Layered object manufacturing apparatus

Abstract

The present invention provides a layered molding device that reduces the amount of inert gas used and has high airtightness. The layered molding device includes a chamber, an inert gas supply device, a material recovery line, a material tank, a material replenishment line, a transfer device, a classification device, a gas exhaust line, and a pump. The transfer device transfers metal powder together with inert gas. The gas exhaust line is connected to the transfer device and the chamber. The pump transports the inert gas discharged from the transfer device to the chamber.

Description

Technical Field

[0001] This disclosure relates to a layered shaping device. Background Technology

[0002] A lamination molding apparatus for powder bed fusion bonding repeatedly performs the following operations: spreading powder material to a specified thickness to form a material layer, and irradiating the material layer with a laser or electron beam to melt or sinter it to form a solidified layer, thereby creating the desired three-dimensional shape. Metal powder is sometimes used as the material.

[0003] When a material layer containing metal powder is irradiated with a laser or electron beam, a metal vapor known as fume is generated. To prevent fume leakage, the lamination process is preferably carried out in a sealed chamber. When the metal powder melts or sinters, it may deteriorate and its quality may be compromised in an atmosphere containing oxygen or other gases. Furthermore, metal powders containing easily oxidizable metals such as aluminum or titanium pose a risk of ignition in an oxygen-containing environment. Therefore, the chamber is preferably filled with a predetermined concentration of inert gas that does not substantially react with the metal powder.

[0004] Residual metal powder supplied to the chamber but not used to form the cured layer can be recovered during or after lamination and reused after removing inclusions. U.S. Patent Publications 10,569,331B2, 10,960,467B2, and US Patent Publication US2022 / 0118524A1 disclose lamination apparatuses including means for recovering and resupplying metal powder. An inert gas flow can be generated during the transport of the metal powder, and the metal powder can be transported by the gas flow. Summary of the Invention

[0005] [The problem the invention aims to solve]

[0006] When metal powder is expelled from the chamber by an inert gas flow, the inert gas inside the chamber is also expelled, thus depressurizing the chamber. External gas can easily flow into the depressurized chamber through unavoidable gaps, reducing the concentration of inert gas inside the chamber.

[0007] To maintain the lamination forming apparatus within an inert gas atmosphere and to reduce the amount of inert gas used, a lamination forming apparatus with high airtightness is sought. In particular, a structure is sought that minimizes the consumption of inert gas when transporting remaining material via an inert gas flow.

[0008] [Technical means to solve the problem]

[0009] This disclosure provides a layered shaping apparatus, comprising: a chamber covering an area capable of creating a three-dimensional shape, i.e., a shaping area, and filled with an inert gas; an inert gas supply device supplying the inert gas to the chamber; a material recovery pipeline connected to the chamber and allowing metal powder discharged from the chamber to flow through; a material tank storing the metal powder; a material replenishment pipeline connected to the material tank and the material recovery pipeline and allowing the metal powder discharged from the material tank to flow through; and a transfer device, comprising: a vacuum container; and a material suction port disposed at the chamber. The system includes a vacuum container connected to the material recovery pipeline; a gas exhaust port disposed in the vacuum container and discharging the inert gas; a material discharge port disposed in the vacuum container and discharging the metal powder, wherein the transfer device transfers the metal powder together with the inert gas; a grading device for removing inclusions from the metal powder transferred by the transfer device; a gas exhaust pipeline connected to the gas exhaust port and the chamber; and a pump disposed in the gas exhaust pipeline and delivering the inert gas discharged from the transfer device to the chamber.

[0010] [The effects of the invention]

[0011] The stacking forming apparatus disclosed herein includes a conveying device that transfers metal powder discharged from a chamber along with inert gas. The gas exhaust port of the conveying device is connected to the chamber via a gas exhaust pipe. A pump installed on the gas exhaust pipe generates an airflow of inert gas to convey the metal powder to the conveying device, and the inert gas discharged from the conveying device is returned to the chamber. This structure reduces the consumption of inert gas, thereby further reducing the amount of inert gas supplied to the chamber and maintaining the inert gas concentration in the chamber at a predetermined value. Furthermore, depressurization within the chamber is prevented, thus inhibiting the intrusion of external gases into the chamber. Attached Figure Description

[0012] Figure 1 This is a schematic diagram showing the structure of the layered forming device of this embodiment.

[0013] Figure 2 This is a cross-sectional view of the transfer device in this embodiment. Detailed Implementation

[0014] The layering forming apparatus described below is only one example, and various modifications can be made without departing from the technical concept of this disclosure. Figure 1 This illustrates an example of the schematic structure of the layered forming apparatus of this embodiment. For convenience, in the following description, [the following will be used as an example]. Figure 1The orientation is defined as a front view, but the positional relationship of the constituent components is not limited. The layered forming device of the present invention includes: a device body 1, a first inert gas supply device 2A and a second inert gas supply device 2B as inert gas supply devices, a smoke collector 3, an irradiation device 4, a coating machine 5, a material recycling device 6, and a chamber 7.

[0015] The various components are connected by piping. The piping includes: transfer piping for conveying the metal powder as material; and gas piping, which is essentially for the flow of inert gases only. Figure 1 In the diagram, transfer piping is represented by solid lines, and gas piping by dashed lines. The transfer piping forms part of the metal powder transfer path and includes: material recovery piping 8A, material replenishment piping 8B, material supply piping 8C, material storage piping 8D, material bottle connection piping 8E, and inclusion discharge piping 8F. The gas piping includes: first gas supply piping 9A, second gas supply piping 9B, fume recovery piping 9C, gas exhaust piping 9D, first bypass piping 9E, second bypass piping 9F, and repressurization piping 9G.

[0016] The device body 1 includes a base 1A, a platform 1B, and a shaping cover 1C. The platform 1B and the shaping cover 1C constitute a chamber 7.

[0017] The base 1A is the basic structure of the device body 1. The base 1A mainly includes a metal frame and metal plates. A shaping container 11 formed by four walls is set near the center of the base 1A. Inside the shaping container 11, the desired three-dimensional shape is stacked.

[0018] The base 1B is a worktable for performing layered shaping. The base 1B is horizontally disposed on the entire surface above the base 1A. A roughly quadrilateral through hole is formed near the center of the base 1B. A shaping platform 12, having an outer shape that conforms to the inner shape of the through hole, is housed in the shaping container 11. The shaping platform 12 essentially functions as the base plate of the shaping container 11.

[0019] The shaping platform 12 has a shaping area, or shaping region, capable of creating the desired three-dimensional shape. The shaping platform 12 is raised and lowered by a drive device equipped with an arbitrary actuator. An annular packing PK is used to seal the shaping platform 12 and the wall constituting the shaping tank 11. When the shaping platform 12 reciprocates in the vertical direction, it slides within the shaping tank 11 through the packing PK. Therefore, when the shaping platform 12 is raised and lowered, metal powder scattered on the shaping platform 12 is prevented from leaking out of the shaping tank 11 and falling onto the base 1A. Alternatively, a base plate BP can be placed on the shaping platform 12, and a three-dimensional shape can be formed on the base plate BP.

[0020] The shaping platform 12 can also be configured to be temperature-adjustable. In this embodiment, a temperature adjustment device 13 is provided directly below the shaping platform 12. The temperature adjustment device 13 includes either a heating device or a cooling device, preferably both. The heating device may be an electric heater. The cooling device may be a cooling pipe configured to allow refrigerant to flow.

[0021] A chute for collecting remaining metal powder is provided on the lower side of the base 1B. In this embodiment, discharge openings are formed at both ends of the base 1B, and a first chute 14A and a second chute 14B are respectively provided directly below each discharge opening. That is, the first chute 14A and the second chute 14B are provided to hold the shaping can 11 in place.

[0022] The remaining metal powder scattered on the base 1B during the layering process is pushed to the discharge opening as the coating machine 5 reciprocates on the base 1B, and thus falls into the first chute 14A or the second chute 14B. Alternatively, if the coating machine 5 is configured to store metal powder internally, by moving the coating machine 5 above the discharge opening, the metal powder inside the coating machine 5 is discharged into the first chute 14A or the second chute 14B. The first chute 14A and the second chute 14B may have a funnel shape. The metal powder discharged from the chamber 7 is stored in the first chute 14A and the second chute 14B. Material sensors MS1 and MS2 are respectively installed in the first chute 14A and the second chute 14B. Material sensors MS1 and MS2 detect the presence of a predetermined amount of metal powder stored in the first chute 14A and the second chute 14B.

[0023] A suction nozzle 18 is disposed within the chamber 7. The suction nozzle 18 is configured to suction metal powder present in the forming can 11 or on the base 1B.

[0024] The shaping cover 1C includes multiple wall panels and one or more top panels. The shaping cover 1C is disposed on the base 1A in such a way that it surrounds and covers the upper surface of the base 1B. In this manner, the chamber 7 including the base 1B and the shaping cover 1C covers the shaping area.

[0025] In the laminated configuration, chamber 7 is filled with inert gas. Chamber 7 is configured to be substantially airtight, but unavoidable gaps exist. For example, a small gap may form between the guide member of the reciprocating motion of the coating machine 5 and the base 1B.

[0026] If the air pressure inside chamber 7 is higher than the external air pressure, the inert gas inside chamber 7 flows out through the gap to the outside of chamber 7. On the other hand, if the air pressure inside chamber 7 is lower than the external air pressure, external gas flows into chamber 7 through the gap. To prevent external gas from intruding into chamber 7 and to maintain the inert gas concentration inside chamber 7 above a predetermined value, it is preferable to maintain the air pressure inside chamber 7 at a value equal to or slightly higher than atmospheric pressure. In this embodiment, the air pressure in chamber 7 is maintained at the desired value by continuously supplying fresh inert gas to the lamination forming apparatus from the inert gas supply device. The oxygen concentration inside chamber 7 is measured using an oxygen concentration meter OS1.

[0027] A window 15 is disposed on the top plate of the shaping cover 1C. The window 15 is configured to allow laser light to pass through. The laser light irradiated by the irradiation device 4 passes through the window 15 and irradiates the material layer containing metal powder formed on the shaping platform 12.

[0028] The anti-pollution device 16 is arranged to surround the window 15. The anti-pollution device 16 is a cylindrical component that supplies inert gas into the window and sprays inert gas downwards. This prevents fumes generated during the formation of the curing layer from adhering to the window 15.

[0029] An opening communicating with the inside and outside of chamber 7 is formed on the front wall of the shaping cover 1C. The operator can access chamber 7 through the opening. A front door 17 is provided at the opening, and the front door 17 is configured to be openable and closable. The front door 17 has an observation window 17A and a glove box 17B. The glove box 17B has a pair of through holes and a pair of gloves to block the through holes. The operator can perform work within chamber 7 with the front door 17 closed by using the glove box 17B. For example, the operator can operate the suction nozzle 18 via the glove box 17B to perform a cleaning operation to remove metal powder from chamber 7 in a substantially sealed state.

[0030] An inert gas supply device directly or indirectly supplies chamber 7 with a clean inert gas of a specified concentration. The inert gas can be any gas that does not substantially react with the metal powder; nitrogen or a rare gas can be used. Nitrogen is advantageous when the metal powder is a material that is not easily nitrided, as it is relatively inexpensive and readily available. When the metal powder is aluminum or titanium, a rare gas is sometimes used to prevent nitriding. Argon is generally used as a rare gas. Aluminum includes not only pure aluminum but also alloys with aluminum as the main component. Titanium includes not only pure titanium but also alloys with titanium as the main component.

[0031] When the inert gas is nitrogen, the inert gas supply device is a nitrogen generating device that generates nitrogen from air or a cylinder that stores nitrogen at a specified concentration. When the inert gas is argon, the inert gas supply device is a cylinder that stores argon at a specified concentration. A control valve may also be installed in the inert gas supply device.

[0032] When using gas cylinders as the inert gas supply device, there is a limitation on the continuous operating time. Furthermore, argon is more expensive than nitrogen. The stacking forming apparatus of this embodiment can suppress the amount of inert gas used, thus it is particularly advantageous when using argon as the inert gas.

[0033] In this embodiment, a first inert gas supply device 2A and a second inert gas supply device 2B are provided as inert gas supply devices. The first inert gas supply device 2A is connected to the chamber 7 and the anti-contamination device 16 via a first gas supply line 9A. The first inert gas supply device 2A supplies inert gas to the chamber 7 and the anti-contamination device 16. The second inert gas supply device 2B is connected to the material recycling device 6 via a second gas supply line 9B. The second inert gas supply device 2B supplies inert gas to the material recycling device 6.

[0034] In this embodiment, two inert gas supply devices are provided, but more than one inert gas supply device is sufficient. For example, one inert gas supply device can also supply inert gas to the chamber 7 and the material recycling device 6. In addition, the inert gas supply device can also be configured to arbitrarily switch the destination of the inert gas supply. For example, the gas piping can also be configured so that inert gas can be selectively supplied to the chamber 7 from either the first inert gas supply device 2A or the second inert gas supply device 2B.

[0035] The smoke collector 3 removes smoke from the inert gas containing smoke discharged from chamber 7 and returns clean inert gas to chamber 7. The smoke collector 3 may have an electrostatic precipitator or a filter. A smoke recovery line 9C connects chamber 7 to the smoke collector 3. Specifically, the smoke recovery line 9C includes: a line 9C1 connected to the inlet of chamber 7 and the smoke collector 3; and a line 9C2 connected to the outlet of the smoke collector 3 and chamber 7. The inert gas discharged from chamber 7 via line 9C1 is conveyed to the smoke collector 3. After removing smoke from the inert gas, the smoke collector 3 returns it to chamber 7 via line 9C2. To facilitate the circulation of the inert gas, a fan may also be installed on the wall of the hood 1C to increase the flow rate of the inert gas delivered to the smoke recovery line 9C. In this embodiment, the smoke collector 3 directly returns inert gas to the chamber 7, but the smoke recovery pipeline 9C can also be connected to the second gas supply pipeline 9B to supply inert gas to the material recycling device 6.

[0036] The location and number of inert gas supply ports for the inert gas supply device and the smoke collector 3 in chamber 7 are not limited. Similarly, the location and number of outlets for discharging inert gas to the smoke collector 3 in chamber 7 are not limited. The supply ports and outlets can be located on the shaping hood 1C or on components such as the coating machine 5 disposed within chamber 7.

[0037] The irradiation device 4 of this embodiment irradiates the shaping area within the chamber 7 with a laser. The irradiation device 4 includes a laser source that outputs the laser and a scanning device that scans the laser. The scanning device is, for example, a galvanoscanner. Alternatively, the irradiation device 4 can be configured to irradiate an electron beam instead of a laser. In this case, the irradiation device 4 includes: a cathode electrode that emits electrons, an anode electrode that collects and accelerates the electrons, a solenoid that forms a magnetic field to focus the electron beam in one direction, and a collector electrode that is electrically connected to the material layer being irradiated and applies a voltage between the collector electrode and the cathode electrode. In other words, the irradiation device 4 can be any device that irradiates a material layer formed in the shaping area with a laser or electron beam to sinter or melt the metal powder at the irradiation location to form a solidified layer.

[0038] The coating machine 5 disperses metal powder in the shaping area and flattens it to form a material layer of a specified thickness. Generally, a base plate BP is placed on the shaping platform 12, and the first material layer is formed on the base plate BP.

[0039] The coating machine 5 of this embodiment is configured to move horizontally while spraying out internally stored metal powder. The coating machine 5 of this embodiment includes: a coating head capable of storing and discharging metal powder from its bottom surface; a scraper mounted on the side of the coating head and spreading the metal powder evenly; and a drive device having an arbitrary actuator that reciprocates the coating head in the horizontal direction. A material sensor MS5 is provided in the coating head of the coating machine 5. The material sensor MS5 detects when the metal powder in the coating head is insufficient and needs to be replenished. The coating machine 5 may not have the function of internally storing metal powder, and is configured to at least enable the scraper to move.

[0040] The lamination forming apparatus may also include a machining device for cutting the cured layers. The machining device may include, for example, a machining head configured to move within a chamber 7; and a spindle disposed on the machining head and rotating a holding cutting tool. The cured layers can be cut whenever a predetermined number of cured layers are formed.

[0041] The material recycling device 6 resupplyes the chamber 7 after recovering the metal powder and removing inclusions. Inclusions include sputtered deposits scattered when the material layer is irradiated with a laser or electron beam, as well as chips generated during machining. The material recycling device 6 includes a transfer device 61, a material container 62, a classification device 63, and a pump 64.

[0042] The transfer device 61, material tank 62, and grading device 63 are housed in the frame 60 and constitute a unit. The frame 60 may be configured to be movable and to be able to contact / separate from the device body 1. In this embodiment, the pump 64 is not housed in the frame 60 but is disposed outside the device body 1. However, the pump 64 may also be housed in the frame 60. The piping on the device body 1 side and the piping on the material recycling device 6 side can be connected using any connecting member such as a ferrule FJ or a connector CP.

[0043] Material tank 62 stores metal powder. In this embodiment, material tank 62 is configured to store both unused metal powder and metal powder recovered from chamber 7. Metal powder recovered from chamber 7 can be conveyed to material tank 62 before or after inclusion removal. Material tank 62 is airtight. A second gas supply line 9B is connected to material tank 62, through which inert gas is filled into the material recycling apparatus 6. Material sensor MS3 and material sensor MS4 are installed in material tank 62. Material sensor MS3 and material sensor MS4 detect the upper and lower limits of the metal powder in material tank 62, respectively.

[0044] The material container 62 is configured to be connected to the material bottle MB via the material bottle connection pipe 8E. When replenishing metal powder from the material bottle MB to the material container 62, firstly, one or more on / off valves V5 provided in the material bottle connection pipe 8E are closed. After the material bottle MB is connected to the material bottle connection pipe 8E, the on / off valves V5 are opened, causing the metal powder stored in the material bottle MB to fall into the material container 62. In this way, metal powder can be replenished to the material container 62 while maintaining an airtight seal. In this embodiment, the material bottle MB is connected to the material container 62, but it can also be configured to be connected to other components such as the material container 65.

[0045] The material recovery pipeline 8A is connected to the chamber 7, that is, directly to the first chute 14A, the second chute 14B, and the suction nozzle 18, and allows the metal powder discharged from the chamber 7 to flow together with the inert gas. Specifically, the material recovery pipeline 8A includes: pipeline 8A1, connected to the first chute 14A and equipped with an on / off valve V1; pipeline 8A2, connected to the second chute 14B and equipped with an on / off valve V2; pipeline 8A3, connected to the suction nozzle 18 and equipped with an on / off valve V3; and pipeline 8A4, connected to pipelines 8A1, 8A2, 8A3, and the transfer device 61.

[0046] Material replenishment line 8B is connected to material tank 62 and material recovery line 8A via line 8A4, allowing metal powder discharged from material tank 62 to flow along with inert gas. An on / off valve V4 is installed in material replenishment line 8B. First bypass line 9E is connected to chamber 7 and material tank 62, allowing inert gas to flow through. Second bypass line 9F is connected to material tank 62 and material replenishment line 8B, also allowing inert gas to flow through. Through the first bypass line 9E and the second bypass line 9F, the pressure between chamber 7, material tank 62, and material replenishment line 8B is equalized, thus allowing appropriate transfer of metal powder from material tank 62.

[0047] When transferring metal powder, the on / off valve corresponding to the transfer source is opened selectively. That is, when metal powder is transferred from the first chute 14A, on / off valve V1 is opened, and on / off valves V2, V3, and V4 are closed. When metal powder is transferred from the second chute 14B, on / off valve V2 is opened, and on / off valves V1, V3, and V4 are closed. When metal powder is transferred from the suction nozzle 18, on / off valve V3 is opened, and on / off valves V1, V2, and V4 are closed. When metal powder is transferred from the material tank 62, on / off valve V4 is opened, and on / off valves V1, V2, and V3 are closed. However, metal powder can also be transferred from multiple locations simultaneously, in which case multiple on / off valves are opened simultaneously.

[0048] The transfer device 61 draws in the metal powder from the chamber 7 and the material container 62 along with inert gas, and then transfers the metal powder along with the inert gas flow. Specifically, in this embodiment, the transfer device 61 is positioned at the highest point of the metal powder's transfer path, and transfers the metal powder to the highest point of the material recycling device 6. By placing the transfer device 61 at the highest point, the supply and recovery of metal powder can be performed using a single transfer device. The structure of the material recycling device 6, with only one transfer device, is advantageous in making the maintenance and management of the material recycling device 6 easier, improving the airtightness of the material recycling device 6, and minimizing contact between the metal powder and external gases.

[0049] The transfer device 61 in this embodiment can be a vacuum conveyor. For example... Figure 2 As shown, the transfer device 61 includes: a vacuum container 61A, a gas exhaust port 61B, a material intake port 61C, a metal powder material discharge port 61D, a bottom cover 61E, and a filter 61F. The vacuum container 61A is configured to be airtight. The gas exhaust port 61B, the material intake port 61C, and the material discharge port 61D are disposed within the vacuum container 61A. The bottom cover 61E is driven by any actuator to open and close the material discharge port 61D. In this embodiment, the material discharge port 61D and the bottom cover 61E are circular, but any shape can be used. The filter 61F is disposed within the gas exhaust port 61B and prevents particles containing metal materials from entering the gas exhaust pipe 9D.

[0050] Gas exhaust port 61B is connected to chamber 7 via gas exhaust pipe 9D and pump 64. In other words, gas exhaust pipe 9D is connected to gas exhaust port 61B and chamber 7. Pump 64 is installed in gas exhaust pipe 9D. That is, the inlet port of pump 64 is connected to the pipe on the transfer device 61 side of gas exhaust pipe 9D, and the exhaust port of pump 64 is connected to the pipe on the chamber 7 side of gas exhaust pipe 9D. Pump 64 has no inlet or outlet for inert gas except for the inlet and exhaust ports. In other words, pump 64 is airtight. Pump 64 functions as the driving source for transfer device 61. Inert gas in chamber 7 flows into vacuum container 61A from material suction port 61C along with metal powder through material recovery pipe 8A via pump 64. Inert gas in vacuum container 61A is discharged from gas exhaust port 61B via pump 64 and returns to chamber 7 via gas exhaust pipe 9D. A pressure gauge PG can be installed in the gas exhaust pipe 9D.

[0051] The material inlet 61C is connected to the first chute 14A, the second chute 14B, the suction nozzle 18, and the material tank 62 via the material recovery pipe 8A and the material replenishment pipe 8B. Pipeline 8A4 is directly connected to the material inlet 61C. When the pump 64 is driven with the material outlet 61D closed using the bottom cover 61E, the bottom cover 61E is sucked up along the direction of the vacuum container 61A and fixed in place while the material outlet 61D is closed. When the material outlet 61D is closed, the vacuum container 61A is substantially airtight.

[0052] With the pump 64 operating continuously while the vacuum container 61A is airtight, the inert gas in the vacuum container 61A is exhausted into the chamber 7 through the gas exhaust pipe 9D. As the vacuum level gradually increases and the pressure inside the vacuum container 61A is gradually reduced, a pressure difference is generated between the vacuum container 61A and the chamber 7, and the inert gas in the chamber 7 is drawn into the transfer device 61.

[0053] Thus, the metal powder, carried by the inert gas flow, is transferred to the vacuum container 61A via the material recovery pipeline 8A. Similarly, when transferring metal powder from the material tank 62, the metal powder is transferred to the vacuum container 61A along with the inert gas.

[0054] The metal powder transferred into the vacuum container 61A falls freely due to its own weight. When the bottom cover 61E is driven to open the material discharge port 61D, the metal powder that has reached the bottom of the vacuum container 61A falls from the material discharge port 61D. Below the material discharge port 61D, a switching valve S1 is provided. The switching valve S1 selectively switches the discharge destination of the metal powder falling from the material discharge port 61D to either the material tank 62 or the classification device 63, which is located lower than the transfer device 61. The switching valve S1 can be configured as follows: Figure 2 It can be integrated with the transfer device 61, or it can be installed independently.

[0055] In the lamination forming apparatus of this embodiment, a circulation path for inert gas is formed connecting the chamber 7 and the transfer device 61. This circulation path is a closed loop that is not connected to the outside of the lamination forming apparatus and is isolated from external gas. That is, when transferring metal powder, the inert gas is not exhausted to the outside of the lamination forming apparatus. The transfer device 61 of this embodiment does not include a pressure-reducing mechanism such as an exhaust fan that is intended to exhaust gas to the outside of the lamination forming apparatus.

[0056] In the material recycling apparatus 6 of this embodiment, while the inert gas in the chamber 7 continuously flows into the vacuum container 61A of the transfer device 61, the inert gas exhausted from the gas exhaust port 61B is not discharged outside the material recycling apparatus 6 but is returned to the chamber 7 by the pump 64. Therefore, even if new inert gas is not frequently supplied to the chamber 7, the chamber 7 is not substantially depressurized, and it is not easy for external gas to enter the chamber 7. In addition, external gas does not substantially flow in during the material recycling apparatus 6. Therefore, metal powder can be discharged from the sealed chamber 7, which is in an inert gas atmosphere.

[0057] The vacuum level in vacuum container 61A only needs to be maintained at a level sufficient to provide suction for transferring the metal powder. Furthermore, the gas exhaust line 9D must be isolated from external gas and prevent external gas from flowing in. Pump 64 can be a vacuum pump. Pump 64 is preferably a pump suitable for high-sealing and relatively low-vacuum regions; for example, a vane pump can be used.

[0058] During the transfer of metal powder in the material recycling device 6, the entire device is under negative pressure. Even after the transfer of metal powder ends and the pump 64 stops, the material recycling device 6 remains under negative pressure. If the material recycling device 6 remains under negative pressure for an extended period, there is a risk of external gas intruding through minute gaps. Furthermore, in this embodiment, during the transfer of metal powder, the material outlet 61D of the transfer device 61 is closed by the bottom cover 61E. If the vacuum container 61A is under negative pressure, it is difficult to open the bottom cover 61E.

[0059] The repressurization line 9G is configured to repressurize the vacuum container 61A after transferring metal powder by supplying inert gas from the chamber 7 to the transfer device 61. Specifically, the repressurization line 9G is connected to the material recovery line 8A4 and the first bypass line 9E, and is supplied with inert gas. The repressurization line 9G connects the material reuse device 6 to the chamber 7 without obstructing the presence of any other device besides the line. The repressurization line 9G can also be directly connected to the chamber 7. However, by directly connecting to the first bypass line 9E, the connector CP connecting the various lines constituting the repressurization line 9G may not be required in the frame 60.

[0060] An on / off valve V7 can be installed in the pressure-reinforcing pipeline 9G to open and close the pipeline. When the pump 64 is running, i.e., when transferring metal materials, the on / off valve V7 is closed. The on / off valve V7 opens after the metal material transfer is complete and the pump 64 stops, thus opening the pressure-reinforcing pipeline 9G. The on / off valve V7 can close after a certain period of time or remain open until the next start of the pump 64. When the pressure-reinforcing pipeline 9G is open, because the air pressure inside the material recycling device 6 is lower than the air pressure in the chamber 7, the inert gas in the chamber 7 flows into the material recycling device 6 through the pressure-reinforcing pipeline 9G. This allows for pressure re-pressurization within the material recycling device 6, making it easy to open the bottom cover 61E.

[0061] Furthermore, if the amount of inert gas discharged from the gas exhaust line 9D exceeds the amount of inert gas supplied from the repressurization line 9G, the vacuum container 61A is depressurized, so there is no need to install the on / off valve V7.

[0062] The grading device 63 is positioned below the transfer device 61, removing inclusions from the metal powder and discharging it downwards. The removed inclusions are transported to the recovery container 66 via the inclusion discharge pipe 8F. A material sensor MS7 can be installed in the recovery container 66. The material sensor MS7 detects when the amount of inclusions in the recovery container 66 reaches a predetermined level. The grading device 63 is, for example, a sieve. In this embodiment, the grading device 63 is an ultrasonic sieve, having a mesh filter, a filter housing housing the mesh filter, and a vibrating element that vibrates the mesh filter. The grading device 63 is airtight. A switching valve S2 is provided below the grading device 63. The switching valve S2 selectively switches the discharge destination of the metal powder falling from the grading device 63 to either a material tank 62 or a material container 65 located below the transfer device 61. The switching valve S2 can be integrated with the grading device 63 or installed independently.

[0063] Material container 65 resupplyes the metal powder conveyed from material recycling device 6 to chamber 7. Material container 65 includes a connecting member that connects material recycling device 6 to chamber 7, and a guiding member that guides the metal powder to the coating head of coating machine 5. The connecting member is, for example, a serpentine passage connecting switching valve S2 to the guiding member. The guiding member includes a storage chute for storing metal powder, and a gate that switches the metal material discharge from the storage chute from the storage chute between ON and OFF. In this embodiment, material container 65 stores the metal powder conveyed from grading device 63 and supplies it to the coating head of coating machine 5. When material sensor MS5 of coating machine 5 detects insufficient metal material in the coating head, material container 65 opens the material outlet and replenishes the coating head with metal material. Material sensor MS6 is provided on the guiding member of material container 65. Material sensor MS6 detects when the metal powder in material container 65 is insufficient and needs to be replenished.

[0064] An oxygen concentration meter OS2 may be installed in the material recycling device 6. In this embodiment, the oxygen concentration meter OS2 is connected to the grading device 63. When the oxygen concentration meter OS2 detects that the oxygen concentration in the material recycling device 6 has increased, it supplies inert gas to the material recycling device 6 from the second inert gas supply device 2B, or increases the amount of inert gas supplied. In this way, the inert gas concentration in the material recycling device 6 is controlled to prevent it from decreasing.

[0065] Material supply line 8C conveys metal powder from transfer device 61 to chamber 7. Material supply line 8C includes: line 8C1, connected to material outlet 61D of transfer device 61 and classifying device 63; and line 8C2, connected to classifying device 63 and material container 65. Material storage line 8D conveys metal powder from transfer device 61 or classifying device 63 to material tank 62. Material storage line 8D includes: line 8D1, connected to material outlet 61D of transfer device 61 and material tank 62; and line 8D2, connected to classifying device 63 and material tank 62.

[0066] Pipelines 8C1 and 8D1 are connected to switching valve S1, which switches the discharge destination of the metal material, including inclusions, falling from the transfer device 61 to material tank 62 or grading device 63. Pipelines 8C2 and 8D2 are connected to switching valve S2, which switches the discharge destination of the metal material, excluding inclusions, falling from the grading device 63 to material tank 62 or material container 65.

[0067] One or more on / off valves V6 and collars FJ can be installed in the pipeline 8D2. It can be configured to recover metal powder, after impurity removal, from an empty material bottle MB midway through the pipeline 8D2. First, the on / off valve V6 is closed, and the pipeline 8D2 is separated at the position of the collar FJ. Then, the material bottle MB is connected to the pipeline 8D2, and the metal material falling from the grading device 63 is recovered into the material bottle MB. The metal material recovered into the material bottle MB can be used as a material for layering and shaping.

[0068] The control unit of the stacking molding apparatus can be constructed by arbitrarily combining hardware and software, and may include a central processing unit (CPU), random access memory (RAM), read-only memory (ROM), auxiliary storage devices, and input / output interfaces. The control unit can also function as a numerical control device for controlling processes related to stacking molding. The control unit is connected to material sensors MS1, MS2, MS3, MS4, MS5, MS6, and MS7, as well as oxygen meters OS1 and OS2, and can use the measurement results for the control of each component. The control unit can control pump 64, on / off valves V1, V2, V3, V4, V5, V6, and V7, and switching valves S1 and S2, thereby switching the path of the metal powder or inert gas to transport the metal powder along the desired path. However, switching valves S1 and S2 can also be manually controlled.

[0069] Here, the operation of the layering shaping device of this embodiment will be explained.

[0070] Before the lamination process, the first inert gas supply device 2A supplies inert gas to chamber 7, creating an inert gas atmosphere within chamber 7. Additionally, the second inert gas supply device 2B supplies inert gas to the material recycling device 6 via material tank 62, creating an inert gas atmosphere within the material recycling device 6. If insufficient metal powder is stored in material tank 62, the operator replenishes material tank 62 with metal powder from material bottle MB.

[0071] Next, metal powder is replenished to the coating machine 5. Switching valve S1 switches the discharge destination of the metal powder from the transfer device 61 to the classifying device 63. Switching valve S2 switches the discharge destination of the metal powder from the classifying device 63 to the material container 65. By driving pump 64 with the on / off valve V4 open, the metal powder in the material tank 62 is transferred by the transfer device 61 and supplied to the material container 65 via the classifying device 63. Then, metal powder is supplied to the coating machine 5 from the material container 65.

[0072] Once the lamination process begins, the lamination apparatus alternately and repeatedly forms material layers and cured layers. The coating machine 5 moves horizontally to form material layers. The irradiation device 4 irradiates the material layers with a laser to form a cured layer. The forming platform 12 descends, forming material layers and cured layers in the same sequence.

[0073] Here, the transfer of metal powder during the lamination process is described. When the material sensor MS5 detects a shortage of metal powder in the coating machine 5, metal powder is replenished to the coating machine 5 from the material container 65. When the material sensor MS6 detects a shortage of metal powder in the material container 65, the transfer device 61 transfers metal powder from the first chute 14A, the second chute 14B, or the material tank 62 and delivers it to the material container 65. At this time, the switching valve S1 selects pipeline 8C1, and the switching valve S2 selects pipeline 8C2. The metal powder supply source can be any of the first chute 14A, the second chute 14B, or the material tank 62, and the priority order in selecting the supply source can be predetermined. In this way, the material recycling device 6 supplies metal material into the chamber 7 via the material container 65. Since the removal of inclusions by the grading device 63 requires a certain amount of time, by storing metal powder in the material container 65, material replenishment to the coating machine 5 can be carried out while the lamination process continues.

[0074] When material sensor MS1 detects that a predetermined amount of metal powder is stored in the first chute 14A, the metal powder can be recovered from the first chute 14A and returned to the material tank 62. When material sensor MS2 detects that a predetermined amount of metal powder is stored in the second chute 14B, the metal powder can be recovered from the second chute 14B and returned to the material tank 62. In this case, if metal powder is recovered after removing inclusions, switching valve S1 selects pipeline 8C1, and switching valve S2 selects pipeline 8D2. If metal powder is recovered without removing inclusions, switching valve S1 selects pipeline 8D1. In this way, the material recycling device 6 recovers the metal powder discharged outside the chamber 7 via the transfer device 61 and collects the recovered metal powder in the material tank 62.

[0075] Here, the transfer of the layered metal powder is described. The operator performs a cleaning operation to recover the metal powder remaining in chamber 7. The operator operates the suction nozzle 18 via glove box 17B to recover the metal powder from chamber 7 to material tank 62. In this way, the operator can perform the cleaning operation with the front door 17 closed and chamber 7 substantially sealed. In addition, the metal powder stored in the first chute 14A and the second chute 14B is also recovered to material tank 62. Inert gas is also supplied from the first inert gas supply device 2A and the second inert gas supply device 2B during the cleaning operation. The amount of inert gas supplied is a small amount that maintains the internal pressure of chamber 7 at around atmospheric pressure.

[0076] When recovering metal powder during cleaning operations, if the metal powder is recovered after removing impurities, switching valve S1 selects pipeline 8C1, and switching valve S2 selects pipeline 8D2. If the metal powder is recovered without removing impurities, switching valve S1 selects pipeline 8D1. Since the amount of metal powder recovered during cleaning operations is relatively large, to optimize operation speed, the metal powder can be recovered without removing impurities.

[0077] According to the stacking forming apparatus of this embodiment, operations can be performed while maintaining the metal powder in an inert gas atmosphere during stacking forming and cleaning. The metal powder, in principle, does not come into contact with external gases, thus preventing deterioration. Furthermore, the inert gas used to transport the metal powder is returned to chamber 7 via a repressurization pipeline 9G, thereby reducing the amount of inert gas used and preventing external gases from entering chamber 7. The stacking forming apparatus of this embodiment is particularly advantageous when relatively expensive argon is used as the inert gas. Additionally, the stacking forming apparatus of this embodiment is particularly advantageous when using metal materials with high reactivity with oxygen, such as aluminum or titanium.

[0078] After the cleaning operation is completed, the metal powder can also be recovered from the material container 62. As mentioned above, the material bottle MB can also be connected to the pipeline 8D2 to recover the metal material into the material bottle MB.

Claims

1. A layered shaping device, comprising: The chamber covers the area capable of creating three-dimensional shapes, i.e., the shaping area, and is filled with inert gas; An inert gas supply device supplies the inert gas to the chamber; A material recovery pipeline is connected to the chamber and allows the metal powder discharged from the chamber to flow through; Material container for storing the metal powder; A material replenishment pipeline is connected to the material tank and the material recovery pipeline, and allows the metal powder discharged from the material tank to flow through; A transfer device includes: a vacuum container; a material inlet disposed in the vacuum container and connected to the material recovery pipeline; a gas outlet disposed in the vacuum container and discharging the inert gas; a material outlet disposed in the vacuum container and discharging the metal powder; and a bottom cover configured to open and close the material outlet, wherein the transfer device transfers the metal powder together with the inert gas. A grading device removes inclusions from the metal powder transferred by the conveying device; A gas exhaust pipe is connected to the gas exhaust port and the chamber; and A pump is installed in the gas exhaust pipeline and delivers the inert gas discharged from the transfer device to the chamber; A repressurization line, configured to supply the inert gas from the chamber to the transfer device and repressurize the vacuum container; and An on / off valve for opening and closing the pressure-reducing pipeline, the valve being configured to close when the pump is running and open after the pump stops. The gas exhaust pipe, the chamber, the repressurization pipe, and the transfer device form a closed loop that is isolated from the external gas.

2. The layered forming apparatus according to claim 1 further includes a first bypass pipe, the first bypass pipe being connected to the chamber and the material tank and allowing the inert gas to circulate. The pressure-recovery pipeline is connected to the material recovery pipeline and the first bypass pipeline.

3. The layered shaping device according to claim 1, wherein, The transfer device is positioned at the highest point of the transfer path of the metal powder.

4. The layered forming apparatus according to claim 1 further includes a frame, the frame housing the material tank, the transfer device, and the grading device.

5. The layered shaping device according to claim 1, wherein, The metal powder is aluminum.

6. The layered shaping device according to claim 1, wherein, The metal powder is titanium.

7. The layered shaping device according to claim 1, wherein, The inert gas supply device is a gas cylinder for storing argon gas.

8. The layered shaping device according to claim 1, wherein, The pump in question is a vane pump.

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