Precision Powder Feeding System Based on Additive Manufacturing with Dense Laser Arrays

Abstract

The present invention discloses a precise powder feeding system based on additive manufacturing with a dense laser array. The characteristics are as follows: the powder feeding unit has a structure of falling material type. The powder bin is located at the top of the working chamber, and the powder freely falls into the working chamber through the powder falling pipeline, and the powder is spread onto the substrate of the forming chamber by the powder spreading unit. The powder falling pipeline is composed of several single pipes arranged vertically, there are gaps between the single pipes, and each pipeline is equipped with a powder falling device, and the powder falling device is provided with a powder storage groove. The powder spreading unit includes a powder guiding groove located below the powder falling device, and the bottom of the powder spreading unit is provided with powder falling ports, and a set of horizontal strip baffles is distributed at the powder falling ports. It greatly improves the powder utilization rate, realizes the on-demand distribution of powder spreading, the discharging is more uniform and self-reaches dynamic balance. The dual-air duct gas circulation system makes the forming environment better, the idea of additive manufacturing is broader, and it is more convenient to take the parts.

Description

Technical Field

[0001] The present invention relates to additive manufacturing technology, in particular to a precise powder supply system based on additive manufacturing with a dense laser array. Background Art

[0002] Selective laser sintering (SLS) technology is one of the important technologies in the field of additive manufacturing. Its working principle is to first preheat the powder to a temperature slightly below its melting point, then spread the powder in the feeding container onto the forming plane and level it. A controlled laser beam is used to scan the cross-section of the part on the newly spread powder plane. The powder material is sintered together under the irradiation of the laser beam to obtain the cross-section of the part, which is bonded to the previously formed part below. Layer by layer sintering is carried out until all layers are sintered. After all sintering is completed, the excess powder is removed to obtain the processed part.

[0003] Whether it is single or multiple laser cross-section scanning where points move to form lines and lines form surfaces, or a dense laser array scanning system, after sintering the forming plane of each layer, the plane of the sintered part is always slightly lower than the plane of the unsintered part. When spreading powder for the next layer, more powder needs to be provided in the sintered area to level it. When the existing powder spreading device takes and spreads powder, it takes an adequate amount of powder and spreads it as a whole, without specifically increasing the amount of powder spreading only in the sintered area. As a result, the excess powder after spreading in the unsintered area directly enters the powder collecting bin and does not participate in part forming. The utilization rate of the powder is low, resulting in the need for more additional powder to participate in production for each forming manufacturing.

[0004] Moreover, in the existing additive manufacturing equipment, during the process of taking out the part after forming, it is necessary to first empty the powder in the forming cylinder and then take out the part, with low efficiency. And as the size of the formed part increases, the time and labor required for taking out the part also increase. Summary of the Invention

[0005] The purpose of the present invention is to solve the above problems and provide a precise powder supply system based on additive manufacturing with a dense laser array, which has the characteristics of high powder utilization rate, good inert gas environment, on-demand powder spreading distribution, more uniform powder discharge and self-reaching dynamic balance, and more convenient part taking.

[0006] The above technical problems of the present invention are mainly solved by the following technical solution: A precise powder supply system based on additive manufacturing with a dense laser array, including a working chamber, a heating unit, a powder supply unit configured for the working chamber, a powder spreading unit embedded with the powder supply unit, a monitoring unit arranged at the flowing water work station, and an intelligent forming chamber located below the working chamber. It is characterized in that the powder supply unit is a falling material type structure, the powder bin is located at the top of the working chamber, and the powder freely falls into the working chamber through the powder dropping pipeline, and the powder spreading unit spreads the powder onto the forming chamber substrate.

[0007] The powder dropping pipeline is composed of several single pipes arranged vertically, with gaps between the single pipes, and each pipe is equipped with a powder dropping device, on which there is a powder storage hopper.

[0008] The powder spreading unit includes a powder guiding groove located below the powder dropping device. At the bottom of the powder spreading unit, there is a powder dropping port, and a set of horizontal baffle plates is distributed at the powder dropping port.

[0009] In the aforementioned fine control powder feeding system based on dense laser array additive manufacturing, preferably, the powder dropping device is a horizontally arranged cylindrical structure, and several powder storage hoppers are evenly arranged along the surface of the cylinder.

[0010] In the aforementioned fine control powder feeding system based on dense laser array additive manufacturing, preferably, in the set of horizontal baffle plates, each baffle has its opening size independently controlled by the control system.

[0011] In the aforementioned fine control powder feeding system based on dense laser array additive manufacturing, preferably, several sets of mutually cooperating horizontal baffle plates are distributed at the powder dropping port, and several sets of horizontal baffle plates constitute the opening shape and size of the powder dropping port at the bottom of the powder spreading unit.

[0012] In the aforementioned fine control powder feeding system based on dense laser array additive manufacturing, preferably, the powder spreading unit spreads the powder onto the forming chamber substrate, including the 3D printing part area and the shell area.

[0013] In the aforementioned fine control powder feeding system based on dense laser array additive manufacturing, preferably, the powder spreading unit adjusts the powder dropping amount during the next powder spreading according to the sintering position and area of the previous layer.

[0014] In the aforementioned fine control powder feeding system based on dense laser array additive manufacturing, preferably, a sensor connected to the control system is provided inside the powder spreading unit, and the control system controls the powder dropping devices configured in the powder dropping pipelines in the corresponding areas. The powder dropping amount falling into the powder spreading unit is restricted by the rotation angle of each powder dropping.

[0015] In the aforementioned fine control powder feeding system based on dense laser array additive manufacturing, preferably, the working chamber has a dual air flow path.

[0016] In the aforementioned fine control powder feeding system based on dense laser array additive manufacturing, preferably, a scraping knife or a powder spreading roller is provided at the mating part between the powder spreading unit and the forming chamber substrate.

[0017] In the aforementioned fine control powder feeding system based on dense laser array additive manufacturing, preferably, the pick-up door of the intelligent forming chamber is a movable multi-stage door structure.

[0018] The mechanical system of the intensive laser array in this technical solution consists of multiple units such as the working chamber. Since the laser array heats the substrate and powder with higher efficiency, research is specifically conducted on each functional system of the intensive laser array.

[0019] First, optimize the design of the powder feeding unit for the falling powder type. In the powder feeding unit, the powder dropping pipes are arranged in multiple pipes, with gaps left between the pipes for the circulating gas to pass through. Each pipe is equipped with a powder dropping device, and multiple powder storage hoppers are arranged along the circumference of the powder dropping device to accommodate the powder. Thus, when controlling the rotation angle of the powder dropping device, the powder dropping amount of each powder dropping pipe can be controlled individually.

[0020] Secondly, it is the powder spreading unit. Inside it, there is a powder guiding groove that can disperse the falling powder, making the powder more evenly distributed inside the powder spreading unit. The powder dropping port at the bottom of the powder spreading unit is blocked by many narrow horizontal strip-shaped baffles. Since each baffle is designed to have an opening size that can be individually controlled by the control system, when multiple baffle groups act together, the opening shape and size of the powder dropping port at the bottom of the powder spreading unit can be controlled, thereby controlling the powder dropping amount at different positions. According to the principle of the 3D printing process, the sintered area should be a little lower than the unsintered area, that is, more powder needs to be dropped during the next layer of powder spreading to cover the sintered area. Usually, enough powder falls uniformly as a whole. Even if the unsintered area does not require so much powder, powder will still fall. Therefore, after the doctor blade passes, there will be more remaining powder falling into the powder collection cylinder, and the powder utilization efficiency is low. This device adjusts the accurate powder dropping amount during the next powder spreading according to the sintering position and area of the upper layer (which can achieve intelligent control), that is, controls the reduction amount in the unsintered area and the increase amount in the sintered area to achieve dynamic balance, thereby preventing powder from falling into the powder collection cylinder and enabling all powder to be utilized, improving the powder utilization rate. Further, during operation, if there is a little excess powder, after running for a period of time, powder will accumulate in some places inside the powder spreading unit. At this time, the sensor inside the powder spreading unit will feedback to the control system, and the control system will control the powder dropping device of the powder dropping pipe above the relative area, adjust the rotation angle of the powder dropping device for each powder drop, and reduce the powder falling into the powder spreading unit, thus realizing intelligent dynamic balance.

[0021] Thirdly, it is the design of the air duct of the gas circulation system. This device designs a double air flow route to discharge the black smoke generated during printing while maintaining an inert gas environment. It can dissipate heat from the laser array head; blow away the possibly floating black ash that has not been blown away too high; the hot air flowing through the laser array head flows through the powder dropping pipe, playing a role in drying the powder in the powder dropping pipe to prevent the powder from getting wet and difficult to drop.

[0022] Fourth, the powder spreading unit spreads powder onto the molding chamber substrate, which has two printing areas: the 3D printing part area and the shell area. Due to the precise control of the powder supply position and quantity, this system specifically adds the shell when printing the part. Combined with the high printing efficiency of the laser array, the shell is printed while the part is being printed. This not only saves time, but also prevents excessive powder spillage and pollution or waste when removing the part. The removal method has changed compared to existing technologies, greatly improving efficiency. The shell can also be reused after the first print, and special services can be provided for some special parts, etc., expanding the concept of additive manufacturing.

[0023] Compared with the existing technology, the beneficial effects of the present invention are: on the basis of high-efficiency additive manufacturing of laser arrays, the optimized design of the falling powder supply, powder spreading and other units greatly improves the powder utilization rate, realizes on-demand distribution of powder spreading, and the discharge is more uniform and reaches dynamic balance by itself. The dual-duct gas circulation system makes the molding environment better, the idea of additive manufacturing is broader, the retrieval of parts is more convenient, and the efficiency is higher. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 This is a schematic diagram of the structure of a dense laser array of the present invention.

[0025] Figure 2 It is a schematic diagram of the mechanical system structure of the present invention.

[0026] Figure 3 yes Figure 2 Schematic diagram of the AA structure.

[0027] Figure 4 It is a structural schematic diagram of a powder supply and spreading unit of the present invention.

[0028] Figure 5 yes Figure 4 Bottom view of the middle powder spreading unit.

[0029] Figures 6 to 9 Schematic diagram of different states of the baffle assembly of the present invention.

[0030] In the figure: 1. Working chamber, 2. Rear air inlet, 3. Powder supply port, 4. Right air outlet, 5. Powder drop duct, 6. Powder scraper, 7. Front air outlet, 8. Molding chamber, 9. Multi-stage door, 10. Powder collection cylinder, 11. Powder collection port, 12. Laser array, 13. Left air inlet, 14. Focusing unit, 15. Scanning motion unit, 16. Fiber optic holder, 17. Diode laser, 18. Fiber optic, 19. Infrared heating unit, 20. Sensor, 21. Camera, 22. Powder dropper, 23. Powder hopper, 24. Powder guide trough, 25. Powder drop port, 26. Horizontal baffle, 26a. Small baffle with medium and large sides, 26b. Large baffle with medium and small sides, 26c. Irregular baffle, 26d. Gradually enlarged baffle. Detailed implementation manners

[0031] The technical solution of the present invention will be further specifically described below through embodiments in combination with the accompanying drawings.

[0032] The additive manufacturing equipment based on the dense laser array 12 mainly consists of a control system, a scanning system, a gas circulation system, and a mechanical system.

[0033] The laser array 12 includes a focusing unit 14, an optical fiber fixing device 16, a plurality of optical fibers 18, and a plurality of lasers. One end of each optical fiber 18 is connected to a diode laser 17. When the laser 17 emits light, the laser beam is led out by the optical fiber. The other ends of the optical fibers are fixed on the optical fiber fixing device 16 to form an optical fiber array. A focusing unit 14 is installed in front of the light-emitting surface of the optical fiber array. As Figure 1 shown, the configuration of the focusing unit 14 is used to focus the light spot of the laser beam.

[0034] The central axes of the portions of the plurality of optical fibers fixed in the optical fiber fixing device 16 are parallel. The light-emitting surface of the optical fiber array forms a light-emitting plane. The portions of the plurality of optical fibers fixed in the optical fiber fixing device 16 are perpendicular to this light-emitting plane. The light-emitting surfaces at the front ends of the plurality of optical fibers are distributed on one straight line, or multiple straight lines, or one broken line, or multiple broken lines, or can also be on one curve, or multiple curves, or can also be distributed on the same plane, or any combination of the above multiple distributions.

[0035] The optical fiber fixing device 16 and the focusing unit 14 at its front end are installed on the scanning motion unit 15. The light-emitting direction of the optical fiber array is vertically downward. The scanning motion unit 15 can move on a horizontal plane. The scanning motion unit is driven by one or more motors.

[0036] In this embodiment, a fine powder supply system for additive manufacturing based on a dense laser array, as Figure 2 shown, includes a working chamber 1, heating units distributed in various parts of the intelligent forming chamber 8 and the working chamber 1, a powder supply unit configured in the working chamber 1, a powder spreading unit embedded with the powder supply unit, a monitoring unit arranged at the flowing water station, and an intelligent forming chamber 8 located below the working chamber 1. A powder collecting port 11 is provided at the bottom of the working chamber 1, and the powder collecting port 11 leads to a powder collecting cylinder 10.

[0037] The heating units include a first heating unit and a contact sensor installed on the side wall of the intelligent forming chamber 8; a second heating unit and a contact sensor installed below the bottom plate of the intelligent forming chamber 8. Multiple pieces of the two external heating units and contact sensors can be provided to respectively heat and monitor different regions of the side wall and the bottom plate of the intelligent forming chamber. An infrared heating unit 19 and a non-contact sensor 20 installed on the top of the working chamber 1, as Figure 3As shown, the infrared heating unit 19 and the non-contact sensor 20 here can also be arranged in multiple places to heat and monitor different areas in the working chamber 1 respectively. A camera 21 is installed directly above the intelligent forming chamber 8 to observe the powder spreading and sintering conditions in real time and analyze the sintered area after powder spreading. The heating unit of the intelligent forming chamber 8 generally plays a heat preservation role, but it can also heat the powder to make the powder temperature close to the melting temperature. The pick-up door of the intelligent forming chamber 8 is a movable multi-stage door 9 structure.

[0038] The powder supply unit has a falling material structure. The powder bin (the warehouse for storing powder) is located at the top of the working chamber 1. The powder freely falls into the working chamber 1 through the powder supply port 3 via the powder dropping pipe 5, and the powder spreading unit spreads the powder onto the forming chamber substrate. The powder dropping pipe 5 consists of a group of multiple single pipes arranged vertically. There are gaps between the single pipes. Each pipe is equipped with a powder dropper 22, and a powder storage hopper 23 is provided on the powder dropper 22. As Figure 4 shown, the powder dropper 22 is a horizontally arranged cylindrical body (pipe body) structure, and 8 powder storage hoppers 23 are evenly arranged along the surface of the cylinder.

[0039] The powder spreading unit includes a powder guiding groove 24 located below the powder dropper 22. There is a powder dropping port 25 at the bottom of the powder spreading unit, and groups of horizontal strip baffles 26 are distributed at the powder dropping port 25. As Figure 5 shown, in the groups of horizontal strip baffles 26, each baffle has a separate mechanical component, and the control system can control the individual movement of each baffle. When needed, the control system can manipulate multiple baffles to move separately, change the baffle positions, and form different opening shapes. Further, there are multiple groups of the horizontal strip baffles 26 and they cooperate with each other. The groups of horizontal strip baffles 26 together constitute the opening shape and size of the powder dropping port 25 at the bottom of the powder spreading unit. Different opening shapes result in different gap sizes and different powder dropping amounts. The opening shapes are as Figures 6 to 9 shown (only listed): such as the state of the large-side small baffle 26a, the shape of the medium-side large baffle 26b, the structure of the irregular baffle 26c, the gradually increasing baffle 26d or the gradually decreasing baffle, etc.

[0040] The powder spreading unit adjusts the powder dropping amount during the next powder spreading according to the sintering position and area of the upper layer. It is internally provided with a sensor connected to the control system. The control system controls the powder dropper 22 of the powder dropping pipe 5 in the corresponding area. The powder dropper 22 determines the amount of powder falling into the powder spreading unit by restricting the rotation angle of each powder dropping.

[0041] A scraping knife 6 is provided at the mating part of the powder spreading unit and the forming chamber substrate, and a powder spreading roller can also be set.

[0042] The working chamber 1 has a dual air flow path. One air path is formed by the left air inlet 13 and the right air outlet 4, and the other air path is formed by the rear air inlet 2 and the front air outlet 7. The dual air flow path adopts a gas circulation system. The air path formed by the left air inlet 13 and the right air outlet 4 in the upper half of the chamber cools the laser head and dries the powder during the air flow. The air path formed by the rear air inlet 2 and the front air outlet 7 in the lower half of the chamber takes away the black ash generated by laser printing. The two gas paths are perpendicular to each other and not in the same plane. Since the black ash is generated by the splashing of laser-melted metal powder and has a certain weight itself, it is not easy for the gas to blow up the black ash. Therefore, the gas only changes the splashing direction of the black ash when the black ash splashes and flies towards the air outlet, so as to discharge the black ash. The two gas paths can meet the requirements by adjusting the air speed. In actual application, while the air inlet blows air inwards, the air outlet can also extract air outwards at the same time.

[0043] The process of this embodiment applied to printing finished products is as follows:

[0044] (1) Import the sliced file of the part into the machine, and the control system reads the file information to determine the cross-section printed for each layer.

[0045] (2) Prepare before printing. Place the printing substrate on the bottom plate of the forming cylinder 8. The working chamber 1 is locked, and the gas circulation system starts to work, filling inert gas and discharging oxygen to make the inside of the working chamber 1 in a low-oxygen state.

[0046] (3) At the same time, the second heating unit starts to heat the bottom plate according to the preset temperature. The heating unit near the uppermost part of the intelligent forming chamber 8 starts to work to heat the side wall. Preheating can also be carried out through the infrared heating unit 19 or laser scanning.

[0047] (4) After all conditions are prepared, the machine starts to print. First, the powder supply unit and the powder spreading unit start to work, spreading the powder evenly on the substrate of the forming chamber 8. The infrared heating unit 19 at the top of the working chamber 1 aligns with the spread powder for the first heating. After the non-contact sensor 20 monitors that the temperature reaches the first preset temperature, the laser array 12 scans parallel from above the substrate of the forming chamber 8. Move from right to left for the first time, turn on all the lasers, and continue to preheat the powder to the second preset temperature; move from left to right for the second time, when passing through the cross-section to be printed, turn on the corresponding lasers to sinter the powder in the cross-section to be printed. In addition, the laser will also sinter and solidify the powder in the outermost circle of the forming chamber 8 to form a shell, wrapping the whole part and other powders in it. The laser moves a distance of one laser spot in the array direction and then moves from right to left for the third time to complete the part that cannot be scanned by the laser spot spacing during the second scan. Thus, one layer thickness scan and sintering is completed.

[0048] Before printing the next layer, the camera 21 will first capture the area of the sintered part of the previous layer. After the control system analyzes the photo, it adjusts the powder spreading amount of the powder spreading device, and performs multi-powder spreading on the sintered part and less powder spreading on the unsintered part in a timely manner.

[0049] (5) During the entire printing process, the non-contact sensor always monitors the temperature of the powder bed on the forming chamber 8, and feeds back to the control system. The control system adjusts the power of the infrared heating unit 19 and the power during laser preheating, so that the powder temperature is maintained within the preset temperature range.

[0050] (6) As the height of the part increases and the part gradually sinks in the intelligent forming chamber 8, the first heating unit near the lower part of the side wall of the intelligent forming chamber 8 will gradually heat up. The supporting contact sensor monitors the temperature in real time and feeds back to the control system to adjust the power as needed. The second heating unit always heats the substrate. The supporting contact sensor monitors the temperature in real time and feeds back to the control system to adjust the power as needed. These two heating units ensure the heat preservation effect of the formed part, so that the temperature difference from the part being formed at the top is not large, so as to prevent defects such as cracks and warping of the part due to excessive stress under the condition of too large temperature difference.

[0051] (7) The gas circulation system works continuously. Inert gas is filled from the left air inlet 13 of the working chamber 1 and leaves from the right air outlet 4 of the working chamber 1. It passes through the laser array 12 in the middle to cool and dissipate heat for the laser array 12. The heated air continues to pass through the powder dropping pipe to dry the powder in the pipe, preventing the powder from getting damp and having smooth powder dropping.

[0052] (8) There is a rear air inlet 2 at the lower position behind the working chamber 1, which is used to blow away the black ash generated during the printing process of the laser array 12. There is a front air outlet 7 at the bottommost position in front of the working chamber 1, and the black ash enters from here and is discharged after cyclic filtration.

[0053] (9) As the printing progresses, the part is printed layer by layer, and finally the printing is completed.

[0054] (10) According to the height of the printed part, open the movable multi-stage door 9 corresponding to the front of the intelligent forming chamber 8. Due to the existence of the outer shell, almost no powder overflows and falls. Use a forklift to fork away the substrate, transfer the part, and simply clean the machine.

[0055] The above embodiments are illustrative of the present invention, not limiting the present invention. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principle of the present invention shall be included within the protection scope of the present invention.

Claims

1. A precise powder supply system based on additive manufacturing with a dense laser array, comprising a working chamber (1), a heating unit, a powder supply unit configured for the working chamber, a powder spreading unit fitted to the powder supply unit, a monitoring unit arranged at a production line station, and a forming chamber (8) located below the working chamber, characterized in that, The powder supply unit has a structure of falling powder type. The powder bin is located at the top of the working chamber, and the powder falls freely through the powder dropping pipeline (5) into the working chamber, and the powder spreading unit spreads the powder onto the substrate of the forming chamber; The powder dropping pipeline is composed of several single pipes arranged vertically. There are gaps between the single pipes, and each pipeline is equipped with a powder dropping device (22), and a powder storage hopper (23) is provided on the powder dropping device; The working chamber has a double air flow path, and the hot air flowing through the laser array head flows through the powder dropping pipeline; The powder spreading unit includes a powder guiding groove (24) located below the powder dropping device. A powder dropping port (25) is provided at the bottom of the powder spreading unit, and a group of horizontal baffles (26) are distributed at the powder dropping port; 2. The fine powder supply system based on additive manufacturing with a dense laser array according to claim 1, characterized in that, The powder dropping device (22) has a horizontally arranged cylindrical structure, and several powder storage hoppers (23) are evenly arranged along the surface of the cylinder; 3. The fine powder supply system based on additive manufacturing with a dense laser array according to claim 1, wherein In the group of horizontal baffles (26), each baffle has the size of the opening controlled separately by the control system; 4. The fine powder supply system based on additive manufacturing with a dense laser array according to claim 1, characterized in that, A group of several mutually cooperating horizontal baffles (26) are distributed at the powder dropping port, and several groups of horizontal baffles form the opening shape and size of the powder dropping port at the bottom of the powder spreading unit; 5. The fine powder supply system based on additive manufacturing with a dense laser array according to claim 1, characterized in that, The powder spreading unit spreads the powder onto the substrate of the forming chamber and has two printing areas. Specifically, the printing areas include a 3D printing part area and a shell area; 6. The fine powder supply system based on additive manufacturing with a dense laser array according to claim 1 or 3 or 4, characterized in that , The powder spreading unit adjusts the powder dropping amount during the next powder spreading according to the sintering position and area of the previous layer; 7. The fine powder supply system based on additive manufacturing with a dense laser array according to claim 1, characterized in that, A sensor connected to the control system is provided inside the powder spreading unit. The control system controls the powder dropping device (22) configured for the corresponding area of the powder dropping pipeline (5), and the powder dropping amount falling into the powder spreading unit is restricted by the rotation angle of each powder dropping; 8. The fine powder supply system based on additive manufacturing with a dense laser array according to claim 1, characterized in that, A scraping knife (6) or a powder spreading roller is provided at the mating part of the powder spreading unit and the substrate of the forming chamber; 9. The fine powder supply system based on additive manufacturing with a dense laser array according to claim 1, characterized in that, The pick-up door of the intelligent forming chamber (8) has a structure of a movable multi-stage door (9);

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