Powder self-circulation device, additive manufacturing production line and powder self-circulation method

Abstract

The invention relates to the field of additive manufacturing. The invention relates to a powder self-circulation device, in particular to a powder self-circulation device, an additive manufacturing production line and a powder self-circulation method. According to the powder self-circulation device used for additive manufacturing, the additive manufacturing production line with the powder self-circulation device and the powder self-circulation method of the additive manufacturing production line, the powder self-circulation device integrates automatic powder conveying, screening and collecting, meanwhile, the powder drying function is integrated, powder is subjected to multi-stage drying in the circulation process, and the powder drying efficiency is improved. And drying of the metal powder is guaranteed, manual powder drying and transferring processes are reduced, closed-loop control over the whole powder treatment process is achieved, the automatic powder treatment efficiency is improved, and practicability is high.

Description

Technical Field

[0001] The present invention relates to the field of additive manufacturing, and more specifically, to a powder self-circulation device, an additive manufacturing production line, and a powder self-circulation method. Background Art

[0002] Additive manufacturing technology, also known as 3D printing, realizes the manufacture of parts by stacking materials layer by layer. Among them, powder bed fusion technology, as a typical additive manufacturing technology, can realize the precise and complex forming of metal parts. In the specific forming process, the processes involving metal powder include: adding powder, spreading powder, powder melting, screening, drying, etc. Generally, manual operation is required, which is inefficient, the powder is also easy to oxidize, and there is also a risk of explosion. Although there is currently a closed-loop powder processing system that integrates automated powder conveying, screening, and collection, such as a 3D printing powder conveying and screening machine and circulation system disclosed in the Chinese invention patent with publication number CN114918126A, it is mainly used to solve the problem of realizing a series of automated circulation control solutions such as powder conveying, screening, and collection in the 3D printing manufacturing process. However, the 3D printing powder conveying and screening machine and the circulation system in the above scheme lack the important powder drying function, and the powder is not dried thoroughly, which will affect the quality of the powder spreading and the subsequent forming effect. Summary of the invention

[0003] The purpose of the present invention is to provide a powder self-circulation device for additive manufacturing, an additive manufacturing production line having the same, and a powder self-circulation method for the additive manufacturing production line. The powder self-circulation device integrates automatic powder transportation, screening, and collection, and also integrates a powder drying function, so that the powder is subjected to multi-stage drying during the circulation process, ensuring the dryness of the metal powder, reducing manual drying of the powder and the transfer process, and controlling the entire powder processing process in a closed loop, thereby improving the efficiency of automatic powder processing and having strong practicality.

[0004] In order to achieve these purposes and other advantages according to the present invention, a powder self-circulation device is provided, including a used powder conveying pipeline, on which a pipeline heating mechanism, a used powder buffer cabin, a separation screen and a powder temporary storage cabin are sequentially provided along the powder transmission direction of the used powder conveying pipeline, a protective gas inlet and outlet are provided on the used powder buffer cabin, a temporary storage cabin controllable valve is provided at the discharge port of the powder temporary storage cabin, the feed port of the used powder conveying pipeline is connected to the used powder buffer cabin through a used powder return air pipeline, and the discharge port of the used powder conveying pipeline and the powder temporary storage cabin are connected through a circulating powder return air pipeline.

[0005] Furthermore, in the powder self-circulation device, the screen of the separation screen is a heating screen.

[0006] Furthermore, the powder self-circulation device also includes a used powder recovery cabin, the discharge port of the used powder recovery cabin is connected to the feed port of the used powder conveying pipeline, and the feed port and discharge port of the used powder recovery cabin are respectively provided with a first used powder recovery cabin controllable valve and a second used powder recovery cabin controllable valve.

[0007] Furthermore, the powder self-circulation device also includes a circulating powder buffer tank, the feed port of the circulating powder buffer tank is connected to the discharge port of the used powder conveying pipeline, and a circulating powder buffer tank controllable valve is provided at the discharge port of the circulating powder buffer tank.

[0008] The present invention also provides an additive manufacturing production line, including a printing device and the above-mentioned powder self-circulation device, wherein the feed port and the discharge port of the used powder conveying pipeline are respectively connected to the used powder outlet and the powder storage compartment of the printing device.

[0009] Furthermore, the additive manufacturing production line also includes a used powder recovery tank and a circulating powder buffer tank. The used powder recovery tank and the feed port are connected with the used powder outlet of the printing device, the discharge port of the circulating powder buffer tank is connected with the feed port of the powder storage tank of the printing device, and the feed port and discharge port of the used powder conveying pipeline are respectively connected with the discharge port of the used powder recovery tank and the feed port of the circulating powder buffer tank.

[0010] The present invention also provides an additive manufacturing powder self-circulation method, which uses the above-mentioned additive manufacturing production line and includes the following steps:

[0011] S1. A used powder recovery tank and a circulating powder buffer tank are provided, wherein the feed port of the used powder recovery tank is connected to the used powder outlet of the printing device, and the discharge port thereof is connected to the feed port of the used powder conveying pipeline; the feed port of the circulating powder buffer tank is connected to the discharge port of the used powder conveying pipeline, and the discharge port thereof is connected to the feed port of the powder storage tank of the printing device;

[0012] S2, the printing device starts working, and the excess powder generated during the working process enters the used powder recovery chamber;

[0013] S3, introducing protective gas into the old powder buffer cabin to perform gas replacement;

[0014] S4, forming a negative pressure in the old powder buffer cabin through the old powder return air pipeline, and the powder in the old powder recovery cabin is transported to the old powder buffer cabin by negative pressure through the old powder transport pipeline, and the old powder is heated when passing through the pipeline heating mechanism. After the old powder in the old powder buffer cabin is sieved by the separation screen, the old powder with qualified particle size enters the powder temporary storage cabin;

[0015] S5, forming a negative pressure in the circulating powder buffer cabin through the circulating powder return air pipeline, and the powder in the powder temporary storage cabin is transported to the circulating powder buffer cabin through the circulating powder return air pipeline under negative pressure;

[0016] S6. When the powder storage chamber of the printing device has insufficient powder, the circulating powder buffer chamber transports powder into the powder storage chamber.

[0017] Furthermore, in the aforementioned method for self-circulating powder in additive manufacturing, a first controllable valve for the old powder recovery cabin and a second controllable valve for the old powder recovery cabin are respectively provided at the inlet and outlet of the old powder recovery cabin, and a controllable valve for the circulating powder buffer cabin is provided at the outlet of the circulating powder buffer cabin. In the initial state, the controllable valve for the temporary storage cabin, the controllable valve for the second old powder recovery cabin and the controllable valve for the circulating powder buffer cabin are all in a closed state, and the controllable valve for the first old powder recovery cabin is in an open state.

[0018] S4 specifically includes:

[0019] S4.1. When the level meter of the used powder recovery tank detects that the used powder storage in the used powder recovery tank has reached its maximum threshold, the controllable valve of the first used powder recovery tank is closed, the controllable valve of the second used powder recovery tank is opened, and after the pipeline heating mechanism and the separation screen start to work, the used powder return air pipeline starts to work, and the powder in the used powder recovery tank is sent to the used powder buffer tank through the used powder conveying pipeline;

[0020] S4.2. When the level meter of the used powder recovery tank detects that the used powder storage in the used powder recovery tank is lower than its minimum threshold, the pipeline heating mechanism and the used powder return air pipeline stop working, the controllable valve of the first used powder recovery tank is opened, and the controllable valve of the second used powder recovery tank is closed;

[0021] S4.3. The old powder in the old powder buffer chamber enters the separation screen. After the old powder is screened and reheated by the separation screen, the old powder enters the powder temporary storage chamber for storage.

[0022] Furthermore, in the additive manufacturing powder self-circulation method, S5 specifically includes:

[0023] S5.1. When the circulating powder buffer tank level meter in the circulating powder buffer tank detects that the old powder storage in the circulating powder buffer tank is lower than its minimum threshold, the controllable valve of the temporary storage tank is opened, and the circulating powder return air pipeline starts to work, and the powder in the powder temporary storage tank is sent to the circulating powder buffer tank through the old powder conveying pipeline;

[0024] S5.2. When the circulating powder buffer tank level meter in the circulating powder buffer tank detects that the old powder storage in the circulating powder buffer tank has reached its maximum threshold, the controllable valve of the temporary storage tank is closed and the circulating powder return air pipeline stops working.

[0025] Furthermore, in the additive manufacturing powder self-circulation method, S6 specifically includes:

[0026] When the powder storage tank level meter in the powder storage tank of the printing device detects that the powder reserve in the powder storage tank is lower than its minimum threshold value, the air pressure detector in the circulating powder buffer tank detects that the air pressure in the circulating powder buffer tank is close to the air pressure in the powder storage tank, and the controllable valve of the circulating powder buffer tank opens, so that the old powder in the powder storage tank enters the powder storage tank under the action of gravity.

[0027] The beneficial effects of the present invention are:

[0028] The present invention adopts a graded drying type powder self-circulation device, and integrates the powder graded drying function into the powder self-circulation system, so that the powder drying efficiency is higher and the effect is better; the manual powder drying process is reduced, and the efficiency of powder processing is improved; and the metal powder is placed in the self-circulation device under a protective gas environment, which reduces its contact with the air environment and greatly reduces the risk of powder oxidation and explosion.

[0029] Other advantages, objectives and features of the present invention will be embodied in part through the following description, and in part will be understood by those skilled in the art through study and practice of the present invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] Figure 1 It is a schematic structural diagram of the additive manufacturing production line described in the present invention.

[0031] Wherein, the reference numerals represent:

[0032] 101-protective gas inlet and outlet, 102-new powder adding port, 103-old powder buffer tank, 104-separation screen, 105-powder temporary storage tank, 106-temporary storage tank controllable valve, 107-old powder conveying pipeline, 108-circulating powder return air pipeline, 109-circulating powder buffer tank, 110-air pressure detector, 111-circulating powder buffer tank level meter, 112-circulating powder buffer tank controllable valve, 113-powder storage tank, 114-powder storage tank level meter, 115-old powder recovery tank, 116-old powder recovery tank level meter, 117-first old powder recovery tank controllable valve, 118-second old powder recovery tank controllable valve, 119-printing equipment, 120-old powder return air pipeline, 121-pipeline heating mechanism. DETAILED DESCRIPTION

[0033] The present invention is further described in detail below in conjunction with embodiments so that those skilled in the art can implement the invention with reference to the description.

[0034] It should be noted that, in the description of the present invention, the terms "lateral", "longitudinal", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside" and "outside" etc. indicating orientations or positional relationships are based on the orientations or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as a limitation on the present invention.

[0035] like Figure 1 As shown, an embodiment of the present invention provides a powder self-circulation device, including a used powder conveying pipeline 107, on which a pipeline heating mechanism 121, a used powder buffer cabin 103, a separation screen 104 and a powder temporary storage cabin 105 are sequentially arranged along the transmission direction of the powder, and the used powder buffer cabin 103, the heating separation screen 104 and the powder temporary storage cabin 105 are distributed from top to bottom, a protective gas inlet and outlet 101 is arranged on the used powder buffer cabin 103, a temporary storage cabin controllable valve 106 is arranged at the discharge port of the powder temporary storage cabin 105, the feed port of the used powder conveying pipeline 107 is connected to the used powder buffer cabin 103 through a used powder return air pipeline 120, and the discharge port of the used powder conveying pipeline 107 and the powder temporary storage cabin 105 are connected through a circulating powder return air pipeline 108.

[0036] In this embodiment, when the powder self-circulation device is in use, the feed port of the old powder conveying pipeline 107 is connected to the old powder recovery cabin 115 and the powder storage cabin 113 of the additive manufacturing equipment respectively. The old powder recovery cabin 115, the old powder buffer cabin 103, the separation screen 104, the powder temporary storage cabin 105 and the powder storage cabin 113 are connected through the old powder conveying pipeline 107 to form a passage, and a protective gas is introduced into the passage to prevent the metal powder from oxidizing. The powder in the old powder recovery cabin 115 enters the powder storage cabin 113 through the above-mentioned passage, realizing the powder self-circulation of the additive manufacturing equipment. Specifically, the old powder return air pipeline 120 and the circulating powder return air pipeline 108 can respectively use existing negative pressure pipelines. The negative pressure pipeline mainly uses the air pump at its outlet end to extract the gas and then form a negative pressure in the pipeline. The negative pressure pipeline can be easily realized by the existing technology and will not be specifically expanded here. The gas in the old powder buffer cabin 103 is extracted outward through the old powder return air pipeline 120 and sent to the old powder recovery cabin 115, forming a negative pressure in the old powder buffer cabin 103. At this time, the old powder in the old powder recovery cabin 115 enters the old powder conveying pipeline 107 and is conveyed to the old powder buffer cabin 103. During this period, the pipeline is heated by the pipeline heating mechanism 121. When the old powder passes through the part of the pipeline heated by the pipeline heating mechanism 121, the old powder can be heated and dried, so that the water and metal powder are initially separated. After all the old powder enters the old powder buffer cabin 103, the old powder return air pipeline 120 stops working, and the powder in the old powder buffer cabin 103 enters the separation screen 104 under the action of gravity. The separation screen 104 is used to screen out and separate some metal powders whose particle size does not meet the requirements of additive manufacturing, and some powders whose particle size meets the requirements of additive manufacturing enter the powder temporary storage cabin 105 through the old powder conveying pipeline 107.

[0037] When the powder collected in the powder temporary storage chamber 105 is needed, the controllable valve 106 of the temporary storage chamber is opened. Similarly, the gas in the powder temporary storage chamber 105 is drawn to the powder storage chamber 113 through the circulating powder return air pipeline 108, forming a negative pressure in the powder temporary storage chamber 105. At this time, the old powder in the powder temporary storage chamber 105 enters the old powder conveying pipeline 107 and is conveyed to the powder storage chamber 113.

[0038] Preferably, as another embodiment of the present invention, the screen of the separation screen is a heating screen.

[0039] In this embodiment, the screen of the separation screen 104 is made of metal wire, and a heating device is arranged on the screen of the separation screen 104, so that the screen of the separation screen 104 is a heating screen. While screening the powder, secondary heating of the powder can also be achieved. The contact area between the powder and the heating screen is large, and the heating and drying effect is better.

[0040] Preferably, as another embodiment of the present invention, it also includes a used powder recovery cabin 115, the discharge port of the used powder recovery cabin 115 is connected to the feed port of the used powder conveying pipeline 107, and the feed port and discharge port of the used powder recovery cabin 115 are respectively provided with a first used powder recovery cabin controllable valve 117 and a second used powder recovery cabin controllable valve 118.

[0041] In this embodiment, when the old powder recovery cabin 115 collects the old powder of the additive manufacturing equipment, the first old powder recovery cabin controllable valve 117 is opened and the second old powder recovery cabin controllable valve 118 is closed, thereby cutting off the connection between the old powder recovery cabin 115 and the old powder conveying pipeline 107; when the old powder in the old powder recovery cabin 115 is conveyed to the powder storage cabin 113, the first old powder recovery cabin controllable valve 117 is closed and the second old powder recovery cabin controllable valve 118 is opened, thereby realizing the connection between the old powder recovery cabin 115 and the old powder conveying pipeline 107 and cutting off the connection between the old powder recovery cabin 115 and the additive manufacturing equipment.

[0042] Preferably, as another embodiment of the present invention, a waste powder recovery chamber level meter 116 is provided in the waste powder recovery chamber 115 .

[0043] In this embodiment, the height of the powder in the used powder recovery chamber 115 , that is, the amount of powder stored in the used powder recovery chamber 115 , is obtained through the used powder recovery chamber level meter 116 .

[0044] Preferably, as another embodiment of the present invention, it also includes a circulating powder buffer tank 109, the feed port of the circulating powder buffer tank 109 is connected to the discharge port of the used powder conveying pipeline 107, and a circulating powder buffer tank controllable valve 112 is provided at the discharge port of the circulating powder buffer tank 109.

[0045] In this embodiment, a circulating powder buffer tank controllable valve 112 is provided at the discharge port of the circulating powder buffer tank 109 to control the connection between the circulating powder buffer tank 109 and the powder storage tank 113 .

[0046] Preferably, as another embodiment of the present invention, a circulating powder buffer tank level meter 111 is provided in the circulating powder buffer tank 109 .

[0047] In this embodiment, the height of the powder in the circulating powder buffer chamber 109 , that is, the amount of powder stored in the circulating powder buffer chamber 109 , is obtained through the circulating powder buffer chamber level meter 111 .

[0048] Preferably, as another embodiment of the present invention, an air pressure detector 110 is provided in the circulating powder buffer cabin 109 .

[0049] In this embodiment, since the protective gas pressure in the additive manufacturing equipment is stable, when the circulating powder buffer cabin 109 transports powder to the powder storage cabin 113, it is necessary to ensure that the air pressure in the circulating powder buffer cabin 109 is not lower than the protective gas pressure in the additive manufacturing equipment. Therefore, the air pressure in the circulating powder buffer cabin 109 can be detected by the air pressure detector 110. When the air pressure in the circulating powder buffer cabin 109 is close to the protective gas pressure in the additive manufacturing equipment, the controllable valve 112 of the circulating powder buffer cabin is opened.

[0050] like Figure 1 As shown, the present invention also discloses an additive manufacturing production line, including a printing device 119, and also includes the above-mentioned powder self-circulation device, the feed port and the discharge port of the old powder conveying pipeline 107 are respectively connected to the old powder outlet of the printing device 119 and the powder storage chamber 113.

[0051] In this embodiment, when the above-mentioned additive manufacturing production line is working, the additive manufacturing powder self-circulation can be realized, specifically, the following steps are included:

[0052] S1. A used powder recovery cabin 115 and a circulating powder buffer cabin 109 are provided. The feed port of the used powder recovery cabin 115 is connected to the used powder outlet of the printing device 119, and the discharge port thereof is connected to the feed port of the used powder conveying pipeline 107. The feed port and discharge port of the used powder recovery cabin 115 are respectively provided with a first used powder recovery cabin controllable valve 117 and a second used powder recovery cabin controllable valve 118; the feed port of the circulating powder buffer cabin 109 is connected to the discharge port of the used powder conveying pipeline 107, and the discharge port thereof is connected to the feed port of the powder storage cabin 113 of the printing device 119, and a circulating powder buffer cabin controllable valve 112 is provided at the discharge port of the circulating powder buffer cabin 109;

[0053] S2, in the initial state, the controllable valve 106 of the temporary storage tank, the controllable valve 118 of the second used powder recovery tank and the controllable valve 112 of the circulating powder buffer tank are all in the closed state, and the controllable valve 117 of the first used powder recovery tank is in the open state;

[0054] The printing device 119 starts to work, and the excess powder generated during the working process enters the old powder recovery chamber 115;

[0055] S3, introducing protective gas into the old powder buffer chamber 103 for gas replacement, so that the oxygen content in the powder self-circulation device is reduced to below 300 ppm;

[0056] S4. When the level meter 116 in the old powder recovery tank 115 detects that the old powder storage in the old powder recovery tank 115 has reached its maximum threshold, the first old powder recovery tank controllable valve 117 is closed, the second old powder recovery tank controllable valve 118 is opened, and the pipeline heating mechanism 121 and the separation screen 104 start to work, the old powder return air pipeline 120 starts to work, and the powder in the old powder recovery tank 115 is sent to the old powder buffer tank 103 through the old powder conveying pipeline 107. The old powder in the old powder buffer cabin 103 is heated at the first stage when passing through the heating mechanism 121, and enters the separation screen 104. A heating device is arranged on the screen of the separation screen 104, so that the screen of the separation screen 104 is a heating screen. While screening the powder, the powder can also be heated at the second stage. The contact area between the powder and the heating screen is large, and the heating and drying effect is better. After the old powder is screened and heated twice by the separation screen 104, the old powder enters the powder temporary storage cabin 105 for storage.

[0057] S5. When the level meter 116 of the waste powder recovery tank detects that the waste powder storage in the waste powder recovery tank 115 is lower than its minimum threshold, the pipeline heating mechanism 121 and the waste powder return air pipeline 120 stop working, the first waste powder recovery tank controllable valve 117 is opened, and the second waste powder recovery tank controllable valves 118118 are closed;

[0058] S6, the old powder in the old powder buffer chamber 103 enters the separation screen 104 under the action of gravity, and after the old powder is screened and reheated by the separation screen 104, the old powder enters the powder temporary storage chamber 105 for storage;

[0059] S7, when the circulating powder buffer tank level meter 111 in the circulating powder buffer tank 109 detects that the old powder storage in the circulating powder buffer tank 109 is lower than its minimum threshold, the temporary storage tank controllable valve 106 opens, and the circulating powder return air pipeline 108 starts to work, and the powder in the powder temporary storage tank 105 is sent to the circulating powder buffer tank 109 through the old powder conveying pipeline 107;

[0060] S8. When the circulating powder buffer tank level meter 111 in the circulating powder buffer tank 109 detects that the old powder storage in the circulating powder buffer tank 109 reaches its maximum threshold, the temporary storage tank controllable valve 106 is closed, and the circulating powder return air pipeline 108 stops working;

[0061] S9, when the powder storage tank level meter 114 in the powder storage tank 113 of the printing device 119 detects that the powder storage amount in the powder storage tank 113 is lower than its minimum threshold value, the air pressure detector 110 in the circulating powder buffer tank 109 detects that the air pressure in the circulating powder buffer tank 109 is close to the air pressure in the powder storage tank 113, and the circulating powder buffer tank controllable valve 112 is opened, so that the old powder in the powder storage tank 113 enters the powder storage tank 113 under the action of gravity;

[0062] S10. When the powder storage tank level meter 114 in the powder storage tank 113 of the printing device 119 detects that the powder storage amount in the powder storage tank 113 reaches its maximum threshold value, the controllable valve 112 of the circulating powder buffer tank is closed.

[0063] Furthermore, in an additive manufacturing production line, a powder storage tank level meter 114 is provided in the powder storage tank 113 of the printing device 119, and a protective gas inlet and outlet 102 is provided on the old powder buffer tank 103.

[0064] In this embodiment, when the powder storage chamber 113 is replenished with powder through the circulating powder buffer chamber 109, if the powder reserve in the powder storage chamber 113 is still insufficient, it indicates that the total powder amount in the powder circulation device is insufficient, and new metal powder needs to be replenished from the protective gas inlet and outlet 102.

[0065] Although the embodiments of the present invention have been disclosed as above, they are not limited to the applications listed in the specification and the implementation modes. They can be fully applied to various fields suitable for the present invention. For those familiar with the art, additional modifications can be easily implemented. Therefore, without departing from the general concept defined by the claims and the scope of equivalents, the present invention is not limited to the specific details and the embodiments shown and described herein.

Claims

1. A powder self-circulation device, characterized in that: It comprises a used powder conveying pipeline, on which a pipeline heating mechanism, a used powder buffer cabin, a separation screen and a powder temporary storage cabin are sequentially arranged along the powder transmission direction, the used powder buffer cabin is provided with a protective gas inlet and outlet, a temporary storage cabin controllable valve is provided at the discharge port of the powder temporary storage cabin, the feed port of the used powder conveying pipeline is connected with the used powder buffer cabin through a used powder return air pipeline, and the discharge port of the used powder conveying pipeline and the powder temporary storage cabin are connected through a circulating powder return air pipeline.

2. A powder self-circulation device as claimed in claim 1, characterized in that: The screen of the separation screen is a heating screen.

3. A powder self-circulation device as claimed in claim 1, characterized in that: It also includes a used powder recovery cabin, the discharge port of the used powder recovery cabin is connected to the feed port of the used powder conveying pipeline, and the feed port and discharge port of the used powder recovery cabin are respectively provided with a first used powder recovery cabin controllable valve and a second used powder recovery cabin controllable valve.

4. A powder self-circulation device as claimed in claim 1, characterized in that: It also includes a circulating powder buffer tank, the feed port of which is communicated with the discharge port of the old powder conveying pipeline, and a circulating powder buffer tank controllable valve is provided at the discharge port of the circulating powder buffer tank.

5. An additive manufacturing production line, comprising a printing device, characterized in that: It also includes the powder self-circulation device as described in any one of claims 1 to 4, wherein the feed port and the discharge port of the used powder conveying pipeline are respectively connected to the used powder outlet and the powder storage compartment of the printing device.

6. An additive manufacturing production line according to claim 5, characterized in that: It also includes a used powder recovery tank and a circulating powder buffer tank. The used powder recovery tank and the feed port are connected with the used powder outlet of the printing device. The discharge port of the circulating powder buffer tank is connected with the feed port of the powder storage tank of the printing device. The feed port and the discharge port of the used powder conveying pipeline are respectively connected with the discharge port of the used powder recovery tank and the feed port of the circulating powder buffer tank.

7. A method for self-circulating powder in additive manufacturing, using the additive manufacturing production line according to claim 5 or 6, characterized in that: The following steps are involved: S1. A used powder recovery tank and a circulating powder buffer tank are provided, wherein the feed port of the used powder recovery tank is connected to the used powder outlet of the printing device, and the discharge port thereof is connected to the feed port of the used powder conveying pipeline; the feed port of the circulating powder buffer tank is connected to the discharge port of the used powder conveying pipeline, and the discharge port thereof is connected to the feed port of the powder storage tank of the printing device; S2, the printing device starts working, and the excess powder generated during the working process enters the used powder recovery chamber; S3, introducing protective gas into the old powder buffer cabin to perform gas replacement; S4, forming a negative pressure in the old powder buffer cabin through the old powder return air pipeline, and the powder in the old powder recovery cabin is transported to the old powder buffer cabin by negative pressure through the old powder transport pipeline, and the old powder is heated when passing through the pipeline heating mechanism. After the old powder in the old powder buffer cabin is sieved by the separation screen, the old powder with qualified particle size enters the powder temporary storage cabin; S5, forming a negative pressure in the circulating powder buffer cabin through the circulating powder return air pipeline, and the powder in the powder temporary storage cabin is transported to the circulating powder buffer cabin through the circulating powder return air pipeline under negative pressure; S6. When the powder storage chamber of the printing device has insufficient powder, the circulating powder buffer chamber transports powder into the powder storage chamber.

8. The method for self-circulating powder in additive manufacturing according to claim 7, characterized in that: The feed port and the discharge port of the waste powder recovery tank are respectively provided with a first waste powder recovery tank controllable valve and a second waste powder recovery tank controllable valve, and the discharge port of the circulating powder buffer tank is provided with a circulating powder buffer tank controllable valve. In the initial state, the temporary storage tank controllable valve, the second waste powder recovery tank controllable valve and the circulating powder buffer tank controllable valve are all in a closed state, and the first waste powder recovery tank controllable valve is in an open state. S4 specifically includes: S4.

1. When the level meter of the used powder recovery tank detects that the used powder storage in the used powder recovery tank has reached its maximum threshold, the controllable valve of the first used powder recovery tank is closed, the controllable valve of the second used powder recovery tank is opened, and after the pipeline heating mechanism and the separation screen start to work, the used powder return air pipeline starts to work, and the powder in the used powder recovery tank is sent to the used powder buffer tank through the used powder conveying pipeline; S4.

2. When the level meter of the used powder recovery tank detects that the used powder storage in the used powder recovery tank is lower than its minimum threshold, the pipeline heating mechanism and the used powder return air pipeline stop working, the controllable valve of the first used powder recovery tank is opened, and the controllable valve of the second used powder recovery tank is closed; S4.

3. The old powder in the old powder buffer chamber enters the separation screen. After the old powder is screened and reheated by the separation screen, the old powder enters the powder temporary storage chamber for storage.

9. The method for self-circulating powder in additive manufacturing according to claim 8, characterized in that: S5 specifically includes: S5.

1. When the circulating powder buffer tank level meter in the circulating powder buffer tank detects that the old powder storage in the circulating powder buffer tank is lower than its minimum threshold, the controllable valve of the temporary storage tank is opened, and the circulating powder return air pipeline starts to work, and the powder in the powder temporary storage tank is sent to the circulating powder buffer tank through the old powder conveying pipeline; S5.

2. When the circulating powder buffer tank level meter in the circulating powder buffer tank detects that the old powder storage in the circulating powder buffer tank has reached its maximum threshold, the controllable valve of the temporary storage tank is closed and the circulating powder return air pipeline stops working.

10. The method for self-circulating powder in additive manufacturing according to claim 8, characterized in that: S6 specifically includes: When the powder storage tank level meter in the powder storage tank of the printing device detects that the powder reserve in the powder storage tank is lower than its minimum threshold value, the air pressure detector in the circulating powder buffer tank detects that the air pressure in the circulating powder buffer tank is close to the air pressure in the powder storage tank, and the controllable valve of the circulating powder buffer tank opens, so that the old powder in the powder storage tank enters the powder storage tank under the action of gravity.

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