated and the removal head (10) is activated.

12. The method according to any one of claims 1 to 4, characterized in that... It has the following sequential steps: - Steps for printing a portion of a 3D object; - Steps to change the height of the stress medium (3) in the printing tray (2); - Steps for printing another part of a 3D object.

13. The method according to any one of claims 1 to 4, characterized in that... It has the following steps: - Preliminary calibration step, in which the relationship between predetermined physical properties and printing depth in stress medium (3) is determined; - The step of selecting a printing depth corresponding to a predetermined value of the physical property; - The step of printing a part in a stress medium at a height corresponding to the selected printing depth.

14. The method according to any one of claims 1 to 4, characterized in that... The stress medium (3) has fluidity.

15. The method according to any one of claims 1 to 4, characterized in that... The printing material is a curable material.

16. An additive manufacturing apparatus, comprising: - A stress medium (3) placed in a printing tray (2), wherein the stress medium is a granular stress medium composed of a solid particle phase and an interstitial gas phase, the solid particle phase being a group of discrete solid components that interact with each other through contact areas between each discrete component and the discrete components surrounding it. - A printhead (4) designed for dispensing printing material has a nozzle (5) that is designed to move in three spatial dimensions in a stress medium (3); The device is characterized in that it has: - A device for changing the height of the stress medium (3) in the printing tray (2).

17. The apparatus according to claim 16, characterized in that... It has a movable diffuser head (9) designed to deposit a layer of constraint material on the stress medium (3).

18. The apparatus according to claim 17, characterized in that... The diffuser head (9) has a controlled dispensing device for controlled dispensing of the constrained material.

19. The apparatus according to any one of claims 17 and 18, characterized in that... It has a head support (7) that supports the print head (4) and the diffuser head (9). In a mode where the print head (4) is deactivated and the diffuser head (9) is activated, the head support (7) can move toward the entire surface of the stress medium (3).

20. The apparatus according to any one of claims 17 and 18, characterized in that... It has a first constraint material reservoir (17) that holds the same material as the material constituting the stress medium (3) in the printing tray (2), and the first constraint material reservoir (17) supplies the diffuser head (9).

21. The apparatus according to any one of claims 17 and 18, characterized in that... It has a second constraint material reservoir (17') that holds a material different from the material constituting the stress medium (3) in the printing tray (2), and the second constraint material reservoir (17') supplies the diffuser head (9).

22. The apparatus according to any one of claims 16 to 18, characterized in that... The device has a movable removal head (10) designed to remove the material layer of the stress medium (3).

23. The apparatus according to claim 22, characterized in that... The removal head (10) is connected to the suction device (23).

24. The apparatus according to claim 22, characterized in that... It has a head support (7) that supports the print head (4) and the removal head (10), and the head support (7) can move toward the entire surface of the stress medium (3) in a mode where the print head (4) is deactivated and the removal head (10) is activated.

25. The apparatus according to claim 22, characterized in that... It has a first constraint material reservoir (17), and the removal head (10) supplies the first constraint material reservoir (17).

26. The apparatus according to any one of claims 16 to 18, characterized in that... The stress medium (3) in the printing tray (2) has fluidity.

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