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 produced by additive manufacturing, which can be considered as part of the so-called unpacking process of the three-dimensional workpiece. The additive manufacturing process is powder bed fusion, such as, but not limited to, selective laser sintering, selective laser melting, or electron beam melting. [Background technology]

[0002] Powder bed fusion is a layering process by which powdered raw materials, in particular metal and / or ceramic raw materials, can be processed into three-dimensional workpieces of complex shape. To this end, a powder layer of the raw material is applied onto a carrier and is site-selectively exposed to radiation (e.g. laser or particle radiation) depending on the desired shape of the workpiece to be produced. The radiation penetrating the powder layer causes heating of the powder particles of the raw material, which results in melting or sintering. Further powder layers of the raw material are then applied successively to the already irradiated layer on the carrier until the workpiece has the desired shape and size. Powder bed fusion can be used to manufacture prototypes, tools, replacement parts, high-value parts or medical prostheses, such as dental or orthopedic prostheses, based on CAD data. Examples of powder bed fusion techniques include selective laser melting, selective laser sintering and electron beam melting.

[0003] Apparatuses for manufacturing one or more workpieces according to the above techniques are known. For example, EP 2961549 A1 and EP 2878402 A1 each describe an apparatus for manufacturing three-dimensional workpieces according to the technique of selective laser melting. The general principles described in such documents can also be applied to the techniques disclosed herein.

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

[0005] Residual powder may refer to the unconsolidated powder in the build cylinder that consolidates and thereby builds the workpiece. After one or more reprocessing steps (washing, drying, sieving, etc.), the residual powder is returned to the build process and a new three-dimensional workpiece is generated from the residual powder.

[0006] Several techniques are known to remove residual powder from the workpiece, for example by moving the side wall of the build cylinder upwards while the substrate of the build cylinder remains on the ground. However, this technique can cause explosive dust clouds. Furthermore, this technique requires an additional axis of movement and requires complex techniques to collect the dripping residual powder in a storage container.

[0007] It is further known to push the substrate upwards on the build cylinder while the side walls of the build cylinder rest on the ground.

[0008] One problem with such prior art techniques is that the workpiece, and any residual powder that may remain thereon, is transported for further processing while at least temporarily exposed to the ambient atmosphere, and further, 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 Summary of the Invention

[0010] It is therefore an object of the present invention to provide a technique that overcomes at least one of the above problems and / or other related problems. In particular, but not by way of limitation, an improved powder removal technique is desired in which the workpiece and residual powder are exposed to the ambient atmosphere as little as possible. In particular, but not by way of limitation, an improved powder removal technique is desired in which contamination of the ambient atmosphere is reduced, thereby improving operational safety.

[0011] This object is addressed by the subject matter of the independent claims. Advantageous embodiments are set forth in the dependent claims.

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

[0013] Additionally, one or more of the following features of the method aspects may be applied to the apparatus of the apparatus aspects described below: In this disclosure, whenever the term "workpiece" is used, it refers to a "three-dimensional workpiece."

[0014] The method may be performed by a powder removal device, which may be part of a so-called unpacking station. The additive manufacturing process that produced the workpiece may be selective laser melting or selective laser sintering, or other process that solidifies and / or bonds powder to form a three-dimensional workpiece.

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

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

[0017] The build cylinder may have an interior space with a generally cylindrical shape. Thus, the cylinder may be cylindrical (with a circular substrate) or the substrate may be, for example, rectangular, square, rectangular with rounded corners, elliptical, etc. The substrate of the cylinder may extend in a horizontal xy plane, while the side walls of the cylinder extend perpendicular to the substrate, for example parallel to the z direction. The substrate may represent a carrier that moves downwards relative to the side walls during the additive manufacturing process.

[0018] The build cylinder fixture may for example comprise a plate to which the build cylinder is mounted (i.e. attached). The mounting may be performed via one or more attachment members such as screws, pins, clamps, etc. The 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 a manipulation means such as at least one or more motors, at least one or more actuators, at least one or more vibration devices, etc. 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 generated on the substrate during the additive manufacturing process. Thus, the workpiece may be directly connected to the substrate, since a 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 and fixed to the substrate after the additive manufacturing process. Furthermore, the workpiece may simply be held by gravity on the substrate, in which case the workpiece is entirely surrounded by the residual powder.

[0020] According to the present disclosure, residual powder may refer to unsolidified (or unbonded) powder in the interior space of the build cylinder. In other words, the residual powder is powder that was applied to the substrate during the additive manufacturing process but was not solidified or bonded during the additive manufacturing process. In the unpacking station, the aim is to remove the residual powder from the workpiece as completely as possible.

[0021] The foil may be transparent. In this way, a user and / or camera may view the workpiece within the foil and monitor the progress of removing the powder from the workpiece. The foil may be a disposable foil to ensure purity and safety during the transport / powder removal process. The foil may be a bag or sachet.

[0022] The foil may be attached such that an opening in the foil is attached to the build cylinder fixture and / or the substrate. The opening in the foil may be an opening in a space formed by the foil. In other words, if the opening is closed, the foil may form an enclosed space. However, there may be multiple openings in the foil, for example when the foil is provided in the form of a tubular foil. The opening may comprise an opening, such as a hole. If the opening is attached, the entire edge area of ​​the opening may be attached. For example, the entire edge of a hole formed in the opening may be attached.

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

[0024] The workpiece may be surrounded by the foil such that the workpiece is within an interior 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 an enclosed space formed by the foil. For example, if the foil is a tubular foil and the workpiece is located within the interior portion (i.e., the interior space) of the tubular foil, the workpiece is also surrounded by the foil. Thus, after the attachment step, it may be said that the "three-dimensional workpiece is surrounded by the foil" or that the "three-dimensional workpiece is laterally surrounded by the foil."

[0025] The method may further include separating the substrate from the build cylinder while the foil remains attached to the build cylinder fixture and / or the substrate.

[0026] Separating the substrate from the build cylinder may include separating the substrate from the sidewall. Separating the substrate from the build cylinder may be performed by moving the substrate relative to the sidewall in a direction parallel to the sidewall. During this movement, the workpiece may remain surrounded by the foil.

[0027] The foil may be a tubular foil. The attachment step may include attaching an opening in the tubular foil to the build cylinder fixture and / or the substrate. The opening in the foil may correspond to one end of two opposing ends of the tubular foil.

[0028] Regarding the openings, see the above description. The tubular foil may be an endless foil. In other words, the tubular foil may be configured to be used for a number of steps according to the first aspect, for example at least 10, at least 20, at least 50 or at least 100 steps. The stretch in the direction between the two 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] The method may further comprise, after the step of separating the substrate from the build cylinder, clamping the tubular foil in a region of the tubular foil between one and the other of the two opposing ends, such that the tubular foil forms a sealed space around the three-dimensional workpiece. Clamping may refer to a process of separating the space of the tubular foil into separate spaces. The clamping may be impermeable to powder and optionally airtight. The clamping may be performed using teaching members such as wires, rubber bands, cable ties, clamps, etc. The clamping may also be performed by forming a knot. After the clamping step, the separated spaces may be cut away from the remaining parts of the tubular foil.

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

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

[0032] The substrate may include a circumferential groove into which the fastening device engages. The fastening device may include wires, rubber bands, cable ties, clamps (e.g., made of metal), and the like. The fastening device is configured to apply a radial force to the substrate, thereby fastening the tubular foil to the substrate. The attachment by the fastening device may be powder-tight and, optionally, air-tight.

[0033] The method may further include removing the substrate from the build cylinder fixture.

[0034] The substrate may be removed together with the workpiece and the foil forming an enclosed space around the workpiece. After removing the substrate, the substrate may be moved to an additional station for storage or post-processing.

[0035] The method may further comprise the step of reusing the build cylinder fixture for additional processes in accordance with the method of claim 1.

[0036] For this purpose, an additional build cylinder may be mounted on the build cylinder fixture, so that the build cylinder fixture can remain part of the unpacking station, while a movable build cylinder is brought from the additive manufacturing apparatus to the unpacking station.

[0037] The tubular foil may be stored in a folded form in a foil storage section, which may surround at least a portion of the build cylinder, or alternatively, the foil storage section may be arranged below the build cylinder.

[0038] The diameter of the foil container may be larger than the diameter of the build cylinder (or more precisely, the diameter of the substrate). The foil container may be ring-shaped. The term ring-shaped as used herein may include not only circular rings but also non-circular rings, such as square rings. In other words, the foil container may be said to be circumferential.

[0039] The method may also include the step of preventing or reducing static electricity on the foil. Alternatively, a method may be included for discharging the foil.

[0040] The method may further include removing a lid from the build cylinder and replacing the lid with a funnel.

[0041] In the closed state, the lid can close the build cylinder airtight. Furthermore, the funnel can close the build cylinder airtight. For this purpose, the funnel can be provided with a valve that is closed when changing.

[0042] The method may further include, after the loading step, rotating the build cylinder about a horizontal axis to place the build cylinder in an upside-down position.

[0043] The provision "after steps A, B" does not necessarily mean that step B follows immediately after step A. Another step may be performed between A and B. The upside-down position may mean that the build cylinder is rotated 180 degrees about a horizontal axis. In other words, in the upside-down position, the substrate on the build cylinder faces up. The funnel (if attached) may face down in the upside-down position. Additional motions (e.g., vibration, rotation, etc.) may be performed before the upside-down state is reached.

[0044] The method may further include opening a valve on the funnel to allow at least a portion of the residual powder to flow downwardly into a storage container.

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

[0046] The downwardly 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 the residual powder, such as clumps, splashes, partially solidified powder, etc., which may prevent the coarse particles from entering the storage bin, potentially reducing additional processing steps to recycle the powder in the storage bin.

[0048] The attachment and detachment steps may be performed in an upside down position.

[0049] Thus, the workpiece may be withdrawn (upwards) from the build cylinder while in an upside down position.

[0050] The method may further include vibrating and / or rotating the build cylinder and / or the substrate. Tooling for vibrating the build cylinder or substrate may be included in the build cylinder fixture or may be provided outside the foil.

[0051] Once the build cylinder is mounted in the build cylinder fixture, any time the build cylinder is vibrated and / or rotated, the residual powder may be pulled away from the workpiece, which may facilitate removal of the residual powder.

[0052] The method may further include, after the attaching step, inserting a tip of a vacuum device into the opening in the foil and using the vacuum device to vacuum an interior region of the foil to remove at least a portion of the residual powder.

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

[0054] The method may further include removing the fastening device and attaching a powder capture device to the tubular foil, the powder capture device having a powder inlet port with an inwardly facing sidewall, and rotating the build cylinder about a horizontal axis such 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 inwards into the powder capture device.

[0056] The method may further include clamping a portion of the tubular foil with a lower portion of the tubular foil in an upside-down position such that at least a portion of the residual powder is trapped within an enclosed space formed by the tubular foil.

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

[0058] The foil may be impermeable to powder. Optionally, the foil may be airtight, in particular to at least one of argon, nitrogen and air. By the foil being impermeable to powder, it is meant that the powder cannot pass through the foil. Thus, if the foil is impermeable to powder and forms a closed space, no powder can escape from the foil's closed space towards the surrounding atmosphere. Furthermore, according to at least one embodiment, if the foil forms a closed space filled with an inert gas (such as argon or nitrogen), the inert gas cannot escape from the closed space and no air from the surrounding atmosphere can enter the closed space.

[0059] According to a second aspect, there is provided an apparatus for removing powder from a three-dimensional workpiece produced by additive manufacturing, the apparatus comprising a build cylinder fixture for mounting a build cylinder to the build cylinder fixture, and a ring-shaped foil housing having a tubular foil housed therein.

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

[0061] The foil may be impermeable to powders. Optionally, the foil may be gas-tight, in particular to at least one of argon, nitrogen and air.

[0062] Any of the optional features and details discussed above with respect to the method of the first aspect may also be applied to the apparatus features of the second aspect, as appropriate. More precisely, the apparatus for powder removal may include one or more of the elements discussed above with respect to the method aspect.

[0063] For example, the apparatus may comprise at least one build cylinder as described above. The build cylinder may comprise at least one lid as described above. The apparatus may comprise at least one funnel as described above. The apparatus may comprise at least one handling device for placing the build cylinder in an upside down position. [Brief description of the drawings]

[0064] Preferred embodiments of the invention will now be described in more detail with reference to the accompanying schematic drawings. [Figure 1] FIG. 1 shows a schematic diagram of an apparatus for producing three-dimensional workpieces by additive manufacturing using exchangeable build cylinders. [Diagram 2] FIG. 2 illustrates, in schematic side view form, a method for removing powder from a three-dimensional workpiece produced by additive manufacturing in accordance with the present disclosure. [Diagram 3] FIG. 3 illustrates, in schematic side view form, a method for removing powder from a three-dimensional workpiece produced by additive manufacturing in accordance with the present disclosure. [Figure 4] FIG. 4 illustrates in cross-section and schematic side view form an alternative method for removing powder from a three-dimensional workpiece produced by additive manufacturing in accordance with the present disclosure. [Diagram 5] FIG. 5 shows a schematic side view showing details of the build cylinder, foil and workpiece. [Figure 6] FIG. 6 shows a schematic side view of a foil-encased workpiece along with a powder capture device. [Figure 7] FIG. 7 illustrates a flow chart of a method for removing powder from a three-dimensional workpiece produced by additive manufacturing in accordance with the present disclosure. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0065] 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] For this reason, only a brief description of the principle of the apparatus 10 will be given. For example, such an apparatus 10 may be an apparatus for selective laser melting or selective laser sintering, in which one or more laser beams 14 may be used to selectively irradiate and solidify a subsequent layer of raw material powder.

[0067] An example of such an apparatus 10 is one that performs the selective laser melting process described below. A typical feature of powder bed fusion is that a raw powder is applied in layers and each layer is selectively irradiated and solidified to produce one layer of the workpiece 12 to be manufactured. After removing excess powder, and optional post-processing steps (e.g., removing residual powder from the workpiece 12, removing one or more support structures), the final workpiece 12 is obtained.

[0068] 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 is sealable against the ambient atmosphere, i.e. the environment surrounding the process chamber 16. A powder application device 18 arranged in the process chamber 16 serves to apply raw powder onto a carrier 20 (also referred to herein as substrate 20). A vertical movement unit 22 is provided, which allows the carrier 20 to be moved vertically, so that as the building height of the workpiece 12 increases, the raw powder is built up in layers on the carrier 20, which can be moved vertically downwards.

[0069] Instead of a movable carrier 20, the carrier 20 may also 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 upwards during the build process (i.e. with an increase in the build height of the workpiece 12). Furthermore, both the carrier 20 and the irradiation device 24 may be independently movable along the Z-direction.

[0070] The carrier surface of the carrier 20 defines a horizontal plane (xy-plane) and the direction perpendicular to this plane is defined as the vertical or build direction (z-direction). Thus, each top layer of feed powder and each layer of the workpiece 12 extends in a plane parallel to the horizontal plane (xy-plane) defined above.

[0071] The apparatus 10 further comprises 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, thereby implementing a gas circuit, to create a continuous gas flow through the process chamber 16. In a preferred embodiment, a unidirectional laminar flow is created above the top feed powder layer.

[0072] The apparatus 10 further includes an irradiation device 24 (also called an irradiation unit or an optical unit) for selectively irradiating the laser beam 14 onto the top layer of the raw material powder applied on the carrier 20. By means of the irradiation device 24, the raw material powder applied on the carrier 20 can be selectively irradiated with the laser depending on the desired form of the workpiece 12 to be manufactured.

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

[0074] The irradiation device 24 is supplied with laser light from a laser source 32. The laser source 32 may be provided inside the irradiation device 24 as shown in FIG. 1, or may be provided externally to the irradiation device 24. If provided internally, the laser source 32 may be considered to be part of the irradiation device 24. If provided externally, the laser beam is generated by the laser source 32 and directed to the irradiation device 24 via an optical fiber 34. Alternatively, the laser beam may be directed to the irradiation device 24 through air or vacuum, for example, using one or more mirrors.

[0075] A laser beam is directed towards the scanning unit 30 from a laser source 32. The laser source 32 may include, for example, a diode-pumped ytterbium fiber laser emitting laser light at a wavelength of approximately 1070-1080 nm (ie, in the infrared wavelength range).

[0076] The illumination 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 Fig. 1, the lenses 36 and 38 both have positive refractive power. The lens 38 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. The lens 36 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 comprises a processor and a 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 motion unit 22, the powder application device 18, the gas flow provided by the gas inlet 26, and the irradiation device 24. User input and output interfaces are provided and may be connected or connectable to the controller 40. Additionally, the control unit 40 has an interface for receiving workpiece data representative of the three-dimensional form of the workpiece 12 to be manufactured.

[0078] The substrate 20 is part of a build cylinder 42, which comprises the substrate 20 and a sidewall 28. The sidewall 28 is vertical, so that it extends parallel to the Z direction and together with the substrate 20 forms a space in which the workpiece 12 is placed once the build process is completed. In addition, unconsolidated raw powder, also called residual powder, surrounds the workpiece 12. The build cylinder 42 of the apparatus 10 is replaceable, i.e., the build cylinder 42 (i.e., at least the sidewall 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 the powder from the workpiece 12, as described below.

[0079] Prior to removal of the build cylinder 42 from the process chamber 16, the build cylinder 42 may be closed with a lid (44, not shown in FIG. 1 ) to maintain an inert gas atmosphere within the build cylinder 42. For example, during the build process, the process chamber 16 and the build cylinder 42 may be filled with an inert gas, such as argon. The lid 44 on the build cylinder 42 may prevent the inert gas from escaping from the build cylinder 42 and may prevent air from entering the build cylinder 42 once the build cylinder 42 is removed from the apparatus 10.

[0080] Below, embodiments of methods for removing powder from the workpiece 12 are discussed. The term "removing powder from the workpiece" generally refers to removing residual powder from the build cylinder 42. Such a process may be performed at a station specifically provided for powder removal, also referred to as an unpacking station. After powder removal, the workpiece 12 may move to one or more additional stations for additional processing. At the stations, for example, any remaining residual powder may be removed from the workpiece 12.

[0081] FIG. 2 illustrates a first of two parts of a powder removal method according to an embodiment of the present disclosure. FIG. 3 illustrates the second part. The individual steps of the method are labeled (a)-(r) and are performed in the order shown. Steps (a)-(r) will now be discussed in detail. In the figures, where not all elements are labeled with reference numbers, it should be understood that like elements retain their previously assigned reference numbers.

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

[0083] In step (b), the lid 44 is removed and replaced by 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) further shows a robot end effector 50, with a fixture 46 attached to the end effector 50. The fixture 46 may be attached to the end effector 50 at a step of the process (e.g., step (b)) or may remain attached to the end effector 50 throughout (i.e., also in step (a) but not shown). The robot end effector 50 allows the build cylinder to be moved around at least one axis, in particular around a horizontal axis, via the fixture 46. In an alternative embodiment, the build cylinder fixture 46 and the robot end effector 50 form one integral element.

[0084] In step (c), the build cylinder 42 is brought into an upside-down position via a movement of the end effector 50. More precisely, the end effector 50, and thus the build cylinder 42, rotates 180° about a horizontal axis, resulting in the build cylinder 42 being upside-down. In other words, the opening of the build cylinder 42, which was facing upwards (upright position) at the start of the process, faces downwards in the upside-down position. In step (c), additional movements about the horizontal axis as well as movements about further (e.g. horizontal or vertical) axes may be performed. Furthermore, step (c) may include a step of vibrating the end effector 50 to shake off the powder from the workpiece 12. At the end of step (c), when the build cylinder 42 is in the upside-down position, a certain amount of residual powder is accumulated at the bottom of the funnel 48.

[0085] In step (d), a storage container 54 is connected to the funnel 48 via a connecting member 52, such as a clamp. The storage container 54 is disposed below the build cylinder 42 and the funnel 48, such that when a valve (not shown) of the funnel 48 is opened, 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 upper part of the storage container 54 may have the form of an inverted funnel (see FIG. 2).

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

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

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

[0089] In the alternative, the foil storage 58 may already be attached to or part of the build cylinder fixture 46 when the build cylinder 42 is attached in step (a). Additionally, the foil storage may be provided in any of steps (b)-(d).

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

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

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

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

[0094] As shown in FIG. 3, an end of the ring-shaped foil 56 is attached to the build cylinder fixture 46 via attachment means 64 (such as clamps). Since a second connection of the end of the ring-shaped foil 56 is made to the substrate 20, the connection of the foil 56 to the fixture 46 may not be powder-tight or gas-tight. The connection of the foil 56 to the substrate 20 is made using a fastening device 62 that surrounds the substrate 20. The fastening device 62 thus fastens the foil 56 between the substrate 20 and the fastening device 62. The substrate 20 may be provided with a groove, so that the fastening device 62 engages in the groove. The connection between the foil 56 and the substrate 20 is powder-tight or gas-tight with respect to the atmosphere in which the workpiece 12 is located and the surrounding atmosphere (e.g. air).

[0095] The connection of the foil 56 to the build cylinder fixture 46 may be performed in step (j) or may be performed in step (g), for example, where the foil recess 58 is provided.

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

[0097] In step (l), the tubular foil 56 is clamped with a clamping member 66, such as a cable tie, adhesive tape, clamp, etc. The clamping ensures that a sealed atmosphere exists around the workpiece 12 even after the foil is cut (as shown through the scissors in FIG. 3). A second clamping member 66 may be used to clamp the foil 56 before the foil is cut between the two clamping members 66, 68 to maintain the atmosphere within the build cylinder 42. Optionally, the foil is twisted about a vertical axis to strengthen the clamping.

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

[0099] In step (n), the fixture 46 is rotated back to its original upright position (i.e. rotated 180° about a horizontal axis). The foil is cut between the attachment means 64 and the fastening device 62.

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

[0101] In step (p), a new substrate 20 is attached to the fixture 46 .

[0102] In step (q), the fixture 46 is rotated back to the upside-down position and a new substrate 20 is mated with the side wall 28 of the build cylinder 42 .

[0103] In step (r), the build cylinder 42 with the new substrate 20 is rotated about the horizontal axis back to the upright position. The build cylinder 42 (the replaceable build cylinder 42) can now be reused for a new build step in the additive manufacturing process.

[0104] With respect to the above method, it should be noted that steps (e) and (f) are optional. Additionally, the step of attaching the foil 56 to the fixture 46 is optional. In some circumstances, it may be sufficient to simply attach the foil 56 to the substrate 20.

[0105] Figure 4 shows the steps of a second embodiment, which can be considered as an alternative method compared to the methods of Figures 2 and 3. Figure 4 shows three steps (A) to (C) that are performed after step (f) of the method of Figures 2 and 3. Thus, 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 Fig. 4(A), but is returned to the upright position. Furthermore, considering steps (A) to (C), the support 46 shown in Fig. 4 is a build cylinder fixture 46.

[0107] In step (A), the build cylinder 42 is mounted on the build cylinder fixture 46. Furthermore, a foil 56 is attached to the upper end of the side wall 28. In this case, the foil 56 may be planar or bag-like (i.e., having one opening) rather than tubular (i.e., having two openings). In step (A), the foil 56 entirely covers the space within the build cylinder 42.

[0108] In step (B), the sidewall 28 of the build cylinder 42 is lowered. Separately, the substrate 20 is lifted upwardly against the sidewall 28. The foil 56 remains attached to the upper end of the sidewall 28.

[0109] Step (C) is performed when substrate 20 has substantially reached the height of the top of sidewall 28. In step (C), foil 56 is removed from sidewall 28 and attached to substrate 20 upon which workpiece 12 rests. Workpiece 12 is now completely surrounded by foil 56 in an enclosed space.

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

[0111] FIG. 5 shows a schematic side view of the build cylinder 42 according to the method of the first embodiment, ie when the foil 56 is mounted in an upside down position.

[0112] Figure 5 may correspond to step (j) of Figure 3. In addition to the elements discussed above with respect to Figures 2 and 3, an antistatic brush 70 may be provided at the exit area of ​​the foil container 58. This makes it possible to avoid electrostatic charging of the foil 56 and to prevent powder from adhering to the foil 56.

[0113] Additionally, an antistatic coating may be applied to the foil 56 to prevent static charging of the foil 56. The foil 56 may be a disposable foil.

[0114] To fix the foil 56 to the substrate 20, according to step (j) or (C) above, the following may be applied: The foil 56 is attached to the substrate 20 using a high-density fastening system 62. For example, rubberized metal elements may be used, the fastening system 62 encircling the substrate 20. The fastening system may be rubberized to improve the tightness and prevent it from slipping off.

[0115] The foil 56 may be provided with an opening for a gas inlet. An inert gas may be supplied to the space within the foil. Additionally, the foil 56 may be provided with an opening for a vacuum device to pierce the foil and operate within the space enclosed by the foil. The funnel 48 may be provided with one or more sieving devices to sieve coarse particles from the remaining powder.

[0116] 6 shows an arrangement that can be applied to both the first and second embodiments. In the upright position of the workpiece 12, on top of the foil 56, a powder catcher 72 is attached to the foil 56. For example, the clamping member 66 in step (l) can be the powder catcher 72. Alternatively, the powder catcher 72 can 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 that the powder capture device 72 does not fall onto the workpiece 12. The powder capture device 72 has a powder inlet with side walls that face inward, i.e., toward the interior space of the powder capture device 72. In the upright position, powder is captured in areas other than the side walls. In the upside-down position, powder can flow through the powder inlet into the powder capture device 72.

[0118] Thus, when the powder catcher 72 is installed, the workpiece 12 can be rotated one or more times about one or more horizontal axes in order to collect as much residual powder as possible in the powder catcher 72. In other words, the workpiece 12 (and the entire system shown in FIG. 6) can be successively placed in an upside-down position and in an upright position several times. The rotation of the system can be visually controlled by the operator, since the foil 56 is transparent. Furthermore, vibration can be applied. Furthermore, the internal space within the foil 56 can be filled with argon.

[0119] Additionally, in all embodiments discussed herein, one or more of the following powder processing steps may be performed within the space enclosed by foil 56:

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

[0121] FIG. 7 shows a flow chart of a method for removing powder from a three-dimensional workpiece produced by additive manufacturing according to the present disclosure. The method includes a step 80 of mounting a build cylinder to a build cylinder fixture. The build cylinder comprises a substrate for holding the three-dimensional workpiece and a sidewall releasably attached to the substrate. The build cylinder contains residual powder from the additive manufacturing process of the three-dimensional workpiece. The method further includes a 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 of FIG. 7.

[0122] One or more embodiments of the present technology may have at least one of the following advantages: By providing the foil 56, the workpiece 12 may be in a sealed (e.g., inert) space for the entire or at least most of the time of the process. Thus, contact of the workpiece and / or residual powder with the ambient atmosphere may be reduced or avoided. Residual powder may be efficiently removed. Furthermore, contamination of the ambient atmosphere may be reduced, thereby improving the safety of the operation.

Claims

1. 1. A method for removing powder from a three-dimensional workpiece (12) produced by additive manufacturing, the method comprising: mounting (80) a build cylinder (42) in a build cylinder fixture (46), the build cylinder (42) comprising a substrate (20) that holds the three-dimensional workpiece (12) and a sidewall (28) detachably attached to the substrate (20), the build cylinder (42) containing residual powder from an additive manufacturing process of the three-dimensional workpiece (12); and attaching (82) a foil (56) to the build cylinder fixture (46) and / or the substrate (20).

2. The method of claim 1 , further comprising separating the substrate (20) from the build cylinder (42) while leaving the foil (56) attached to the build cylinder fixture (46) and / or the substrate (20).

3. said foil (56) being a tubular foil; In the mounting step (82), an opening of the tubular foil (56) is mounted to the build cylinder fixture (46) and / or the substrate (20); The method of claim 2, wherein the opening in the foil (56) corresponds to one of two opposing ends of the tubular foil (56).

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

5. 5. The method of claim 3 or 4, wherein the opening in the tubular foil (56) is attached to the substrate (20) using a fastening device (62) that surrounds the substrate (20) and fastens the tubular foil (56) between the fastening device (62) and the substrate (20).

6. The method of any one of claims 3 to 5, further comprising removing the substrate (20) from the build cylinder fixture (46).

7. The method of claim 6, further comprising reusing the build cylinder fixture (46) for additional processes according to the method of claim 1.

8. 8. The method according to claim 3, wherein the tubular foil (56) is stored in a foil storage section (58) in a folded form, optionally the foil storage section (58) surrounding at least a portion of the build cylinder (42).

9. The method of any one of claims 1 to 8, further comprising removing a lid (44) of the build cylinder (42) and replacing the lid (44) with a funnel (48).

10. 10. The method of claim 2, further comprising, after the mounting step (80), rotating the build cylinder (42) about a horizontal axis such that the build cylinder (42) is in an upside-down position.

11. 11. The method of claim 10 in combination with claim 9, further comprising the step of opening a valve of the funnel (48) such that at least a portion of the residual powder flows downwardly into a storage container (54).

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

13. 13. The method of any one of claims 10 to 12, wherein the attaching (82) and separating (84) steps are performed in the upside-down position.

14. The method of any one of claims 1 to 13, further comprising vibrating and / or rotating the build cylinder (42) and / or the substrate (20).

15. 15. The method of any one of claims 1 to 14, further comprising, after the attaching step (80), inserting a tip of a vacuum device into an opening in the foil (56) and using the vacuum device to vacuum an interior region of the foil (56) to remove at least a portion of the residual powder.

16. removing the fastening device (66) and attaching a powder capture device (72) to the tubular foil (56), the powder capture device (72) having a powder inlet portion with an inwardly facing sidewall; 6. The method of claim 5, further comprising rotating the build cylinder (42) about a horizontal axis such that at least a portion of the residual powder is captured in the powder capture device (72).

17. 14. The method according to any one of claims 10 to 13, further comprising the step of clamping a portion of the tubular foil (56) with a lower portion of the tubular foil (56) in the upside-down position, such that at least a portion of the residual powder is trapped within an enclosed space formed by the tubular foil (56).

18. 18. The method according to any one of the preceding claims, wherein the foil (56) is impermeable to powder, and optionally the foil (56) is gas-tight, in particular to at least one of argon, nitrogen and air.

19. 1. An apparatus for removing powder from a three-dimensional workpiece produced by additive manufacturing, the apparatus comprising: a build cylinder fixture (46) for attaching the build cylinder (42) to said build cylinder fixture (46); a foil housing (58) having a tubular foil (56) housed therein.

20. 20. The apparatus of claim 19, wherein the foil storage portion (58) is configured to surround at least a portion of the build cylinder (42) when the build cylinder (42) is mounted to the build cylinder fixture (46).

21. 21. Apparatus according to claim 19 or 20, wherein the foil (56) is impermeable to powder, and optionally the foil (56) is gas-tight, in particular to at least one of argon, nitrogen and air.

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