DEVICE AND METHOD FOR GENERATIVE MANUFACTURING

Description

Domaine technique

[0001] The invention relates to a device and a method for additive manufacturing. The invention is suitable for many additive manufacturing methods, including those involving material spraying, sintering or selective melting of material in a material bed, and selective spraying of binder onto a material bed.

[0002] Additive manufacturing involves creating a part layer by layer. Each layer corresponds to the addition of material, regardless of the method, to the previous layer, with a defined thickness and shape. This material addition is achieved using an end effector which, depending on the additive manufacturing method, either directly deposits material (as in the case of projection) or reconstitutes solid, cohesive material from a previously deposited, non-cohesive material. The shape of the layer is obtained by controlling the relative trajectory of the end effector during the material deposition process. Technique antérieure

[0003] The movements of a tool during a manufacturing process by material removal and of an effector during an additive manufacturing process are similar, so that the means, machine and computer chain, used in the field of machining by material removal can be used after some adaptations for the implementation of an additive manufacturing process.

[0004] In fact, according to the prejudices of the man of the trade, additive manufacturing is implemented using the same or very similar machines to those used for machining by material removal, reproducing the kinematics of machine tools, with serial or parallel kinematics, or using multi-articulated robots.

[0005] These kinematic solutions include at least 3 driven axes and most often 5 or 6 axes, which makes these machines complex to manufacture. Furthermore, they only allow one end effector to move at a time, and even if it is possible to mount several end effectors on the head of a machine tool or at the end of a robot arm, they necessarily follow parallel trajectories.

[0006] These prior art solutions are also limited by their work volume. A machine tool has a fixed work volume, as does a multi-articulated robot, and while it is possible to combine several multi-articulated robots to cover a larger volume, the programming becomes complex.

[0007] GB2525400A discloses a robot intended for the manufacture of a part by additive manufacturing, comprising a rotating arm. Exposé de l'invention

[0008] The invention aims to overcome these drawbacks and, to this end, relates to a robot intended for manufacturing a part by additive manufacturing using volume elements or voxels, said robot comprising: a base; a rotating arm comprising a plurality of additive manufacturing effectors distributed radially on said arm; means for moving the rotating arm in translation, in a direction parallel to its axis of rotation; means for guiding the rotating arm in translation and rotation relative to the base; means for controlling the action of the additive manufacturing effectors according to the position of the rotating arm in space.

[0009] Thus, for each end effector of the arm, the combination of the arm's rotation and translation defines a cylindrical swept surface in terms of trajectory. Activating the additive manufacturing end effector for a specific time while it traverses this swept surface produces an elementary volume of material, or voxel.

[0010] This principle, applied to all the additive manufacturing effectors present on the arm, makes it possible to create a grid of voxels occupying the robot's working volume.

[0011] The part to be manufactured is a subset of this voxel grid. It is obtained by controlling each of the effectors during the helical movement of the rotating arm so as to create only the voxels corresponding to the part.

[0012] Thus, all effectors are subject to the same kinematics imposed by the rotating arm, but each effector is activated / deactivated individually to build the part by an assembly of elementary volumes, so that in practice, all effectors work at the same time and cooperate to create the volume although they are all driven by the same device.

[0013] Thus, by making all the effectors work at the same time, the device that is the subject of the invention allows high productivity while using simple and easily programmable kinematics.

[0014] Potentially any shape is achievable in the volume swept by the rotating arm with a resolution that depends on the size of the voxel of material achievable by an effector, the step size and the number of effectors installed on the arm.

[0015] The system is adaptable to the production of a small or very large part and in its simplest version, the robot which is the subject of the invention comprises only 2 axes, which can be driven by a single motor, which reduces the cost of production for the same volume of work compared to solutions of the prior art.

[0016] The Invention is advantageously implemented according to the embodiments and variants set out below, which are to be considered individually or in any technically feasible combination.

[0017] Advantageously, the robot of the invention comprises a plurality of rotating arms carrying effectors. This arrangement makes it possible to increase both the resolution and productivity of the robot, as well as the distribution of the different functions between the arms.

[0018] Thus, according to an example of implementation, adapted to the implementation of an additive manufacturing process by selective aggregation of a granular material contained in a bed of material, one of the rotating arms includes an assembly for depositing granular material onto the bed of material.

[0019] Advantageously, the dispensing assembly includes a dispensing hopper with a plurality of discharge ports. This embodiment of the dispensing assembly is particularly compact and adaptable to the robot that is the subject of the invention for continuous additive manufacturing.

[0020] Advantageously, the robot of the invention comprises a scraper, in the form of a blade or roller acting on the material bed and driven by a rotating arm. In a particular embodiment, the scraper is connected to the same arm as the hopper.

[0021] In one embodiment, the robot includes a workpiece support comprising means for moving the workpiece during manufacturing. This embodiment improves both contour resolution and increases the volume of parts that can be produced by the robot.

[0022] In one particular embodiment, the robot of the invention includes means for moving the effectors along a rotating arm. This embodiment increases the robot's resolution in the manufacturing of parts.

[0023] Advantageously, the base includes means for moving the entire robot in space. This embodiment makes it possible both to increase the volume of the part that can be produced by a single robot, but more advantageously, it allows several robots to cooperate on demand, to produce very large parts.

[0024] The Invention also relates to a method for the additive manufacturing of a part using a robot of the invention according to any of its embodiments, comprising the steps of: (i) obtaining a volume discretized into volumetric meshes corresponding to the manufacturing volume of the robot; (ii) inserting the digital model of the part into the volume obtained in step i); (iii) determining the volumetric meshes included in the volume of the digital model and delimiting the contours of said model according to a predefined offset tolerance; (iv) manufacturing the part by associating with each mesh determined in step iii) an activation of an effector in the corresponding position.

[0025] This process is simple to implement both from the point of view of programming and of controlling the robot being built.

[0026] In an embodiment of the process of the invention implementing an additive manufacturing process by selective sintering or agglomeration of a bed of material, step iv) includes the activation of an effector for the realization of the means of retention of said bed of material.

[0027] In an advantageous embodiment of the process of the invention, step iv) includes the association of several robots mounted on mobile bases and cooperating to enlarge the manufacturing volume, and step i) includes obtaining the total manufacturing volume of the set of combined robots. Description sommaire des dessins

[0028] The invention is described below according to its preferred, non-limiting embodiments, and with reference to figures 1 à 10 , in which: Fig. 1 [ Fig. 1 ] shows, from a bottom view, examples of the realization of a robot, the object of the invention, figure 1A, comprising the same type of effector on all arms, figure 1B, comprising different effectors on the arms; Fig. 2 [ Fig. 2 [ ] represents, according to front views, different embodiments of the robot that is the subject of the invention, figure 2A in a ground-based configuration, and figure 2B in a ceiling-mounted configuration; Fig. 3 [ Fig. 3 ] illustrates, using perspective views, the principle of additive manufacturing of a part for an effector of the robot that is the subject of the invention, figure 3A during a single rotation of the arm, figure 3B by stacking the elementary volumes of the figure 3A et figure 3C according to a variant of the volume stacking scheme of the figure 3A ; Fig. 4 [ Fig. 4 illustrates the manufacturing of a part according to the principles shown. figure 3 , figure 4A from a perspective view for an individual effector, figure 4B According to a top view, the principle of determining the manufacturing meshes from the digital model of the part and the discretized manufacturing volume of the robot and the figure 4C shows according to a perspective and sectional view AA defined figure 4B , an example of how to create the part from its digital definition figure 4B ; Fig. 5 [ Fig. 5 [ ] shows, from a top view, an example of cooperation between several robots, the subject of the invention, by comparing the tetragonal volume achievable by one robot, figure 5B , to the tetragonal volume achievable by the association of robots; Fig. 6 [ Fig. 6 ] shows, according to a schematic top view, the association of 8 robots for the production of a part; Fig. 7 [ Fig. 7 ] represents, according to a perspective view, figure 7A, et figure 7B according to a cross-sectional view AA defined figure 3A , an example of the realization of a deposit hopper adaptable to an arm of the robot which is the subject of the invention; Fig. 8 [ Fig. 8 ] represents in top view an example of implementation of the robot which is the subject of the invention using an additive manufacturing process by sintering or selective agglomeration of a bed of material; Fig. 9 [ Fig. 9 ] represents a logic diagram of the process that is the subject of the invention; Fig. 10 [ Fig. 10 ] schematically shows, from a front view, a robot, the object of the invention, mounted on a mobile base. Meilleure manière de réaliser l'invention

[0029] Figure 1 According to schematic embodiment examples, the robot of the invention comprises one or more arms (101, 102, 103, 104), preferably four arms, driven in rotation by suitable means around a central axis (100). Each arm includes one or more additively manufactured end effectors (110), distributed radially at regular or irregular intervals along the arm.

[0030] According to embodiment examples, not all arms have the same number of effectors, and the effectors are radially offset by a distance d possibly variable along the arm, so that the combined action of the effectors covers the entire work volume of the robot in terms of additive manufacturing capacity.

[0031] According to one embodiment, the effectors are movable radially, individually or in groups, along the arm.

[0032] To this end, an effector or set of effectors is mounted on a motorized carriage on the arm. Similar to the radial offset of effectors from one arm to the other, this arrangement, compatible with such radial offset, allows for coverage of the work area with higher resolution.

[0033] According to examples of implementation, the arm length ranges from 5 cm to 5 m. Thus, in principle, the robot that is the subject of the invention is suitable for a very wide range of parts.

[0034] The Invention is applicable to the following additive manufacturing processes: melting or sintering on a powder bed, spraying of binder onto a granular material, spraying of material.

[0035] Thus, the device that is the subject of the invention is suitable for the production of parts in metal, polymer, ceramic or sand according to the additive manufacturing process used.

[0036] Depending on the additive manufacturing process considered, the effectors are nozzles for projecting molten material, nozzles for projecting a binder, a laser for melting a material, a device for depositing non-agglomerated granular material, or a scraper, in the form of a blade or a roller, for leveling a layer of deposited granular material.

[0037] In addition, some effectors perform functions ancillary to the additive manufacturing operation, such as the projection of a protective gas over the area being melted, or a gas capable of accelerating the setting of the projected binder, or even a local heating function, for example by infrared radiation.

[0038] Thus, according to an example embodiment, figure 1B, two of the arms are provided with a multi-orifice hopper (1202, 1204) for discharging a granular material and a scraper (1302, 1304) to level the layer of material deposited, and the other two arms (101, 103) are provided with effectors to selectively agglomerate, by melting or by binding, the layer of material deposited.

[0039] One of the arms (101) selectively agglomerates the layer of material deposited by one of the hopper and scraper assemblies (1202, 1302) and the other arm (103) selectively agglomerates the layer of material deposited by the other hopper and scraper assembly (1204, 1304).

[0040] Figure 2 In addition to the rotational movement, for the production of a part (251, 252, 253), the arms are guided and moved vertically at a controlled speed parallel to their axis (100) of rotation, which the figure 2 schematically represented by the presence of a guide shaft (201, 202). According to these examples, the guide shaft (201, 202) and consequently all the means of manufacturing the robot, are mounted on a base (2001, 2002).

[0041] THE figures 2A et 2B To simplify the representation, the part (251, 252, 253) being manufactured is produced by a material projection process. In the case where the part is manufactured by agglomeration or selective sintering of a material bed, said part is located within the material bed, and the device includes means for retaining said material bed, as shown. figure 8 .

[0042] Figure 2A According to a first embodiment, the base (200) supporting the shaft (201) is placed on the ground, and the part or plurality of parts (251, 252) is produced by additive manufacturing on a table (241) extending around the guide shaft (201). This embodiment is simpler and less expensive in terms of robot manufacturing. However, the central area occupied by the shaft limits the volume of parts that can be produced.

[0043] Figure 2B In another embodiment, the base (200 2) supporting the shaft (202) is placed on the ceiling. In this embodiment, it is possible to place effectors (110) close to the center of rotation of the arms, and the work volume and the functional surface of the table (242) are not limited by the presence of the shaft (202). The parts that can be manufactured (253) are larger for the same overall volume of the robot, compared to the solution of the figure 2A .

[0044] The robot that is the subject of the invention can be used in all its embodiments for 2.5D or 3D manufacturing.

[0045] Preferably, in both cases, during additive manufacturing, the arms rotate at a constant speed.

[0046] In 2.5D, the part is created by successive planes perpendicular to the axis of rotation. The additive manufacturing operation is performed in a plane, by one or more rotations of the arms at a constant altitude. Then, the arms are moved parallel to the axis of rotation by one increment, and a new additive manufacturing phase is performed in a plane parallel to the previous one, and so on. This solution requires stopping the additive manufacturing process—melting, sintering, projection, and possibly deposition of a material layer—between two increments, even if the arms continue to rotate.

[0047] In 3D, the rotational movements of the arms and their axial displacement along their axis of rotation are combined so that each end effector follows a helical trajectory with a variable pitch, depending on the specific implementation. With this implementation, the additive manufacturing process is continuous and productivity is higher.

[0048] Moreover, this embodiment simplifies the construction of the robot that is the subject of the invention, by using only one drive motor to rotate the arms, which then move vertically via a helical guide along the shaft.

[0049] THE figures 3 And 4These diagrams schematically illustrate the manufacturing process of a part using the robot that is the subject of the invention. For clarity, the process depicted is a 2.5D manufacturing process, and the voxels are represented at much larger dimensions relative to the finished part than they actually are. Transitioning to a 3D manufacturing configuration is straightforward by considering (450, 451) meshes and (350) voxels in a helical segment.

[0050] The movements, as well as the activation / deactivation of the effectors, are controlled by a numerical control system (not shown). The device includes sensors, so the angular and vertical position of the arm on its axis of rotation is known at all times. The radial and vertical positions of the effectors on the arm are also known and entered into the tables of the numerical control system, so the spatial position of the material projected or agglomerated by the effector is also known at all times to the numerical control system.

[0051] Figure 3A With the arm rotating around its axis (100), each end effector (110) installed on said arm follows a circular trajectory (helical in the case of a 3D process). The activation of the additive manufacturing end effector, that is, the activation of the material projection by this end effector, the projection of a binder in the case of the agglomeration of a granular material, or the triggering of the laser source emission of the end effector for the melting or sintering of the material, during a determined time / displacement, produces an elementary volume of material (350) or voxel.

[0052] The smallest achievable volume of material depends, for a given process, on the minimum activation-deactivation-reactivation time of the end effector and the relative speed of movement of the end effector with respect to the part, the latter being a function of the angular velocity of the arm and the radial position of the end effector on the arm.

[0053] Thus, in this example of a non-limiting 2.5D implementation, each effector is capable of producing a crown of voxels (350) during a rotation of the arm.

[0054] Figure 3B , the repetition of this operation at different altitudes gives each effector (110) the ability to create a cylindrical tubular volume by stacking the voxels (350).

[0055] Figure 3C According to one implementation example, the voxels are not directly stacked on top of each other as represented by the figure 3A , but are stacked in a staggered pattern or according to some other pattern from one plane to the other.

[0056] In all cases the volume of material potentially agglomerated, projected or sintered by an effector is located in a circular tubular volume, and the position as well as the dimension of each voxel depends on the activation and deactivation positions of the effector.

[0057] Figure 4A During the movement of the arm, each effector is activated / deactivated according to the contour to be made, so as to realize a portion of its potential tubular volume.

[0058] Thus, by combining several effectors so that their tubular fabrication volumes are contiguous or overlap, the fabrication volume is a cylinder discretized into elementary volumes.

[0059] Figure 4B From a numerical point of view, this manufacturing volume is discretized into volumetric meshes (460), corresponding to all the voxels realizable by each effector in this volume.

[0060] Figure 4B , according to an example of the realization of a helix-shaped part represented in top view to simplify the image, the volumetric digital model of the part (450) is placed in this volume discretized also in digital form.

[0061] Through appropriate digital processing, the cells (461) of the manufacturing volume that are located within, or that approximately define, the volume of the part's model (450), based on a defined offset tolerance, will correspond to voxels created during the additive manufacturing operation. This digital operation of selecting the cells (461) is relatively simple to perform using solid modeling software.

[0062] In the case of the figure 4B The mesh was optimized to account for the possibility of angularly shifting the generated voxels from one effector to another and also from one plane to another. This operation is very easily performed numerically, for example by rotating each ring of meshes (460) in each altitude plane so as to better follow the contour of the digital model (450).

[0063] Figure 4C The part is made by stacking the voxels (350) corresponding to the meshes (461) identified during the digital processing.

[0064] Compared to prior art techniques which require the definition of trajectories, the transition from digital processing to manufacturing is also simplified in the case of the robot that is the subject of the invention.

[0065] As an example, the creation of the piece shown figure 4 Using conventional techniques, this requires creating trajectories along three axes from the point of application / agglomeration of the material onto the workpiece. The execution of these trajectories by the machine or robot results in combinations of movements along the axes of articulation or displacement of the machine or robot, necessitating, at the level of its numerical control director, the determination of these movements by inverse kinematics relative to the programmed trajectory.

[0066] Physically, during manufacturing, following these trajectories using prior art means results in permanent accelerations / decelerations on the axes of movement or articulation of the machine or robot, although the trajectory of the point of application / agglomeration on the part is traversed at a substantially constant speed by the kinematic combination of these movements.

[0067] In the case of the device that is the subject of the invention, in its simplest implementation, only two axes of movement of the effectors are used: the rotation of the arm and its vertical movement along its axis of rotation. These two movements are performed at constant speeds and, according to a simplified embodiment, are driven by a single motor. There is no trajectory programming; the part is produced by activating / deactivating the effectors in given positions, corresponding directly to the meshes (461) identified during the numerical processing.

[0068] The position-controlled activation / deactivation of the effectors is an on / off function that does not require inverse kinematics for its implementation. A modern numerical control system is potentially capable of controlling a number of these effectors far exceeding what is necessary for the implementation of the manufacturing process by the device that is the subject of the invention.

[0069] The implementation of movable end effectors along the arm, or of a variable displacement step parallel to the arm's axis of rotation, are improvements primarily aimed at increasing the manufacturing resolution of the device that is the subject of the invention. These are easily incorporated numerically in the mesh definition used for programming the part, and fall largely within the control capabilities of numerical control systems.

[0070] Contrary to what one might think figures 3 And4 The device that is the subject of the invention and its implementation are by no means limited to the production of parts of revolution. Any shape of part can be produced as long as its volume falls within the manufacturing volume of the device in question.

[0071] Figure 10 In one embodiment, the base (1000) is provided with means of movement (1100). According to this example, the robot is placed on a trolley equipped with wheels or tracks to move in a defined space, for example in a workshop or in a structure under construction such as a ship hull, an aircraft fuselage or a civil engineering structure.

[0072] Advantageously, each robot mounted on its trolley includes allothetic or idiothetic, absolute or relative positioning means (1051, 1052), both in its environment or relative to another robot, by triangulation of positioning beacons, processing of video images, radar, lidar, or measurement on its means of movement, alone or in combination.

[0073] Thus, a plurality of such robots becomes a plurality of cobots capable of joining together in varying numbers depending on the need. The cobots are therefore able to operate according to several successive association patterns, possibly on platforms at different heights, in order to create a very large structure.

[0074] Manufacturing a part by combining several cobots of this type is preferably done in 2.5D to simplify collision avoidance.

[0075] Alternatively, the mobile base is mounted to the ceiling, for example suspended on a network of rails covering the intended workspace.

[0076] Alternatively, the mobile base is supported by a cable robot.

[0077] Figure 5 The manufacturing volumes of several robots can be combined to obtain a much larger total manufacturing volume.

[0078] So, figure 5A In one example, four robots (501, 502, 503, 504) are combined so that their work volumes overlap. The extent of the overlaps varies depending on the shape of the part to be machined and the required resolution. Thus, in this schematic but not exhaustive example, the trajectories of the arm tips of two of the robots (501, 503) are tangent, but they could very well intersect to better cover the central area. The same applies to the other two robots in this example (502, 504).

[0079] The position and rotation speed of each robot's arms are synchronized to avoid any collision.

[0080] According to this non-limiting implementation example, the robots are of the "ground-based" type and their individual work volume includes an inaccessible central area corresponding to the position of the guide shaft.

[0081] So, figure 5B , the perimeter (551) of the maximum tetragonal volume achievable in one piece with such a robot (500) including a central shaft, is limited by the presence of this central shaft.

[0082] Returning to the figure 5A , the combination of 4 robots of the same type as the one shown figure 5B , allows to achieve a tetragonal realization volume whose perimeter (550) is twice as large, i.e. the volume 4 times larger, compared to that of a single robot.

[0083] The association of several robots of the invention is not limited to robots placed on the ground and works just as well with robots mounted on the ceiling.

[0084] Figure 6, potentially, it is thus possible to combine the work volumes of any number of cobots according to a multiplicity of arrangements to cover a desired manufacturing volume (650).

[0085] To this end, each cobot is advantageously equipped with proximity, contact, alignment and positioning sensors, for example capable of interacting with radio or ultrasonic beacons, so as to position themselves relative to each other, and with wired or radio communication means so as to create between them a network including master-slave relationships, for the synchronization of their actions.

[0086] Programming the cobots thus associated benefits from all the advantages indicated above for the individual programming of a robot that is the object of the invention.

[0087] Returning to the figure 2 In one embodiment, the part (251, 252, 253) is mobile during its fabrication relative to the robot's axis of rotation (100). To this end, figure 2A , according to an example of an embodiment adapted to the case of a robot whose shaft (201) is placed on the ground, the table (241) includes one or more trolleys (245) movable relative to the table by devices such as ball screws or linear motors controlled by the numerical control director of the machine.

[0088] In this case, figure 2B , of a robot whose shaft (202) is mounted on the ceiling, the table (242) is itself coupled to piloted means of movement.

[0089] According to one embodiment, the movements thus allowed of the table (242) or of the trolleys (245) are linear movements in a plane perpendicular to the axis of rotation (100) of the arms, for example along orthogonal directions.

[0090] The same result is obtained using a fixed table and a robot whose base is equipped with means of movement ( figure 10 ).

[0091] According to another embodiment, compatible with the previous one, the movements of the table (242) or the trolley (245) include angular orientations along an axis parallel or an axis perpendicular to the axis of rotation of the arms.

[0092] These embodiments make it possible to increase the robot's manufacturing resolution and to increase the volume of parts that can be produced.

[0093] Returning to Figure 1B, for the implementation of an additive manufacturing process by selective agglomeration or sintering, one of the robot's arms (102, 104) is advantageously equipped with a discharge hopper (1202, 1204) to deposit the successive layers subjected to agglomeration or sintering.

[0094] This method of implementation can be used in both 2.5D and 3D manufacturing.

[0095] The hopper is advantageously a multi-orifice hopper which, combined with scraping means, allows the deposition of a layer of material of uniform thickness in the kinematic configuration of the arm.

[0096] Figure 7 , according to an example of an embodiment the hopper (700) adaptable on an arm of the robot object of the invention comprises an upper part (710) and a lower part (720) called discharge part comprising two inclined walls (721, 722) converging towards the multiple lower openings, distributed along a transverse direction (y).

[0097] The hopper (700) includes in its upper part means (750) for fixing it to a robot arm, in particular by bolting.

[0098] The two inclined walls (721, 722) of the lower part (320) of the hopper are inclined symmetrically with respect to a transverse vertical plane ( x, y ) , from an angle θ 1 = θ 2 . These angles ( θ 1 , θ 2 ) are in all cases less than 40° and preferably less than 30°, so that the angle of the overturning cone ( θ 1 +θ 2 ) between the two inclined transverse walls (721, 722) of the lower part, is at most equal to 80° and preferably less than 60°.

[0099] Figure 3B , the hopper (700) is compartmentalized in its lower part (720). Each compartment corresponds to an opening (731, 732, 733, 734, 735), the hopper comprising several openings aligned along the transverse direction ( y ). Each compartment constitutes a conical hopper with a rectangular cross-section that evolves in the discharge section (720) of the hopper. This "sub-hopper" opposite each opening is delimited along the longitudinal direction ( x ) by the inclined walls (721, 722) of the hopper and along the transverse direction ( y) by compartmentalization walls (741, 742) inclined with respect to a longitudinal vertical plane ( x , z ) and converging towards an orifice.

[0100] Each partition wall is inclined at an angle ( θ 3 , θ 4) less than 40°, preferably less than 30°, so that the opening angle ( θ 3 + θ 4) The angle between two partition walls opening onto an orifice is at most 80° and preferably less than 60°. The conduit thus created between the inclined walls and the partition walls, up to the outlet of the orifice, does not include any surface inclined at an angle greater than 40° to the vertical direction. These conditions ensure a fluid flow of the granular material contained in the hopper (700), in the form of a mass flow, towards each of the orifices (731, 732, 733, 734, 735) of the hopper.

[0101] The geometry of the compartments bringing the material to the orifices is such that the effective flow area through an orifice is equal or substantially equal to the orifice area for almost the entire emptying time of the hopper.

[0102] These conditions allow for an almost constant discharge rate through each of the orifices, this rate being determined by the nature of the material being discharged, in particular its density and particle size and the geometry of the hopper, i.e. without the use of specific means of controlling the discharge rate.

[0103] The contiguous partition walls (742, 743) of two successive compartments are connected to each other in the lower part (720) of the hopper by a sharp joint, the connected walls forming a tooth or wedge with a point angle of less than 60°, preferably less than 40°, depending on the respective inclination of the surfaces (742, 743) thus connected. This feature ensures easy separation of the flow streams to the multiple orifices of the hopper.

[0104] The opening section of the orifices is advantageously different along the transverse direction.

[0105] Thus, during the rotation of the arm, the orifice (731) with the smaller opening follows a circular trajectory closer to the center of curvature and consequently with a smaller radius, while the orifice with the larger opening (735) follows a trajectory further from the center of curvature and with a larger radius.

[0106] The material is deposited in a strip opposite each orifice and distributed over the surface of the material bed by a scraper also attached to the robot arm (figure 1B).

[0107] Figure 8 The use of the robot of the invention for implementing an additive manufacturing process using a selectively agglomerated or sintered material bed requires a retention tray to contain said material bed. Advantageously, according to one embodiment of the robot of the invention, the means (840) for retaining the material bed are created within the material itself, by sintering or agglomeration simultaneously and as the part (850) is produced.

[0108] Figure 9 , according to an example of the embodiment of the process which is the subject of the invention, it comprises two numerical steps (910, 920).

[0109] During a step (910) defining the work volume, the work volume discretized into volumetric meshes of the robot or a plurality of associated robots is defined. The volumetric meshes correspond, for example, to the smallest voxels achievable by each of the effectors carried by the robot or the plurality of robots.

[0110] During a balancing step (920), the digital model of the part to be produced is positioned in the discretized volume determined in the previous step (910).

[0111] During a modeling step (930) the elementary volumetric cells included in the volume of the digital model and those whose edges follow the contour of said model according to a predefined step tolerance are determined.

[0112] During a programming step (940), each volumetric mesh determined during the modeling step (930), corresponding either to the part produced or to the creation of a means of retaining a bed of material, is translated into a spatial position for the activation and deactivation of each of the effectors.

[0113] According to a step (950) the part is created by stacking voxels from the program obtained.

[0114] The above description and examples demonstrate that the invention achieves its intended purpose, in particular by enabling higher productivity and simpler programming of additive manufacturing operations compared to conventional kinematic solutions. The robot is also less expensive to manufacture for the same workload. The robot of the invention can be produced in a wide range of sizes and is suitable for implementing several additive manufacturing processes. The ability to have multiple robots cooperate allows for the production of very large parts, such as naval or aeronautical structures, tooling, or civil engineering structures. At the opposite end of the scale, depending on the additive manufacturing technology, the density of effectors along an arm can reach 25 effectors per millimeter, thus providing high resolution for small parts.

Claims

1. A robot intended to manufacture a part (251, 252, 253, 450) by additive manufacturing using volume elements or voxels (350), said robot comprising: a base (2001, 2002, 1000); a rotary arm (101, 102, 103, 104) comprising a plurality of effectors (110) for additive manufacturing radially distributed on said arm such that their tubular manufacturing volumes are joined or overlap; a central shaft connected to the base for translationally and rotationally guiding the rotary arm relative to the base (2001, 2002); means for translationally moving the rotating arm by rotation on the central shaft, in a direction parallel to its axis (100) of rotation such that for each effector of the arm, the combination of the rotation and the translation of the arm defines, in terms of trajectory, a cylindrical tubular volume and the combination of the tubular volumes of each effector defines the manufacturing volume of the robot; means for controlling the action of the effectors (110) for additive manufacturing according to the position of the rotary arm in space by activating and deactivating the effector for a determined time while it crosses its tubular volume, so as to create a voxel (350), the position and also the dimension of said voxel being determined by the activation and deactivation position of the effector.

2. The robot according to claim 1, comprising a plurality of rotary arms (101, 102, 103, 104) bearing effectors (110).

3. The robot according to claim 2, adapted for implementing an additive manufacturing method by selective aggregation of a granular material comprised in a material bed, wherein one of the rotary arms (102, 104) comprises a deposition assembly (1202, 1204, 1302, 1304) of the granular material on the material bed.

4. The robot according to claim 3, wherein the deposition assembly comprises a deposition hopper (1202, 1204 ,700) comprising a plurality of discharge orifices (731.. 735).

5. The robot according to claim 4, comprising a scraper (1302, 1304) acting on the material bed, actuated by a rotary arm.

6. The robot according to claim 1, comprising a part support (241, 242) comprising means for moving the part being manufactured7. The robot according to claim 1, comprising means for moving the effectors along a rotary arm.

8. The robot according to claim 1, wherein the base (1000) comprises means (1100) for moving the robot in space.

9. A method for additive manufacturing of a part implementing a robot according to claim 1, comprising steps of: (i) obtaining (910) a volume discretised into volumetric meshes (460) corresponding to the manufacturing volume of the robot; (ii) inserting (920) the digital model (450) of the part into the volume obtained in step i); (iii) determining (930) the volumetric meshes (461) comprised in the volume of the digital model and delimiting the contours of said model according to a predefined projection tolerance; (iv) producing (950) the part by associating (940) with each mesh (451) determined in step iii) an activation and deactivation of an effector in the corresponding position so as to create the volumetric mesh, the arm rotating at a constant speed about its axis of rotation.

10. The method according to claim 9, implementing an additive manufacturing method by selective sintering or agglomeration of a material bed, wherein step iv) comprises activating an effector for producing the retention means (840) of said material bed.

11. The method according to claim 9, implementing robots according to claim 8, wherein step iv) comprises associating several cooperating robots (501, 502, 503, 504) to increase the manufacturing volume (550), and step i) comprises obtaining the total manufacturing volume of all combined robots.