Technology for removing powder and / or particles from a powder bed

Abstract

This invention relates to an apparatus for removing powder and / or particles from a powder bed. The apparatus includes a rotatably mounted roller with a porous outer wall and a plurality of chambers formed within the roller. The apparatus also includes a connector for supplying negative pressure, the connector being designed to supply negative pressure to at least one of the chambers at a given point in time. At least one of the chambers has an opening adapted to supply negative pressure to that chamber.

Description

Technical Field

[0001] This invention relates to an apparatus and method for removing powder and / or particles from a powder bed. The proposed technique can be used, in particular, in conjunction with selective electron beam melting, selective laser melting, or selective laser sintering to remove a defined amount of powder from a powder bed. Background Technology

[0002] In generative processes for producing three-dimensional workpieces, particularly in layer-by-layer generative construction processes, it is known to apply initially amorphous or shape-neutral molding compounds of raw materials (e.g., raw material powders) layer by layer onto a carrier and solidify the molding compound by irradiation at specific locations (e.g., by melting or sintering) to ultimately obtain a workpiece with a desired shape. Irradiation can be carried out by means of electromagnetic radiation, for example, in the form of electron or laser radiation. Initially, the molding compound may be in the form of granules, powder, or liquid molding compound and can be selectively, or in other words, location-specifically, solidified by irradiation. The molding compound may include, for example, ceramic, metallic, or plastic materials, as well as mixtures of these materials. A variation of the layer-by-layer generative construction process involves laser beam melting in a so-called powder bed, wherein, particularly under laser beam irradiation, metallic and / or ceramic raw material powder materials are solidified into a three-dimensional workpiece.

[0003] To produce individual workpiece layers, it is also known to apply raw material powder in the form of a raw material powder layer onto a carrier and selectively irradiate the raw material powder according to the geometry of the workpiece layer to be produced. Laser radiation penetrates the raw material powder and solidifies it, for example, by heating (causing melting or sintering). Once the workpiece layer is solidified, a new layer of untreated raw material powder is applied onto the already produced workpiece layer. Known coating devices or powder application devices can be used for this purpose. Subsequently, the currently top-level, untreated raw material powder layer is irradiated again. Thus, the workpiece is constructed layer by layer, each layer defining the cross-sectional area and / or contour of the workpiece. In this context, it is also known to use CAD or similar workpiece data to manufacture workpieces substantially automatically.

[0004] It should be understood that all aspects explained above are also available within the scope of this invention.

[0005] Furthermore, it is known that at least two materials can be combined in a build process, enabling the production of workpieces composed of these at least two materials. This is achieved, in particular, by alternately applying powder layers of different materials. If a single material is applied over the entire layer, the uncured portions of the previous powder layer of other materials must be removed before applying a new coating. It is desirable to remove the previous powder layer as completely as possible to avoid contaminating the subsequently applied powder.

[0006] Currently, it is known to use a funnel to remove the previous layer. However, this step is often performed in an indeterminate manner and results in powder loss. This powder loss may mean that powder must be added, for example, in a quantity factor of 100. If a powder mixture is extracted to a depth of 3 mm for every 30 micrometer layer, a 1-liter cylinder volume of the component yields 100 liters of waste powder or mixed powder, which can then be unusable or must be reprocessed in a laborious manner (e.g., washing and separating into at least two original powder materials).

[0007] Therefore, a technology that can reliably and definitively remove powder is needed.

[0008] Furthermore, it is known that even when using conventional beam melting (i.e., using a single material), particles are deposited on the surface of the powder bed, such as weld spatter generated during material curing. Since these particles can cause interference during the subsequent application and curing of new powder layers, it is desirable to remove them from the powder bed.

[0009] Therefore, there is a need for a technology that can reliably remove particles from a powder bed, especially without removing a large amount of additional material. Summary of the Invention

[0010] Therefore, the object of the present invention is to provide a technique for removing powder and / or particles from a powder bed, which solves at least one of the above-mentioned or related problems.

[0011] Therefore, according to a first aspect, the present invention relates to an apparatus for removing powder and / or particles from a powder bed. The apparatus includes a rotatably supported roller having a porous outer wall, and a plurality of chambers formed within the roller. The apparatus also includes a negative pressure supply port configured to supply negative pressure to at least one of the chambers at a given time. The at least one chamber has an opening adapted to supply negative pressure to that chamber.

[0012] A powder bed can be one or more layers of raw material powder applied to a carrier, particularly for the purpose of selective laser melting or selective laser sintering. The powder can include, for example, metal powder, ceramic powder, and / or plastic powder. Specifically, the equipment can be configured to remove different types of powder, particularly powders made of different materials. Removal can be performed layer by layer.

[0013] The roller can be rotatably supported, allowing it to rotate relative to its support. The device may include a drive configured to cause the roller to rotate. In particular, an electrically driven actuator, such as a servo motor or stepper motor, may be provided for this purpose. As an alternative to an electrically driven device, the roller's rotational movement can be set by means of negative and / or positive pressure, using ports described below for negative or positive pressure. In another alternative, the roller may mechanically roll above the powder bed, with rotational movement caused by friction between the powder bed and / or the build chamber floor extending near the powder bed (on one hand) and the roller (on the other hand).

[0014] If an electric drive is provided, a control unit for controlling the electric drive can also be provided. The control unit can be configured to drive the roller at an adjustable rotational speed. Furthermore, the device can include a horizontal movement device configured to move the roller horizontally across the powder bed (translational movement). In this way, the roller can perform both rotational and translational movements. The horizontal movement device can include, for example, an electric actuator (e.g., a motor). The horizontal movement device can also be controlled by the control unit.

[0015] The control unit can be configured to adjust the rotational and translational movements of the rollers, such that the translational movement corresponds to the rotational movement on the outer wall of the rollers. In this way, the rollers can remove a thick layer of powder that has adhered to them due to suction. Furthermore, the control unit can also control the rollers to rotate faster or slower, thereby achieving different rotational speeds relative to the translational speed. In this way, the amount of powder removed from the powder bed by the rollers can be adjusted.

[0016] Furthermore, the device may include a vertical moving device for adjusting the vertical position of the roller. Here, the vertical position corresponds to the height above the powder bed. Preferably, the vertical moving device may also be controlled by a control unit. The control unit may be configured to adjust the vertical position of the roller such that the height of the lower side of the roller corresponds to the height of the powder bed. Therefore, the height of the roller corresponds to a height below which the roller rolls above or is about to roll above the powder bed. In other words, the roller is placed on the powder bed. However, the vertical position of the roller may also be adjusted such that a constant predetermined distance exists between the roller and the powder bed during roller operation. In this case, the suction force of the roller can draw powder beyond this distance. The suction force can be further adjusted by controlling the generation of negative pressure.

[0017] The above and following explanations also apply to the suction of particles (especially molten spatter) from the top of a powder bed. Rollers can be configured to remove not only powder from the surface of the powder bed, but also larger particles. Furthermore, it is conceivable that the height and / or suction force of the rollers can be adjusted so that the rollers primarily or even solely remove larger particles (i.e., particles larger than the powder used) from the surface of the powder bed.

[0018] The porous outer wall of the roller is porous because it allows some gas to pass through but impermeable to powder and / or particles (greater than a certain diameter). For example, the minimum diameter of the powder can be from 5 micrometers to 30 micrometers. The outer wall of the roller can be designed to have pore sizes smaller than 10 micrometers or smaller than 5 micrometers. Generally, the pore size of the roller is such that it does not allow the powder used to pass through. The roller can use some kind of surface filter (especially a membrane or coated fabric) as its porous outer wall. The roller can also have multiple layers, such as a support mesh and / or a coarse-pore structure (such as a sponge structure) located below the outermost layer, to uniformly distribute pressure on the outer wall.

[0019] In a preferred embodiment, a plurality of chambers formed within the roller are fixed to the roller. In this case, the plurality of chambers are fixedly connected to the roller because the rotational movement (i.e., rotational motion) of the roller causes the chambers to rotate within them. In other words, the plurality of chambers formed within the roller can be rotatably fixedly connected to the roller. Thus, the chambers rotate with the roller. Therefore, a fixed connection does not mean that the inner wall of the chamber must be mechanically connected to the outer wall of the roller (e.g., by welding, gluing, etc.). Rather, a fixed connection simply means that there is a rigid mechanical connection between the roller and the chamber. This can also be achieved, for example, by fastening the outer wall of the roller and the inner partition of the chamber to the same rotatable support shaft, or if the roller itself consists of a flexible medium stretched on a frame formed by the chambers.

[0020] As an alternative to a rotatably fixed chamber, the roller can also move independently of the chamber, especially in cases where the chamber can be designed to be non-rotatable. In this case, the roller rotates above the chamber. Alternatively, the roller can be formed from a web of flexible media that is driven above the chamber. For this purpose, a support grid structure can also be provided, above which the web moves.

[0021] For the purposes of this application, any bearings on the roller that return the outer wall to its initial position along the closed movement path are understood to be rotatably supported. It is readily apparent that, for the sense of this application, the roller does not necessarily have to have a cylindrical shape, but may have, for example, a polygonal cross-section, or, in the case of a web of material, the roller itself does not need to have a fixed shape, but rather obtains this shape through stretching.

[0022] The openings of one or more chambers can be configured, for example, in the form of circular apertures. The chamber openings can be located within the corresponding walls of the chambers, which are not formed by the porous outer walls of the rollers. For example, the chamber openings can be located within the walls of the corresponding chambers, which define an elongated chamber at one end. Alternatively or additionally, the openings can be located on inwardly oriented walls, such as centrally positioned hollow shafts. Each chamber can have one or more (e.g., two) openings.

[0023] The device also includes a negative pressure supply port configured to supply negative pressure to at least one of the chambers at a given time. In this case, the negative pressure is supplied via an opening in the respective chamber.

[0024] The port may include a tube or a hose. The port can be configured to contact the opening of the corresponding chamber at a given moment. As used herein, the term "given moment" is intended to mean any moment during the rotational movement of the roller. In this respect, "given moment" defines a snapshot, and there are, for example, previous and subsequent moments at which contact may be made with another chamber among a plurality of chambers. Negative pressure may be adapted to draw powder from the powder bed onto the porous outer wall of the roller.

[0025] The chambers can extend along the axis of rotation of the rollers, and each chamber can be defined by a section of the porous outer wall.

[0026] Preferably, the chambers are defined by a volume and walls (chamber walls) defining that volume. As defined above, a portion of these chamber walls is formed by the porous outer wall of the roller. In other words, each chamber may have a wall that is a segment of the porous outer wall. Additionally, one or more partition walls may be provided to define the multiple chambers apart from each other. Thus, the chambers can extend along the axis of rotation of the roller. Each chamber may have a porous outer wall extending along the axis of rotation.

[0027] In the context of this application, at least one chamber may also be provided, having a very small volume, or even no volume at all, thus forming a perforated chamber. The perforated chamber is thus defined on one hand by a porous outer wall and on the other hand by a solid wall that can directly contact the porous outer wall. Preferably, the fixed wall can be stationary, and the perforated roller can move past the fixed wall. In this embodiment, the extension of the perforated chamber along the circumference of the roller can be greater than 0.5 cm, particularly greater than 1 cm, and particularly greater than 3 cm. This may result in a lower negative pressure at the center of the perforated chamber compared to adjacent chambers.

[0028] The apparatus may also include a suction device for removing powder drawn up by the rollers, the suction device being arranged opposite a chamber in the rollers that is not supplied with negative pressure at a given time.

[0029] The suction device may include, for example, an opening for suctioning powder from the rollers. Furthermore, the suction device may be connected to a device for generating negative pressure. This could be, for example, the same device that provides negative pressure to at least one chamber of the rollers. The apparatus may also include a collection container for collecting the powder suctioned out by the suction device. Additionally, the apparatus may include a separation device for separating the suctioned powder from the airflow. The separated powder may be introduced into the collection container. The collection container may also be formed of an overflow vessel disposed in a manufacturing apparatus (plant) including the suction device for receiving excess powder applied during layer-by-layer generation. In addition to the suction device, the apparatus may also have a brush, or include a brush or scraper. The brush or scraper is configured to further separate the powder suctioned onto the rollers, allowing the powder to be drawn away by the suction device.

[0030] The negative pressure supply port can be fixedly connected to the support of the roller. The chambers can be rotatably and fixedly connected to the roller, each chamber having an opening adapted to supply positive or negative pressure to the chamber. The supply section and chambers can be designed such that negative pressure is supplied to the chambers during roller rotation.

[0031] The device may also include a positive pressure supply port configured to supply positive pressure to at least one chamber at a given time via an opening of at least one chamber that is not supplied with negative pressure at a given time.

[0032] The positive pressure supply port can be fixedly connected to the roller support. The supply section and chamber can be designed such that negative and positive pressure are alternately supplied to the chamber during roller rotation.

[0033] A chamber supplied with positive pressure at a given time can be positioned opposite a suction device. In this way, powder can be said to be blown from the rollers into the suction device. On the rollers, which are therefore empty of powder, new powder can now be drawn in and absorbed by means of negative pressure.

[0034] As described above, the positive pressure supply port and the negative pressure supply port can be fixedly connected to the support of the roller and are designed such that positive pressure and negative pressure are alternately supplied to the chamber during the rotation of the roller.

[0035] In other words, the rotational movement of the rollers occurs relative to the negative pressure supply port, and, if applicable, relative to the positive pressure supply port. Alternating supply of positive and negative pressure means supplying negative pressure to any selected chamber at a given moment, supplying positive pressure at a later moment, then supplying negative pressure again, and so on.

[0036] The equipment can be designed such that during the rotation of the rollers, the opening of the chamber is contacted once by the negative pressure supply port, thereby supplying negative pressure to the corresponding chamber, and the opening of the chamber is contacted once by the positive pressure supply port, thereby supplying positive pressure to the corresponding chamber.

[0037] The device can also be designed so that the chamber has multiple different negative pressure supply ports and positive pressure supply ports.

[0038] The roller can be formed into a cylindrical shape, and one or more openings can be provided in the base surface of the cylindrical body.

[0039] Therefore, one or more openings can be provided in the base plane of the first end of the roller. In addition, for each chamber, another opening can be provided in the other (opposite) base plane of the cylinder.

[0040] As an alternative to providing openings in the base surface of the cylindrical body formed by the roller, openings can be provided in the porous outer wall of the cylindrical body. Therefore, these openings point radially outward. In this case, the ports can be built into the roller's support and point radially inward. Alternatively, the openings of the chambers can be oriented radially inward (towards the roller's axis of rotation). In this case, an inner shaft rigidly connected to the support can be provided, in which the cavity for negative pressure extends. Therefore, the port for negative pressure can point radially outward. Furthermore, the cavity for positive pressure can extend in the shaft. Therefore, the port for positive pressure can point radially outward. Openings for both negative and positive pressure can also be provided on multiple protruding walls. The opening for negative pressure can be in the same wall as the opening for positive pressure, or the opening for negative pressure can be in other walls, where the opening for positive pressure is different from the opening for negative pressure. The opening for negative pressure can be provided in the base surface of the roller cylinder with a first radius, and the opening for positive pressure, different from the opening for negative pressure, can be provided in the base surface of the roller cylinder with a second radius.

[0041] At least three chambers may be formed inside the roller, wherein at least one chamber is always supplied with negative pressure, and two chambers are supplied with negative pressure at least temporarily.

[0042] At least three chambers may be formed inside the roller, wherein an optional positive pressure supply port is designed to simultaneously supply positive pressure to multiple chambers of these chambers, and / or wherein a negative pressure supply port is designed to simultaneously supply negative pressure to multiple chambers of these chambers. In particular, at least four chambers may be formed inside the roller.

[0043] For example, eight chambers can be arranged within the rollers. At any given moment, negative pressure is simultaneously supplied to multiple chambers (i.e., at least two chambers). Furthermore, at any given time, positive pressure can be supplied to at least one of these chambers. One or more chambers can also be left unsupplied with either negative or positive pressure, thus maintaining atmospheric pressure or their previous pressure state. Atmospheric pressure can be the pressure within the build chambers of a system used to produce three-dimensional workpieces.

[0044] An optional positive pressure supply port may have an elongated orifice that simultaneously exposes the openings of multiple chambers. A negative pressure supply port may have an elongated orifice that simultaneously exposes the openings of multiple chambers.

[0045] The opening of the chamber can be circular. Uncovered is the opposite of covered. In other words, a corresponding uncovered opening can be supplied with negative or positive pressure through corresponding port contact. Elongated orifices can be curved, particularly along arcs.

[0046] The device may also include a shaft extending within the rollers, wherein multiple chambers are formed by multiple grooves formed in the shaft.

[0047] Preferably, the chambers may have the same dimensions. Preferably, the walls between the chambers are as thin as possible, particularly at least in the region transitioning to the porous outer wall, with a thickness of less than 5 mm, 3 mm, or 1 mm.

[0048] In a device having a non-rotating chamber and rollers moving above the chamber, the chambers can have different dimensions. Furthermore, only one chamber can be permanently supplied with negative pressure. Alternatively, only one chamber or no chamber can be supplied with positive pressure.

[0049] The device may also include a negative pressure generating device connected to a negative pressure supply port and adapted to generate negative pressure at least during device operation.

[0050] The negative pressure generating device can be, for example, a vacuum pump. This device can also be connected to other components of a system used to produce three-dimensional workpieces that require negative pressure.

[0051] The device may also include a positive pressure generating device connected to a positive pressure supply port and adapted to generate positive pressure at least during device operation.

[0052] The positive pressure generating device can be, for example, a pump or a blower. This device can also be connected to other components of a system used to produce three-dimensional workpieces that require positive pressure.

[0053] According to a second aspect, a system for producing three-dimensional workpieces is provided, the system including apparatus according to a first aspect for removing powder and / or particles from a powder bed. More specifically, the system includes a carrier for receiving multiple layers of powder to form a powder bed, at least one powder application device for applying powder to the carrier, at least one irradiation unit for irradiating the uppermost powder layer of the powder bed at a predetermined location, and apparatus according to a first aspect for removing powder and / or particles from the powder bed.

[0054] Systems for producing three-dimensional workpieces can be selective laser melting (SLM) systems or selective laser sintering (SLS) systems, possessing the common components and functions of such systems. Systems for producing three-dimensional workpieces include, for example, a carrier for applying multiple layers of powder to form a powder bed. Furthermore, one or more powder application devices can be provided for applying powder, and, if desired, for applying powder of different materials. A separate powder application device can be provided for each material. The carrier can be moved vertically downwards by means of a vertical moving device, such that the uppermost powder layer is always maintained at the same height relative to the system's build chamber. Additionally, the system can include one or more irradiation units. Each irradiation unit includes a beam source (particularly a laser beam source) and an optical system having one or more optical components (e.g., beam expander, focusing unit, scanner, F-theta (F-θ) lens) for shaping and deflecting the beam.

[0055] In addition, the system may include a control unit configured to control components of the system. In particular, the control unit may be configured to control equipment for removing powder (e.g., controlling the rotational and / or translational movement of rollers).

[0056] The device for removing powder can be arranged in the system's build chamber. In particular, the device can be coupled to the powder application device. The coupling can be designed so that the device for removing powder can move together with the powder application device (horizontally and / or vertically).

[0057] In other words, the device can be coupled to a powder application apparatus, and the system can include a moving device configured to move the device and the powder application apparatus together.

[0058] Specifically, the system may include a cleaning station for cleaning the equipment used to remove powder. The cleaning station may be positioned such that the equipment used to remove powder can be moved to the cleaning station and cleaned there. For this purpose, the cleaning station may include, for example, one or more nozzles by means of which the rollers of the equipment used to remove powder can be blown clean and free of powder. Alternatively or additionally, the cleaning device may also have a suction device for drawing the rollers, as well as scrapers, brushes, or similar mechanical cleaning devices.

[0059] The chamber supplied with negative pressure can be located on the side of the roller facing the powder bed.

[0060] Specifically, during equipment operation, the chamber supplied with negative pressure can be in contact with the powder bed, or at least arranged to be directly opposite the powder bed, thereby drawing in powder and causing the powder to adhere to the porous outer wall of the roller. The equipment can be configured such that negative pressure is supplied to more than one chamber at a given time.

[0061] According to a third aspect, the present invention relates to a method for removing powder and / or particles from a powder bed. The method includes rotating a rotatably supported roller having a porous outer wall. The roller has a plurality of chambers formed within it. At least one of these chambers has an opening adapted to supply negative pressure to the chamber. The method further includes supplying negative pressure to the at least one chamber via the opening of the at least one chamber. In particular, each chamber may have an opening.

[0062] All aspects discussed in conjunction with the aforementioned devices or systems can also be applied to the method of the third aspect. In other words, the apparatus of the first aspect and / or the system of the second aspect can be configured to perform the method of the third aspect.

[0063] Regarding powder removal, the method may also include one or more of the following aspects: Powder is drawn from the powder bed by negative pressure in a chamber supplied with negative pressure. At least while maintaining negative pressure, the drawn-out powder remains adhered to the porous outer wall of the roller. While maintaining negative pressure, powder is drawn into a section of the wall forming the chamber on the porous outer wall of the roller. Due to the selected pore size, the drawn-out powder does not penetrate into the interior of the roller. During the rotational movement of the roller, powder continues to be drawn in until the point at which the corresponding chamber is no longer supplied with negative pressure (i.e., the position of the roller until the corresponding chamber is no longer supplied with negative pressure). Powder that is no longer drawn in is then extracted by a suction device, and additionally brushed or scraped off the roller if necessary. Alternatively, positive pressure can be applied to the opening of the corresponding chamber that was previously supplied with negative pressure, which facilitates extraction by the suction device. Thus, the collected powder is blown into the suction device. The corresponding section of the roller is now again free of powder and ready to receive new powder from the powder bed. The amount of powder drawn up can be adjusted by controlling the rotation speed of the roller relative to its translation speed. Particles (e.g., welding spatter) can be removed from the powder bed, either as powder or as a substitute for powder.

[0064] The chambers can extend along the axis of rotation of the rollers, and each chamber can be defined by a portion of the porous outer wall.

[0065] The supply of negative pressure to at least one chamber via an opening of at least one chamber can be achieved at a given time via a negative pressure supply port.

[0066] The chamber supplied with negative pressure can be located on the side of the roller facing the powder bed.

[0067] The method may also include suctioning the powder drawn up by the rollers by a suction device arranged opposite a chamber in the rollers that is not supplied with negative pressure at a given time.

[0068] The method may also include supplying positive pressure to at least one chamber at a given time via an opening in at least one chamber that is not supplied with negative pressure at the given time.

[0069] The positive pressure supply port and the negative pressure supply port can be fixedly connected to the support of the roller, and the method can also include alternately supplying positive pressure and negative pressure to the chamber during the rotation of the roller.

[0070] The method may further include rotating the roller such that during the rotation of the roller, the opening of the chamber is contacted once by the negative pressure supply port, thereby supplying negative pressure to the corresponding chamber, and the opening of the chamber is contacted once by the positive pressure supply port, thereby supplying positive pressure to the corresponding chamber.

[0071] The roller can be formed into a cylindrical shape, and the opening can be set in the base surface of the cylinder.

[0072] At least three chambers may be formed within the roller. The method may include simultaneously supplying positive pressure to multiple chambers via a positive pressure supply port. The method may also include simultaneously supplying negative pressure to multiple chambers within the roller via a negative pressure supply port.

[0073] The positive pressure supply port may have an elongated orifice that exposes the openings of multiple chambers simultaneously. The connection for negative pressure supply may have an elongated orifice that exposes the openings of multiple chambers simultaneously. Attached Figure Description

[0074] The invention will be explained below with reference to the accompanying drawings. These drawings represent:

[0075] Figure 1 According to an embodiment of the present disclosure, a perspective side view of a system for producing three-dimensional objects, the system having equipment for removing powder and / or particles from a powder bed of the system;

[0076] Figure 2 A schematic side view of an apparatus for removing powder and / or particles from a powder bed, illustrating the technical principles of this disclosure;

[0077] Figure 3a Cross-sectional view of a device according to an embodiment of the present disclosure;

[0078] Figure 3b : Figure 3a A perspective sectional view of the equipment;

[0079] Figure 3c : Figure 3a A perspective view of the device, which has a control panel including elongated holes for connecting negative and positive pressure respectively;

[0080] Figure 3d : Figure 3aA perspective view of the device, which has pipe connectors for connecting negative and positive pressure.

[0081] Figure 4a : Figure 3a A perspective sectional view of the device, which has a grooved shaft, a perforated disc with an opening, and a control disc with an elongated hole;

[0082] Figure 4b :and Figure 4a Similar views Figure 3a A perspective sectional view of the device, in which the grooved shaft has been removed;

[0083] Figure 4c :and Figure 4b Similar views Figure 3a A perspective sectional view of the device, in which the perforated disc with the opening has been removed;

[0084] Figure 5 : Figure 3a A cross-sectional view of the equipment taken along the axis of rotation of the roller. Detailed Implementation

[0085] exist Figure 1 The diagram illustrates a system 1 for producing a three-dimensional object 2, wherein the system 1 includes a device 51 for removing powder and / or particles from a powder bed 3 of the system 1. Apart from the device 51, the system 1 is a conventional system for selective laser melting with known components. The selective laser melting technology used in the system 1 is well known to those skilled in the art and will be briefly explained here based solely on selective laser melting in the powder bed 3.

[0086] First, a first layer of raw material powder is applied to the carrier 5 of system 1 and irradiated by one or more laser beams 7a, 7b in a position-specific manner, causing the desired area of ​​the powder to be solidified. This example illustrates system 1 with two irradiation units, each including lasers 9a, 9b and optical systems 11a, 11b. Therefore, the irradiation unit including laser 9a and optical system 11a is configured to emit laser beam 7a and guide it to the desired location of the uppermost powder layer of powder bed 3. Similarly, the irradiation unit including laser 9b and optical system 11b is configured to emit laser beam 7b and guide it to the desired location of the uppermost powder layer of powder bed 3. Optical systems 11a, 11b each include components for beam shaping and beam deflection, such as lenses, deflecting mirrors, scanning mirrors, etc.

[0087] All components of system 1 are controlled by control unit 13, particularly the lasers 9a and 9b, the scanning mirrors of optical systems 11a and 11b, the movement of carrier 5, and the functions of powder application devices 15a and 15b and device 51, which are further described below.

[0088] After the first layer of powder is cured as needed, another layer of powder is applied on top of the previous powder layer, and the top layer is irradiated and cured again.

[0089] To maintain a constant distance between the top layer and the optical unit, the carrier 5 can be lowered and / or the optical unit (along the vertical direction defined herein as the z-direction) can be raised during the ongoing construction process. In this way, the three-dimensional workpiece 2 to be produced is constructed layer by layer. Subsequently, the uncured powder can be removed, and if necessary, it can be reused.

[0090] Figure 1 A special feature of the system 1 shown is that the workpiece 2 consists of two parts 2a and 2b, for which two different powder materials are used. These powder materials may differ, for example, due to the type of powder used, but may also differ due to the particle size of the respective powders used.

[0091] To construct a workpiece consisting of two parts 2a and 2b, a first powder material is first applied to each workpiece layer using a first powder application device 15a. Subsequently, laser beams 7a and 7b are used to solidify the corresponding layer of workpiece 2 to be formed from the first powder. In the next step, the first powder material is removed again from the powder bed 3 using device 51. Then, a second powder is applied using a second powder application device 15b, and the area of ​​workpiece 2 below the layer previously irradiated with the first powder is solidified; this area will be formed from the second powder material. In a subsequent step, the carrier 5 is lowered, and a new layer of the first powder is applied using the first powder application device 15a.

[0092] like Figure 1As indicated by the double arrows, the two powder application devices 15a and 15b can move horizontally above the powder bed 3 to apply the corresponding powder. In the example shown, device 51 is fixedly connected to the first powder application device 15a and moves together with it. This has the advantage that device 51 does not require an additional moving device, as it can move together with one or more moving devices (horizontal moving devices and, optionally, vertical moving devices) of the first powder application device 15a. Another advantage is that height calibration (i.e., calibration along the z-axis) between the powder application device 15a and device 51 can be omitted. Furthermore, powder can be removed by device 51 if needed during the process, and powder can be applied simultaneously by powder application device 15a (when device 15a and device 51 move along the z-axis). Figure 1 (When moving to the right in the positive x direction as shown in the diagram and performing the operation simultaneously).

[0093] The gas supply device 17 supplies inert gas to the build chamber 19 of the system 1, so that an inert gas atmosphere exists in the build chamber 19. In addition, a gas extraction system (not shown) can be provided to extract the inert gas from the build chamber 19, thereby generating an airflow through the build chamber 19 (especially above the powder bed 3).

[0094] In addition to, or as an alternative to, the possibility of removing the powder layer during construction using two powder materials, as described above, the apparatus 51 can also be used to remove particles from the surface of the powder bed 3. Specifically, this can be welding spatter generated during the curing of the powder by laser beams 7a and 7b.

[0095] The apparatus 51 for removing powder and / or particles from the powder bed 3 is explained in detail below.

[0096] Figure 2 A schematic side view of a device 51 for removing powder and / or particles from a powder bed 3 is shown. (By means...) Figure 2 This can explain the principles of the technology disclosed herein.

[0097] The basic principle of device 51 (hereinafter also referred to as "suction roller") is that a porous (especially microporous) tube (e.g., made of sintered material or fabric such as felt, or a tube with fine pores) draws in and releases powder in a defined manner by means of an internal pressure difference. The porous tube forms the porous outer wall 53 of roller 54.

[0098] In operation, the roller 54 rolls over the powder bed 3 over a very short distance, performing a combination of rotational and translational movements to produce a "cutting" speed similar to that in machining (e.g., milling). In other words, the rotational and translational speeds of the roller 54 can be arbitrarily adjusted by the control unit 13. For example, these speeds can be set such that the translational speed corresponds to the rotational speed of the outer wall 53 of the roller 54 as it rolls over the powder bed. In this way, exactly one layer of powder can be removed. However, the roller 54 can also rotate faster or slower relative to the translational movement, which allows, for example, control over the amount of powder removed.

[0099] The powder is drawn in by a negative pressure (“-p”) inside the roller 54 in the lower region, which draws the powder particles away from the powder bed 3. The particles are trapped in the porous tube 53, thus limiting the localized suction capacity of the roller 54 so that only a defined layer depth is sucked in. In the upper region, there is an optional overpressure region (“+p”) within the roller 54, which ensures that the sucked powder particles are discharged from the roller 54. Additionally, a suction funnel (hereinafter also referred to as suction device 69) with a negative pressure flow (“-p”) is located above the roller 54, which removes the discharged powder.

[0100] The negative pressure region and the positive pressure region are separated into two chambers of approximately equal size by a fixed wall 52. The roller 54 is formed by a rotating porous outer wall 53.

[0101] As an alternative to the principle of utilizing a positive pressure zone (“+p”) described above, the positive pressure zone can be omitted and replaced, for example, by a zone where atmospheric pressure prevails. Atmospheric pressure here refers to the pressure within the construction chamber 19 of system 1. Furthermore, additional components, such as brushes or scrapers, can be provided for removing powder from the area of ​​the suction device 69.

[0102] Figures 3a to 3d Different views of the apparatus 51 for removing powder and / or particles from the powder bed 3 are shown.

[0103] Figure 3a A cross-section perpendicular to its axis of rotation passing through roller 54 is shown. Figure 3b A perspective sectional view is shown. Figure 3c and Figure 3d A perspective view is shown, illustrating other components of device 51.

[0104] Figure 2The pressure range shown is achieved within the roller 54 through a multi-chamber design. The core of the roller 54 is formed by a longitudinally slotted shaft 55, and a porous tube, serving as the porous outer wall 53 of the roller 54, is mounted on the shaft 55. The shaft 55 rotates together with the roller 54, and therefore with the porous outer wall 53. In other words, the chambers 59 formed within the roller 54 retain a portion of the porous outer wall 53 of the roller 54. Therefore, the position of the chambers 59 relative to the outer wall 53 of the roller 54 remains unchanged.

[0105] The walls between chambers 59 are made as narrow as possible where chamber 59 transitions into the porous outer wall 53. This also generates sufficient negative pressure on the outer wall, in the regions of these walls.

[0106] The lower region of roller 54 faces the powder bed 3, and the chamber 59 located in this lower region is supplied with negative pressure. Adjacent to the upper region of roller 54 is a suction device 69, by means of which powder sucked onto the outer wall 53 of roller 54 can be drawn out again and supplied to a collection container (not shown). In this embodiment, the chamber 59 opposite to suction device 69 is supplied with positive pressure. Alternatively, atmospheric pressure can prevail in the chamber 59 opposite to suction device 69.

[0107] At the end of roller 54 there is a plate (perforated plate) having a plurality of openings 57 (e.g., drilled holes, see below) at the location where the groove of shaft 55 terminates. Figure 3c The plate is connected to and rotates with the roller 54. Within the housing 61, which serves as a support for the roller 54, a so-called control disk 63 abuts the perforated plate. The control disk 63 forms part of both a positive pressure port and a negative pressure port. Inside the control disk 63 are two curved elongated holes 65. The elongated holes 65 are curved along an arc, the center of which forms the intersection of the axis of rotation of the roller 54 and the control disk 63. Each of the elongated holes 65 is shaped such that at a given moment, some of the multiple openings 57 are simultaneously exposed. Therefore, at a given moment, negative pressure can be supplied to some of the multiple chambers 59. Similarly, positive pressure can be supplied to some of the multiple chambers 59 simultaneously.

[0108] The elongated hole 65 contacts via tube connectors 67a and 67b (see...) Figure 3d ).

[0109] In the accompanying drawings, for clarity, not all of the above-mentioned elements have their own reference numerals; rather, in some cases, only one of the elements (e.g., only one of the chambers 59) has its own reference numeral.

[0110] Furthermore, according to the embodiment, the positive pressure supply port can be omitted; instead, a port open to the atmosphere can be provided. For this purpose, for example, the upper tube connector 67b can remain open to the atmosphere.

[0111] In this regard, it should be noted that the pipe connector 67a of the negative pressure supply port is connected, for example, by means of a pipe or hose to a device (not shown) for generating negative pressure. This device can be understood as part of the equipment 51. The device for generating negative pressure can be, for example, a vacuum pump. This could be a vacuum pump that also supplies negative pressure to other components of system 1. Similarly, the pipe connector 76b of the positive pressure supply port is connected, for example, by means of a pipe or hose to a device (not shown) for generating positive pressure. This device can be understood as part of the equipment 51. The device for generating positive pressure can be, for example, a pump or a blower. This could be a pump that also supplies positive pressure to other components of system 1.

[0112] The entire device 51, which includes a housing (support 61) and a suction device 69, is mounted on a powder application device 15a and moves above the powder bed 3 together with the powder application device 15a.

[0113] Figures 4a to 4c It shows Figures 3a to 3d Other cross-sectional views of device 51. To improve clarity, in Figure 4b In the middle, axis 55 was removed. Figure 4c In this design, the perforated plate with opening 57 of chamber 59 is omitted. Between the perforated plate with opening 57 and the control panel 63, a seal (e.g., in the form of a Teflon ring) may be present to prevent powder from the powder bed from penetrating into the interior of the rollers and / or negative pressure lines.

[0114] Figure 5 It shows the path along the axis of rotation of roller 54. Figures 3a to 3d The cross-section of device 51. Figure 5 As can be seen, the suction device 69 has a funnel-shaped cross-section.

[0115] It can also be seen that the negative pressure port and the positive pressure port are arranged at one end 71 of the roller 54. At the other opposite end 73 of the roller 54, an actuator (e.g., a servo motor or stepper motor, not shown) is provided to drive the rotation of the roller 54. The actuator is controlled by the control unit 13.

[0116] As an alternative to an electric actuator, roller 54 can be driven by a pressure difference provided by corresponding negative and positive ports. Furthermore, roller 54 can roll over the powder and be rotated by the resulting friction.

[0117] During operation, the device 51 removes a defined amount of powder from the powder bed 3 in the following manner.

[0118] Negative pressure is supplied to the chamber 59 located in the lower region of the roller 54 facing the powder bed 3 via a control disc 63 (more precisely, via an elongated hole 65 in the control disc 63). Figure 3c As can be seen, for example, three chambers 59 can simultaneously contact and be supplied with negative pressure. Powder is drawn out of the powder bed 3 at the porous outer walls 53 of these chambers 59 (i.e., in the regions forming the outer walls of these chambers 59). A powder layer of defined thickness is formed on the roller 54. The drawn-out powder is conveyed into the interior of the device 51 by the rotation of the roller 54 and is transported along the direction of the suction device 69. Along this path, the chambers 59 lose their negative pressure and are then supplied with positive pressure through the upper elongated orifice 65 of the control disc 63. Therefore, the drawn-out powder is blown away from the roller 54. This occurs in the lower (upper) region of the device 51, where the suction device 69 is located. In this region, powder is drawn out and supplied to a collection container (not shown).

[0119] The roller 54, which is now free of powder, continues to rotate and is able to draw new powder from the powder bed 3.

[0120] As described above, the two elongated holes 65 of the control panel 63 are designed such that they can simultaneously supply negative or positive pressure to some of the multiple chambers 59. In an alternative embodiment, at any given time, only one chamber 59 is supplied with negative pressure, and only one chamber 59 is supplied with positive pressure.

[0121] Furthermore, any number of ways in which negative or positive pressure comes into contact with chamber 59 are possible. In the illustrated embodiment, roller 54 makes contact via the base surface of the cylindrical body formed by roller 54.

[0122] Alternatively, contact in support 61 can be achieved via inwardly oriented ports (towards roller 54). As another alternative, roller 54 can rotate on a shaft fixedly connected to support 61. The shaft has cavities for contacting one or more chambers in chamber 59 with negative pressure. For this purpose, the cavities have one or more radially outwardly oriented openings. Similarly, cavities can exist in the shaft for contacting one or more chambers in chamber 59 with positive pressure. These cavities also have one or more radially outwardly oriented openings.

[0123] Using the above-described technique, a defined amount of powder can be reliably removed from a powder bed. Alternatively or additionally, particles such as welding spatter can be removed.

Claims

1. Device (51) for removing powder and / or particles from a powder bed (3), said device comprising: - a roller (54) rotatably supported by a support (61) of said roller (54), said roller having a porous outer wall (53); and - a plurality of chambers (59) formed within said roller (54), - a negative pressure supply port configured to supply negative pressure to at least one of these chambers (59) at a given instant, said at least one of these chambers (59) having an opening (57) adapted to supply negative pressure to this chamber (59), said device (51) further comprising: - a suction device (69) for suctioning powder sucked by said roller (54), said suction device (69) being arranged opposite to one of these chambers (59) of said roller (54) which is not supplied with negative pressure at a given instant.

2. The device (51) according to claim 1, wherein said chambers (59) extend along an axis of rotation of said roller (54), each chamber (59) being delimited by a section of said porous outer wall (53).

3. The device (51) of claim 1, wherein, said negative pressure supply port is fixedly connected to the support (61) of said roller (54), and wherein said chambers (59) are rotationally fixedly connected to said roller, and each chamber has an opening (57) adapted to supply positive pressure or negative pressure to said chamber (59), and said negative pressure supply port and said chambers are designed so that negative pressure is supplied to said chambers (59) during rotation of said roller (54).

4. The device (51) of claim 1, wherein, said device further comprising: - a positive pressure supply port configured to supply positive pressure to at least one of said chambers (59) which is not supplied with negative pressure at a given instant, via the opening (57) of said at least one chamber (59) which is not supplied with negative pressure at a given instant.

5. The device (51) according to claim 3, wherein said device further comprising a positive pressure supply port configured to supply positive pressure to at least one of said chambers (59) which is not supplied with negative pressure at a given instant, via the opening (57) of said at least one chamber (59) which is not supplied with negative pressure at a given instant, wherein said positive pressure supply port is fixedly connected to the support (61) of said roller (54), and wherein said negative pressure supply port, said positive pressure supply port and said chambers are designed to alternately supply negative pressure and positive pressure to said chambers (59) during rotation of said roller (54).

6. The device (51) according to claim 5, wherein said device (51) being designed so that, during rotation of said roller (54), the opening (57) of a chamber (59) is contacted by said negative pressure supply port once so that negative pressure is supplied to the corresponding chamber (59), and the opening of said chamber is contacted by said positive pressure supply port once so that positive pressure is supplied to the corresponding chamber (59).

7. The device (51) of claim 1, wherein, said roller (54) is formed in the shape of a cylindrical body, one or more openings (57) being provided in the bottom face of said cylindrical body.

8. The apparatus (51) of claim 4, wherein, at least three chambers (59) are formed within said roller (54), wherein the positive pressure supply port is configured to supply overpressure to multiple of the chambers (59) simultaneously, and / or wherein the negative pressure supply port is configured to supply negative pressure to multiple of the chambers (59) simultaneously.

9. The device (51) according to claim 8, wherein the positive pressure supply port has an elongated aperture (65) that simultaneously exposes openings (57) of multiple chambers (59), and / or wherein the negative pressure supply port has an elongated aperture (65) that simultaneously exposes openings (57) of multiple chambers (59).

10. The apparatus (51) of claim 1, wherein, The device further comprises: - a shaft (55) extending within the roller (54), wherein the plurality of chambers (59) is formed by a plurality of grooves formed in the shaft (55).

11. System (1) for producing a three-dimensional workpiece, the system comprising: - a carrier (5) for receiving a plurality of layers of powder, thereby forming a powder bed (3), - at least one powder application device (15a, 16b) for applying powder to the carrier (5), and - at least one irradiation unit for irradiating an uppermost powder layer of the powder bed (3) at a predetermined location, and - a device (51) for removing powder and / or particles from a powder bed (3) according to claim 1.

12. The system (1) according to claim 11, wherein, The device (51) is coupled to the powder application device (15a), and wherein the system (1) comprises a movement device configured to move the device (51) and the powder application device (15a) together.

13. The system (1) according to claim 11 or 12, wherein, The chambers (59) supplied with negative pressure are located on a side of the roller (54) facing the powder bed (3).

14. Method for removing powder and / or particles from a powder bed (3), the method comprising: - rotating a rotatable supported roller (54) having a porous outer wall (53), the roller (54) having a plurality of chambers (59) formed within the roller (54), at least one of the chambers (59) having an opening (57) adapted to provide negative pressure to the chamber (59); - at a given moment in time, supplying negative pressure to the at least one chamber (59) via the opening (57) of the at least one chamber (59); and - sucking out powder sucked by the roller (54) via a suction device (69) arranged opposite to one of the chambers (59) of the roller (54) that is not supplied with negative pressure at a given moment in time.

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