Machine and method for powder-based additive manufacturing

Abstract

The machine presents a working zone that is defined in an upper part of a build sleeve which is fixedly mounted in a chassis. Within the working zone, the object is supported by a build plate which slides inside the build sleeve when driven in vertical translation by the head of an actuating cylinder which is placed along a central axis of the sleeve. The build plate is positioned inside a transport container which is arranged removably between the sleeve and the actuating cylinder. The machine also includes a means for moving the transport container vertically into contact with the build sleeve. The container is open at its top and at its bottom so that, when the actuating cylinder is actuated, the head thereof can transfer the plate between the transport container and the build sleeve which forms a build envelope around the plate.

Claims

1. A machine for the additive manufacture of a three-dimensional object by sintering or melting powder using a beam of energy acting on a layer of powder comprising: a working zone, wherein the working zone is defined in an upper part of a build sleeve in which the three-dimensional object is manufactured, wherein the build sleeve has a height which defines a maximum height for the three-dimensional object to be manufactured such that the entire three-dimensional object remains in the build sleeve during manufacturing; a chassis, in which the build sleeve is fixedly mounted; a build plate which supports the three-dimensional object, and which slides inside the build sleeve when driven in vertical translation; a head of an actuating cylinder placed along the central axis of the build sleeve, and which drives the build plate in vertical translation; wherein the build plate is positioned inside a transport container which is made as a separate piece from the sleeve and which is arranged removably below a lower edge of the build sleeve and above the actuating cylinder; a raising device that is configured to move the transport container vertically upwardly into contact with the build sleeve; and wherein the transport container is open at its top and at its bottom so that, when the actuating cylinder is actuated, the head transfers the plate from the transport container to the build sleeve, which forms a build envelope around the build plate, and so that the head of the actuating cylinder are retractable out of the bottom of the transport container such that the transport container with the build plate and the three-dimensional object can be transported away from the build sleeve and away from the actuating cylinder.

2. The machine according to claim 1, wherein the central axis of the actuating-cylinder head is aligned with the central axis of the build sleeve, and further comprising an indexing means for orienting the transport container relative to the chassis of the machine, and a centering means for centering between the build plate relative to the head of the actuating cylinder.

3. The machine according to claim 2, wherein the raising device comprises push rods belonging to a box fixedly mounted on the chassis and which collaborate with orifices made in the bottom part of the transport container.

4. The machine according to claim 2, wherein the indexing means comprises studs made on a bottom rim of the build sleeve and collaborating with openings made on a top rim of the transport container.

5. The machine according to claim 2, wherein the centering means comprises two diametrically opposite orifices on a bottom face of the build plate which collaborate with protuberances situated on a frontal face of the head of the actuating cylinder.

6. The machine according to claim 1, wherein the build plate slides freely inside the build sleeve and inside the transport container.

7. The machine according to claim 1, wherein a sliding clearance for sliding of the build plate inside the transport container is greater than a sliding clearance for sliding of the build plate inside the build sleeve.

8. The machine according to claim 1, wherein the transport container comprises a sealed flexible bellows arranged between the build plate and its bottom wall.

9. The machine according to claim 1, wherein the build sleeve comprises a periphery having lateral openings outside of the working zone which are made to communicate with a transport container when it is placed underneath.

10. The machine according to claim 9, wherein the transport container comprises an internal chamber for accepting the build plate, which internal chamber is surrounded by a peripheral corridor communicating at its top with the said lateral openings of the build sleeve.

11. The machine according to claim 1, wherein the actuating cylinder drives the build plate via an intermediate plate.

12. The machine according to claim 1, wherein the raising device includes a frame actuated in a horizontal translational movement.

13. A method for the additive manufacture of a three-dimensional object by sintering or melting powder using a beam of energy acting on a layer of powder in a working zone of a machine according to claim 1, wherein the working zone is defined in the upper part of the fixed build sleeve in which the object is manufactured, the object being supported by a build plate which slides inside the build sleeve when driven in vertical translation by the head of the actuating cylinder placed along the central axis of the build sleeve, comprising: positioning the plate inside the transport container, which is open at its top and at its bottom; removably arranging the transport container between the build sleeve and the actuating cylinder vertically moving the transport container until it comes into contact with the build sleeve; and transferring the build plate between the transport container and the build sleeve which forms a build envelope around the build plate using the actuating cylinder.

14. The method according to claim 13, comprising successively: bringing the build plate to the top of the build sleeve, depositing a layer of powder on the build plate, melting the powder particles using a pre-established melting strategy, repeating the depositing and melting steps layer by layer while at the same time progressively lowering the build plate down inside the build sleeve until the object is obtained, lowering the build plate and with the object out of the build sleeve and into the transport container only after the depositing and melting steps are completed, lowering the build plate to the bottom of the transport container, moving the actuating cylinder until it is detached from the build plate, and removing the transport container from the machine with the unmelted and previously melted powder particles inside the transport container.

Description

BRIEF DESCRIPTION OF DRAWINGS

(1) The embodiments of invention will be better understood by virtue of the remainder of the description, which is supported by the following figures:

(2) FIG. 1 is a schematic view in cross section of a machine according to an embodiment of the invention;

(3) FIG. 2 is a schematic view in cross section of the container with which the machine of an embodiment of the invention is equipped, in the work position during the manufacture of the object;

(4) FIG. 3 is a schematic view in cross section of the container with which the machine of an embodiment of the invention is equipped, at the end of the object-manufacturing operation, the container still being fixed to the chassis of the machine;

(5) FIG. 4 is a schematic view in cross section of the container with which the machine of an embodiment of the invention is equipped at the end of the object-manufacturing operation, the container being detached from the chassis of the machine and the actuating cylinder being retracted;

(6) FIGS. 5 to 7 illustrate, in perspective and side views, one example of the mounting of a container actuator within the machine of an embodiment of the invention;

(7) FIGS. 8 to 10 illustrate a perspective view, a view in longitudinal section and a view from beneath of one embodiment of a container with which the machine of an embodiment of the invention is equipped;

(8) FIG. 11 illustrates, in a cross-sectional view, a container with which the machine of an embodiment of the invention is equipped in an alternative form of embodiment of the invention.

(9) In the various figures, elements that are identical or similar bear the same references. Their structure and function is therefore not systematically re-described.

DETAILED DESCRIPTION OF SPECIFIC EMBODIMENTS

(10) FIG. 1 schematically depicts one exemplary embodiment of a machine 1 for the additive manufacture of a component 20. As described in the preamble for the application, the invention in actual fact applies to all types of powder-based additive manufacture using the sintering or total melting of the particles of the said powder using a beam of energy such as an electromagnetic radiation (for example a laser beam) or a beam of particles (for example an electron beam).

(11) An energy source, in this instance a laser source 10, emits a laser beam 11 the orientation of which is controlled by galvanometric mirrors 12. An optical lens 14 allows the beam 11 to be focused on the working zone 4 so as to heat the top layer of the powder 2 in a precise pattern and thus selectively cause the powder to melt. After one layer of powder has been treated by the laser beam, the build plate 7 is lowered by a unit thickness (which corresponds to that of a layer of powder) and is covered with a new layer of powder, and so on, in order, layer after layer, to form the component 20. Depending on the type of energy beam and powders used, the thickness of a layer of powder may vary from a few micrometres (for example 10 m) to several hundreds of micrometres (for example 500 m=0.5 mm). When the component 20 is finished, namely when all the layers necessary for building it have been successively solidified, the component is removed from the working zone.

(12) The machine 1 also comprises a layering device 50 that allows a new layer of powder to be applied to the working zone 4. The layering device 50 of FIG. 1 comprises a feed hopper 5 and a spreader roller 6 for spreading the powder 2 over the working zone 4. The feed hopper 5 at its lower part comprises a metering roller 8 comprising grooves 8a the purpose of which is to transfer a precise quantity or dose of powder 2 from the hopper 5 to the spreader roller 6. The layering device 50 further comprises a compacting roller 9. The final thickness of the layer of powder is therefore the result of two successive operations. A first thickness is defined by the spreader roller 6, this thickness then being reduced and made even more uniform by the action of the compacting roller 9. The compacting roller 9 moves with the feed hopper 5 and the spreader roller 6. The feed hopper 5, the spreader roller 6 and the compacting roller 9 are carried by one or more carriages which are able to move between the powder-storage means (not depicted) and the working zone 4.

(13) The working zone 4 is delimited within a fixed chassis 40 of the machine 1 by a sleeve 41 inside which the build plate 7 slides, this build plate being driven in vertical translation by an actuating cylinder 31 as indicated by the double-headed arrow in FIG. 1. The sleeve 41 is secured to the chassis 40, being fixedly mounted on the chassis 40 or produced as one piece therewith. The sleeve 41 has a cross section of circular, square or rectangular shape, or any other suitable shape, and is situated within the chassis 40 facing the zone of action of the laser source 10. The sleeve 41 comprises a central opening 43 for the passage of the plate 7 and lateral passages or openings 42. The lateral openings 42 are made in the periphery of the sleeve 41, over the entire height thereof, so as to allow excess powder 2 during the layering to be removed. The plate 7 has a cross section of the same shape as the sleeve 41 and dimensions similar thereto inside which it slides with a clearance j1. The plate 7 forms a support for the three-dimensional object that will be built. The sleeve 41 constitutes the build envelope of the object and has a height at least equal to that of the three-dimensional object that is to be built, plus the thickness of the plate 7.

(14) The actuating cylinder 31 belongs to a translational-movement assembly 30. What is meant by an actuating cylinder is a lifting device, for example of the pantograph type or, for preference, of the type comprising a tubular body inside which there moves in a translational manner a rigid rod allowing the transmission of a movement and a speed at its end. The actuating cylinder 31 may be of hydraulic, pneumatic or electric type. In a preferred alternative form of embodiment of the invention, use is made of an electric actuating cylinder, by which the movement of the rod can be controlled very precisely. The translational-movement assembly 30 comprises an external box secured to the chassis 40 of the machine and means (not depicted in the drawings) for guiding the translational movement of the actuating cylinder 31. The actuating cylinder 31 is guided in translational movement inside the external box of the assembly 30 between a raised position (FIG. 2) and a lowered position (FIG. 4), the head 32 of the actuating cylinder 31 being intended to engage with the plate 7 (see FIG. 4). To simplify the drawings and make them clearer, the various components of the assembly 30 have been omitted, except for the actuating cylinder 30 the vertical movement of which allows for a better description of an embodiment of the invention.

(15) According to an embodiment of the invention, the machine 1 comprises a transport container 60, inside which the plate 7 is arranged, the container being arranged underneath the sleeve 41 and open at the top and at the bottom so that the head 32 of the actuating cylinder 31 can transfer the plate 7 between the transport container 60 and the sleeve 41. The transport container 60 is installed within the chassis 40 under the sleeve 41, for example by sliding it along horizontal rails of the latter. In an embodiment depicted in FIG. 2, the transport container 60 comprises lateral bearing fins 64 which slide along the horizontal rails 44 of the chassis 40 until they come fully into abutment, allowing precise positioning facing the sleeve 41. The transport container 60 is then pushed vertically upwards to be pressed firmly against the sleeve 41, by spring-loaded push rods 81 (see FIG. 3), and is then kept in this position using the locking device 80 that comprises means holding the push rods 81 in position. The peripheral rim of the transport container 60 comprises a seal which is pressed firmly against the opposing face of the sleeve 41 so as to prevent any powder leaving the transport container 60.

(16) The transport container 60 comprises an internal chamber 61 in which the plate 7 moves in vertical translation under the action of the actuating cylinder 31. The cross section of the internal chamber 61 has a shape and dimensions similar to those of the plate 7, the clearance between the external periphery of the plate 7 and the walls of the internal chamber 61 being j2, with j2>j1. As can be seen better in FIGS. 2 and 9, the transport container 60 is produced in the form of a box with vertical double walls, the internal chamber 61 being surrounded by a peripheral corridor 62 and being separated therefrom by vertical walls 68. The peripheral corridor 62 is open at its top to communicate with the openings 42 of the chassis 40 and is closed at its bottom so as to be able to store the powder 2. The corners of the vertical walls 68 are bevelled so as better to guide the powder towards the peripheral corridor 62 (the plate 7 in this case having rounded or bevelled corners). The cross section of the peripheral corridor 62 is greater than that of a corresponding opening 42, the peripheral corridor 62 being dimensioned so as to be able to store all of the quantity of powder recovered during the various successive layerings required to manufacture the component 20. The transport container 60 comprises a peripheral seal 67 to seal frontally with the sleeve 41 (see FIG. 8).

(17) According to one advantageous aspect of the invention, the build plate 7 slides freely inside the sleeve 41, no seal being provided on the periphery of the plate between the latter and the sleeve 41. This is because it has been found during tests performed in a laboratory that, for certain sleeve and plate roughness values and for certain values of the clearance between these components, powder particles from the working zone do not block the gap between the internal walls of the build sleeve 41 but allow the plate 7 to slide. Moreover, in order to guarantee correct confinement of the powder to inside the transport container 60 and protect the other components of the machine 1, a bellows 70 is arranged in the central part of the transport container 60, the bottom end 71 of the bellows 70 being fixed to the bottom wall 63 of the internal chamber 61, and the top end 72 to the bottom face of the plate 7 (see FIG. 9).

(18) In a preferred embodiment of the invention, as visible in FIGS. 5 to 7, the machine 1 comprises a support box 90 fixed on the chassis 40 of the machine and into which the removable or mobile transport container 60 is introduced. The box 90 is of parallelepipedal overall shape and comprises a bottom wall 91, a central circular passage 92 through which allows the passage of the actuating cylinder 31, closed lateral walls, at least one of which is able to open to allow the transport container 60 to pass, and a top rim 94 comprising a peripheral seal 95 to seal the box 90 against dust. Projecting through the bottom wall 91 of the box 90 are four push rods 96, 97 the vertical axes of which are positioned in the corners of a rectangle having the same centre as the passage 92. Diagonally opposite push rods are identical, two push rods 96 each have a conically shaped top end and the other two push rods 97 each have a cylindrically shaped top end. The push rods 96, 97 engage with correspondingly shaped orifices made in the transport container 60, as will be explained later on.

(19) The push rods 96, 97 are moved in a vertical translational movement by a frame 100 when it itself is driven in a horizontal translational movement by an actuator 101 (FIGS. 6 and 7). More specifically, the frame 100 is rectangular in shape, the external contour of the frame 100 having dimensions similar to those of the base of the box 90. The frame 100 is fitted with cams 102 along each longitudinal side (FIG. 7). The cams 102 have ramps 103 along which followers 104 mounted at the bottom ends of the push rods 96, 97 run. A cam 102 comprises two parallel ramps 103 each fixed to one lateral face of the side 105. The bottom end of each push rod 96, 97 is fitted with two followers 104 each coming into contact with one ramp 103. The ramp 103 takes the form of a furrow cut into the thickness of the cam and ending in a flexible tab 109. The tab 109 is a flexible beam that makes it possible to absorb differences in thickness between several containers 60, while at the same time guaranteeing that the transport container 60, more particularly the peripheral seal 67 thereof, which is pressed firmly against the sleeve 41, is held sufficiently tightly. In addition, the ramps 103 allow the container to lower progressively when detached from the chassis 40 at the end of the manufacturing operation.

(20) In another alternative form (which has not been depicted), the ramps 103 are rigid, the push rods 96, 97 in that case being provided with height-adjustment means so as to adapt to the height of the container and ensure that the latter is kept pressed firmly against the sleeve 41 of the machine.

(21) Four mounting supports 106 (FIG. 6) for the bottom rollers 107, 107 project outside the bottom wall 91 of the box 90, these bottom rollers being arranged in such a way that two rollers 107, 107 come into contact with the bottom part of each longitudinal side 105 of the frame 100. Two rollers 107 are V-shaped rollers sliding along a V-shaped rail to guide the frame 100 laterally, the other two rollers 107 themselves being flat rollers in contact with a flat rail. A top roller 108 is fixed to the bottom wall 91 of the box 90 in such a way that it presses on the top part of each side 105 of the frame 100 and thus compensates for the play in the assembly of this frame. The frame 100 is thus guided in its horizontal translational movement with respect to the box 90 when driven by the actuator 101. The actuator 101 is advantageously of electric type and is operated in such a way as to lock the transport container 60 when installed inside the box 90.

(22) FIGS. 8 to 10 illustrate one embodiment of a transport container 60 of the invention which can be introduced into the box 90 and collaborate with the push rods 96, 97 thereof. As can be seen better in FIG. 10, the bottom wall 63 is provided with means of connecting the transport container 60 to the push rods 96, 97 of the box 90. Thus, two protuberances which are diametrically opposed with respect to the center of the opening 66 each comprise an orifice of circular shape 111 designed to engage with a conical-end push rod 96 in order to center the transport container 60. Two further protuberances that are diametrically opposed with respect to the centre of the opening 66 each comprise an oblong-shaped orifice 110 designed to engage with a cylindrical-end push rod 97 in order to orientate the transport container 60 with respect to the box 90. When the transport container 60 is installed inside the box 90, the actuator 101 commands the attachment of the transport container 60 which is then pressed firmly against the sleeve 41.

(23) In a preferred alternative form of embodiment of the invention and as illustrated better in FIG. 9, the bellows 70 is held inside the transport container 60 by an intermediate plate 73. The intermediate plate 73 is made to come into contact with the head 32 of the actuating cylinder 31 and with the plate 7 (which is not depicted in FIGS. 8 to 10) and it rests on the bottom of the transport container 60 when the actuating cylinder 31 is in the lowered position. Vertical protuberances for supporting the plate 7 are provided in the bottom of the container so as to prevent the bellows 70 from being crushed.

(24) The plate 7 and, when present, the intermediate plate 73, each comprise centering means 98 of centering one relative to the other and relative to the head 32 of the actuating cylinder 31. Thus, as visible in FIGS. 8 and 10, the intermediate plate 73 comprises two diametrically opposed orifices 112, 113 which collaborate with protuberances situated on the frontal face of the head 32 of the actuating cylinder 31. The frontal face 114 of the intermediate plate is also provided with protuberances identical to those of the head 32 (a first protuberance 115 being visible in FIG. 8, the other being diametrically opposite the first) to collaborate with orifices situated on the bottom face of the plate 7. The protuberance 115 has a prismatic shape and constitutes an open centering feature for preventing the plate from rotating about the axis Z (axis vertical to the plane of the plate), the diametrically opposite protuberance having a cylindrical shape and constitutes a full centering feature which prevents translational movements along the axes X and Y (concurrent axes belonging to the plane of the plate).

(25) FIG. 11 illustrates an alternative form of embodiment of the invention in a view in section taken on a vertical plane passing through the diagonal of the plate. A working sleeve 41 of rectangular cross section is fixed to the chassis 40 of the machine. The transport container 60 has a parallelepipedal overall shape and is illustrated in the position in which it is introduced into the machine, between the working sleeve 41 and the actuating-cylinder head (which has not been illustrated in this figure). In the bottom of the transport container 60 there are a plate 7 and a bellows 70 which are held by a peripheral support plate and through which the head of the actuating cylinder passes. The machine comprises indexing means 99 that allow the transport container 60 to be orientated relative to the working sleeve 41 during the installation of the container, prior to the start of the operation of manufacturing the object. The indexing means 99 comprise two studs 120 produced on the bottom rim of the working sleeve 41, arranged on the diagonal thereof, which studs collaborate with orifices 130 made on the top rim of the transport container 60. The orifices are deep enough that they can store any powder residue without impeding the guiding of the studs 120. The transport container 60 is moved vertically by movement means (not depicted) and presses in a sealed manner against the bottom rim of the working sleeve 41. By way of example, part of the stroke of the actuating cylinder can be used to move the transport container 60 towards the working sleeve 41. Centering means 98 are also provided, notably two diametrically opposed orifices 112, 113 (situated along the same diagonal of the plate) and collaborate with protuberances provided for that purpose on the frontal face of the head 32 of the actuating cylinder 31. These protuberances are advantageously of the same type as those described with reference to FIGS. 8 to 10.

(26) In operation, to start off with, the machine 1 is supplied with a transport container 60 inside which there is a plate 7 which rests directly on the bottom of the transport container 60 via a bellows 70 or, in an alternative form, on an intermediate plate 73. The transport container 60 also comprises a bellows 70 which is in the compressed state in the bottom of the container. The transport container 60 is arranged underneath the sleeve 41, for example by sliding it along rails 44, into a position of abutment, or by placing it on the push rods 96, 97. The container is in the same position with respect to the sleeve 41 and to the actuating cylinder 31 as the position illustrated in FIG. 4. Thus, the top edge 65 of the transport container 60 is situated underneath the working sleeve 41, at a distance e with respect to the facing bottom face 45 of the sleeve. When the transport container 60 is correctly positioned with respect to the chassis of the machine, a locking device 80 that locks the chassis with respect to the sleeve 41 is actuated or, in an alternative form, the frame 100 is given a horizontal translational movement and causes the push rods 96, 97 to effect a vertical translational movement in order to press the transport container 60 firmly against the sleeve 41, the transport container 60 being in the position illustrated in FIG. 3. The transport container 60 is held in this position throughout the manufacturing of the component 20. Once the container has been fixed to the chassis 40, the control means of the machine allow the actuating cylinder 31 to be actuated in an upwards translational movement until its head 32 comes to bear against the bottom face of the plate 7 (or, where present, of the intermediate plate 73).

(27) For preference, the head 32 is immobilized on the plate 7 via vacuum, means being provided for that purpose in the two components (these not being illustrated in the figures). The build plate 7 is pushed upwards by the actuating cylinder 31, controlled by the control means of the machine, through the internal chamber 61 and the build sleeve 41 until it reaches the same level as the top face of this sleeve. The plate 7 is now ready to receive a layer of powder from the layering device 50. The layer of powder deposited is heated by the laser beam and solidified at precise points on its surface, according to the instructions received from a control unit of the machine 1. After the first layer of powder has solidified, the plate is lowered by a distance equivalent to a powder layer thickness, driven by the actuating cylinder 31, so that manufacture can continue with the deposition and solidification of a new layer of powder. At the end of the operation for manufacturing the component 20, the actuating cylinder 31 is lowered and the plate 7 leaves the working sleeve 41, the actuating cylinder continuing its stroke until the plate 7 supporting the manufactured object is at the bottom of the transport container 60, as illustrated in FIG. 3. The actuating-cylinder head 32 is lowered further and detached from the plate 7. The locking device 80, or the frame 100, are then actuated in order to disconnect the transport container 60 from the chassis 40 as visible in FIG. 4. The transport container 60 can now be removed from the chassis 40 and transported (manually by an operator or preferably automatically using mechanical means such as a chain conveyor, a robot arm, etc.) to another workstation that allows the component 20 and the plate 7 to be recovered from the internal chamber 61 and allows recovery of any powder 2 present in the peripheral corridor 62.

(28) The powder used is preferably a metallic or ceramic powder. The preferred particle size for the powder may vary from a few microns (for example 5 m) to 300 or 400 m according to the type of energy beam used and the target final layer thickness.

(29) Other alternative forms and embodiments of the invention may be envisaged without departing from the scope of these claims.