PRINTING UNIT FOR AN ADDITIVE MANUFACTURING MACHINE

Description

[0001] The field of invention is that of the design and manufacture of additive manufacturing machines.

[0002] More specifically, the invention relates in particular to a print block (also called a print head) for an additive manufacturing machine. Additive manufacturing machines are more widely known as "3D printers".

[0003] In the field of additive manufacturing, several technologies coexist, including material deposition manufacturing.

[0004] Material deposition manufacturing, particularly the most well-known type which involves depositing a viscous material (for example, plastic), uses a printing block into which a material enters in solid form, this material is then melted to adopt a viscous state and is deposited onto a printing platform by a nozzle.

[0005] Typically, the printing block includes a frame on which are mounted means for heating the viscous material and a nozzle for extruding the viscous material.

[0006] The printing block and the printing platform have a relative displacement movement which allows a part to be made by adding material in three dimensions, that is to say in two orthogonal directions extending in the plane of the printing platform and in a third direction orthogonal to the first two directions and transverse to the printing platform.

[0007] In the category of plastic material deposition, the material to be melted can be in the form of a wire packaged on a reel, or in the form of a powder (or granules).

[0008] The term powder is understood here to refer both to small particles and to large particles also commonly known as granules.

[0009] In the case of depositing a material other than plastic, for example concrete, it is impossible to condition the material to be deposited in the form of a thread; only powders or granules can be used.

[0010] When the material is in the form of a filament, the flow rate of material to be deposited can be adapted simply and responsively by controlling the advance speed of the filament of material in the printing block.

[0011] On the other hand, although the use of powder has a more advantageous operating cost than wire (on the order of six to ten times lower), flow control is more difficult, as described below.

[0012] Speed ​​variations cause inertia in the printing block, which can lead to manufacturing defects. This inertia is even greater when the solid material, which must be melted to make it viscous, is in the form of a powder or granules.

[0013] These manufacturing defects can, for example, take the form of "porosity," that is, localized absences of material, or, on the contrary, "burrs," that is, excess material.

[0014] These porosities or burrs are mainly due to the combination of inertia with the relative displacement between the print block and the print bed.

[0015] Following manufacturing, manual finishing operations are necessary to fill visible and accessible pores with material and remove burrs. These finishing operations increase manufacturing time and therefore manufacturing costs. Conversely, when pores are not visible or accessible (for example, gas inclusions), the finishing step cannot be performed, and the mechanical structure of the part may be compromised.

[0016] At the beginning of the manufacturing cycle, the inertia of the print block can cause a delay in material delivery, and therefore a delay in material deposition onto the build plate (due to a faulty flow rate), even though the relative movement between the build plate and the print block has already begun, which generates porosity. This porosity can then be located between the build plate and the new layer of material, or between the build plate and a substrate that can take the form of an existing part (a defect that is generally visible and accessible) or a previously deposited layer (a defect that is generally invisible and inaccessible and can compromise the structural integrity of the printed part).

[0017] Inertia is notably due to the viscosity of the materials, here non-Newtonian, which are sensitive to their rate of shear stress.

[0018] On the contrary, at the end of the manufacturing cycle, the inertia of the printing block can lead to a maintenance of the melting of the material, and therefore a continuous deposition of material on the platform or on a substrate, while the relative movement between the printing platform and the printing block is stopped or outside the printing area, which causes burrs.

[0019] The end of the cycle and the beginning of the cycle can also correspond respectively to a temporary stop in material deposition and a resumption of deposition during the same manufacturing process, between which takes place a rapid relative movement between the printing platform and the printing block for example to change the material deposition area.

[0020] To avoid this, print block control algorithms have been developed.

[0021] Thanks to these algorithms, it is possible to advance or delay the heating of the material to make it coincide with the relative movement between the printing platform and the printing block.

[0022] However, these algorithms are cumbersome and require significant computing resources.

[0023] Furthermore, these algorithms do not take into account the different compositions of matter.

[0024] Indeed, meltable plastics can be made from various compositions. Thus, to obtain a material with the same name, different compositions can be used, or at the very least, different proportions of the same components can be applied. These materials with the same name can therefore exhibit different viscosities.

[0025] The result is that flow parameters can change depending on the material used, the speeds of application and the thermal conditions, although the material retains the same name.

[0026] Therefore, even if they are reduced or limited in number, porosities and burrs remain present and require a finishing step following manufacturing.

[0027] WO 2020 / 136383 A1 discloses the preamble of claim 1.

[0028] The invention aims in particular to overcome the drawbacks of the prior art.

[0029] More specifically, the invention aims to provide a printing block that limits the adverse effects of transient flow regimes, due to inertia, on manufacturing.

[0030] The invention also aims to provide such a printing block allowing control of the material to be deposited on the printing platform or substrate.

[0031] The invention also aims to provide such a printing block that is simple to manufacture and maintain.

[0032] These objectives, as well as others that will appear subsequently, are achieved thanks to the invention, which relates to a printing block for an additive manufacturing machine using the deposition of viscous material obtained from powder, the printing block comprising: means for supplying viscous material, including a screw conveyor for conveying the viscous material, means for depositing viscous material, in which the printing block also includes: at least one viscous material storage chamber delimited by an internal wall having at least one movable portion, the chamber defining a storage volume and being interposed between the feeding means and the depositing means;at least one actuator acting on the displacement of the moving portion to change the volume of the storage chamber, characterized in that the printing block includes means for pumping viscous material, interposed between the storage chamber and the dispensing means, and in that the printing block includes a frame in which the storage chamber is made, and in that the pumping means include: a conduit made in the frame, the conduit forming a passageway for viscous material from the storage chamber to the dispensing means, a hood fixedly mounted on the frame, the hood closing the conduit, a gear mechanism arranged in the conduit, the gear mechanism driving the viscous material from the storage chamber to discharge it towards the dispensing means.

[0033] The viscous material storage chamber compensates for the inertia of the printing block at each significant variation in material flow, particularly at each change of speed, for example at the beginning and end of printing.

[0034] Indeed, thanks to the actuator which acts on the movement of the moving portion of the storage chamber, it is possible to eject the viscous material out of the chamber towards the depositing means or, on the contrary, to retain it in the chamber.

[0035] At the start of printing, or when resuming printing, the time required to start up the viscous material feeding system, particularly the rotation of the screw, causes a delay in feeding the deposition system and therefore a risk of porosity if the cycle has already begun (relative movement between the print bed and the print block). This delay can be compensated for by reducing the volume of the storage chamber and thus feeding the deposition system with viscous material.

[0036] Thus, the viscous material can be deposited directly via the depositing means to start printing quickly without waiting for the desired nominal flow rate to be obtained from the feeding means.

[0037] On the contrary, during a significant reduction in flow rate, for example at the end or stoppage of a printing cycle, the actuator can allow the volume of the chamber to be enlarged so that the viscous material produced by the screw is contained in the storage chamber and no longer feeds the deposition means, thus preventing burrs.

[0038] In addition, the quality of the interface between each layer of deposited material is increased, which benefits the mechanical characteristics of the printed part.

[0039] Such a print block allows for precise control of the material flow rate under all circumstances, ensuring it is proportional to the travel speed. In other words, this block enables real-time control of the extruded material flow rate to conform to the print programming instructions.

[0040] The pumping means make it possible to obtain a controlled flow rate of supply to the depositing means.

[0041] Thus, depending on the pumping speed, it is possible to adapt the flow rate of viscous material deposited by the depositing means from the pumping means.

[0042] Furthermore, when the relative movement speed between the print bed and the print block is high, the pumped material flow rate can be increased, whereas when the relative movement speed is low, the pumped material flow rate can be reduced.

[0043] Furthermore, the use of pumping devices can achieve a higher print quality than known screw extrusion techniques for powder or granules, by adapting the amount of material deposited according to the characteristics of the part being manufactured. The resulting print quality is then comparable to that of wire-based molten metal deposition techniques, where the flow rate is proportional to the wire feed speed.

[0044] In other words, the storage chamber provides a buffer stock of viscous material under pressure and always available, which compensates for the inertia of the screw feed means, and the pumping means then ensure the controlled flow of viscous material transmitted to the depositing means.

[0045] In this case, the storage chamber also allows the pumping equipment to be supplied without over-stressing it mechanically or hydraulically, which could cause it to block or, in the worst case, deteriorate prematurely.

[0046] By using the gear mechanism, it is possible to finely control and manage the quantity of material conveyed from the storage chamber to the depositing means by the pumping means.

[0047] Indeed, the space formed between the teeth of the gears on the one hand, and between the gears and the conduit on the other, remains constant, which allows for pumping material at an equivalent flow rate under almost all conditions. The flow rate is thus proportional to the rotation of the gear mechanism.

[0048] According to an advantageous aspect, the feeding means also include a heating element surrounding at least the worm screw.

[0049] The heating element thus allows, for certain materials, to change said materials from their solid state (for example in powder) to their viscous state allowing their deposition by the means of deposition.

[0050] Another advantage is that the printing block also includes: means for measuring pressure in the storage chamber; means for controlling the auger, the control means being configured to control the drive of the powder by the screw from pressure information measured by the pressure measuring means.

[0051] The control of the screw by the control means from pressure information measured by the pressure measuring means allows optimal responsiveness to control the flow of viscous material feeding the depositing means.

[0052] Thus, unlike existing techniques, this control of the power supply means makes it possible to compensate for the latency of the power supply means.

[0053] According to an advantageous aspect, the printing block also includes a shutter interposed between the storage chamber and the depositing means.

[0054] The shutter allows the dispensing means to be isolated from the storage chamber.

[0055] Thus, regardless of its viscosity, it is possible to prevent viscous material from reaching the deposition means and therefore from creating unwanted burrs during printing or at the end of the printing cycle.

[0056] In other words, the shutter provides a safety feature to prevent burrs from forming on the printed parts.

[0057] According to an advantageous aspect, the hood has a first cavity and a second cavity intended to be positioned above the gear mechanism, the first cavity communicating with the conduit on the side of the storage chamber, and the second cavity communicating with the conduit on the side of the removal means.

[0058] The first and second cavities facilitate the passage of material through the pumping means. The viscosity of the viscous material can lead to a risk of clogging the pumping means; this risk is thus avoided, or at least limited, thanks to the presence of the cavities which ensure easy passage for the viscous material.

[0059] One advantageous aspect of the printing block is that it includes: secondary means of depositing, upstream of the pumping means, fluidly connected to the storage chamber, a shut-off valve interposed between the secondary means of depositing and the storage chamber.

[0060] Secondary deposition methods, fluidly connected to the storage chamber, make it possible to create an additional discharge path to meet high flow rate requirements in particular.

[0061] For example, secondary depositing methods can be used when the relative movement is rapid and / or the print quality is of the draft type.

[0062] Furthermore, the use of a shut-off valve allows all of the viscous material to be directed towards the dispensing means when the pumping means are not in use.

[0063] One advantageous aspect of the printing block is that it includes a cylinder comprising: a rod, one end of which forms the movable portion of the inner wall, and a body relative to which the rod is movable in translation. and in that the actuator takes the form of a compression spring interposed between the rod and the body, the compression spring tending to move the rod away from the body.

[0064] Using a jack allows the storage volume of the storage chamber to be changed quickly.

[0065] The use of a compression spring makes it easier and automatic to change the volume of the storage chamber to obtain a desired pressure inside the storage chamber.

[0066] Indeed, by precisely calibrating the spring, it will cause a displacement of the rod so as to position it in a position ensuring a desired and predetermined volume and pressure inside the storage chamber.

[0067] Alternatively, the printing block includes a cylinder comprising: a rod, one end of which forms the movable portion of the inner wall, and a body relative to which the rod is movable in translation. and in that the actuator takes the form of a motor cooperating with the rod to move the rod relative to the body.

[0068] Using a jack allows the storage volume of the storage chamber to be changed quickly.

[0069] Furthermore, the use of a motor allows both fine adjustment and modification of the pressure and volume of the storage chamber, but also to significantly decrease or increase the size of the storage chamber to expel the material present in the storage chamber or, conversely, to fill the storage chamber in preparation for a future cycle start.

[0070] According to an advantageous aspect, the control means are also configured to control the actuator from pressure information measured by the pressure measuring means.

[0071] Controlling the actuator based on pressure information measured by pressure measurement devices ensures optimal filling or emptying of the storage chamber.

[0072] Indeed, depending on the desired pressure inside the storage chamber, it is possible to control the actuator to increase or decrease the volume and thus obtain a desired pressure inside the storage chamber.

[0073] For example, at the end of the cycle, it may be preferable to cut off the supply means and empty the storage chamber completely until a threshold pressure corresponding to a completely empty storage chamber is obtained.

[0074] The invention also relates to an additive manufacturing machine using viscous material obtained from powder, characterized in that it comprises a printing block as previously described.

[0075] Other features and advantages of the invention will become more apparent upon reading the following description of a preferred embodiment of the invention, given by way of illustrative and non-limiting example, and the accompanying drawings, among which: [ Fig.1 ] there [ Fig.1 ] is a detailed schematic representation illustrating an additive manufacturing machine according to the invention, this machine comprising a printing block according to a first embodiment; [ Fig.2 ] there [ Fig.2 ] is a schematic cross-sectional representation of a detail of an additive manufacturing machine according to the invention, this machine comprising a printing block according to a second embodiment; [ Fig.3 ] there [ Fig.3 ] is a schematic top view of the print block of the [ Fig.2 ], this figure illustrating means of pumping the print block; [ Fig.4 ] there [ Fig.4 ] is a schematic representation of the operation of the pumping means of the printing block of the figures 2 And 3 ; Fig.5 ] there [ Fig.5 ] is a schematic cross-sectional representation of a detail of an additive manufacturing machine according to the invention, this machine comprising a printing block according to a third embodiment; [ Fig.6 ] there [ Fig.6 ] is a schematic representation of a printing block according to the invention, in a first embodiment, illustrating a storage chamber having at least one movable portion, the block including an actuator acting on the displacement of the movable portion of the storage chamber, the movable portion being represented in a first position; Fig.7 ] there [ Fig.7 ] is a schematic representation of a printing block according to the invention, according to a second embodiment, illustrating a storage chamber having at least one moving portion, the block including an actuator acting on the movement of the moving portion of the storage chamber, the moving portion being represented in a second position.

[0076] With reference to figures 1 , 2 And 5 , an additive manufacturing machine 1 according to the invention is illustrated.

[0077] More specifically, the [ Fig.1 ] concerns a first embodiment of machine 1, the figures 2 à 4 concern a second embodiment of machine 1 and the [ Fig.5 ] concerns a third embodiment of machine 1.

[0078] The additive manufacturing machine 1 includes a printing platform 100 and a printing block 2 allowing the deposit of viscous material onto the printing platform 100. The deposit of the viscous material can be done directly onto the printing platform 100, or onto a substrate in the form of a layer of material previously deposited, or a part onto which the material is intended to be deposited for the purpose of overprinting for example.

[0079] For the production of three-dimensional parts from viscous material, the additive manufacturing machine 1 operates by relative movement of the printing platform 100 with respect to the printing block 2.

[0080] More specifically, and according to existing technologies, the print bed 100 can move while the print block 2 remains fixed or conversely, the print block 2 can move while the print bed 100 remains fixed.

[0081] With reference to figures 1 , 2 And 5 , the printing block 2 includes a chassis 21 on which are mounted means for feeding 22 with viscous material and means for depositing 23 with viscous material.

[0082] The feeding means 22 include in particular a hopper 221 and a screw conveyor 222 mounted inside the hopper 221.

[0083] The feeding means 22 also include a heating element 223 for heating the material inside the hopper 221 to melt it. The heating element 223 can be activated or not depending on the material received in the hopper. Indeed, some materials are already viscous, allowing them to be deposited by the dispensing means 23.

[0084] The worm screw 222, for its part, allows the viscous material to be directed towards the depositing means 23.

[0085] The heating element 223 is, for example, an electrical circuit or a heat transfer fluid pipe surrounding the hopper 221 to heat the material to be melted. The material to be melted is, for example, a plastic powder. The term "powder" here refers to both small particles and large particles, also commonly known as granules.

[0086] The deposition means 23 include a tube 231 extending from the frame 21 and a nozzle 232 located at a distal end of the tube 231. The viscous material flows through the nozzle 232 onto the printing platform 100.

[0087] The printing block 2 also includes a storage chamber 24 located between the feeding means 22 and the depositing means 23.

[0088] The storage chamber 24 allows the storage of viscous material from the feeding means 22.

[0089] This storage chamber 24 is delimited by an internal wall 241 having at least one movable portion 242.

[0090] Storage chamber 24 thus defines a volume V for the storage of viscous material.

[0091] The printing block 2 also includes an actuator 25.

[0092] The actuator 25 acts on the displacement of the moving portion to change the volume V in the storage chamber 24.

[0093] More specifically, print block 2 includes a cylinder 26 including: a body 261; a rod 262, one end of which forms the movable portion 242 of the inner wall 241 of the storage chamber 24.

[0094] The rod 262 is movable in translation relative to the body 261.

[0095] The mobility of the rod 262 relative to the body 261 is ensured in particular by the actuator 25.

[0096] According to a first form of realization illustrated in the [ Fig.6 ], the actuator 25 is in the form of a compression spring 251 interposed between the rod 262 and the body 261.

[0097] With reference to the [ Fig.7 ], and according to a second embodiment, the actuator 25 takes the form of a motor 252.

[0098] The printing block 2 also includes control means 27.

[0099] These control means 27 are intended in particular for controlling the worm gear 222 of the feeding means 22.

[0100] The printing block 2 further includes pressure measurement means 28 in the storage chamber 24.

[0101] The pressure measurement means 28 allow the sending of pressure data inside the storage chamber 24 to the control means 27 in order to control the supply means 22.

[0102] According to the first embodiment illustrated on the [ Fig.1 ], the printing block 2 incorporates a shutter 3 interposed between the storage chamber 24 and the depositing means 23.

[0103] The shutter 3 allows or prevents the deposition of material onto the printing platform 100 by the deposition means 23.

[0104] In other words, the obturator 3 allows the viscous material from the feeding means 22 to be retained in the storage chamber 24, or on the contrary allows fluidic communication, via the storage chamber 24, between the feeding means 22 and the depositing means 23.

[0105] In this first embodiment, the actuator 25 is in the form of a compression spring 251 as illustrated in the [ Fig.6 ].

[0106] The use of a compression spring 251 allows the volume V of the storage chamber 24 to be adjusted automatically, i.e. without dedicated piloting, in order to seek to obtain a constant pressure inside the storage chamber 24.

[0107] In other words, the compression spring 251 tends to push back the movable portion 242 of the inner wall 241 of the storage chamber 24 so as to obtain a constant, or almost constant, pressure inside the storage chamber 24 when the storage chamber 24 is filled with viscous material.

[0108] In this first embodiment, the control means 27 are configured to control the supply means 22 according to the pressure measured by the pressure measuring means 28 in the storage chamber 24.

[0109] In use, during a manufacturing cycle start-up, the control means 27 command the activation of the feeding means 22 to supply the deposition means 23 and deposit viscous material onto the printing platform 100.

[0110] To compensate for the inertia of the feeding means 22, in particular linked to the reduction in viscous matter of the powder inside the hopper 221, the viscous matter present in the storage chamber 24 is used to feed the depositing means 23, or on the contrary, to prevent their feeding.

[0111] Inertia is primarily due to the heating of the material, which can require: a heating time of the heating element 23 before starting to melt the powder at the start of a cycle, or a cooling time of the heating element 23 during which the powder is still melted.

[0112] This inertia in flow rate can therefore lead to manufacturing defects.

[0113] At the beginning of the manufacturing cycle, the inertia of print block 2 can cause a delay in material deposition onto print platform 100, even though the relative movement between print platform 100 and print block 2 has already begun. The resulting defects then take the form of porosity, i.e., a localized absence of material.

[0114] Conversely, at the end of the manufacturing cycle, the inertia of print block 2 can lead to a sustained material flow, resulting in additional material being deposited on the print bed 100, even though the relative movement between the print bed 100 and print block 2 is stopped or outside the printing area. The resulting defects then take the form of burrs, i.e., a localized excess of material.

[0115] The end of the cycle and the beginning of the cycle can also correspond respectively to a temporary stop of material deposition and a resumption of deposition during the same manufacturing process, between which occurs a relative movement at accelerated speed between the printing platform 100 and the printing block 2 for example to change the material deposition zone.

[0116] More specifically, the rod 262 of the cylinder 26 is pushed back by the actuator 25 so as to reduce the volume V of the storage chamber 24 by moving the movable portion 242.

[0117] Thus, the viscous material in the storage chamber 24 is directed to the deposition means 23 to allow the manufacture of a part on the printing platform 100.

[0118] Chamber 24 is then supplied again with viscous material by the feeding means without lengthening the manufacturing cycle or risking a lack of material in the manufactured part.

[0119] In other words, the use of the viscous material present in the storage chamber allows the deposition means 23 to be fed quickly without the inertia of the feeding means 22 affecting the cycle either by delaying it or by generating porosity, i.e. absences of material in the manufactured part.

[0120] In addition, the presence of the shutter 3 allows the storage chamber 24 to be filled without the material from the feeding means 22 being directly deposited on the printing platform 100.

[0121] In other words, the sealing means 3 allow the storage chamber 24 to be filled to compensate for the inertia of the feeding means 22.

[0122] According to a second embodiment illustrated on the [ Fig.2 ], the printing block 2 incorporates pumping means 4.

[0123] The pumping means 4 are interposed between the storage chamber 24 and the deposition means 23.

[0124] The pumping means 4 allow the pumping of viscous material present in the storage chamber 24 to supply the dispensing means 23.

[0125] As illustrated on the [ Fig.2 ], pumping means 4 include: a conduit 41; a hood 42 mounted on the chassis; a gear mechanism 43 arranged in the conduit 41.

[0126] The wheels of the gear mechanism 43 are, for example, driven in rotation by a dedicated motor not shown in the figures.

[0127] More specifically, the conduit 41 is made in the chassis 21 and forms a passageway for viscous material from the storage chamber 24 to the dispensing means 23.

[0128] The hood 42 is fixedly mounted on the chassis so as to close the conduit 41.

[0129] As illustrated on the figures 3 And 4 , the gear mechanism 43 includes a first gear 431 and a second gear 432.

[0130] The first wheel 431 and the second wheel 432 mesh together to drive the viscous material from the storage chamber 24 to the depositing means 23.

[0131] The conduit 41 is delimited by a wall 411. The wall 411 defines with the first wheel 431 and the second wheel 432 notches 412 inside which the viscous material is carried to reach the dispensing means 23.

[0132] With reference to the [ Fig.4 ], the first wheel 431 and the second wheel 432 rotate in opposite directions to drive the viscous material.

[0133] Furthermore, this ensures that if one of the first wheel 431 and the second wheel 432 loses power, the other wheel will drive the wheel that is no longer being driven. Thus, the pumping system 4 maintains a safety measure for its operation and therefore for the operation of the printing unit 2 and the additive manufacturing machine 1.

[0134] As illustrated on the [ Fig.2 ], the hood 42 has a first cavity 431 and a second cavity 422 intended to be positioned above the gear mechanism 43.

[0135] The first cavity 421 communicates with the conduit 41 on the side of the storage chamber 24, and the second cavity 422 communicates with the conduit 41 on the side of the depositing means 23.

[0136] The first cavity 421 and the second cavity 422 provide a passageway for the viscous material from the feeding means 22, while limiting the viscosity of the material from clogging the pumping means.

[0137] In this second embodiment, the actuator 25 is advantageously a motor 252, for example an electric motor such as is shown in the [ Fig.7 ].

[0138] The electric motor 252 can be controlled by the control means 27 to increase or decrease the volume V of the storage chamber 24 as required.

[0139] In this embodiment, the printing block 2 is thus without a shutter located between the depositing means 23 and the storage chamber 24.

[0140] In use, the pumping means 4 draw the viscous material from the storage chamber 24 to the deposition means 23 to produce the part to be printed on the printing platform 100.

[0141] As the storage chamber 24 empties of viscous material, the cylinder 26, by moving the rod 262, reduces the volume V of the storage chamber 24, which has the effect of continuously supplying the first cavity 421 of the pumping system 4.

[0142] As the pressure decreases in the storage chamber 24, the control means 27 control the feeding means 22 to heat the powder contained in the hopper 221 and rotate the screw 222.

[0143] With reference to the [ Fig.5 ], a third embodiment of the print block 2 is now described.

[0144] This third embodiment corresponds to an assembly of the first embodiment illustrated by the [ Fig.1 ] and the second embodiment illustrated by the figures 2 , 3 And 4 .

[0145] In this embodiment, print block 2 is based on print block 2 described with reference to figures 2 , 3 , 4 that is to say, the second embodiment.

[0146] The printing block 2 includes, in addition to feeding means 22, depositing means 23, pumping means 4 and storage chamber 24, secondary depositing means 29.

[0147] These secondary depositing means 29 are positioned upstream of the pumping means 4, and are fluidly connected to the storage chamber 24.

[0148] Furthermore, according to this third embodiment, the printing block 2 includes a shutter flap 5.

[0149] The sealing valve 5 is positioned between the secondary depositing means 29 and the storage chamber 24.

[0150] The sealing flap 5, like the shutter 3, prevents the material present in the storage chamber 24 from being deposited on the printing platform 100 by the secondary depositing means 29, outside of the printing cycle.

[0151] The secondary dispensing means 29 thus allow the dispensing of viscous material either in parallel with the dispensing means 23, or in place of the dispensing means 23. This proves particularly useful when the dispensing means 23 are not supplied with viscous material by the pumping means 4, for example when the pumping means 4 are defective.

[0152] Thus, by using the control means 27, the supply means 22, the pressure measurement means 28 and the actuator 25, it is possible, via the sealing valve 5 and the secondary depositing means 29, to deposit viscous material onto the printing platform 100. This makes it possible to produce a three-dimensional part even when the depositing means 23 are obstructed or the pumping means 4 are not working.

[0153] With reference to the [ Fig.5 ], the secondary deposition means 29 include a tube 291 extending from the frame 21 and a nozzle 292 located at a distal end of the tube 291. The viscous material flows through the nozzle 292 onto the printing platform 100.

[0154] In use, during a manufacturing cycle start-up, the control means 27 command the activation of the feeding means 22 to supply the deposition means 23 and the secondary feeding means 29, and to deposit viscous material onto the printing platform 100.

[0155] To compensate for the inertia of the printing block 2, in particular the reduction in viscous matter of the powder inside the hopper 221, the viscous matter present in the storage chamber 24 is used to feed the depositing means 23 and / or the secondary depositing means 29.

[0156] More specifically, the rod 262 of the cylinder 26 is pushed back by the actuator 25 so as to reduce the volume V of the storage chamber 24 by moving the movable portion 242.

[0157] Thus, the viscous material in the storage chamber 24 is directed to the depositing means 23 and the secondary depositing means 29 to allow the manufacture of a part on the printing platform 100.

[0158] Chamber 24 is then supplied again with viscous material by the feeding means without lengthening the manufacturing cycle or risking a lack of material in the manufactured part.

[0159] The presence of the sealing valve 5 allows the storage chamber 24 to be filled without the material from the feeding means 22 being directly deposited on the printing platform 100 by the secondary depositing means 29.

[0160] The shut-off valve 5 can for example be opened to allow the supply of the secondary deposition means 29 when the pumping means 4 are inactive.

[0161] The printing block 2 and the additive manufacturing machine 1 which have just been described make it possible to limit, or even eliminate, the inertial effects of the feeding means 22 and in particular the transformation of powder into viscous material for the production of parts to be printed in three dimensions via the deposition means 23.

[0162] Indeed, thanks to the use of the storage chamber 24, it is possible to retain a quantity of viscous material to compensate for the inertia of the feeding means 22.

[0163] In other words, when machine 1 stops or a production cycle stops, the feeding means 22, by their inertia and in particular by the melting of the powder and the rotation of the screw, generate a quantity of material which could be deposited on the printing platform 100 which would create burrs on the printed part.

[0164] Thanks to the storage chamber 24 and the actuator 25 which allows the volume V of the storage chamber 24 to be varied, it is possible to temporarily store the viscous material from the feeding means 22 in order to avoid burrs on the printed part.

[0165] The presence of the obturator 3 or the pumping means 4, and possibly the sealing valve 5, allows the viscous material to be kept inside the storage chamber 24.

[0166] Furthermore, in the absence of the storage chamber 24, the inertia of the feeding means 22 and in particular the melting of material and the rotational drive of the screw or the absence of rotational drive of the worm screw could generate an overpressure inside the hopper 221 and a risk of explosion of the latter.

[0167] In the event of a cycle start-up, the storage chamber 24 allows direct feeding of the dispensing means 23 and / or the secondary dispensing means 29, by reducing the volume V of the storage chamber 24. The distribution of material in the dispensing means 23 and / or the secondary dispensing means 29 thus creates a vacuum inside the storage chamber 24. This vacuum is then detected and measured by the pressure measuring means 28, and then transmitted to the feeding means 22 to refill the storage chamber 24, and supply the dispensing means 23 and / or the secondary dispensing means 29.

[0168] In other words, when a cycle starts, the viscous material is immediately available, which avoids: either having to wait for the viscous material to reach the deposition means 23 and / or the secondary deposition means 29, thus lengthening the duration of the manufacturing cycle, or on the contrary, the cycle starting without the viscous material being able to be deposited, which generates porosity in the manufactured parts, and implies a finishing step.

[0169] The pressure measurement means 28 allow the control of the supply means to authorize or prevent the filling of the storage chamber 24.

[0170] The result, thanks to the printing machine 1 and the printing block 2, according to the invention, is an increase in the production quality of three-dimensionally printed parts and a reduction in the cost of execution by the use of a viscous material obtained from powder, compared to the solutions of the prior art.

[0171] Indeed, the throughput of print block 2 remains constant despite changes in speed and the use of a powdered material.

[0172] The printing block just described can be adapted to any type of powdered (or granulated) material that can pass from a liquid to a solid state via a viscous state, such as metal, ceramic, concrete, or even a composite material, that is to say a hybrid material made up of at least two materials.

[0173] At the very least, the printing block just described can be adapted to any non-Newtonian type material.

[0174] A non-Newtonian material is a material that does not follow Newton's law of viscosity, that is, it maintains a constant viscosity regardless of the stress or strain applied to it.

[0175] In this case, a non-Newtonian material is a material that does not behave the same way depending on the speed of the worm screw.

[0176] In other words, a non-Newtonian material does not flow faster if the speed of the screw increases (there is no proportionality between the speed of the screw and the flow rate of the non-Newtonian material).

Claims

1. Printing unit (2) for a machine (1) for additive manufacturing by deposition of viscous material obtained from powder, the printing unit (2) comprising: - means (22) for feeding viscous material, said means including an endless screw (222) for conveying the viscous material, - means (23) for depositing viscous material, the printing unit (2) also comprising: - at least one chamber (24) for storing viscous material, said chamber being delimited by an internal wall (241) having at least one movable portion (242), the chamber defining a storage volume (V) and being interposed between the feed means (22) and the depositing means (23); - at least one actuating device (25) acting on the movement of the movable portion (242) to change the volume (V) of the storage chamber (24), characterized in that the printing unit (2) comprises means (4) for pumping viscous material, said means being interposed between the storage chamber (24) and the depositing means (23), and in that the printing unit (2) comprises a frame (21) in which the storage chamber (24) is formed, and in that the pumping means (4) comprise: - a duct (41) provided in the frame (21), the duct (41) forming a passageway for viscous material from the storage chamber (24) to the depositing means (23), - a cover (42) fixedly mounted on the frame (21), the cover (42) closing the duct (41), - a gear mechanism (43) arranged in the duct (41), the gear mechanism (43) conveying the viscous material from the storage chamber (24) to deliver it toward the depositing means (23).

2. Printing unit (2) according to the preceding claim, characterized in that the feed means (22) also comprise a heating element (223) surrounding at least the endless screw (222).

3. Printing unit (2) according to claim 1 or 2, characterized in that it also comprises: - means (28) for measuring pressure in the storage chamber (24); - means (27) for controlling the endless screw (222), the control means (27) being configured to control, on the basis of information relating to pressures measured by the pressure measurement means (28), the conveying of the powder by means of the endless screw (222).

4. Printing unit (2) according to any of the preceding claims, characterized in that it also comprises a stopper (3) interposed between the storage chamber (24) and the depositing means (23).

5. Printing unit (2) according to the preceding claim, characterized in that the cover (42) has a first recess (421) and a second recess (422) that are intended to be positioned above the gear mechanism (43), the first recess (421) being in communication with the duct (41) on the storage chamber (24) side, and the second recess (422) being in communication with the duct (41) on the depositing means (23) side.

6. Printing unit (2) according to any of the preceding claims, characterized in that it comprises: - secondary depositing means (29), upstream of the pumping means (4), fluidically connected to the storage chamber (24), - a shut-off valve (5) interposed between the secondary depositing means (29) and the storage chamber (24).

7. Printing unit (2) according to any of the preceding claims, characterized in that it comprises an actuator (26) including: - a rod (262), one end of which forms the movable portion (242) of the inner wall (241), - a body (261) in relation to which the rod (262) is translatably movable, and in that the actuator (25) takes the form of a compression spring (251) interposed between the rod (262) and the body (261), the compression spring (251) tending to move the rod (262) away from the body (261).

8. Printing unit (2) according to any of claims 1 to 6, characterized in that it comprises an actuator (26) including: - a rod (262), one end of which forms the movable portion (242) of the inner wall (241), - a body (261) in relation to which the rod (262) is translatably movable, and in that the actuator (25) takes the form of a motor (252) interacting with the rod (262) to move the rod (262) relative to the body (261).

9. Printing unit (2) according to claim 3, characterized in that the control means (27) are also configured to control the actuator (25) on the basis of information relating to pressures measured by the pressure measurement means (28).

10. Machine (1) for additive manufacturing using viscous material obtained from powder, characterized in that it comprises a printing unit (2) according to one of the preceding claims.