Depowdering process for an object obtained by additive synthesis of the powder binding type

Abstract

Title: Process for depowdering an object obtained by additive synthesis of the powder binding type. A process for depowdering an object (O) obtained by additive synthesis of the powder binding type, characterized in that it comprises: - a step of transferring, by lateral displacement, a mass (M) comprising said object (O) and unbound particles (P), onto a separation device (12), the separation device comprising a separator (21) with a mesh size adapted to allow the passage of unbound particles and adapted to retain said object, the separator extending in a plane inclined at a non-zero angle (A1) with respect to a horizontal plane, and - a step of vibrating the separator so as to separate the unbound particles of said object and so as to advance said object on the separator. Figure to be published with the abbreviation: Figure 3

Description

Title of the invention: Method for depowdering an object obtained by additive synthesis of the powder binding type Technical field of the invention

[0001] The invention relates to the field of manufacturing methods by additive synthesis of the powder binding type, commonly called "binder jetting". More specifically, the invention relates to a method for depowdering an object obtained by additive synthesis of the powder binding type. The invention also relates to depowdering equipment configured to implement such a depowdering method and to a manufacturing installation by additive synthesis of the powder binding type comprising such depowdering equipment. State of the prior art

[0002] Powder binding additive manufacturing, also known as "Binder Jetting" or "InkJet Powder Printing", is a process using a binding agent, deposited locally on a thin layer of powder, layer by layer, according to a three-dimensional model. In practice, an automated roller spreads a thin layer of powder on a manufacturing plate. A print head applies a liquid binder to the powder, thus creating a layer of the object. Then, the manufacturing plate descends by a predetermined step to allow the addition of a new layer of powder on which binder is again applied. The process is thus repeated until the object is created. This process makes it possible to manufacture three-dimensional objects of varied and complex shapes and does not require the creation of specific supports, the unbound powder itself playing this role.The process therefore does not require specific tools and can be used to manufacture prototypes or small series of objects. The process can also be used to manufacture objects whose complex shape is not compatible with traditional manufacturing by molding or machining.

[0003] However, this manufacturing process requires subsequent processing steps. Indeed, the objects thus manufactured must be depowdered, that is to say, freed from particles not bound to the object. Then, the objects must be consolidated, in particular by sintering (that is to say by heating them in a furnace) or by applying a coating to the object. The depowdering process is complex because, before being consolidated, the objects are particularly fragile. For depowdering these objects, techniques of suction or blowing compressed air onto the objects are known. Manual depowdering processes are also known, in particular using brushes. These techniques are ineffective and tedious, in particular due to the complex shape of the manufactured objects, as well as due to the small size of unbound particles which can pose a risk of inhalation. The manual depowdering process is therefore generally carried out using a laboratory glove box. Such processes do not allow for the implementation of depowdering on a large scale. Presentation of the invention

[0004] The aim of the invention is to provide depowdering equipment and a depowdering method which overcomes the above drawbacks and improves the equipment and methods known from the prior art.

[0005] More specifically, a first objective of the invention is depowdering equipment and a depowdering method which is efficient, automated, and preserves the integrity of objects manufactured by powder bonding. Summary of the invention

[0006] The invention relates to a method for depowdering an object obtained by additive synthesis of the powder binding type, comprising: - a step of transferring, by lateral movement, a mass comprising said object and unbound particles, onto a separation device, the separation device comprising a separator with a mesh size adapted to allow the unbound particles to pass through and adapted to retain said object, the separator extending in a plane inclined at a non-zero angle relative to a horizontal plane, and - a step of vibrating the separator so as to separate the unbound particles of said object and so as to move said object forward on the separator.

[0007] The separation device may comprise a structure and an electroacoustic converter configured to transmit ultrasound to the structure, the separator being fixed to the structure, and the separator being vibrated by ultrasound during said vibration step, and / or the vibration of the separator may be obtained by ultrasonic waves of frequency between 20 kHz and 80 kHz inclusive, in particular between 25 kHz and 45 kHz inclusive, and / or the vibration step may comprise an alternation of vibration phases of the separator and rest phases where the separator does not vibrate.

[0008] The separation of said object and unbound particles and the advancement of said object on the separator may result solely from vibrations of the separator combined with a force of gravity.

[0009] The separator may extend in an inclined plane at an angle less than or equal to 20° with a horizontal plane, in particular an angle between 5° and 10° inclusive with a horizontal plane.

[0010] The transfer of said mass can be carried out by means of a scraper movable in translation and / or by a vibration generation means operating according to the principle of the vibrating corridor.

[0011] The transfer of said mass can be carried out by a vibration generating means operating according to the principle of the vibrating corridor, and the separator can be vibrated by the vibration generating means during said vibration step.

[0012] The separation device may comprise a first separator and a second separator positioned below the first separator, a mesh size of the second separator being strictly smaller than a mesh size of the first separator, and the dedusting method may comprise: - a step of vibrating the first separator so as to separate the unbound particles of said object and so as to advance said object on the separator, and - a vibration step of the second separator so as to sift the unbound particles.

[0013] The separation device may comprise a single structure and an electroacoustic converter configured to transmit ultrasound to the structure, the first separator and the second separator being fixed to the structure, the first separator and the second separator being vibrated by ultrasound during the steps of vibration of the first separator and the second separator, the separation device further comprising an opening for evacuating rejects from the second separator, the opening comprising a common edge with the second separator, in particular the opening being formed directly in the second separator.

[0014] The invention also relates to a method of manufacturing an object, comprising: - a phase of manufacturing said object by additive synthesis of the powder binding type using a manufacturing unit, then - the implementation of the method of depowdering said object as defined previously.

[0015] The manufacturing unit may comprise a translationally movable bottom, the movable bottom being capable of descending progressively to manufacture said object layer by layer, and the transfer of said mass onto the separator may be preceded by a step of raising the movable bottom.

[0016] The invention also relates to depowdering equipment for depowdering an object manufactured by additive synthesis of the powder binding type, the depowdering equipment comprising: - a transfer device configured to laterally move a mass comprising an object to be dedusted and unbound particles, - a separation device comprising a separator and a means for vibrating the separator, the separator comprising a mesh size adapted to allow unbound particles to pass through and adapted to retain said object, the separator extending in a plane inclined at a non-zero angle with a horizontal plane.

[0017] The invention also relates to an additive synthesis manufacturing installation of the powder binding type, comprising a container comprising a bottom that can move in translation, the bottom that can move progressively downwards to manufacture said object layer by layer and then upwards, and comprising depowdering equipment as defined above, the transfer device being fixed above the container. Presentation of figures

[0018] These objects, characteristics and advantages of the present invention will be explained in detail in the following description of a particular embodiment made without limitation in relation to the attached figures among which:

[0019] [Fig.l] is a diagram of an additive synthesis manufacturing installation comprising depowdering equipment according to a first embodiment of the invention, an object manufactured by powder binding being in place in a container used for its manufacture.

[0020] [Fig. 2] is a diagram of the manufacturing facility of [Fig. 1], said object and unbound powders around said object being transferred to a separator of the depowdering equipment.

[0021] [Fig. 3] is a diagram of the manufacturing facility of [Fig. 1], said object and unbound powders around said object being on a separator of the depowdering equipment.

[0022] [Fig.4] is a diagram of an additive synthesis manufacturing installation comprising depowdering equipment according to an alternative embodiment.

[0023] [Fig. 5] is a diagram of an additive synthesis manufacturing installation comprising depowdering equipment according to another embodiment variant.

[0024] [Fig.6] is a diagram of a device for separating the dedusting equipment according to another variant embodiment.

[0025] [Fig.7] is a diagram of a device for separating the dedusting equipment according to another embodiment variant.

[0026] [Fig.8] is a schematic top view of a first separator of the separation device of [Fig.7].

[0027] [Fig.9] is a schematic top view of a second separator of the separation device of [Fig.7]. Detailed description

[0028] [Fig.l] schematically illustrates a manufacturing installation 1 by powder binding type additive synthesis according to a first embodiment of the invention. The manufacturing installation 1 comprises on the one hand a manufacturing unit 2 configured to manufacture at least one object by powder binding type additive synthesis and, on the other hand, depowdering equipment 3 configured to depowder the previously manufactured object. It is considered that the manufacturing installation 1 rests on a horizontal ground. The terms "lower", "upper", "lower" and "high" are intended to specify a particular arrangement relative to a vertical axis.

[0029] The manufacturing unit 2 comprises a container 4 provided with a movable bottom 5, movable in translation parallel to a vertical axis. The movable bottom 5 can in particular be actuated by a jack controlled by an electronic control unit. The container 4 also comprises fixed side walls 6, extending vertically and arranged around the movable bottom 5. The movable bottom 5 can have any geometric shape, in particular a rectangular shape. It is movable between a low position (shown for example in [Fig.l]) and a high position (shown for example in Figures 2 and 3). In the high position, an upper surface of the movable bottom 5 can rise to the level of an upper edge of the side walls 6 or above them. The movable bottom 5 is able to descend progressively to manufacture an object O layer by layer and then to rise again. The internal volume of the container 4 is therefore variable and is maximum when the movable bottom 5 is in the low position.At the end of a step of manufacturing the object O by additive synthesis, the container 4 therefore contains a mass M comprising the object O and unbound particles P, that is to say particles in powder form. The object O is therefore embedded in the middle of the unbound particles P. In the following description, it is considered that this mass M contains a single object O, however the mass M could very well contain several objects manufactured simultaneously in the container 4, which would optimize the use of the volume of the container.

[0030] The manufacturing unit 2 may comprise on the one hand a means for applying a succession of layers of particles in the container and on the other hand a means for projecting a binder, or print head, adapted to locally agglomerate particles together. The means for applying a succession of layers of particles and the means for projecting binder may be arranged in a removable manner above the container 4. Thus, at the end of a phase of manufacturing the object O by additive synthesis in the container 4, these means may be moved aside to make room for the depowdering equipment 3, part of which is fixed above the container 4.

[0031] Before being bound, said particles form a powdery material, that is to say they are in the powder state. The particles may in particular be metal particles, ceramic particles, gypsum particles, sand particles or even polymer particles. The particles may also be non-metallic and / or inorganic, such as oxides, carbides, nitrides or borides. The particle size can be, for example, between 100 μm and 80 μm. The binder is an adhesive, preferably in a liquid state, the nature of which is chosen according to the particles used.

[0032] The dedusting equipment 3 mainly comprises a transfer device 11 and a separation device 12. The transfer device 11 is configured to laterally move the mass M containing the object O to be dedusted and the unbound particles P. The transfer device 11 comprises in particular a cover 13 removably attached to the container 4, above the latter. The cover 13 is a frame comprising a set of side walls 14 arranged in the extension of the side walls 6 of the container 4. The height of the side walls 14 is sufficiently large for the cover 13 to accommodate the mass M, that is to say the assembly formed by the object O surrounded by the unbound particles P. The height of the side walls 14 may be at least equal to the travel of the movable bottom 5 between its high position and its low position.One of the side walls 14 is provided with an opening 15 whose width and height are at least equal respectively to the width and height of the mass M. The transfer device 11 may also comprise a guide ramp 16 opposite the opening 15, which is configured to guide the lateral movement of the mass M. The guide ramp may be inclined downwards so as to promote the evacuation of the mass M from the cover 13. The cover 13 and / or the guide ramp 16 may optionally be provided with a cover to prevent any dispersion or suspension of unbound particles during the lateral movement of the mass M.

[0033] The transfer device 11 also comprises an actuator 17 configured to exert a mechanical action on the mass M. According to the first embodiment, illustrated in FIGS. 1 to 3, the actuator 17 comprises a scraper 18 movable in horizontal translation. The scraper 18 is arranged on the side of the cover 13 opposite the opening 15, and positioned so that its lower edge extends at the level of the upper surface of the movable bottom 5 when it is in the high position or slightly above this upper surface. The scraper 18 is configured to exert lateral support on the mass M so as to push it horizontally through the opening 15 then onto the guide ramp 16. In particular, the scraper 18 may comprise a support surface which extends over the entire width and over the entire height of the mass M so as to generate a uniform thrust thereon.As a note, the mass M may contain a superposition of several layers of objects obtained by binding powder. In this case, the actuator 17 may be configured to exert a mechanical action only on the upper layer of the mass M. In particular, the scraper 18 may comprise a support surface which extends only over the height. of such a layer. Once this first layer has been transferred to the depowdering equipment 3, the movable bottom 5 can rise by a height equal to the height of a layer, so as to transfer the next layer to the depowdering equipment 3. This results in a transfer of the mass M layer by layer.

[0034] The separation device 12 comprises a separator 21 and a means 22 for vibrating the separator. The separator 21, or grid 21, is a sieve-type instrument. It is formed from a network of calibrated meshes which serves to separate particles according to their size. The separator may be, for example, a woven fabric of threads. The threads of the fabric may be metal wires, in particular steel or stainless steel, or even nylon threads. The separator may also be a plate pierced with holes. The separator 21 comprises a mesh size adapted to allow the unbound particles P to pass through and to retain the object O. The mesh size of the separator may be, for example, between 50 pm and 3 mm inclusive, preferably between 200 pm and 1 mm inclusive. As a note, the unbound particles may possibly form aggregates of several particles whose size, however, remains much smaller than the size of the object O.Advantageously, the mesh size of the separator 21 is also adapted to allow such aggregates of particles to pass through. In addition, the roughness or surface condition of the separator (which depends on the type of weaving of the fabric or the method of creating the plate pierced with holes) can be adapted to obtain a satisfactory compromise between effective depowdering and preservation of the object: The higher the roughness, the more effective the depowdering and the lower the roughness, the lower the risk of damaging the object. This roughness can be determined experimentally as a function of the fragility of the objects to be treated and as a function of the cohesion of the unbound particles on these objects.

[0035] The separator 21 is supported by a structure 23 arranged at the periphery of the separator 21. The structure 23 is fixed to a lower face of the separator, in particular by gluing. The upper face of the separator 21 extends generally in a plane and is devoid of any element of the structure 23 so as not to hinder the sliding of the object O on its surface. Slides may nevertheless be provided along each side of the separator to prevent the object O or unbound particles from falling. In addition, a recovery tank 24 may be provided under the separator 21 in order to recover the unbound particles P that have passed through the separator 21.

[0036] The separator 21 extends in a plane inclined at a non-zero angle Al with a horizontal plane. The slope of the separator can be chosen so that the object O and the unbound particles P descend along the separator 21 only when the separator is vibrated. Thus, only the combination of the vibrations of the separator and the force of gravity makes it possible to move the object along the separator. The angle Al is preferably less than or equal to 20°, in particular between 5° and 10°.

[0037] According to the first embodiment, the vibration means 22 is an electroacoustic converter 25 configured to transmit ultrasound to the structure 23. In particular, the electroacoustic converter 25 can be fixed in the upper part of the structure 23, in particular on an upper edge of the structure. The separator 21 can thus be made to vibrate via the structure 23. Preferably, the electroacoustic converter 25 is configured to vibrate the separator 21 at a frequency between 25 kHz and 45 kHz inclusive, in particular between 30 kHz and 40 kHz inclusive, or even a frequency of the order of 35 kHz. The electroacoustic converter 25 can also be configured to emit ultrasound periodically, by alternating phases of vibration of the separator and rest phases where the separator does not vibrate.The electroacoustic converter 25 can also be configured to emit ultrasound whose frequency varies in the range from 25kHz to 45kHz, or even in the range from 30kHz to 40kHz.

[0038] Advantageously, a decoupling element 26 is provided interposed between the transfer device 11 and the separation device 12, in particular between the guide ramp 16 and the separator 21. This decoupling element 26 may be, for example, a membrane or any flexible element capable of absorbing vibrations. It is even possible to provide a simple clearance between the separator 21 and the guide ramp 16. Thus, neither the transfer device 11 nor the container 4 to which the transfer device 11 is fixed are set into vibration by the electroacoustic converter 25. Advantageously, the decoupling element 26 forms a sealed interface between the transfer device 11 and the separation device 12, which makes it possible to prevent unbound particles from being dispersed outside the dedusting equipment.

[0039] Advantageously, the separation device also comprises an evacuation ramp 32 in the extension of the separator 21. This evacuation ramp 32 can be arranged at a lower edge of the structure 23. The evacuation ramp 32 can even be formed directly in the structure 23. It allows evacuation of the object without shock towards a conveyor belt.

[0040] To manufacture the object O using the manufacturing installation 1, the first step is to carry out an additive synthesis phase of the powder binding type. A thin layer of particles is distributed on the movable base 5, it is compacted using a roller, then the binder is locally applied to the powder, thus creating a layer of the object. Then, the movable base 5 descends by a predetermined step to allow the addition of a new layer of particles. The process is thus repeated until the creation of the object O. The object O is therefore a stratified block made up of bound particles. The movable base 5 is then in the low position and the object O is embedded in the middle of unbound particles P as shown in [Fig.l].

[0041] Then, the movable bottom 5 rises to its high position. The mass M is then positioned inside the cover 13, opposite the opening 15. The transfer device 11 is then actuated so as to transfer the mass M laterally (i.e. move it laterally) from the cover 13 to the separator 21 via the opening 15. The mass M therefore moves in a substantially horizontal direction. In particular, any operation of overturning or turning over the mass M is avoided, which could shock the object it contains and possibly damage it. This transfer operation is illustrated schematically in [Fig.2].

[0042] The separator 21 is then set into vibration, which causes on the one hand the separation of the unbound particles P from the object O, and the progressive descent of the object O onto the separator. At each vibration the unbound particles in contact with the separator 21 are projected above the separator in a direction generally perpendicular to the separator 21. Thus the projected unbound particles gradually advance towards the lower edge of the separator 21. When the unbound particles fall back onto the separator 21, they may possibly pass through its meshes. The unbound particles which do not pass through the meshes are again projected into the air during a subsequent vibration of the separator and thus benefit from a new chance to pass through the meshes of the separator.Advantageously, the slope of the separator, the length of the separator, as well as the frequency of the vibratory waves are different operating parameters that can be adapted in order to obtain complete or almost complete depowdering of the object O when the latter reaches the lower edge of the separator 21. The ultrasonic waves make it possible, given their frequency and their amplitude, to disintegrate the unbound particles and to promote their flow through the separator 21, without damaging the object O. In addition, the unbound particles absorb the ultrasonic waves to the detriment of the object O, which makes it possible to preserve the latter. An alternation of vibration phases of the separator and rest phases where the separator does not vibrate allows the particles to pass more easily through the mesh of the separator 21.Indeed, if several unbound particles form a pile above a hole in the separator during a rest phase, this pile collapses during the following vibration phase, which causes some of the unbound particles in this pile to pass through the hole. The unbound particles which pass through the separator are recovered in the recovery tank 24. In [Fig. 3], a first arrow F1 illustrates the direction of advancement of the object O on the surface of the separator 21. A second arrow F2 represents the flow of . all unbound particles passing through the separator 21 and which are then recovered in the recovery tank 24.

[0043] Thanks to the invention, it is therefore possible to depowder objects obtained by additive synthesis of the powder binding type in an efficient and completely automated manner. The depowdering of the object O and its advancement on the separator 21 can result solely from the vibrations of the separator 21 combined with the force of gravity. A depowdered object O is recovered at the outlet of the separator, ready to be consolidated, in particular by a sintering step or by a coating. The depowdering process may not require any handling of the object O, nor an operation of blowing off the unbound particles, nor any other mechanical action on the object O or on the unbound particles. Alternatively, the object O can be largely depowdered at the end of the depowdering process. A manual depowdering operation of the object which would follow the depowdering process previously described would be greatly facilitated.Indeed, on the one hand the quantity of unbound particles to be removed would be reduced, but on the other hand these unbound particles having already undergone vibrations they would be in a powdery form, easier to remove. The process also makes it possible to avoid the suspension in the air of large quantities of unbound particles. The process is thus compatible with the use of very small particles whose handling requires great care due to the risk of inhalation. Thanks to the invention, we therefore obtain a simple and inexpensive means of depowdering objects obtained by powder binding. The very promising technology of additive synthesis by powder binding can thus be deployed on an industrial scale.

[0044] Various alternative embodiments of the depowdering equipment are now described. Unless otherwise indicated, these alternative embodiments can be freely combined with the first embodiment or with each other. To simplify the description, only the differences with respect to the first embodiment are described. Where possible, the same references used for the description of the first embodiment are used to describe the elements of the various alternative embodiments of the depowdering equipment.

[0045] According to a first embodiment variant illustrated in [Fig. 4], the actuator 17 is a vibration generating means 19 capable of generating vibrations tending to move the M through the opening 15. In particular, the vibration generating means 19 is configured to operate according to the principle of the vibrating corridor: The cap 13 is vibrated along an axis XI, perpendicular to the plane in which the opening 15 extends. The movement of the cap 13 in the direction of the opening 15 is slower than the movement of the cap 13 in the direction opposite to the opening. Such a vibrational background asymmetry induces a movement of the mass M in the direction of the opening 15. The use of the vibration generating means 19 according to the principle of the vibrating corridor is advantageous because it provides a transfer means 11 which does not include any elements articulated or sliding relative to each other. This prevents unbound particles from getting stuck in the evacuation device 11 and impairing its operation.

[0046] Other embodiments of the actuator 17 could be envisaged. For example, the movable bottom 5 or even the assembly formed by the manufacturing unit 2 surmounted by the cover 13 could be inclined towards the opening 15. According to another embodiment, the transfer device 11 could be integrated directly into the manufacturing unit 2. In this hypothesis, the opening 15 would be formed in one of the side walls 6. This opening would then be closed by a side door during the manufacturing phase by additive synthesis and then opened to allow the evacuation of the mass M.

[0047] According to the embodiment variant illustrated in [Fig. 4], the manufacturing installation 1 comprises on the one hand the vibration generation means 19, and on the other hand the vibration means 22 in the form of an electroacoustic converter 25. The amplitude of the vibration waves generated by the vibration generation means 19 (of the order of 1 mm) can be significantly greater than the amplitude of the vibration waves generated by the electroacoustic converter 25.

[0048] According to another alternative embodiment illustrated in [Fig. 5], the vibration means 22 of the separator 21 corresponds to the vibration generation means 19. This eliminates the need for an electroacoustic converter. In this case, it is preferable to provide a rigid connection between the cap 13 and the separation device 12 so that the vibration waves propagate from one to the other. It is therefore the same vibration means which makes it possible to evacuate the mass M from the cap 13, to depowder the object O and to make it progress on the separator 21.

[0049] The invention not only makes it possible to remove and depowder objects manufactured by additive synthesis but it also makes it possible to treat the recovered unbound particles P. With reference to [Fig. 6], the depowdering device 12 can advantageously comprise a first separator 21A and a second separator 21B positioned below the first separator 21A. Each of the two separators 21A, 21B can comprise a frame 23A, 23B which is specific to it and can be vibrated by a vibration means such as an electroacoustic converter 25A, 25B fixed to the corresponding frame. A mesh size of the second separator 21B is strictly smaller than a mesh size of the first separator 21A. In particular, the mesh size of the first separator 21A is adapted on the one hand to allow the unbound particles P and the aggregates of unbound particles to pass through and on the other hand to retain the object O.The mesh size of the second separator 21B is adapted. to retain the unbound particles P in aggregate form and to allow the unbound particles P not agglomerated between them to pass. In other words, the second separator 21B is configured to sieve the unbound particles P from the object O at the end of the additive synthesis manufacturing phase. The first separator 21A and the second separator 21B each extend in a plane forming a non-zero angle with the horizontal plane, in particular an angle Al as described previously. The first separator 21A may be parallel to the second separator 21B. In [Fig.6], a first arrow F1 illustrates the direction of advancement of the object O on the surface of the first separator 21A. A second arrow F2 represents the flow of all the unbound particles filtered by the first separator 21A. A third arrow F3 represents the direction of advancement of the aggregates of unbound particles on the surface of the second separator 21B.A fourth arrow F4 represents the flow of unbound particles sieved by the second separator 21B. The unbound particles thus sieved can thus be reused in a new additive synthesis manufacturing cycle.

[0050] Figures 7, 8 and 9 illustrate yet another improvement of the invention. Like the embodiment variant shown in [Fig.6], the separation device 12 also comprises a first separator 21A and a second separator 21B. The two separators 21A and 21B are fixed to the same structure 23. The first separator and the second separator both extend in a plane forming a non-zero angle with the horizontal plane, in particular an angle A1 as described previously. The first separator 21A can extend parallel to the second separator 21B. The structure 23 and the two separators 21A and 21B define an interior volume 27 of the separation device 12. The structure 23 is made to vibrate by a single electroacoustic converter 25. This electroacoustic converter 25 is therefore capable of making the first separator 21A and the second separator 21B vibrate via the structure 23.

[0051] The separation device comprises an opening 28 configured to evacuate particles contained in the interior volume 27, that is to say to evacuate rejects from the second separator. This opening comprises a common edge with the second separator 21B so that no particles remain stuck on the second separator. The opening 28 is arranged in the lower part of the second separator so that the unbound particles move towards the opening 28 by the combined action of gravity and vibrations of the second separator.

[0052] The opening 28 may be formed in the frame 23, however, in such a case, the second separator 21B is no longer held by the frame at this opening. Such an arrangement would make it particularly difficult to use a stretched screening cloth for the second separator 21B. Indeed, the use of a stretched screening cloth preferably requires that it be fixed over its entire periphery. Originally, the opening 28 can be formed directly in the second separator 21B. The opening 28 is thus coplanar with the second separator. The opening 28 can be in the form of an area of ​​the second separator 21B having a larger mesh size, in particular a mesh size larger than the mesh size of the first separator.

[0053] In particular, the second separator 21B may be formed by the association of two sieve cloths 21B1 and 21B2. The first sieve cloth 21B1 comprises a mesh size strictly smaller than the mesh size of the first separator 21A, for example a mesh size between 25 μm and 100 μm inclusive. The second sieve cloth 21B2 comprises a mesh size strictly greater than the mesh size of the first separator 21A, for example strictly greater than 250 μm. The second sieve cloth 21B1 is positioned below the second sieve cloth 21B2, that is to say that the particles present on the surface of the second separator move from the first sieve cloth 21B1 towards the second sieve cloth 21B2 under the effect of the vibrations of the second separator combined with gravity.

[0054] The two screening cloths 21B1, 21B2 may be glued to each other at a covering strip 29 comprising the two superimposed screening cloths 21B1 and 21B2. Advantageously, a lower face of the first screening cloth 21B1 is glued to an upper face of the second screening cloth 21B2, which forms a downward step for the particles moving from the first screening cloth 21A to the second screening cloth 21B. This prevents particles from being retained at the interface between the two screening cloths. The recovery tank 24 comprises two compartments separated by a partition 31. The partition 31 may extend vertically substantially at the level of the covering strip 29.

[0055] When the separation device 12 is operating, the object O is discharged at the outlet of the first separator 21A according to the arrow FL. The unbound particles in aggregate form are recovered in the compartment 242 by passing through the opening 28 according to the arrow F3. The unbound particles sieved by the first sieve cloth 21B1 are recovered in the compartment 241. This provides a dedusting device that is both compact and simple to manufacture. This dedusting device makes it possible to dedust the object O, to convey it to the lower edge of the first separator, and to sift the unbound particles for reuse in a new additive synthesis manufacturing cycle.

Claims

Claims

1. Method for depowdering an object (0) obtained by additive synthesis of the powder binding type using a binding agent, deposited locally on a thin layer of powder, layer by layer, according to a three-dimensional model, characterized in that it comprises: - a step of transferring, by lateral movement, a mass (M) comprising said object (0) and unbound particles (P), onto a separation device (12), the separation device comprising a separator (21) with a mesh size adapted to allow the unbound particles to pass through and adapted to retain said object, the separation device comprising a structure (23) and an electroacoustic converter (25) configured to transmit ultrasound to the structure, the separator being fixed to the structure, the separator extending in a plane inclined at a non-zero angle (Al) relative to a horizontal plane,and - a step of ultrasonic vibration of the separator so as to separate the unbound particles of said object and so as to advance said object on the separator.,

2. Dedusting method according to the preceding claim, characterized in that: - the vibration of the separator (21) is obtained by ultrasonic waves of frequency between 20 kHz and 80 kHz inclusive, in particular between 25 kHz and 45 kHz inclusive, and / or - the vibration step comprises an alternation of vibration phases of the separator (21) and rest phases where the separator does not vibrate.

3. A dedusting method according to one of the preceding claims, characterized in that the separation of said object (0) and unbound particles (P) and the advancement of said object on the separator (21) result solely from vibrations of the separator combined with a force of gravity.

4. A dedusting method according to one of the preceding claims, characterized in that the separator (21) extends in a plane inclined at an angle less than or equal to 20° with a horizontal plane, in particular an angle between 5° and 10° inclusive with a horizontal plane.

5. Dedusting method according to one of the preceding claims, characterized in that the transfer of said mass (M) is carried out by means of a scraper (18) movable in translation and / or by a vibration generation means (19) operating according to the principle of the vibrating corridor.

6. A dedusting method according to one of the preceding claims, characterized in that the transfer of said mass (M) is carried out by a vibration generating means (19) operating according to the principle of the vibrating corridor, and in that the separator (21) is vibrated by the vibration generating means (19) during said vibration step.

7. A dedusting method according to one of the preceding claims, characterized in that the separation device (12) comprises a first separator (21A) and a second separator (21B) positioned below the first separator, a mesh size of the second separator being strictly smaller than a mesh size of the first separator, and in that the dedusting method comprises: - a step of vibrating the first separator (21A) so as to separate the unbound particles of said object and so as to advance said object (0) on the separator, and - a step of vibrating the second separator (21B) so as to sift the unbound particles (P).

8. A dedusting method according to the preceding claim, characterized in that the separation device (12) comprises a single structure (23) and an electroacoustic converter (25) configured to transmit ultrasound to the structure, the first separator (21 A) and the second separator (21B) being fixed to the structure, the first separator and the second separator being vibrated by ultrasound during the vibration steps of the first separator and the second separator, the separation device (12) further comprising an opening (28) for evacuating rejects from the second separator (21B), the opening comprising a common edge with the second separator (21B), in particular the opening (28) being formed directly in the second separator (21B).

9. Method for manufacturing an object, characterized in that it comprises: - a phase of manufacturing said object by additive synthesis of the powder binding type using a manufacturing unit (2), then - the implementation of the method of depowdering said object according to one of the preceding claims.

10. Manufacturing method according to the preceding claim, characterized in that the manufacturing unit (2) comprises a movable bottom (5) in translation, the movable bottom being able to descend progressively to manufacture said object layer by layer, and in that the transfer of said mass (M) onto the separator (12) is preceded by a step of raising the movable bottom.

11. Manufacturing installation (1) by additive synthesis of the powder binding type, characterized in that it comprises a container (4) comprising a movable bottom (5) in translation, the movable bottom being able to descend progressively to manufacture said object layer by layer then to rise, and in that it comprises depowdering equipment (3) for depowdering an object (0) manufactured by additive synthesis of the powder binding type, the depowdering equipment comprising: - a transfer device (11) configured to laterally move a mass (M) comprising an object (0) to be depowdered and unbound particles (P), - a separation device (12) comprising a separator (21) and a means (22) for vibrating the separator, the separator comprising a mesh size adapted to allow the unbound particles to pass through and adapted to retain said object, the separator (21) extending in a plane inclined at a non-zero angle (Al) with a horizontal plane,the transfer device (11) being fixed above the container (4).,

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