Powder removal technology from 3D workpieces produced by additive manufacturing.

Abstract

A method for removing powder from a three-dimensional workpiece produced by additive manufacturing is provided. The method includes mounting a build cylinder to a build cylinder fixture. The build cylinder includes a substrate for holding the three-dimensional workpiece and a sidewall releasably attached to the substrate. The build cylinder includes residual powder from the additive manufacturing process of the three-dimensional workpiece. The method further includes attaching a foil to the build cylinder fixture and / or the substrate. Additionally, an apparatus is provided for removing powder from a three-dimensional workpiece produced by additive manufacturing.

Description

Technical Field

[0001] The present invention generally relates to powder removal from a three-dimensional workpiece generated by additive manufacturing. Powder removal can be considered as part of the so-called unpacking process of the three-dimensional workpiece. The additive manufacturing process is powder bed fusion bonding such as selective laser sintering, selective laser melting or electron beam melting, but is not limited to those listed here.

Background Art

[0002] Powder bed fusion bonding is a lamination process capable of processing powdery raw materials, particularly metallic and / or ceramic raw materials, into a three-dimensional workpiece with a complex shape. For this purpose, a powder layer of the raw material is applied onto a carrier and selectively exposed to radiation (e.g., laser or particle radiation) site-by-site according to the desired shape of the workpiece to be manufactured. The radiation penetrating the powder layer causes heating of the powder particles of the raw material, resulting in melting or sintering. Thereafter, a raw material powder layer is continuously applied onto the layer on the already radiation-treated carrier until the workpiece reaches the desired shape and size. Based on CAD data, powder bed fusion bonding can be used to manufacture prototypes, tools, replacement parts, high-value parts or medical prostheses, e.g., dental or orthopedic prostheses. Examples of powder bed fusion bonding techniques include selective laser melting, selective laser sintering and electron beam melting.

[0003] Devices for manufacturing one or more workpieces according to the above techniques are known. For example, Patent Document 1 (European Patent Application Publication No. 2961549) and Patent Document 2 (European Patent Application Publication No. 2878402) each describe a device for manufacturing a three-dimensional workpiece according to the technique of selective laser melting. The general principles described in such documents can also be applied to the technology of the present disclosure.

[0004] Once a three-dimensional workpiece has been generated layer by layer in the powder bed, residual powder must be removed from the workpiece so that it can be used and / or further processed. During powder removal, contamination by the surrounding air (especially oxygen) must be avoided to prevent oxidation and other issues. Furthermore, to prevent explosions and other issues, the formation of dust clouds must be avoided or controlled by inactivation. For this reason, powder removal is preferably carried out in a controlled environment (e.g., an inert gas atmosphere such as an argon atmosphere) under controlled conditions.

[0005] Residual powder may refer to the unsolidified powder within the build cylinder that was constructed by solidifying the workpiece. After one or more reprocessing steps (washing, drying, sieving, etc.), the residual powder is returned to the construction process, and a new 3D workpiece is generated from the residual powder.

[0006] Several techniques are known for removing residual powder from workpieces. For example, one method involves moving the sidewall of the build cylinder upward while leaving the build cylinder substrate on the ground. However, this technique can generate an explosive dust cloud. Furthermore, this technique requires an additional axis of movement and complex techniques for collecting the dripping residual powder into a storage container.

[0007] Furthermore, it is known that the build cylinder's substrate can be pushed upward while the side walls of the build cylinder remain on the ground.

[0008] One of the problems with such conventional technologies is that the workpiece and any residual powder that may remain on the workpiece are transported for further processing while being exposed to the ambient atmosphere, at least temporarily. Furthermore, the residual powder may spread into the ambient atmosphere. [Prior art documents] [Patent Documents]

[0009] [Patent Document 1] European Patent Application Publication No. 2961549 [Patent Document 2] European Patent Application Publication No. 2878402 [Overview of the Initiative]

[0010] Therefore, the present invention aims to provide a technology that solves at least one of the aforementioned problems and / or other related problems. In particular, but not limited to, an improved powder removal technology is desired in which the workpiece and residual powder are exposed to the ambient atmosphere as little as possible. In particular, but not limited to, an improved powder removal technology is desired in which contamination of the ambient atmosphere is reduced, thereby improving operational safety.

[0011] This objective is addressed by the subject matter of the independent claim. Favorable embodiments are shown in the dependent claims.

[0012] According to a first embodiment, a method is provided for removing powder from a three-dimensional workpiece produced by additive manufacturing. The method includes the step of attaching a build cylinder to a build cylinder fixture. The build cylinder comprises a substrate for holding the three-dimensional workpiece and side walls detachably attached to the substrate. The build cylinder contains residual powder from the additive manufacturing process of the three-dimensional workpiece. The method further includes the step of attaching a foil to the build cylinder fixture and / or the substrate.

[0013] In addition, one or more of the following features of the embodiments of the method may be applied to the apparatus of the embodiments of the apparatus described below. In this disclosure, when the term “workpiece” is used, it always refers to a “three-dimensional workpiece.”

[0014] This method may be carried out by a powder removal device, which may be part of a so-called unpacking station. The additive manufacturing process that produces the workpiece may be selective laser melting or selective laser sintering, or other processes that solidify and / or bond powders to form a three-dimensional workpiece.

[0015] Therefore, the build cylinder may be a build cylinder used in an additive manufacturing apparatus such as a selective laser melting apparatus or a selective laser sintering apparatus. The build cylinder may be equipped with a lid to maintain an inert atmosphere inside the build cylinder. For example, the build cylinder may be closed with a lid inside the additive manufacturing apparatus, while the build cylinder remains in an inert atmosphere (e.g., an argon atmosphere). Alternatively, a hopper or funnel may be attached to the build cylinder in a selective laser sintering apparatus to maintain an inert atmosphere. Next, the closed build cylinder is moved to an unpacking station, where the process according to the first embodiment is carried out.

[0016] According to this application, powder removal from a three-dimensional workpiece generally means removing powder from the internal space of the build cylinder while the workpiece is held by the substrate. Therefore, the removed powder may or may not be in direct contact with the workpiece.

[0017] The build cylinder may have an internal space that is generally cylindrical in shape. For this reason, the cylinder may be cylindrical (with a circular substrate), or the substrate may be, for example, rectangular, square, a rectangle with rounded corners, or an ellipse. The substrate of the cylinder may extend in the horizontal xy plane, but the side walls of the cylinder may be perpendicular to the substrate and extend, for example, parallel to the z direction. The substrate may correspond to a carrier that moves downward relative to the side walls during the additive manufacturing process.

[0018] The build cylinder fixture may comprise, for example, a plate on which the build cylinder is mounted (i.e., attached). Mounting may be carried out via one or more mounting members such as screws, pins, or clamps. Mounting may ensure a stable but removable connection between the build cylinder and the build cylinder fixture. The build cylinder fixture may be attached to operating means such as at least one or more motors, at least one or more actuators, or at least one or more vibrators. In particular, the build cylinder fixture may be attached to a robot end effector.

[0019] The fact that the substrate holds the workpiece may mean that the workpiece was created on the substrate during the additive manufacturing process. Therefore, the workpiece may be directly connected to the substrate, as the first layer of the workpiece is directly bonded to the substrate. However, the workpiece may also be indirectly bonded to the substrate via one or more support structures extending from the substrate to the workpiece. Furthermore, the workpiece may be attached to and fixed to the substrate after the additive manufacturing process. Finally, the workpiece may simply be held in place by gravity on the substrate, in which case the workpiece is entirely surrounded by residual powder.

[0020] According to this disclosure, residual powder may refer to unsolidified (or unbonded) powder within the internal space of the build cylinder. In other words, residual powder is powder that was applied to the substrate during the additive manufacturing process but was neither solidified nor bonded during the additive manufacturing process. The unpacking station aims to remove residual powder from the workpiece as completely as possible.

[0021] The foil may be transparent. In this way, the user and / or a camera may observe the workpiece inside the foil and monitor the progress of powder removal from the workpiece. The foil may be disposable to ensure purity and safety during the transport / powder removal process. The foil may be in the form of a bag or a large pouch.

[0022] The foil may be attached such that the opening of the foil is attached to the build cylinder fixture and / or the substrate. The opening of the foil may be the opening of the space formed by the foil. In other words, when the opening is closed, the foil may form a sealed space. However, for example, when the foil is provided in the form of a tubular foil, the foil may have a plurality of openings. The opening may be provided with an opening such as a hole. When the opening is attached, the entire edge region of the opening may be attached. For example, the entire edge of the hole formed in the opening may be attached.

[0023] The attachment may be performed airtightly. The foil may be attached to only one of the build cylinder fixture and the substrate, or may be attached to both of them. For example, the foil may first be attached to the build cylinder fixture (e.g., in a non-airtight manner), and then be airtightly attached to the substrate.

[0024] The workpiece may be surrounded by the foil such that there is a workpiece within the internal space formed by the foil. However, this does not necessarily mean that the workpiece is entirely surrounded by the foil and that the workpiece is within the sealed space formed by the foil. For example, when the foil is a tubular foil and the workpiece is disposed within the inner portion (i.e., the internal space) of the tubular foil, the workpiece is surrounded by the foil. Therefore, after the attachment step, it may be said that "the three-dimensional workpiece is surrounded by the foil" or "the three-dimensional workpiece is surrounded along the side by the foil".

[0025] This method may further include the step of separating the substrate from the build cylinder while the foil is attached to the build cylinder fixture and / or the substrate.

[0026] The step of separating the substrate from the build cylinder may include the step of separating the substrate from the side wall. The step of separating the substrate from the build cylinder may be performed by moving the substrate in a direction parallel to the side wall with respect to the side wall. During this movement, the workpiece may remain surrounded by the foil.

[0027] The foil may be a tubular foil. In the attachment step, the opening of the tubular foil may be attached to the build cylinder fixture and / or the substrate. The opening of the foil may correspond to one of the two opposite ends of the tubular foil.

[0028] Regarding the opening, refer to the above description. The tubular foil may be an endless foil. In other words, the tubular foil may be configured to be used in a plurality of steps according to the first aspect, for example, at least 10 steps, at least 20 steps, at least 50 steps or at least 100 steps. The extension in the direction between both ends of the tubular foil in the unfolded state may be at least 5 times the diameter of the opening, at least 10 times the diameter of the opening, at least 20 times the diameter of the opening, at least 30 times the diameter of the opening, at least 50 times the diameter of the opening or at least 100 times the diameter of the opening.

[0029] This method may further include, after the step of separating the substrate from the build cylinder, clamping the tubular foil in the region of the tubular foil between one and the other of the two opposite ends, such that the tubular foil forms a sealed space around the three-dimensional workpiece. Clamping may refer to the step of separating the space of the tubular foil into separate spaces. The clamping may be airtight optionally without allowing powder to pass through. The clamping may be performed using teaching members such as wires, rubber bands, cable fasteners, clamps, etc. Alternatively, the clamping may be performed by forming a knot. After the clamping step, the separated space may be separated from the remaining part of the tubular foil.

[0030] This method may further include, after the step of separating the substrate from the build cylinder, a step of shrinking the foil surrounding the three-dimensional workpiece, for example, to reduce the amount of gas trapped inside the foil.

[0031] The opening of the tubular foil may be attached to the substrate by fastening the tubular foil between the fastening device and the substrate using a fastening device that surrounds the substrate.

[0032] The substrate may have circumferential grooves into which the fastening device engages. The fastening device may include wires, rubber bands, cable ties, clamps (e.g., metal), etc. The fastening device is configured to apply radial force to the substrate, thereby fastening the tubular foil to the substrate. The fastening device is powder-proof and optionally airtight.

[0033] This method may further include the step of removing the circuit board from the build cylinder fixture.

[0034] The substrate may be removed along with the foil that forms a sealed space around the workpiece. After the substrate is removed, it may be moved to an additional station for storage or post-processing.

[0035] This method may further include the step of reusing the build cylinder fixture in an additional step, in accordance with the method of claim 1.

[0036] Therefore, additional build cylinders may be mounted on the build cylinder fixture. Thus, the build cylinder fixture may remain part of the unpacking station, while the movable build cylinders are transported from the additive manufacturing unit to the unpacking station.

[0037] The tubular wheel may be stored in a folded state in the wheel storage compartment. The wheel storage compartment may surround at least a portion of the build cylinder. Alternatively, the wheel storage compartment may be located below the build cylinder.

[0038] The diameter of the wheel housing may be greater than the diameter of the build cylinder (or more precisely, the diameter of the substrate). The wheel housing may be ring-shaped. As used herein, the term "ring-shaped" may include not only circular rings but also non-circular rings, such as square rings. In other words, the wheel housing may be said to surround the periphery.

[0039] This method may also include steps to prevent or reduce static electricity on the foil. Separately, it may include a method for discharging static electricity from the foil.

[0040] This method may further include the step of removing the lid of the build cylinder and replacing the lid with a funnel.

[0041] When closed, the lid can airtightly seal the build cylinder. Furthermore, the funnel can airtightly seal the build cylinder. For this purpose, the funnel may be equipped with a valve that can be closed during replacement.

[0042] This method may further include a step after the mounting step of rotating the build cylinder around a horizontal axis to position the build cylinder upside down.

[0043] The instruction "after steps A and B" does not necessarily mean that step B follows immediately after step A. Another step may be performed between A and B. The inverted position may mean that the build cylinder rotates 180 degrees around the horizontal axis. In other words, in the inverted position, the base plate of the build cylinder faces upward. The funnel (if attached) may face downward in the inverted position. Additional motion (e.g., vibration, rotation, etc.) may be performed before the inverted state is reached.

[0044] This method may further include the step of opening the valve of the funnel so that at least a portion of the residual powder flows downward into the storage container.

[0045] In other words, residual powder may flow from the build cylinder through the funnel into the storage container. The storage container may optionally be airtightly connected to the funnel to prevent the powder from passing through.

[0046] The downward-flowing powder may pass through at least one sieving station to remove coarse particles from the powder.

[0047] The sieving station may be configured to remove coarse particles from residual powder, such as clumps, droplets, and partially solidified powder. This prevents coarse particles from flowing into the storage container. This may reduce the number of additional processing steps required to recycle the powder in the storage container.

[0048] The installation and separation steps may be performed in an inverted position.

[0049] Therefore, the workpiece may be pulled out of the build cylinder (upward) while in an upside-down position.

[0050] This method may further include steps of vibrating and / or rotating the build cylinder and / or substrate. The tool for vibrating the build cylinder or substrate may be included in the build cylinder fixture or may be supplied from outside the wheel.

[0051] After the build cylinder is mounted in the build cylinder fixture, any vibration and / or rotation of the build cylinder may cause residual powder to be drawn away from the workpiece. This may facilitate the removal of residual powder.

[0052] This method may further include, after the mounting step, the step of inserting the tip of a vacuum device into the opening of the wheel and using the vacuum device to vacuum-suction the internal area of ​​the wheel to remove at least a portion of the residual powder.

[0053] The vacuum device may be a vacuum cleaner. The opening may be formed, for example, by cutting. Furthermore, the opening may already be present in the foil when the foil is attached. Similar to vacuum suction, other operating steps (e.g., brushing, blowing, etc.) may be performed through the opening and / or additional openings in the foil.

[0054] This method further includes the steps of removing a fastening device and attaching a powder capture device to a tubular wheel, the powder capture device having a powder inlet with an inwardly facing side wall, and rotating a build cylinder around a horizontal axis so that at least a portion of the residual powder is captured within the powder capture device.

[0055] The inlet may form a substantially unidirectional path for the powder. The inlet may be formed in the form of a funnel facing inward toward the powder capture device.

[0056] This method may further include the step of clamping a portion of the tubular foil with the lower part of the tubular foil in an inverted position so that at least a portion of the residual powder is trapped in the sealed space formed by the tubular foil.

[0057] In other words, the lower part of the tubular foil, where residual powder has accumulated due to gravity, is held in place by the remaining space. In this way, when the build plate or build cylinder is returned to its original upright position (not upside down), this powder will not fall back onto the substrate and / or into the build cylinder.

[0058] The foil may be impermeable to powders. Optionally, the foil may be airtight, particularly to at least one of argon, nitrogen, and air. The impermeability of the foil means that powders cannot pass through it. Therefore, when an impermeable foil forms a sealed space, powders will not flow out of the sealed space of the foil into the ambient atmosphere. Furthermore, according to at least one embodiment, when the foil forms a sealed space filled with an inert gas (such as argon or nitrogen), the inert gas will not flow out of the sealed space, and air from the ambient atmosphere will not flow into the sealed space.

[0059] According to a second embodiment, an apparatus for removing powder from a three-dimensional workpiece produced by additive manufacturing is provided. This apparatus comprises a build cylinder holder for mounting a build cylinder onto a build cylinder holder, and a ring-shaped foil storage section containing a tubular foil.

[0060] The ring-shaped wheel storage section may be configured to surround at least a portion of the build cylinder when the build cylinder is mounted on a build cylinder fixture.

[0061] The foil may be impermeable to powders. Optionally, the foil may be airtight, particularly to at least one of argon, nitrogen, and air.

[0062] Any of the optional features and details discussed above regarding the method of the first embodiment can be applied to the features of the apparatus of the second embodiment as needed. More precisely, the apparatus for powder removal may include one or more of the elements discussed above regarding the embodiment of the method.

[0063] For example, the apparatus may include at least one build cylinder as described above. The build cylinder may include at least one lid as described above. The apparatus may include at least one funnel as described above. The apparatus may include at least one operating device for inverting the build cylinder. [Brief explanation of the drawing]

[0064] Preferred embodiments of the present invention will be described in further detail with reference to the accompanying schematic diagrams. [Figure 1] Figure 1 shows a schematic diagram of an apparatus for manufacturing three-dimensional workpieces by additive manufacturing using interchangeable build cylinders. [Figure 2] Figure 2 shows a schematic side view of a method for removing powder from a three-dimensional workpiece produced by additive manufacturing in accordance with this disclosure. [Figure 3] Figure 3 shows a schematic side view of a method for removing powder from a three-dimensional workpiece produced by additive manufacturing in accordance with this disclosure. [Figure 4] Figure 4 shows a schematic side view of a cross-section of an alternative method for removing powder from a three-dimensional workpiece produced by additive manufacturing according to this disclosure. [Figure 5] Figure 5 shows a schematic side view illustrating the details of the build cylinder, wheel, and workpiece. [Figure 6] Figure 6 shows a schematic side view of a workpiece surrounded by foil, along with a powder capture device. [Figure 7] Figure 7 shows a flowchart of a method for removing powder from a three-dimensional workpiece produced by additive manufacturing according to this disclosure. [Modes for carrying out the invention]

[0065] Figure 1 shows a schematic diagram of an apparatus 10 for manufacturing a three-dimensional workpiece 12. The apparatus 10 is well known to those skilled in the art and may be, for example, a typical additive manufacturing apparatus.

[0066] Therefore, only a brief explanation of the principle of the apparatus 10 will be given. For example, such an apparatus 10 is an apparatus for selective laser melting or selective laser sintering, which can selectively irradiate and solidify a subsequent raw material powder layer using one or more laser beams 14.

[0067] An example of a device 10 that performs the selective laser melting process described below is provided. Typical features of powder bed fusion include coating raw material powder in layers and selectively irradiating each layer to solidify it, thereby generating one layer of the workpiece 12 to be manufactured. After removing excess powder, the final workpiece 12 is obtained through optional post-processing steps (for example, a step to remove residual powder from the workpiece 12, a step to remove one or more support structures).

[0068] Figure 1 shows an apparatus 10 for manufacturing a three-dimensional workpiece 12 by selective laser melting. The apparatus 10 comprises a process chamber 16. The process chamber 16 can be sealed from the ambient atmosphere, i.e., the environment surrounding the process chamber 16. A powder coating apparatus 18 located within the process chamber 16 is responsible for coating the raw material powder onto the carrier 20 (also referred to herein as the substrate 20). A vertical movement unit 22 is provided to move the carrier 20 vertically, so that as the construction height of the workpiece 12 increases, the raw material powder is layered onto the carrier 20 and the carrier 20 can be moved vertically downward.

[0069] Instead of a movable carrier 20, the carrier 20 may be provided as a stationary (or fixed) carrier (particularly with respect to the vertical Z direction). In this case, the irradiation device 24 (see below) and the process chamber 16 are configured to move upward during the construction process (i.e., as the construction height of the workpiece 12 increases). Furthermore, both the carrier 20 and the irradiation device 24 may be independently movable along the Z direction.

[0070] The surface of the carrier 20 defines a horizontal plane (xy plane), and the direction perpendicular to this plane is defined as the vertical direction or the construction direction (z direction). Therefore, each uppermost layer of the raw material powder and each layer of the workpiece 12 extend in a plane parallel to the horizontal plane (xy plane) defined above.

[0071] The apparatus 10 further includes a gas inlet 26 for supplying an inert gas (e.g., argon) to the process chamber 16. A gas outlet (not shown) may be provided to generate a continuous gas flow through the process chamber 16 by implementing a gas circuit. In a preferred embodiment, a unidirectional laminar flow is generated over the top raw material powder layer.

[0072] The apparatus 10 further comprises an irradiation device 24 (also called an irradiation unit or optical unit) for selectively irradiating the uppermost layer of raw material powder coated on the carrier 20 with a laser beam 14. The irradiation device 24 allows the raw material powder coated on the carrier 20 to be selectively irradiated with a laser according to the desired shape of the workpiece 12 to be manufactured.

[0073] The irradiation device 24 includes a scanning unit 30 configured to selectively irradiate a raw material powder coated on a carrier 20 with a laser beam 14. The scanning unit 30 is controlled by a control unit 40 of the device 10. The scanning unit 30 may include one mirror that can be tilted with respect to two orthogonal axes. Alternatively, the scanning unit 30 may include two tiltable mirrors, each configured to tilt with respect to a corresponding axis. The tiltable mirrors may be, for example, galvanometer mirrors.

[0074] The irradiation device 24 is supplied with laser light from the laser light source 32. The laser light source 32 may be located inside the irradiation device 24 or outside the irradiation device 24, as shown in Figure 1. If located inside, the laser light source 32 can be considered part of the irradiation device 24. If located outside, the laser beam is generated by the laser light source 32 and guided to the irradiation device 24 via the optical fiber 34. Alternatively, the laser beam may be guided to the irradiation device 24 via air or vacuum, for example, using one or more mirrors.

[0075] The laser beam is directed from the laser light source 32 to the scanning unit 30. The laser light source 32 may include, for example, a diode-pumped ytterbium fiber laser that emits laser light at a wavelength of approximately 1070-1080 nm (i.e., within the infrared wavelength range).

[0076] The irradiation device 24 further comprises two lenses 36 and 38 configured to focus the laser beam 14 to a desired focal position along the Z axis. In the embodiment shown in Figure 1, both lenses 36 and 38 have positive refractive power. Lens 38, located further upstream in the beam path, is configured to collimate the laser light emitted by the fiber 34, resulting in a collimated or substantially collimated laser beam. Lens 36, located further downstream in the beam path, is configured to focus the collimated (or substantially collimated) laser beam to a desired Z position.

[0077] The control unit 40 includes a processor and memory, in which instructions for controlling the individual components of the apparatus 10 are stored. For example, the control unit 40 may be configured to control one or more of the vertical movement unit 22, the powder coating device 18, the gas flow supplied by the gas inlet 26, and the irradiation device 24. User input and output interfaces are provided and may be connected to or connectable to the control unit 40. Furthermore, the control unit 40 has an interface for receiving workpiece data representing the three-dimensional shape of the workpiece 12 to be manufactured.

[0078] The substrate 20 is part of the build cylinder 42, which includes the substrate 20 and the side wall 28. The side wall 28 is vertical and extends parallel to the Z direction, and together with the substrate 20, forms the space in which the workpiece 12 is placed when the construction process is complete. Furthermore, unsolidified raw material powder, also called residual powder, surrounds the workpiece 12. The build cylinder 42 of the apparatus 10 is replaceable. That is, the build cylinder 42 (i.e., at least the side wall 28 and the substrate 20) can be removed from the apparatus 10 and transported to one or more post-processing stations for further processing. For example, the build cylinder 42 can be moved to an unpacking station to remove powder from the workpiece 12, as will be described later.

[0079] Before removing the build cylinder 42 from the process chamber 16, the build cylinder 42 may be closed with a lid (44, not shown in Figure 1) to maintain an inert gas atmosphere inside the build cylinder 42. For example, during the construction process, the process chamber 16 and the build cylinder 42 may be filled with an inert gas such as argon. The lid 44 of the build cylinder 42 prevents the inert gas from leaking out of the build cylinder 42 and prevents air from entering the build cylinder 42 when the build cylinder 42 is removed from the apparatus 10.

[0080] The following describes embodiments of a method for removing powder from the workpiece 12. The term "removal of powder from the workpiece" generally refers to the removal of residual powder from the build cylinder 42. Such a process may be carried out at a station specifically designed for powder removal, also called an unpacking station. After powder removal, the workpiece 12 may be moved to one or more additional stations for further processing. At these stations, for example, any remaining residual powder may be removed from the workpiece 12.

[0081] Figure 2 shows the first of two parts of a powder removal method according to an embodiment of the present disclosure. Figure 3 shows the second part. The individual steps of the method are labeled (a) to (r) and are performed in the order shown. Steps (a) to (r) are discussed in detail here. In the figures, if not all elements are labeled with reference numerals, the same elements retain the previously assigned reference numerals.

[0082] In the first step (a), the build cylinder 42 is mounted on the build cylinder fixture 46. In this state, the build cylinder 42 is closed by the lid 44 and an inert gas atmosphere is maintained inside the build cylinder 42. The build cylinder 42 is secured to the fixture 46 by appropriate fastening means that allow for a removable connection. Furthermore, the connection must be strong enough to allow the build cylinder 42 to rotate through the fixture 46. For example, screws, bolts, clamps, etc., may be used as fastening means. The build cylinder fixture 42 may be a simple element such as a plate, or may have simple elements.

[0083] In step (b), the lid 44 is removed and replaced with a funnel 48. The funnel 48 is positioned in the upper opening of the build cylinder 42 where the lid 44 was previously positioned. Section (b) also shows a robot end effector 50, with the fixture 46 attached to the end effector 50. The fixture 46 may be attached to the end effector 50 in a step of the process (e.g., step (b)) or may have been attached to the end effector 50 throughout the process (i.e., in step (a), although not shown). The robot end effector 50 allows the build cylinder to be moved around at least one axis (in particular, around the horizontal axis) via the fixture 46. In an alternative embodiment, the build cylinder fixture 46 and the robot end effector 50 form a single integrated element.

[0084] In step (c), the build cylinder 42 is inverted via the movement of the end effector 50. More precisely, the end effector 50, and thus the build cylinder 42, rotates 180° around the horizontal axis, resulting in the build cylinder 42 being inverted. In other words, the opening of the build cylinder 42, which was facing upward (upright) at the start of the process, faces downward in the inverted position. Step (c) may also involve movements around other axes (e.g., horizontal or vertical) in addition to the additional movement around the horizontal axis. Furthermore, step (c) may include a step of vibrating the end effector 50 to shake off powder from the workpiece 12. At the end of step (c), when the build cylinder 42 is inverted, a certain amount of residual powder accumulates at the bottom of the funnel 48.

[0085] In step (d), the storage container 54 is connected to the funnel 48 via a connecting member 52 such as a clamp. The storage container 54 is positioned below the build cylinder 42 and the funnel 48, so that when the valve (not shown) of the funnel 48 is opened, any residual powder from the funnel 48 falls into the storage container 54. The storage container 54 has an opening that fits the outlet of the funnel 48. For example, the top of the storage container 54 may have the shape of an inverted funnel (see Figure 2).

[0086] In step (e), additional rotational motion along one or more axes and / or lateral motion along one or more directions are performed. This draws any residual powder remaining in the build cylinder 42 after step (d) away from the workpiece 12 and / or the build cylinder 42, causing it to fall downward into the funnel 42, which is then closed again by its valve.

[0087] In step (f), the storage container 54 is reconnected, just as in step (d), and the residual powder accumulated in step (e) falls into the storage container 54.

[0088] In step (g), a wheel storage section 58 is provided. The wheel storage section 58 is ring-shaped in the sense that it surrounds the build cylinder 42. In other words, the wheel storage section 58 surrounds the periphery. For this reason, the wheel storage section 58 may be, for example, square, rectangular, or circular. The wheel storage section 58 holds a tubular wheel 56. In other words, the tubular wheel 56 is stored in the wheel storage section 58 in a folded form. The wheel 56 is transparent and may also be called an endless wheel. The term endless wheel refers to the fact that it can be used in multiple processes, not just one. In each process, only a portion of the endless wheel 56 is used and removed, but the remaining portion of the endless wheel 56 remains in the storage section 58 and can be used in the next process.

[0089] In an alternative method, the wheel storage section 58 may already be attached to the build cylinder fixture 46 when the build cylinder 42 is installed in step (a), or it may be part of the fixture. Furthermore, the wheel storage section may be provided in any of steps (b) to (d).

[0090] A rack 60 is provided below the build cylinder 42, and in step (g), the build cylinder 42 moves downward toward the rack 60.

[0091] In step (h), the build cylinder 42 is placed on the rack 60 and held in place by the rack 60.

[0092] In step (i), the substrate 20 is released from the rest of the build cylinder 42. More precisely, the releaseable connection between the substrate 20 and the side wall 28 is released.

[0093] In step (j), the build cylinder fixture 46 moves upward together with the substrate 20 mounted on the build cylinder fixture 46 and the workpiece 12 held by the substrate 20.

[0094] As shown in Figure 3, the end of the ring-shaped wheel 56 is attached to the build cylinder fixture 46 via mounting means 64 (such as a clamp). Since a second connection of the end of the ring-shaped wheel 56 is made to the substrate 20, the connection of the wheel 56 to the fixture 46 may not be powder-impermeable or airtight. The connection between the wheel 56 and the substrate 20 is made using a fastening device 62 surrounding the substrate 20. In this way, the fastening device 62 fastens the wheel 56 between the substrate 20 and the fastening device 62. A groove may be provided in the substrate 20 so that the fastening device 62 engages with the groove. The connection between the wheel 56 and the substrate 20 is powder-impermeable or airtight with respect to the atmosphere in which the workpiece 12 is located and the ambient atmosphere (e.g., air).

[0095] The connection of the wheel 56 to the build cylinder fixing device 46 may be performed in step (j), or, for example, in step (g), in which the wheel housing 58 is provided.

[0096] In step (k), the build cylinder fixture 46 moves further upward together with the substrate 20 and the workpiece 12, so that the workpiece 12 is surrounded by the wheel 56. In other words, the wheel 56 surrounds the workpiece 12 along its sides, and a sealed atmosphere is ensured as the funnel 48 closes the atmosphere in which the workpiece 12 is placed from below.

[0097] In step (l), the tubular wheel 56 is clamped by a clamping member 66 such as a cable tie, adhesive tape, or clamp. The clamping ensures that a sealed atmosphere exists around the workpiece 12 even after the wheel is cut (as shown through the scissors in Figure 3). To maintain the atmosphere inside the build cylinder 42, the wheel 56 may be clamped using a second clamping member 66 between the two clamping members 66, 68 before the wheel is cut. Optionally, the wheel is twisted around its vertical axis to reinforce the clamping.

[0098] In step (m), the build cylinder fixture 46 is lifted further upward from the build cylinder 42. The workpiece 12 is completely surrounded by the clamped wheel 56, thereby forming a sealed atmosphere around the workpiece 12.

[0099] In step (n), the fastener 46 rotates back to its original upright position (i.e., rotates 180° around the horizontal axis). The wheel is cut between the mounting means 64 and the fastening device 62.

[0100] In step (o), the substrate 20 is removed from the fastener 46 along with the workpiece 12 surrounded by the wheel 56.

[0101] In step (p), the new circuit board 20 is attached to the fixing device 46.

[0102] In step (q), the fastener 46 rotates back to its upside-down position, and the new substrate 20 is joined to the side wall 28 of the build cylinder 42.

[0103] In step (r), the build cylinder 42, equipped with a new substrate 20, rotates around the horizontal axis to return to an upright position. The build cylinder 42 (replaceable build cylinder 42) can now be reused in a new construction step in the additive manufacturing process.

[0104] Regarding the method described above, please note that steps (e) and (f) are optional. Furthermore, the step of attaching the wheel 56 to the fastener 46 is optional. Depending on the situation, it may be sufficient to simply attach the wheel 56 to the substrate 20.

[0105] Figure 4 shows the steps of a second embodiment, which can be considered an alternative method compared to the methods in Figures 2 and 3. Figure 4 shows three steps (A) to (C) that are performed after step (f) of the methods in Figures 2 and 3. Therefore, up to step (f), the method of the second embodiment is the same as the method of the first embodiment.

[0106] However, in the second embodiment, the build cylinder 42 does not remain in the upside-down position as shown in Figure 4(A), but is returned to the upright position. Furthermore, considering steps (A) to (C), the support column 46 shown in Figure 4 is the build cylinder fixing device 46.

[0107] In step (A), the build cylinder 42 is mounted on the build cylinder fixture 46. Furthermore, a wheel 56 is attached to the upper end of the side wall 28. In this case, the wheel 56 may be tubular (i.e., having two openings), flat, or bag-shaped (i.e., having one opening). In step (A), the wheel 56 completely covers the space inside the build cylinder 42.

[0108] In step (B), the side wall 28 of the build cylinder 42 is lowered. Separately, the substrate 20 is lifted upward relative to the side wall 28. The wheel 56 remains attached to the upper end of the side wall 28.

[0109] Step (C) is performed when the substrate 20 substantially reaches the height of the upper edge of the side wall 28. In step (C), the wheel 56 is removed from the side wall 28 and attached to the substrate 20 on which the workpiece 12 is mounted. The workpiece 12 is now completely surrounded by the wheel 56 in a sealed space.

[0110] In the next step, the substrate 20 may be removed from the build cylinder fixture 46 and processed further.

[0111] Figure 5 shows a schematic side view of the build cylinder 42 according to the method of the first embodiment, i.e., a view in which the wheel 56 is mounted in an upside-down position.

[0112] Figure 5 may correspond to step (j) in Figure 3. In addition to the elements discussed above with respect to Figures 2 and 3, an antistatic brush 70 may be provided in the outlet area of ​​the wheel storage section 58. This prevents electrostatic charging of the wheel 56 and prevents powder from adhering to the wheel 56.

[0113] Furthermore, to prevent the foil 56 from becoming electrostatically charged, an antistatic coating may be applied to the foil 56. Disposable foil may be used as the foil 56.

[0114] To secure the wheel 56 to the substrate 20, the following may be applied according to step (j) or (C) above: The wheel 56 is attached to the substrate 20 using a high-density fastener 62. For example, rubberized metal elements may be used, and the fastener 62 surrounds the substrate 20. The fastener may be rubberized to improve airtightness and prevent slippage.

[0115] An opening may be provided in the foil 56 as a gas inlet. An inert gas may be supplied to the space inside the foil. Furthermore, an opening may be provided in the foil 56 for inserting the tip of the vacuum device into the foil and operating the vacuum device within the space enclosed by the foil. One or more sieving devices may be provided in the funnel 48 to separate coarse particles from the residual powder.

[0116] Figure 6 shows an arrangement applicable to both the first and second embodiments. In the upright position of the workpiece 12, the powder capture device 72 is attached to the top of the wheel 56. For example, the clamping member 66 of step (l) may be the powder capture device 72. Alternatively, the powder capture device 72 may be attached later, for example, by removing the clamping member 66.

[0117] The powder capture device 72 is held by a retaining bracket 74, so as a result, the powder capture device 72 does not fall onto the workpiece 12. The powder capture device 72 has a powder inlet with side walls facing inward, i.e., toward the internal space of the powder capture device 72. In the upright position, powder is captured in areas other than these side walls. In the upside-down position, powder can pass through the powder inlet and flow into the powder capture device 72.

[0118] Therefore, if a powder capture device 72 is installed, the workpiece 12 can be rotated one or more times around one or more horizontal axes in order to collect as much residual powder as possible in the powder capture device 72. In other words, the workpiece 12 (and the entire system shown in Figure 6) can be rotated in an inverted position and an upright position several times in succession. The rotation of the system may be visually controlled by the operator because the wheel 56 is transparent. Furthermore, vibration may be applied. Furthermore, the internal space within the wheel 56 may be filled with argon.

[0119] Furthermore, in all embodiments discussed herein, one or more of the following powder processing steps may be carried out within a space enclosed by the foil 56.

[0120] The space may be filled with argon. The wheel 56 may have one or more openings (e.g., an opening for operation). A vibrator may be installed on the workpiece 12 from the outside through the wheel 56. For example, manual operation of the workpiece 12 is possible through the wheel 56. The wheel 56 may have an opening for a vacuum device. A blower can be installed below the wheel 56. In an inverted position, the lower part of the wheel 56 may be clamped, for example by twisting, to capture the powder at its lower part. In this way, residual powder may be separated from the remaining space in the wheel 56. The powder capture 72 discussed above may be attached to the end of the wheel 56. An outlet system may be provided via a tube provided at the end of the tubular wheel 56.

[0121] Figure 7 shows a flowchart of a method for removing powder from a three-dimensional workpiece produced by additive manufacturing according to this disclosure. The method includes step 80 of mounting a build cylinder onto a build cylinder fixture. The build cylinder comprises a substrate that holds the three-dimensional workpiece and side walls that are detachably attached to the substrate. The build cylinder contains residual powder from the additive manufacturing process of the three-dimensional workpiece. The method further includes step 82 of attaching a foil to the build cylinder fixture and / or the substrate. The details discussed above may be applied to the method in Figure 7.

[0122] One or more embodiments of this technology may have at least one of the following advantages: By providing the foil 56, the workpiece 12 can be contained within a sealed (e.g., inert) space for the entire duration of the process or at least most of it. This may reduce or avoid contact between the workpiece and / or residual powder and the ambient atmosphere. Residual powder can be efficiently removed. Furthermore, contamination of the ambient atmosphere may be reduced, thereby improving operational safety.

Claims

1. A method for removing powder from a three-dimensional workpiece produced by additive manufacturing, wherein the method is: A step of mounting a build cylinder to a build cylinder fixture, wherein the build cylinder comprises a substrate for holding the three-dimensional workpiece and side walls detachably attached to the substrate, and the build cylinder contains residual powder from the additive manufacturing process of the three-dimensional workpiece, A method comprising the step of attaching a tubular foil to the build cylinder fixture and / or the substrate, wherein the three-dimensional workpiece is surrounded by the tubular foil in such a manner that the three-dimensional workpiece is located within the internal space formed by the tubular foil.

2. The method according to claim 1, further comprising the step of separating the substrate from the build cylinder while the tubular wheel remains attached to the build cylinder fixture and / or the substrate.

3. In the mounting step, the opening of the tubular wheel is attached to the build cylinder fixing device and / or the substrate. The method according to claim 2, wherein the opening of the tubular foil corresponds to one of the two opposing ends of the tubular foil.

4. The method according to claim 3, further comprising the step of, after the step of separating the substrate from the build cylinder, clamping the tubular foil in the region of the tubular foil between one end and the other of the two opposing ends, so that the tubular foil forms a sealed space around the three-dimensional workpiece.

5. The method according to claim 4, wherein the opening of the tubular foil is attached to the substrate by fastening the tubular foil between the fastening device and the substrate using a fastening device that surrounds the substrate.

6. The method according to claim 3, further comprising the step of removing the substrate from the build cylinder fixing device.

7. The method according to claim 1, further comprising the step of reusing the build cylinder fixture as an additional step according to the method according to claim 1.

8. The method according to claim 3, wherein the tubular wheel is stored in a folded state within the wheel storage section, and optionally the wheel storage section surrounds at least a portion of the build cylinder.

9. The method according to claim 1, further comprising the step of removing the lid of the build cylinder and replacing the lid with a funnel.

10. The method according to claim 2, further comprising the step of rotating the build cylinder around a horizontal axis after the mounting step so that the build cylinder is in an upside-down position.

11. The steps of removing the lid of the build cylinder and replacing the lid with a funnel, The method according to claim 10, further comprising the step of opening the valve of the funnel so that at least a portion of the residual powder flows downward into the storage container.

12. The method according to claim 11, wherein the downward-flowing powder passes through at least one sieving station to remove coarse particles from the powder.

13. The method according to claim 10, wherein the mounting step and the separation step are performed in the inverted position.

14. The method according to claim 1, further comprising the step of vibrating and / or rotating the build cylinder and / or the substrate.

15. The method according to claim 1, further comprising the step of inserting the tip of a vacuum device into the opening of the tubular foil after the mounting step, and using the vacuum device to vacuum-suction the internal region of the tubular foil to remove at least a portion of the residual powder.

16. The steps include removing the fastening device and attaching the powder capture device to the tubular wheel, wherein the powder capture device has a powder inlet portion with an inwardly facing side wall, The method according to claim 5, further comprising the step of rotating the build cylinder around a horizontal axis so that at least a portion of the residual powder is captured in the powder capture device.

17. The method according to claim 10, further comprising the step of clamping a portion of the tubular foil with the lower part of the tubular foil in the inverted position described above, so that at least a portion of the residual powder is trapped in the sealed space formed by the tubular foil.

18. The method according to claim 1, wherein the tubular foil is impermeable to powder, and optionally, the tubular foil is airtight to at least one of argon, nitrogen, and air.

19. An apparatus for removing powder from a three-dimensional workpiece produced by additive manufacturing, wherein the apparatus is A build cylinder fixing device for mounting a build cylinder, wherein the build cylinder comprises a base plate for holding a three-dimensional workpiece, A device comprising: a wheel storage section for storing a tubular wheel, wherein the wheel storage section is configured such that the three-dimensional workpiece can be surrounded by the tubular wheel in such a way that the three-dimensional workpiece is located within the internal space formed by the tubular wheel.

20. The apparatus according to claim 19, wherein the wheel storage section is configured to surround at least a portion of the build cylinder when the build cylinder is mounted on the build cylinder fixing device.

21. The apparatus according to claim 19, wherein the tubular foil is impermeable to powder, and optionally, the tubular foil is airtight to at least one of argon, nitrogen, and air.

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