Method for manufacturing a 3d-printed silicone part by extrusion, and part obtained

Abstract

The invention relates to a method for manufacturing a 3D-printed silicone part (12) by extrusion, in which a poloxamer in gel form is used as a support material for printing support layers forming external supports (17) and / or internal supports (14, 16, 18) in contact with the silicone part; the external and / or internal poloxamer supports are subsequently removed by liquefaction of the poloxamer by exposing the obtained assembly to a temperature below the gelling temperature of the poloxamer used. Optionally, a peripheral support made of a rigid material is also printed. The method makes it possible to use very soft, unmodified silicones and to manufacture complex parts which are provided with internal cavities and / or convoluted outer faces.

Description

Description Title of the invention: Method for manufacturing a silicone part by 3D printing using extrusion and part obtained

[0001] The invention relates to the field of additive manufacturing, also known as 3D printing. It also relates to the field of manufacturing silicone parts.

[0002] Silicones are polymers distinguished by two fundamental properties: strong Si-O bonds, which give silicones high chemical inertness, good UV resistance, and a high degradation temperature; and the flexibility of their polymer chain, which gives silicones low viscosity, a low glass transition temperature, and low temperature dependence of their mechanical properties. This allows for the production of flexible and elastic objects.

[0003] Silicones are notably used in the automotive and aerospace industries for the creation of seals, bellows and other parts requiring resistance to extreme temperatures and increased durability, in the medical field for the manufacture of prostheses, implants and personalized anatomical models, thanks to their biocompatibility, or in the field of soft robotics to manufacture flexible elements such as actuators or grippers.

[0004] Traditionally, silicone parts are produced by molding, by injecting room-temperature, uncured liquid silicone into a mold, then heating the part to accelerate curing and thus the hardening of the silicone. However, manufacturing a mold is expensive, and given its advantages, 3D printing has naturally opened up new possibilities for silicone part manufacturers. Additive manufacturing, in particular, allows for the production of custom parts, tailored to the specific needs of users, with reduced production times.

[0005] However, due to their viscosity (relatively high for 3D printing) and thermal resistance, silicones pose challenges for additive manufacturing processes, some of which have been overcome thanks to techniques such as the extrusion of liquid or viscous materials and photopolymerization.

[0006] Silicones are generally packaged as a two-component product consisting of a liquid to low-viscosity silicone base and a crosslinking agent. The two components are mixed immediately before use. In the case of 3D printing, the two components are mixed in the print head, immediately upstream of the extrusion nozzle.

[0007] There are also single-component silicones (categorized RTV-1) with thermal or UV curing.

[0008] Despite the advances mentioned above, to date not all silicones are 3D printable.

[0009] RTV-1 single-component silicones are generally printable, but they require the use of a printer incorporating heating and / or UV irradiation means, which increases manufacturing time and costs.

[0010] Furthermore, standard two-component silicones are generally not printable. They must be modified to provide viscosity, curing kinetics, and geometric stability compatible with 3D printing.

[0011] Indeed, in order to be printable, a silicone must have properties compatible with the constraints of the printing process used.

[0012] In particular, the silicone must have a suitable viscosity. In extrusion processes, the silicone must be fluid enough to flow through a nozzle, but viscous enough not to spread, run, or sag under its own weight after deposition—that is, to maintain its geometry immediately after application. An ideal viscosity range for 3D printing by extrusion is generally between 10,000 and 100,000 mPa·s.

[0013] Standard silicones are often too viscous or too fluid, preventing precise deposition control. To be 3D printed, a standard silicone that is initially too fluid must be modified by adding a thickening agent (reinforcing silicas, plasticizers, etc.). The thickening agent is added to the silicone base of the two-component product, before the silicone base is mixed with its crosslinking agent.

[0014] These thickening agents have the disadvantage of ultimately modifying the mechanical properties of silicone, and in particular increasing its rigidity, so that 3D printing does not currently allow the printing of silicone parts with a hardness of less than 5 on the Shore A scale and even less so silicones of Shore 00.

[0015] Similarly, for a silicone to be printable, it must have a suitable curing rate: fast enough to solidify the printed part in a reasonable time, but not so fast as to cause hardening in the nozzle. The use of standard silicones with slow or unpredictable curing (e.g., condensation-curing silicones, which depend on ambient humidity) is therefore unsuitable. The same applies to silicones whose vulcanization requires very high temperatures or agents incompatible with 3D printers. Some standard silicones whose curing rate is not initially suitable for 3D printing can be modified by adding a catalyst to the silicone base of the two-component product, for example, a platinum catalyst.

[0016] Like the thickening agents mentioned earlier, these catalytic agents have the disadvantage of ultimately altering the mechanical properties of silicone.

[0017] Throughout the description, the expression "unmodified silicone" refers to any silicone whose silicone base has not been modified by the addition of a thickening agent or a catalyst.

[0018] To manufacture a part using 3D printing, the part is virtually divided into print slices; for each print slice, a layer of construction material (the expression "construction material" here referring to the constituent material of the part to be made, for example silicone) is printed simultaneously or successively in the areas corresponding to said part and a support layer not part of the part but intended to support the part under construction.

[0019] Throughout the patent application, if we observe a part on the 3D printer's build platform at the end of the printing process:

[0020] - The term "internal face of the part" refers to a face delimiting an internal cavity; the expression "internal cavity" designates a generally closed cavity, that is to say, a cavity which is connected to the outside of the part only by a channel of small cross-section compared to the cross-section of the cavity itself; this channel serves in particular to evacuate, once the part is fully printed, the internal support which was used to form the internal cavity.

[0021] - The term "external face of the part" refers to a face of the part oriented towards the outside of the part; an external face can be

[0022] — a lower face, that is to say an external face of the part oriented downwards, in other words an external face extending towards the printing platform of the 3D printer, in contact with it or at a distance from it,

[0023] — a top face, that is to say an external face of the part oriented upwards,

[0024] — a lateral face, that is to say, a vertical or inclined external face of the part located on one side of it,

[0025] — a face delimiting a recess, the term “recess” designating (as opposed to the aforementioned internal cavities) an open cavity, in other words a cavity which communicates with the outside of the part by a passage of equivalent cross-section to that of the cavity itself; such a recess can be a lower recess if it is open downwards, a upper recess if it is open upwards, a lateral recess if it is open on one side of the part; a recess is delimited by faces having various orientations but for the sake of simplicity these faces are all designated by the expression “recess faces” regardless of their orientation.

[0026] To create a part using 3D printing, two types of supports may be needed depending on their location:

[0027] - internal supports, configured to form internal cavities within the part, in other words configured to shape internal faces of the part,

[0028] - external supports, which support and / or shape external faces of the part; these external supports will be called bottom face supports, top face supports, side face supports or recess supports depending on the face concerned; thus for example, a bottom face (external) support is by definition configured to shape a bottom face, while a recess (external) support is by definition an external support configured to shape the different faces of a recess.

[0029] Furthermore, two categories of media are distinguished based on the surface on which the media is printed:

[0030] - supports described as "lower" supports, which are printed directly onto the 3D printer platform; lower supports are therefore by definition external supports; a lower support can be a bottom face support, a side face support, a bottom recess support or a side recess support (if the side recess extends to the printing platform, as is the case for example with a vertical groove cut into a side face to the bottom of the part);

[0031] - supports described as "upper" supports, which are printed on a portion of the part; by definition, internal supports and (external) top face supports are therefore upper supports; moreover, upper supports can also be (external) side face supports, (external) side recess supports or (external) top recess supports.

[0032] As previously indicated, the (external) side face supports can be lower supports (if they are provided in a lower part of the room or over its entire height) or upper supports (if they are provided in a higher part of the room).

[0033] The distinction between all types of supports (external or internal; lower or upper; lower, upper, lateral or recessed) will be better understood later upon reading the description relating to figures 3 to 5 attached.

[0034] Support materials, commonly used to create print supports in 3D printing, vary depending on the additive manufacturing technology used, the specific properties required for the support, and the material of the part to be produced.

[0035] In the case of a part printed by extruding a rigid construction material, PVA (polyvinyl alcohol) and PLA (polylactic acid) are known to be used as support materials. PVA is preferred because it offers the advantage to be soluble in water, so that the supports can easily be removed by immersing the resulting block (including the part and the supports) in water.

[0036] When the build material is silicone, PLA and PVA cannot be used to print internal or external supports. This is because it is impossible to print a support layer of PVA or PLA on top of a silicone layer, as PVA and PLA do not adhere to silicone. Therefore, suppliers of printable silicones and 3D printers for silicone have developed proprietary materials to support their silicones, which limits the supply of compatible support materials and results in high production costs.

[0037] This is why, despite the significant advances in 3D printing technologies, they are still little (and sometimes not at all) used to manufacture silicone parts, especially when it comes to obtaining very flexible and / or complex parts, including parts with internal cavities and / or external faces with intricate geometric shapes and recessed portions.

[0038] In particular, it is currently impossible to manufacture by 3D printing a flexible, deformable actuator comprising a succession of interconnected internal cavities. Description of the invention

[0039] The invention aims to overcome at least one of the aforementioned drawbacks by proposing a new method for manufacturing silicone parts using 3D printing by extrusion, enabling the production of particularly flexible and / or complex parts quickly and at a lower cost. One objective of the invention is, in particular, to provide a 3D printing process that allows the use of standard, unmodified silicones and the creation of supports that are compatible with these silicones and easy to remove.

[0040] To this end, the invention proposes a method for manufacturing a silicone part by 3D printing by extrusion, characterized in that a poloxamer in gel form is used as a support material to print support layers forming external and / or internal supports in contact with the silicone part, and in that said external and / or internal poloxamer supports are subsequently removed by liquefying the poloxamer by exposing the assembly obtained to a temperature lower than the gelation temperature of the poloxamer used.

[0041] Using a gelatinous poloxamer as a support material allows the use of unmodified silicone as a build material for printing layers corresponding to the part to be manufactured. The presence of the poloxamer supports allows the silicone to be deposited in a liquid or near-liquid state (and therefore without the need to add a thickening agent), as the silicone layer is contained within these supports.

[0042] Indeed, since the two materials (silicone and poloxamer) have similar densities, they do not mix when successively deposited one on top of the other, or against each other, in liquid (silicone) or gel (poloxamer) form. Furthermore, these two materials have different crosslinking windows and compatible melting, extrusion, and curing temperatures: silicones crosslink and cure at very high temperatures, and they do not change or exhibit long curing times at room temperature or below, while poloxamers are liquid at a cold temperature below their gelling temperature (typically between 4°C and 10°C, depending on the formulation and poloxamer concentration), and they remain in a gel state, without significant change, above their gelling temperature, and therefore at room temperature and above.

[0043] Consequently, when liquid silicone (hot or at room temperature) is deposited onto a previously deposited room-temperature poloxamer layer, the gelatinous consistency and contours of the poloxamer layer are not altered by the heat of the deposited silicone. Conversely, when room-temperature poloxamer is deposited onto a liquid or curing silicone layer, the cooling effect of the poloxamer in contact with the silicone does not change the consistency and contours of the silicone layer.

[0044] Thus, the use of poloxamer as a support material allows the use of unmodified silicone as a construction material, and in particular low hardness silicone, including silicones with a Shore A hardness of less than 5 and even silicones with a Shore hardness of 00 for parts of relatively low height, which makes it possible to obtain by 3D printing parts of unprecedented flexibility.

[0045] The use of poloxamer as a support material also eliminates the need for UV exposure (or other types of heating) in the case of slow-curing one-component or two-component silicones, allowing the use of a simpler design printer and reducing printing times.

[0046] According to particular embodiments of the invention, the 3D printing process according to the invention also meets the following characteristics, implemented individually or in any technically possible and operational combination.

[0047] In some embodiments, a silicone with a Shore A hardness of 5 or less, or a Shore hardness of 00, is used as the construction material for the part, and this silicone is extruded without prior modification by the addition of a thickening agent or catalyst; furthermore, the printed external supports include at least external (lower and / or upper) lateral supports configured to form all the lateral faces of the part and to contain each layer of printed silicone.

[0048] If the geometric shape of the part's external faces allows it, the side supports can potentially be fully printed before printing the silicone layers. This method is reserved for parts with simple shapes.

[0049] For more complex shapes, the poloxamer side supports should be printed layer by layer simultaneously with the silicone layers of the part. In this case, for each new slice of the part to be produced, a layer of poloxamer corresponding to the side supports, and possibly other necessary supports, is printed. Then, a complementary silicone layer is printed to complement the poloxamer layer. The gelatinous poloxamer initially printed for the slice being produced, and in particular the poloxamer forming the side supports, helps to contain the liquid silicone deposited subsequently.

[0050] Alternatively, if the silicone used is sufficiently viscous, the silicone layer of the slice can possibly be printed before the poloxamer layer of said slice.

[0051] In some embodiments, a layer of poloxamer is printed on a layer of silicone in order to create at least one internal cavity in the silicone part.

[0052] In some embodiments, for printing a complex part requiring on the one hand one or more internal supports and / or one or more upper external supports (i.e., in both cases, supports printed on a portion of the part) and on the other hand one or more lower external supports (i.e., printed on the printing platform of the 3D printer):

[0053] - Besides silicone (used to print the layers corresponding to the part to be produced) and poloxamer, a third material is used, chosen from among rigid materials that can be extruded, such as PLA (polylactic acid), PVA (polyvinyl alcohol), ABS (acrylonitrile butadiene styrene), TPU (thermoplastic polyurethanes), metals...,

[0054] - Poloxamer is used to print the internal support(s) and / or the upper external support(s), while the third, rigid material is used to print at least part (i.e., some or all) of said lower external supports, including a peripheral support that extends continuously around the entire part. If necessary, one or more other lower supports can also be printed with this third material, such as a bottom face support, a bottom recess support, or a support for a side recess that extends to the bottom edge of the part.

[0055] For low-height parts, the production of lower external supports (including a peripheral support) in poloxamer is possible and sufficient to contain the silicone.

[0056] Conversely, when a relatively large layer of silicone needs to be printed above or inside a lower external support (and particularly inside a peripheral support), the accumulation of silicone layers can lead to the silicone sagging under its own weight and deformation of the lower or peripheral external support if it is made of poloxamer. Using a third, rigid material and providing continuous peripheral support all around the part made of this rigid material helps to mitigate this risk; the peripheral support and any other lower supports (see above) made of rigid material then act as a mold capable of withstanding the pressure exerted by the silicone layer. These supports are easy to remove at the end since they are only lower external supports (the part can therefore be easily demolded from the top).

[0057] Preferably, the lower external supports made of rigid material are printed layer by layer simultaneously with the part layers (made of silicone) and the upper internal and / or external support layers (made of poloxamer). Alternatively, a rigid "mold" (lower external support including at least one peripheral support) can be used, pre-printed in its entirety. However, this option complicates the printing of the silicone and poloxamer, potentially even requiring the use of steerable extrusion nozzles, which are complex to operate.

[0058] Simultaneous printing, layer by layer, of rigid material supports, poloxamer supports and the silicone part allows the use of a simple design printer, and the printing of "tall" parts in soft silicone (with Shore A hardness less than or equal to 5 or Shore hardness 00).

[0059] As previously mentioned, the use of a third, rigid material and the provision of continuous peripheral support around the part made of this rigid material are optional. The part height beyond which it is recommended to use a third material and provide such peripheral support depends in particular on the hardness of the silicone used and the shape of the part to be printed, but also on the tolerance imposed on the dimensions of the part (a very slight deformation of the supports may be considered acceptable within this tolerance, in which case printing all supports in poloxamer may be deemed sufficient).

[0060] In some embodiments, the poloxamer is selected from poloxamer 407, marketed under the name Pluronic® E 127 or Kolliphor® P407 by BASE or under the name Synperonic® PE / F 127 by Croda International, poloxamer 188, marketed under the name Pluronic® F 68 or Kolliphor® 188 by BASF, and more generally any poloxamer that is in a gel state at room temperature and presents a gelling temperature between 0°C and 15°C, preferably between 0°C and 10°C, or even between 5°C and 10°C.

[0061] In some embodiments, poloxamer in gel form is obtained by mixing 60% to 80% by mass, preferably 70% by mass, of demineralized water with 20% to 40% by mass, preferably 30% by mass, of said poloxamer powder.

[0062] The manufacturing process according to the invention is particularly advantageous for the production of flexible deformable parts, which until now could only be obtained by injection molding processes, such as the pneumatic flexible actuators used in the food industry for gripping and handling fruits and vegetables.

[0063] Thus, the 3D printing manufacturing process according to the invention can be applied to the production of a flexible robot part such as a pneumatic flexible actuator comprising an elongated deformable body (made of silicone) provided with a succession of interconnected internal cavities.

[0064] The 3D printing process according to the invention is also applicable to the production of a prosthetic or medical orthosis part.

[0065] Of course, the invention extends to silicone parts obtained by implementing the process described above.

[0066] The invention, according to an exemplary embodiment, will be better understood and its advantages will become clearer upon reading the following detailed description, given by way of example and in no way limiting, with reference to the attached drawings in which: • Fig. 1 represents the two final steps of a process according to the invention for producing a flexible silicone actuator, which actuator is seen in longitudinal section; • Figure [Fig. 2] represents the flexible actuator of Figure [Fig. 1] in longitudinal section, inflated with air, • Fig. 3 illustrates another part obtained by a 3D printing process according to the invention, which part is seen in perspective. • Figures 4 and 5 illustrate the part of [Fig.3] during manufacturing, at two printing stages.

[0067] Identical elements represented in the aforementioned figures are identified by identical numerical references.

[0068] Figure 1 shows a part produced by the 3D printing process according to the invention, at two stages of its manufacture. The part in question is a flexible actuator 20 forming a finger of a flexible gripper such as those used in industry, for example the food industry, to grasp fragile objects, for example fruits or vegetables. The actuator 20 can be observed at rest on the part to the right of [Fig. 1] and inflated with air on [Fig. 2]. It comprises a silicone body 12, generally cylindrical at rest (which body may have a circular, square, or any other cross-section), provided with four cavities 24 aligned along a longitudinal axis of the body 12 and connected in series by channels 26; one of the outermost cavities of the actuator communicates with the exterior of the body 12 via a channel 28 forming an air inlet through which the actuator can be connected to a means (not shown) for injecting compressed air into the body 12. Note that the channels 26, 28 constitute internal cavities within the meaning of paragraph

[0020] supra.

[0069] Given the flexibility and elasticity of silicone, the injection of air into the actuator causes the cavities 24 to swell and the whole body 12 to flex elastically, as illustrated in [Fig.2].

[0070] Such an actuator is well known in the field of soft robotics. Actuators with a similar appearance to the one illustrated already exist, but these are generally produced by molding.

[0071] Part 20 according to the invention is obtained by 3D printing, that is, by successive deposition of layers of silicone and poloxamer, in a 3D printer (not shown) equipped with a silicone printing nozzle, configured to extrude silicone in a low-viscosity liquid form, and a poloxamer printing nozzle, configured to extrude poloxamer in gel form. The silicone constitutes the construction material of the actuator body 12, while the poloxamer is used as a support material.

[0072] A digital model of the actuator is developed and virtually divided into horizontal slices. For each slice, a layer of liquid silicone is deposited on the parts of the slice corresponding to the body 12 and a layer of poloxamer in gel form is deposited on the parts of the slice that correspond either to external supports 17 delimiting the periphery of the body 12 or to internal supports 14, 16, 18 intended to form the cavities 24 and the channels 26, 28 in the body 12.

[0073] Poloxamer is printed at room temperature, at which point it is in gel form. Silicone is extruded in liquid form, for example, at room temperature; the temperature at which the silicone passes through the print nozzle is adjusted to prevent it from beginning to crosslink before printing and clogging the nozzle. If necessary, the silicone is heated downstream of the print nozzle, for example, by heating the print platform or the internal volume of the printer. A high temperature of the deposited silicone (after extrusion) ensures good adhesion of each silicone layer to the previous one. Indeed, if the previous layer has already hardened, partially or completely, the heat from the layer being printed will... The upper surface of the previous layer softens, allowing it to blend and re-polymerize with the layer being printed. Conversely, the high temperature of the deposited silicone also ensures that a poloxamer layer already printed (to form the internal supports 14, 18 and external supports 17) which receives a layer of hot silicone remains in a gelatinous, or even slightly hardened, state, thus fulfilling its role as a support.

[0074] For guidance purposes only and not as a limitation, it should be noted that the printed silicone and poloxamer layers can have a thickness between 300pm and 600pm, preferably around 400pm.

[0075] When all the slices are printed, we obtain the block 10 illustrated on the left side of [Fig.1], which includes the body 12 provided with the internal supports 14, 16, 18 in gelatinous poloxamer corresponding respectively to the cavities 24 and channels 26, 28, as well as the external supports 17. The internal supports 14, 16, 18 in poloxamer gel form inserts allowing to support the last layers of silicone forming the upper part of the body 12.

[0076] Once the printing is complete, the silicone body 12 is allowed to fully vulcanize; this step may include baking the block 10 (hardened silicone body 12 + external and internal supports of gelatinous poloxamer) in an oven. The block 10 is then exposed for approximately 10 minutes to a temperature lower than the gelation temperature of poloxamer, for example, to a temperature of around 5°C if the gelation temperature is 8°C to 10°C. After this cooling step, the poloxamer is in liquid form 30 and can be easily removed, as illustrated on the right side of [Fig. 1]. The internal supports 14, 16, 18 then give way to cavities 24, and channels 26, 28. Particularly fine channels can be obtained using this method.

[0077] Figure 3 represents another example of a part, referenced as 30, which can be produced by the 3D printing process according to the invention. Said part 30 comprises a silicone body comprising three cubic parts 32, 34, 36, the first and second cubic parts 32, 34 being aligned in a horizontal direction and connected to each other by a first hollow connecting bridge 38, while the second and third cubic parts 34, 36 are aligned in a vertical direction and connected to each other by a second hollow connecting bridge 40. Each cubic part 32, 34, 36 has a cavity 42, 44, 46. Each connecting bridge 38, 40 has a conduit 48, 50 which opens respectively into the cavities 42, 44 and 44, 46. The silicone body of part 30 is shown here in transparency so that the cavities and conduits it incorporates can be observed. Note that the conduits 48, 50 constitute internal cavities within the meaning of paragraph

[0020] supra.

[0078] Part 30 has a lower face 60, lateral faces 62, 68 and upper faces 64, 66. Part 30 also has a lower recess 70, an upper recess 72 and lateral recesses 74, which separate the first and second cubic portions 32, 34 and delimit the first connecting bridge 38. Similarly, the second connecting bridge 40 is formed by lateral recesses 76.

[0079] To produce such a part, the process according to the invention uses a 3D printer comprising a print head of silicone in liquid to low-viscosity form, and a print head of poloxamer at room temperature or optionally heated to be in gel form. In any case, the poloxamer is extruded at a temperature above its gelling temperature to be in gel form. Similarly, the silicone is extruded at a temperature above the gelling temperature of the poloxamer, for example, at room temperature or higher. In a possible embodiment detailed later, a printer is used that includes a third print head configured to extrude a third, rigid material, for example, PVA or PLA.

[0080] Figure 4 shows part 30 being printed, with the last printed slice located above the internal cavities 42,44 of the cubic portions 32,34 and below the upper face 66 of the first cubic portion 32.

[0081] Fig. 5 shows part 30 being printed, the last printed slice being located above the upper face 66 of the first cubic portion 32 and below the third cubic portion 36. Fig. 5 therefore corresponds to a horizontal cross-sectional view of the part at the level of the second connecting bridge 40.

[0082] The third cubic portion 36 of the piece, not yet printed on figures 4 and 5, is nevertheless represented there in dotted lines.

[0083] To obtain part 30 using a process according to the invention, layers of poloxamer and / or layers of a third material are to be printed simultaneously with the silicone layers that form the body of the part, in order to form:

[0084] - on the one hand, internal supports enabling the creation of internal cavities 42, 44, 46 and conduits 48, 50; only one of these internal supports, in this case the internal support 52 forming the conduit 50 between the internal cavities 44 and 46, is visible in figures 4 and 5,

[0085] - and on the other hand external supports allowing the shaping of the lateral faces 62, the lower recess 70, the lateral recesses 74 and 76 and the upper recess 72.

[0086] Some of these external supports are bottom supports because they are printed directly on the 3D printer's build platform 100, notably to support the first connecting bridge 38 or to laterally hold the faces verticals 62 of the cubic parts, with the exception of face 68 of the third cubic part.

[0087] External upper supports, so named because they are printed on portions of the silicone part, are necessary to form the upper recess 72 and the lateral face 68 above the first connecting bridge 38 and to form the lateral recesses 76 around the second connecting bridge 40. In particular, in Figures 4 and 5, one can observe the upper recess support 82 (external support delimiting the upper recess 72) above the first connecting bridge 38 and the lateral recess support 86 (external support delimiting the lateral recess 76) around the second connecting bridge 40. In the illustrated example, the upper recess support 82 is extended by an upper support 84 above the upper face 66 of the first cubic portion 34, which upper support 84 extends to the peripheral support 80 (defined below) and is therefore held by the latter.

[0088] The internal supports 52 and the upper external supports 82, 84, 86 are printed in poloxamer, for example in Pluronic® F127.

[0089] The lower external supports can be printed in poloxamer. Alternatively, for greater accuracy or if the dimensions of the part justify it, a third, rigid material can be used to print at least part of the lower external supports, including a continuous peripheral support 80 all around the part (see [Fig.4] and 5).

[0090] In the example illustrated in Figures 4 and 5, the peripheral support 80 forms a solid wall all around the room. Alternatively, to limit the amount of material consumed, it could be a hollow wall made up of two parallel walls separated by lattice-like ribs.

[0091] In the illustrated example, the lateral recess supports on either side of the first connecting bridge 38 (external supports defining the lateral recesses 74) are integrated into the peripheral support 80 and printed in rigid material. Alternatively, they could be printed in poloxamer inside the peripheral support 80 if the heights of the first connecting bridge 38 and the third cubic portion 36 allow it.

[0092] Furthermore, the lower recess support (not visible in the figures because it is surrounded by the peripheral support 80), necessary to form the lower recess 70 and support the first connecting bridge 38, is preferably also made of a rigid material. Alternatively, it could be made of poloxamer, if the dimensions of the part allow.

[0093] The peripheral support 80 made of rigid material forms a mold which prevents the superimposed printed layers from sagging under their own weight before the silicone has fully hardened.

[0094] To allow for the subsequent removal of the internal poloxamer supports present inside the part, at least one drainage channel (not shown) is formed using an internal poloxamer support (not shown) between one of the internal cavities 42, 44, 46 or one of the conduits 48, 50 and the outside of the part. Unlike the channel 28 of the pneumatic actuator in Figures 1 and 2, if this drainage channel is used only for removing the internal supports, its cross-section is preferably as small as possible.

[0095] Once the part is fully printed, the block comprising the silicone part 30 and the poloxamer supports is demolded, i.e. separated from the rigid peripheral support 30. This block is then refrigerated so that the poloxamer in its gelatinous state liquefies; this step could, alternatively, be carried out before demolding.

[0096] All poloxamer media can then be removed, including internal media, with liquid poloxamer like water being able to flow out of the room through the drain channel.

[0097] The printing process according to the invention allows the use of all types of silicone, including very soft silicones that are too fluid to be printed in known 3D printers without modification. It therefore offers the possibility of rapidly manufacturing very flexible parts, as well as parts with complex structures, particularly parts with multiple internal cavities and / or intricate external surfaces.

Claims

Demands

1. A method for manufacturing a silicone part (12; 30) by 3D printing by extrusion, characterized in that a poloxamer in gel form is used as a support material to print support layers forming external supports (17; 82, 84, 86) and / or internal supports (14, 16, 18; 52) in contact with the silicone part, and in that said external and / or internal supports in poloxamer are subsequently removed by liquefying the poloxamer by exposing the assembly obtained (10) to a temperature lower than a gelation temperature of the poloxamer used.

2. A method for manufacturing a silicone part by 3D printing according to claim 1, characterized in that the construction material for the part is silicone having a Shore A hardness of less than or equal to 5 or a Shore hardness of 00, in that this silicone is extracted without prior modification by the addition of a thickening agent or catalyst, and in that the external supports printed comprise at least lateral supports configured to form all the lateral faces of the part and to contain each layer of printed silicone.

3. A method for manufacturing a silicone part by 3D printing according to one of claims 1 or 2, characterized in that a layer of poloxamer is printed on a layer of silicone in order to create at least one internal cavity (14, 16, 18; 42, 44, 46, 48, 50) in the silicone part.

4. A method for manufacturing a silicone part by 3D printing according to any one of claims 1 to 3, for printing a part requiring on the one hand one or more internal supports (52) and / or one or more upper external supports (82, 84, 86), and on the other hand one or more lower external supports (80), characterized in that: - In addition to silicone and poloxamer, a third material is used, chosen from rigid materials that can be extruded, such as PLA (polylactic acid), PVA (polyvinyl alcohol), ABS (acrylonitrile butadiene styrene), TPU (thermoplastic polyurethanes), metals, - Poloxamer is used to print the internal support(s) (52) and / or the upper external support(s) (82, 84, 86), while the third, rigid material is used to print at least part of the lower external supports, including a peripheral support (80) which extends continuously all around the part.

5. A method for manufacturing a silicone part by 3D printing according to any one of claims 1 to 4, characterized in that the poloxamer is selected from poloxamer 407 or Pluronic© F 127, poloxamer 188 or Pluronic® F 68, any poloxamer which is in a gel state at room temperature and has a gelation temperature between 0°C and 10°C.

6. A method for manufacturing a silicone part by 3D printing according to any one of claims 1 to 5, characterized in that the poloxamer in gel form is obtained by mixing 60% to 80% by mass of demineralized water with 20% to 40% by mass of said poloxamer powder.

7. A method for manufacturing a silicone part by 3D printing according to any one of claims 1 to 6, applied to the production of a flexible robot part such as a deformable pneumatic actuator comprising an elongated deformable body (12) provided with a succession of interconnected internal cavities (14, 16, 18).

8. Method of manufacturing a silicone part by 3D printing according to any one of claims 1 to 6, applied to the production of a prosthetic or medical orthosis part.

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