Forming cylinder device capable of rapidly removing powder, 3D printing equipment and operation method

Abstract

The invention relates to the technical field of 3D printing, in particular to a forming cylinder device capable of rapidly removing powder, 3D printing equipment and an operation method.The forming cylinder device capable of rapidly removing powder comprises a piston, and an inflatable sealing ring is embedded in the side wall of the piston; the piston is arranged in an inner cavity of the cylinder sleeve, a boss is arranged at the bottom of the cylinder sleeve, a groove and a powder cleaning runner are formed in the boss, and an inflatable sealing ring is arranged in the groove; and the powder cleaning assembly comprises a plurality of groups of powder blowing parts arranged on the side wall of the cylinder sleeve, the powder blowing parts obliquely output inert gas downwards, gas output ports of the powder blowing parts are located below the plane where the upper surface of the piston is located, and the powder cleaning assembly further comprises a powder receiving part. By means of the arrangement, flying dust is effectively restrained, the powder cleaning efficiency is improved, the secondary utilization rate and the powder recycling rate of recycled metal powder are effectively improved, the problem that a powder cleaning gap between the piston and the cylinder sleeve is prone to being blocked is solved, the powder residual rate of the side wall of the piston is effectively reduced, the machining difficulty of the cylinder sleeve is reduced, and the service life of the cylinder sleeve is prolonged. The printing efficiency is ensured, and the production cost is reduced.

Description

Technical Field

[0001] The present invention relates to a forming cylinder device for rapid powder cleaning, a 3D printing device and an operation method, belonging to the technical field of 3D printing. Background Art

[0002] 3D printing is a kind of rapid prototyping technology, also known as additive manufacturing. It is a technology that constructs objects by layer-by-layer printing based on digital model files. Currently, selective laser melting technology (SLM) is often used for 3D printing of metal parts. Through layer-by-layer printing and layer-by-layer stacking and forming, parts with almost any shape and function can be produced. After the 3D printing of metal powder is completed, it is necessary to clean the metal powder in the forming cylinder for the next printing.

[0003] The existing powder cleaning methods are mostly upward powder suction, including using a hand-held explosion-proof powder suction machine to absorb powder or setting a robotic arm inside the printing chamber to control the powder suction pipeline for powder cleaning operations. However, the existing powder cleaning methods are extremely prone to generating dust during the powder cleaning process, which is likely to pollute the optical system, resulting in poor printing accuracy and low printing quality. An excessive dust concentration is extremely likely to pose an explosion risk when the inert environment is unstable, and there is also the problem of a long powder cleaning cycle due to a large dust concentration. Moreover, due to the need for the piston to move up and down in the cylinder sleeve and the existing machining errors, there will be a gap between the two. Metal powder with a smaller particle size is extremely likely to enter the gap between the piston and the cylinder sleeve. Over time, the piston is extremely likely to get stuck, or during the up and down movement of the piston, the sealing ring is worn, resulting in damage and destruction of the seal. Therefore, it is of great practical significance to study a forming cylinder device, a 3D printing device and an operation method with downward powder suction that can take into account the dust concentration, powder cleaning efficiency, powder recovery rate, service life of the device and sealing performance. Summary of the Invention

[0004] Aiming at the deficiencies existing in the prior art, the present invention provides a forming cylinder device for rapid powder cleaning, a 3D printing device and an operation method.

[0005] The technical solution of the present invention to solve the above technical problems is as follows: A forming cylinder device for rapid powder cleaning, comprising: a piston, the upper surface of the piston is configured as a printing platform, at least one sealing ring groove is circumferentially provided on its side wall, an inflatable sealing ring is embedded in the sealing ring groove, and a driving part for driving the piston to reciprocate up and down is provided at the bottom of the piston; a cylinder sleeve, the cylinder sleeve is a hollow structure with openings at both ends, the piston is coaxially arranged in the inner cavity of the cylinder sleeve, the shape of the cylinder sleeve is adapted to the shape of the piston and there is a predetermined gap between its inner wall and the side wall of the piston, a boss extending towards the inner cavity of the cylinder sleeve is circumferentially arranged around the bottom of the cylinder sleeve, a groove and a plurality of powder cleaning channels penetrating the boss are provided on the boss, an inflatable sealing ring is provided in the groove, when the piston descends to the lowest point, its bottom is in sealing contact with the groove; a powder cleaning assembly, including a plurality of groups of powder blowing parts opened on the side wall of the cylinder sleeve and communicating with the inner cavity of the cylinder sleeve, the powder blowing parts are connected to an inert gas source, the powder blowing parts output inert gas obliquely downward and the gas outlet thereof is located below the plane where the upper surface of the piston is located, at least two groups of powder blowing parts are arranged circumferentially around the side wall of the cylinder sleeve at intervals of 90 degrees, and a powder receiving part connected below the powder cleaning channel is further included, one side of the powder receiving part is connected to an inert gas source and the other side is connected to a metal powder collection mechanism.

[0006] Further, the powder blowing part includes a main air duct vertically opened in the side wall of the cylinder sleeve along the extending direction of the axis of the cylinder sleeve and connected to the inert gas source, and a plurality of sub-air ducts communicated with the main air duct and arranged in an up-and-down array along the extending direction of the axis of the cylinder sleeve, the sub-air ducts are opened in the side wall of the cylinder sleeve and communicated with the inner cavity of the cylinder sleeve, the sub-air ducts are arranged to be inclined downward at a predetermined angle, when the piston descends to abut against the boss, all the air duct outlets included in the powder blowing part are located below the plane where the upper surface of the piston is located.

[0007] Further, the sub-air duct is sequentially communicated by a contraction air duct at the air inlet end, a middle air duct and an expansion air duct at the air outlet end, the bottoms of the contraction air duct, the middle air duct and the expansion air duct are all in the same plane, the cross-sectional area of the contraction air duct gradually decreases along the air inlet direction, the cross-sectional area of the middle air duct remains unchanged along the air inlet direction, and the cross-sectional area of the expansion air duct gradually increases along the air inlet direction.

[0008] Further, the cross-sectional shape of the sub-air duct is rectangular, the length K1 of the long side of the rectangular cross-section of the middle air duct is 2.1 - 2.5 times the length K2 of the short side, and the relationship between the bottom length L1 of the expansion air duct, the bottom length L2 of the middle air duct and the bottom length L3 of the contraction air duct is: L1:L2:L3 = (7 - 10):1:(1.8 - 2.3).

[0009] Further, the outward expansion angle α1 of the top wall of the expansion air duct facing its bottom satisfies 8° ≤ α1 ≤ 15°, and the outward expansion angle α2 of the two side walls of the expansion air duct satisfies 30° ≤ α2 ≤ 40°.

[0010] Further, the relationship between the inclination angle β of the plane where the bottom of the sub-air passage is located with respect to the side wall of the cylinder liner and the outward expansion angle α1 of the top wall of the expansion air passage satisfies the following formula: β = -3.46α1 + 81.9, where the unit of the angle β is degree.

[0011] Further, the gap D1 between the inner wall of the cylinder liner and the side wall of the piston satisfies 2 mm ≤ D1 ≤ 3.5 mm; the relationship between the distance S between the outlet ends of the adjacent upper and lower sub-air passages, the gap D1, and the inclination angle β of the sub-air passage satisfies the following formula: where the unit of the distance S is mm.

[0012] Further, the powder receiving part includes a powder delivery pipe and a plurality of diversion pipes equidistantly distributed along the axis of the powder delivery pipe. One end of the powder delivery pipe is connected to an inert gas source as the air inlet end, and the other end is connected to a metal powder collection mechanism as the powder outlet end. One end of the diversion pipe is communicated with the powder cleaning channel, and the other end is communicated with the inside of the powder delivery pipe. The included angle γ between the axis of the diversion pipe and the axis of the powder delivery pipe satisfies 50° ≤ γ ≤ 70°.

[0013] The present invention also provides a 3D printing device, which includes the forming cylinder device described above, and also includes a printing chamber for accommodating the forming cylinder device, and a powder cleaning device, a laser printing device, and a powder spreading device disposed inside the chamber body and above the printing platform for sweeping the residual metal powder into the powder cleaning gap between the cylinder liner and the piston.

[0014] The present invention also provides an operation method, which is applied to the forming cylinder device described above, and its features include:

[0015] S1, driving the piston to move downward until its bottom abuts against the boss;

[0016] S2, inflating the inflatable seal ring arranged in the groove until the inflatable seal ring is in close contact with the bottom of the piston;

[0017] S3, evacuating the inflatable seal ring circumferentially embedded in the piston, and the inflatable seal ring retracts into the seal ring groove;

[0018] S4, the metal powder flows downward through the gap between the inner wall of the cylinder liner and the side wall of the piston, passes through the powder cleaning channel, and enters the powder delivery pipe;

[0019] S5, the powder blowing part is communicated with the inert gas source, and an inert gas with a pressure of 0.25 Mpa - 0.4 Mpa is introduced;

[0020] S6, the powder delivery pipe is communicated with the inert gas source, and the flow rate of the inert gas flow in the powder delivery pipe is adjusted to be higher than the flow rate of the inert gas flow blown into the cylinder liner through the powder blowing part, and the metal powder enters the metal powder collection mechanism along the powder delivery pipe;

[0021] After S7 and after the flour cleaning is completed, inflate the inflatable sealing ring embedded in the circumferential direction of the piston until the inflatable sealing ring is in close contact with the inner wall of the cylinder liner;

[0022] S8, drive the piston to move upward to the printing station;

[0023] S9, evacuate the inflatable sealing ring arranged in the groove, and the inflatable sealing ring retracts into the groove.

[0024] The beneficial effects of the present invention are as follows:

[0025] (1) By providing a powder blowing part, and the powder blowing part outputs inert gas obliquely downward, so as to generate an oblique downward guide for the metal powder, and the air flow coverage area is large. The present invention not only solves the problems of easy dust generation during the powder cleaning process, resulting in a poor working environment and easy pollution of the optical system, effectively inhibits dust, greatly reduces the explosion risk, but also solves the problem of long powder cleaning cycle, effectively shortens the time required for the powder cleaning working condition, improves the powder cleaning efficiency. The forming cylinder device provided by the present invention can increase the powder cleaning efficiency by 30% when cleaning the printing residual powder with a particle size of 25 - 50 microns of metal powder, and the dust concentration ≤ 5g / m 3 ;

[0026] (2) On the premise of improving the powder cleaning efficiency and reducing dust, the present invention can blow some caked metal powder during the falling process, effectively improves the secondary utilization rate of the recycled metal powder, reduces the post-treatment difficulty of the recycled metal powder, solves the problem of easy blockage of the powder cleaning gap between the piston and the cylinder liner, and the output inert air flow can contact the side wall of the piston, which can effectively reduce the powder residue rate on the side wall of the piston, improve the powder recovery rate, solves the problem of seal ring wear caused by residual metal powder on the side wall of the piston after the powder cleaning working condition, and effectively extends the service life;

[0027] (3) The present invention can achieve the above technical effects without setting too many groups of powder blowing parts, effectively ensures that the cylinder liner has sufficient structural strength, not only reduces the processing difficulty of the cylinder liner, but also reduces the control difficulty of the airtightness of the powder blowing part, and is more conducive to controlling the oxygen content within the limited range;

[0028] (4) During the powder cleaning working condition, the present invention will not destroy the inert gas environment in the printing chamber, avoiding the problems of low printing efficiency and high production cost caused by repeated gas washing. Description of the Drawings

[0029] Figure 1 It is a schematic three-dimensional structure diagram of the forming cylinder device provided by Embodiment 1 of the present invention;

[0030] Figure 2Schematic three-dimensional structure diagram of the cylinder liner and the powder receiving part after connection provided by Embodiment 1 of the present invention;

[0031] Figure 3 Top view of the cylinder liner provided by Embodiment 1 of the present invention;

[0032] Figure 4 Front view of the cylinder liner and the powder receiving part after connection provided by Embodiment 1 of the present invention;

[0033] Figure 5 is Figure 4 Cross-sectional view taken along line A-A in

[0034] Figure 6 is Figure 5 Enlarged view at B in

[0035] Figure 7 is Figure 6 Enlarged view at C in

[0036] Figure 8 is Figure 7 Enlarged view of the sub-air passage in

[0037] Figure 9 Top view of the sub-air passage provided by Embodiment 1 of the present invention;

[0038] Figure 10 Partial three-dimensional schematic diagram of the connection between the boss and the powder receiving part provided by Embodiment 1 of the present invention;

[0039] Figure 11 Front view of the powder receiving part provided by Embodiment 1 of the present invention.

[0040] Reference numerals: 100, piston; 101, inflatable sealing ring; 200, cylinder liner; 201, outer cylinder body; 202, boss; 2021, groove; 2022, powder cleaning flow channel; 300, powder blowing part; 301, main air passage; 302, sub-air passage; 3021, constricted air passage; 3022, middle air passage; 3023, expanded air passage; 30231, top wall; 30232, side wall; 400, powder receiving part; 401, powder conveying pipe; 01, air supply end; 02, powder outlet end; 402, diversion pipe; 403, powder receiving groove. Detailed implementation manners

[0041] The following makes a detailed description of the specific implementation manners of the present invention. The present invention can be implemented in many other ways different from those described herein. Those skilled in the art can make similar improvements without departing from the connotation of the present invention. Therefore, the present invention is not limited by the specific embodiments disclosed.

[0042] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present invention. Apparently, the described embodiments are some, but not all, of the embodiments of the present invention. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts shall fall within the protection scope of the present invention. Therefore, the detailed description of the embodiments of the present invention provided in the accompanying drawings is not intended to limit the scope of the claimed present invention, but merely represents selected embodiments of the present invention.

[0043] In the present invention, unless otherwise clearly defined and limited, the terms "install", "connect", "couple", "fix", etc. shall be construed in a broad sense. For example, it may be a fixed connection, a detachable connection, or an integral one; it may be a mechanical connection or an electrical connection; it may be directly connected or indirectly connected through an intermediate medium, and it may be the internal communication of two elements or the interaction relationship between two elements. For those of ordinary skill in the art, the specific meanings of the above terms in the present invention can be understood according to specific circumstances. In addition, the terms "first", "second", "third", etc. are only used for descriptive distinction and cannot be construed as indicating or implying relative importance.

[0044] In the present invention, unless otherwise clearly defined and limited, the first feature being above or below the second feature may include the direct contact between the first and second features, or may include the situation where the first and second features are not in direct contact but in contact through additional features therebetween. Moreover, the first feature being above, over, and on the second feature includes the first feature being directly above and obliquely above the second feature, or simply indicating that the horizontal height of the first feature is higher than that of the second feature. The first feature being below, under, and beneath the second feature includes the first feature being directly below and obliquely below the second feature, or simply indicating that the horizontal height of the first feature is lower than that of the second feature.

[0045] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by those of ordinary skill in the technical field to which the present invention belongs. The terms used are only for describing specific embodiments and are not intended to limit the present invention.

[0046] Example 1

[0047] As Figures 1-6As shown in the figure, the present invention provides a forming cylinder device for rapid powder cleaning, comprising: a piston 100, the upper surface of the piston 100 is configured as a printing platform for 3D printing, at least one sealing ring groove is circumferentially arranged on its side wall, an inflatable sealing ring 101 is embedded in the sealing ring groove, and a driving part for driving the piston 100 to reciprocate up and down is arranged at the bottom of the piston 100. It should be noted that, in order to ensure the stability of the inert environment during the printing process, the present invention is provided with two sealing ring grooves, and an inflatable sealing ring 101 is embedded in each sealing ring groove. The inflatable sealing ring 101 is connected to an inert gas source and can be inflated and expanded or evacuated and retracted; the driving part adopts a reciprocating hydraulic cylinder well-known to those skilled in the art, which is not shown in the figure and will not be elaborated here;

[0048] A cylinder sleeve 200, the cylinder sleeve 200 is a hollow structure with openings at both ends, the piston 100 is coaxially arranged in the inner cavity of the cylinder sleeve 200, the shape of the cylinder sleeve 200 is adapted to the shape of the piston 100, and a predetermined gap is provided between its inner wall and the side wall of the piston 100. It should be noted that, in order to ensure the sealing consistency between the piston 100 and the cylinder sleeve 200 during the printing process, the cross-sections of both the cylinder sleeve 200 and the piston 100 are set as squares. An outer cylinder body 201 for strengthening the structural strength with a cross-sectional shape adapted to the outside of the cylinder sleeve 200 is sleeved. A convex platform 202 extending towards the inner cavity of the cylinder sleeve 200 is arranged circumferentially around the bottom of the cylinder sleeve 200. A groove 2021 and several powder cleaning channels 2022 penetrating through the convex platform 202 are arranged on the convex platform 202. An inflatable sealing ring 101 is arranged in the groove 2021. When the piston 100 descends to the lowest point, its bottom is in sealing contact with the groove 2021; it can be understood that the gap between the cylinder sleeve 200 and the piston 100 serves as a flow channel for metal powder during the powder cleaning operation and is used to accommodate the downward flow of metal powder. The number of powder cleaning channels 2022 is such that during the printing operation, the inflatable sealing ring 101 embedded in the side wall of the piston 100 is inflated and expanded to contact the inner wall of the cylinder sleeve 200 to achieve sealing. During the powder cleaning operation, the inflatable sealing ring 101 embedded in the side wall of the piston 100 is evacuated and retracted into the sealing ring groove to open the metal powder flow channel, so that the metal powder flows through the gap between the cylinder sleeve 200 and the piston 100 to the powder cleaning channels 2022; when the piston 100 descends to the lowest point, the bottom of the piston 100 avoids the powder cleaning channels 2022 and only abuts against the position of the groove 2021. The inflatable sealing ring 101 arranged in the groove 2021 adopts the same type of inflatable sealing ring 101 embedded in the piston 100. During the powder cleaning operation, the inflatable sealing ring 101 arranged in the groove 2021 is inflated and expanded to contact the bottom of the piston 100 to achieve sealing. During the printing operation, the inflatable sealing ring 101 arranged in the groove 2021 is evacuated and retracted into the groove 2021;

[0049] The powder cleaning assembly includes several groups of powder blowing parts 300 opened on the side wall of the cylinder liner 200 and communicated with the inner cavity of the cylinder liner 200. The powder blowing parts 300 are connected to an inert gas source. The powder blowing parts 300 output inert gas obliquely downward, and the gas outlet thereof is located below the plane where the upper surface of the piston 100 is located. At least two groups of powder blowing parts 300 are arranged at intervals of 90 degrees circumferentially around the side wall of the cylinder liner 200. It further includes a powder receiving part 400 connected below the powder cleaning channel 2022. One side of the powder receiving part 400 is connected to an inert gas source, and the other side is connected to a metal powder collection mechanism. The powder blowing part 300 includes a main air duct 301 connected to the inert gas source and vertically opened in the side wall of the cylinder liner 200 along the extending direction of the axis X of the cylinder liner 200, and several branch air ducts 302 communicated with the main air duct 301 and arranged in an up-and-down array along the extending direction of the axis X of the cylinder liner 200. The branch air ducts 302 are opened in the side wall of the cylinder liner 200 and communicated with the inner cavity of the cylinder liner 200. The branch air ducts 302 are arranged to incline downward at a predetermined angle. When the piston 100 moves downward to abut against the boss 202, the outlets of all the branch air ducts 302 included in the powder blowing part 300 are located below the plane where the upper surface of the piston 100 is located. It can be understood that by arranging the gas outlet of the powder blowing part 300 below the plane where the upper surface of the piston 100 is located, during the powder cleaning process, it is avoided that the inert gas output by the powder blowing part 300 directly blows above the printing platform, effectively avoiding dust flying. In the present invention, since the cross-section of the cylinder liner 200 is set as a square, at least two groups of powder blowing parts 300 are arranged in parallel on each side. Preferably, to ensure the structural strength of the cylinder liner 200 and solve the problem of increased probability of seal leakage caused by excessive arrangement of the powder blowing parts 300, on the premise of ensuring the powder cleaning efficiency, two groups of powder blowing parts 300 are arranged in parallel on each side of the cylinder liner 200 of the present invention. The powder receiving part 400 is hermetically connected to the powder cleaning channel 2022. During the powder cleaning process, the powder receiving part 400 is connected to the inert gas source, and the metal powder falling through the gap between the piston 100 and the cylinder liner 200 to the powder receiving part 400 is blown by the inert gas to the metal powder collection mechanism. It should be noted that the metal powder collection mechanism adopts the well-known technology of those skilled in the art and is not shown in the drawings;

[0050] First of all, by setting the powder blowing part 300 in the present invention, and the powder blowing part 300 outputs inert gas obliquely downward, so as to generate an oblique downward guidance for the metal powder, and the air flow coverage area is large. It not only solves the problems of easy dust flying during the powder cleaning process, resulting in poor working environment and easy pollution of the optical system, effectively inhibits dust flying, greatly reduces the explosion risk, but also solves the problem of long powder cleaning cycle, effectively shortens the time required for the powder cleaning operation, and improves the powder cleaning efficiency. The forming cylinder device provided by the present invention can achieve a 30% improvement in powder cleaning efficiency and a dust concentration ≤ 5g / m when cleaning the printing residual powder with a particle size of 25 - 50 microns of metal powder. 3; Secondly, on the premise of improving the purifying efficiency and reducing dust emission, the present invention can blow away some caked metal powders during the falling process, effectively improving the secondary utilization rate of the recycled metal powders, reducing the post-treatment difficulty of the recycled metal powders, solving the problem that the purifying gap between the piston 100 and the cylinder liner 200 is easily blocked, and the output inert gas flow can contact the side wall of the piston 100, effectively reducing the powder residue rate on the side wall of the piston 100, improving the powder recovery rate, avoiding the problem that the sealing ring is worn due to the residual metal powder on the side wall of the piston 100 after the purifying operation, and effectively extending the service life; Then, the present invention can achieve the above technical effects without setting too many groups of powder blowing parts 300, effectively ensuring that the cylinder liner 200 has sufficient structural strength, reducing both the processing difficulty of the cylinder liner 200 and the control difficulty of the airtightness of the powder blowing parts 300, and making it easier to control the oxygen content within the limited range; Finally, during the purifying operation, the present invention will not damage the inert gas environment in the printing chamber, avoiding the problems of low printing efficiency and high production cost caused by repeated gas washing.

[0051] Specifically, such as Figures 5-9As shown, the sub-air passage 302 is successively formed by connecting a converging air passage 3021 at the intake end, a middle air passage 3022, and a diverging air passage 3023 at the outlet end. The bottoms of the converging air passage 3021, the middle air passage 3022, and the diverging air passage 3023 are all in the same plane. The cross-sectional area of the converging air passage 3021 gradually decreases along the intake direction, the cross-sectional area of the middle air passage 3022 remains unchanged along the intake direction, and the cross-sectional area of the diverging air passage 3023 gradually increases along the intake direction. It can be understood that the converging air passage 3021 is connected to the main air passage 301, and the sub-air passage 302 is an integral structure formed by processing. With the above settings, first, when the inert gas source is connected, the inert gas passes through the converging air passage 3021 for transition. After gradually increasing the air flow velocity, it then enters the middle air passage 3022 for acceleration, which can stably increase the air flow velocity, reduce the probability of turbulence. Then, through the acceleration of the converging air passage 3021 and the middle air passage 3022, the air flow uniformly and quickly passes through the diverging air passage 3023 and is guided and blown out into the powder cleaning gap between the piston 100 and the cylinder liner 200. Only by connecting an inert gas source with a relatively low pressure can the coverage area of the inert air flow be increased, the powder cleaning blind area be reduced, the powder residue rate on the side wall of the piston 100 be further reduced, the powder recovery rate be increased, the air flow shear force be increased, and the ability to blow and break up agglomerates be further enhanced. Moreover, the relatively low pressure of the inert gas source reduces the requirement for the sealing performance of the forming cylinder device of the present invention. Secondly, by setting the bottoms of the converging air passage 3021, the middle air passage 3022, and the diverging air passage 3023 to be in the same plane, it can not only prevent the accumulation of metal powder at the inner bottom of the sub-air passage 302, but also ensure that there is no stepped change in the bottom cross-section, avoid local turbulence at the bottom position of the air flow, and further reduce the probability of air flow interference with the adjacent sub-air passage 302 below, thereby reducing the difficulty of air flow regulation between adjacent sub-air passages 302. Preferably, the cross-sectional shape of the sub-air passage 302 is rectangular. The length K1 of the long side of the rectangular cross-section of the middle air passage 3022 is 2.1 - 2.5 times the length K2 of the short side. The relationship between the bottom length L1 of the diverging air passage 3023, the bottom length L2 of the middle air passage 3022, and the bottom length L3 of the converging air passage 3021 is: L1:L2:L3 = (7 - 10):1:(1.8 - 2.3).Through the limitation of the above relationships, the present invention functions to further coordinate the relationship between the pressure of the inert gas source and the purifying efficiency. Since a number of sub-air channels 302 are arranged in an upper and lower array, by setting the cross-section of the sub-air channel 302 as a rectangle, the sub-air channel 302 can obtain a suitable cross-sectional area in a limited space, further ensuring that the inert gas flow has sufficient coverage area to improve the purifying efficiency, reduce the powder residue rate on the side wall of the piston 100, and improve the powder recovery rate. If the length K1 of the long side is less than 2.1 times the length K2 of the short side, the air flow resistance is too large at this time, resulting in energy loss, poor uniformity of the output inert gas flow field, the air flow coverage area cannot be guaranteed, the metal powder locally adhered to the side wall of the piston 100 cannot be removed, and there is also a problem that the gas shear force is too large, local turbulence is easily formed, and the dust cannot be effectively suppressed. If the length K1 of the long side is greater than 2.5 times the length K2 of the short side, the cross-sectional area becomes larger at this time, and the air flow resistance becomes smaller. However, for too large a cross-sectional area, when applied to a low-pressure inert gas source, it will result in insufficient acceleration of the air flow, so that the expansion air channel 3023 cannot effectively diffuse the inert gas flow, and there will still be a problem of poor uniformity of the gas flow field. Only by increasing the intake pressure can it be improved. Correspondingly, when increasing the intake pressure, it is necessary to cooperate with enhancing the sealing performance of the forming cylinder device, resulting in an increase in manufacturing and management difficulties; further, by setting the cooperative ratio between the bottom length L1 of the expansion air channel 3023, the bottom length L2 of the middle air channel 3022, and the bottom length L3 of the contraction air channel 3021, the relationship between them is: L1:L2:L3=(7-10):1:(1.8-2.3), further coordinating and cooperating to avoid excessive attenuation of the air flow energy while enabling the inert gas flow to stably enter the middle air channel 3022 and fully diffuse to the purifying gap through the expansion air channel 3023, thereby further improving the purifying efficiency, reducing the powder residue rate, and improving the metal powder recovery rate.

[0052] Specifically, as Figure 8 , 9 shown, the outward expansion angle α1 of the top wall 30231 of the expansion air channel 3023 facing its bottom satisfies 8°≤α1≤15°, and the outward expansion angle α2 of the two side walls 30232 of the expansion air channel 3023 satisfies 30°≤α2≤40°. It should be noted that Figure 9The middle dotted line X1 is the central axis of the branch air passage 302. The outward expansion angle α1 of the top wall 30231 of the expansion air passage 3023 is used to balance the diffusion efficiency of the inert gas flow and the stability of the air flow boundary layer. While increasing the longitudinal coverage area of the inert gas flow, it ensures that the inert gas flow in the expansion air passage 3023 can be output evenly and stably, avoiding the problem of air flow interference with the adjacent upper branch air passage 302 caused by local turbulence. It should be noted that the longitudinal direction is parallel to the axis X of the cylinder liner 200, and the transverse direction is perpendicular to the axis X of the cylinder liner 200; the outward expansion angle α2 of the two side walls 30232 of the expansion air passage 3023 is used to guide the lateral diffusion of the air flow and control the air flow coverage width. If α2 < 30°, it will lead to insufficient lateral diffusion at this time, and the air flow is concentrated, resulting in too high local flow velocity. This will not only lead to a small lateral coverage area of the air flow, a large powder cleaning blind area, and a high powder residue rate on the side wall of the piston 100, but also because the local air flow velocity is too fast, it will exacerbate the collision and rebound of metal powders and cannot effectively suppress dust. If α2 > 40°, when applied to a low-pressure inert gas source, the probability of generating lateral eddy currents increases. Instead of increasing the lateral coverage area of the air flow, it will entrain metal powders and cause local deposition; through the above parameter design, the two achieve an equal energy distribution, increasing both the lateral coverage area of the air flow and ensuring the uniformity of air flow diffusion.

[0053] Specifically, as Figure 7 shown, the relationship between the inclination angle β of the plane where the bottom of the branch air passage 302 is located with respect to the side wall of the cylinder liner 200 and the outward expansion angle α1 of the top wall 30231 of the expansion air passage 3023 satisfies the following formula: β = -3.46α1 + 81.9, where the unit of the angle β is degree. Preferably, 35° ≤ β ≤ 50°. During the powder cleaning process, by designing the inclination angle of the branch air passage 302, the relationship between suppressing dust and the powder residue rate on the side wall of the piston 100 is balanced. If the inclination angle β is less than 35°, the cleaning force of the inert gas flow blown out on the metal powder adhered to the side wall of the piston 100 is insufficient at this time, resulting in too high a powder residue rate of the metal powder on the side wall of the piston 100 and shortening the service life of the sealing ring; if the inclination angle β is greater than 50°, although the powder residue rate of the metal powder on the side wall of the piston 100 can be reduced at this time, the impact force of the inert gas flow blown out on the side wall of the piston 100 is too large, resulting in the collision and rebound of metal powders with each other and unable to effectively suppress dust; and by coordinating the relationship between the inclination angle β and the expansion angle α1 of the top wall 30231, they are negatively correlated with each other, avoiding the problem that both of them are too large or too small, which will affect the air flow coverage area and air flow impact force on the side wall of the piston 100, and thus affect the dust suppression and powder cleaning quality.

[0054] With the above settings, when purging metal powder with a particle size in the range of 25 - 50 microns, the powder blowing part 300 only needs to be connected to low-pressure inert gas in the range of 0.25 Mpa - 0.4 Mpa. The pressure of the inert gas is reduced by 50% compared with the past, and the dust concentration ≤ 5 g / m 3 can be achieved simultaneously, and the powder recovery rate ≥ 97%. Moreover, the low-pressure inert gas reduces the requirement for sealing performance. The sealing requirement of the forming cylinder device described in the present invention is reduced by 37.5%, stabilizing the oxygen content in the printing chamber below 3% and further reducing the explosion risk.

[0055] Specifically, as Figure 7 shown, the gap D1 between the inner wall of the cylinder liner 200 and the side wall of the piston 100 satisfies 2 mm ≤ D1 ≤ 3.5 mm; the relationship between the distance S between the outlet ends of the adjacent sub-air channels 302 above and below, the gap D1, and the inclination angle β of the sub-air channel 302 satisfies the following formula: where the unit of the distance S is mm. The above gap range balances the requirements of thermal expansion compensation and the sealing fit of the sealing ring, ensuring the stable movement of the piston 100 and the airtightness to make the inert environment highly stable, while reducing the probability of blockage during the powder purging process; and by designing the relationship between the distance S, the gap D1, and the inclination angle β, the three cooperate with each other to avoid the problems of low powder purging efficiency, large powder purging blind area, and low powder recovery rate caused by all being too large for the distance S, the gap D1, and the inclination angle β, and to avoid the problem of excessive dust concentration caused by all being too small, which affects each other between the inert gas flows. According to the requirements, the distance between the outlet ends of the sub-air channels 302 is regulated. By coordinating the cooperation of the three parameters, it is more beneficial for the forming cylinder device described in the present invention to achieve a powder recovery rate ≥ 97% and a dust concentration ≤ 5 g / m 3 under the supply of a low-pressure inert gas source with the same pressure within a variety of different structural size ranges.

[0056] Specifically, as Figure 10 、 11As shown in the figure, the powder receiving part 400 includes a powder receiving groove, a powder conveying pipe 401, and a plurality of diversion pipes 402 equidistantly distributed along the axis of the powder conveying pipe 401. The powder receiving groove, the diversion pipes 402, and the powder conveying pipe 401 are an integral structure formed by processing. One end of the powder conveying pipe 401 is connected to an inert gas source as the gas conveying end 01, and the other end is connected to a metal powder collection mechanism as the powder outlet end 02. The powder receiving groove is connected below the powder cleaning flow channel 2022. One end of the diversion pipe 402 is communicated with the powder receiving groove, and the other end is communicated with the powder conveying pipe 401. The diversion pipe 402 is inclined towards the advancing direction of the air flow in the powder conveying pipe 401, and the included angle γ between the axis X2 of the diversion pipe 402 and the axis X3 of the powder conveying pipe 401 satisfies 50° ≤ γ ≤ 70°. After the metal powder falls through the gap between the piston 100 and the cylinder sleeve 200 and sequentially passes through the powder cleaning flow channel 2022, the powder receiving groove, and the diversion pipes 402, it enters the powder conveying pipe 401 and is carried and conveyed to the metal powder collection mechanism by the inert gas flow flowing in the powder conveying pipe 401. By setting the diversion pipe 402 to be inclined towards the air flow movement direction in the powder conveying pipe 401 and designing the included angle to satisfy 50° ≤ γ ≤ 70°, its function is to coordinate the efficient conveying of metal powder and suppress dust. If the included angle γ is less than 50°, at this time, there is a large change in the air flow operation path at the inlet of the diversion pipe 402. When the inert gas flow blown by the powder blowing part 300 carries the metal powder and falls to the inlet of the diversion pipe 402, it is easy to collide with the inner wall of the diversion pipe 402, resulting in local turbulence and mutual collision of metal powders, which is not conducive to suppressing dust and will also lead to low conveying efficiency of metal powders in the diversion pipe 402. If the included angle γ is greater than 70 degrees, although the collision kinetic energy between the inert gas flow carrying the metal powder and the inner wall of the diversion pipe 402 can be reduced at this time, the movement direction of the inert gas flow carrying the metal powder after being output from the diversion pipe 402 approaches perpendicular to the air flow direction in the powder conveying pipe 401, resulting in local turbulent flow at the outlet position of the diversion pipe 402 and seriously affecting the conveying efficiency of metal powders. Preferably, the flow rate of the inert gas in the powder conveying pipe 401 is set to be 1.4 - 1.7 times the flow rate of the inert gas blown into the cylinder sleeve 200 by the powder blowing part 300. Due to the relatively fast flow rate, a negative pressure environment is formed in the powder conveying pipe 401, which can further improve the powder cleaning efficiency.

[0057] Embodiment 2

[0058] The present invention also provides a 3D printing device, which includes the forming cylinder device described in Embodiment 1, and further includes a printing chamber for accommodating the forming cylinder device, and a powder cleaning device, a laser printing device, and a powder spreading device disposed inside the chamber body and above the printing platform for sweeping the residual metal powder into the powder cleaning gap between the cylinder sleeve 200 and the piston 100.

[0059] Embodiment 3

[0060] The present invention also provides an operation method, which is applied to the forming cylinder device described in Embodiment 1 and includes:

[0061] S1, driving the piston 100 to move downward until its bottom abuts against the boss 202;

[0062] S2, inflating the inflatable seal ring 101 disposed in the groove 2021 until the inflatable seal ring 101 is in close contact with the bottom of the piston 100;

[0063] S3, evacuating the inflatable seal ring 101 circumferentially embedded in the piston 100, and the inflatable seal ring retracts into the seal ring groove;

[0064] S4, the metal powder flows downward through the gap between the inner wall of the cylinder sleeve 200 and the side wall of the piston 100 and enters the powder delivery pipe 401 through the powder cleaning flow channel 2022;

[0065] S5, connecting the powder blowing part 300 to an inert gas source and introducing an inert gas with a pressure of 0.25 Mpa - 0.4 Mpa;

[0066] S6, connecting the powder delivery pipe 401 to an inert gas source, adjusting the flow rate of the inert gas in the powder delivery pipe 401 to be higher than the flow rate of the inert gas blown into the cylinder sleeve 200 through the powder blowing part 300, and the metal powder enters the metal powder collection mechanism along the powder delivery pipe 401;

[0067] S7, after powder cleaning is completed, inflating the inflatable seal ring 101 circumferentially embedded in the piston 100 until the inflatable seal ring 101 is in close contact with the inner wall of the cylinder sleeve 200;

[0068] S8, driving the piston 100 to move upward to the printing station;

[0069] S9, evacuating the inflatable seal ring 101 disposed in the groove 2021, and the inflatable seal ring 101 retracts into the groove 2021.

[0070] The technical features of the above-described embodiments can be combined arbitrarily. For the sake of brevity of description, all possible combinations of the technical features in the above embodiments are not exhausted. However, as long as there is no contradiction in the combination of these technical features, it should be considered as the scope recorded in this specification.

[0071] For those of ordinary skill in the art, without departing from the concept of the present invention, several modifications and improvements can still be made, and these all belong to the protection scope of the present invention. The protection scope of the present invention is subject to the appended claims.

Claims

1. A rapid powder cleaning forming cylinder device, characterized in that: include: A piston, wherein the upper surface of the piston is configured as a printing platform, and the side wall thereof is provided with at least one sealing ring groove in the circumference thereof, an inflatable sealing ring is embedded in the sealing ring groove, and a driving part is provided at the bottom of the piston to drive the piston to reciprocate up and down; The cylinder sleeve is a hollow structure with openings at both ends. The piston is coaxially arranged in the inner cavity of the cylinder sleeve. The shape of the cylinder sleeve matches the shape of the piston and there is a predetermined gap between its inner wall and the side wall of the piston. A boss extending toward the inner cavity of the cylinder sleeve is circumferentially arranged around the bottom of the cylinder sleeve. A groove and a plurality of powder cleaning channels passing through the boss are provided on the boss. An inflatable sealing ring is provided in the groove. When the piston descends to the lowest point, its bottom is sealed and abutted against the groove. The powder cleaning component includes a plurality of powder blowing parts which are opened on the side wall of the cylinder liner and communicated with the inner cavity of the cylinder liner, the powder blowing parts are connected to an inert gas source, the powder blowing parts output inert gas obliquely downward and the gas output port thereof is located below the plane where the upper surface of the piston is located, at least two groups of powder blowing parts are arranged at intervals of 90 degrees around the circumference of the side wall of the cylinder liner, and also includes a powder receiving part connected to below the powder cleaning flow channel, one side of the powder receiving part is connected to the inert gas source, and the other side is connected to a metal powder collecting mechanism.

2. A rapid powder cleaning forming cylinder device according to claim 1, characterized in that: The powder blowing portion includes a main air duct connected to an inert gas source and vertically opened in the side wall of the cylinder liner along the extension direction of the cylinder liner axis, and a plurality of branch air ducts connected to the main air duct and arranged in an up and down array along the extension direction of the cylinder liner axis. The branch air ducts are opened in the side wall of the cylinder liner and communicate with the inner cavity of the cylinder liner. The branch air ducts are inclined downward at a predetermined angle. When the piston descends to abut against the boss, all branch air duct outlets included in the powder blowing portion are located below the plane where the upper surface of the piston is located.

3. A rapid powder cleaning forming cylinder device according to claim 2, characterized in that: The airway is composed of a contraction airway at the air inlet end, a middle airway and an expansion airway at the air outlet end, which are connected in sequence. The bottoms of the contraction airway, the middle airway and the expansion airway are all in the same plane. The cross-sectional area of ​​the contraction airway gradually decreases along the air inlet direction, the cross-sectional area of ​​the middle airway remains unchanged along the air inlet direction, and the cross-sectional area of ​​the expansion airway gradually increases along the air inlet direction.

4. A rapid powder cleaning forming cylinder device according to claim 3, characterized in that: The cross-sectional shape of the airway division is a rectangle, the long side length K1 of the rectangular cross-section of the middle airway is 2.1-2.5 times the short side length K2, and the relationship between the bottom length L1 of the expansion airway, the bottom length L2 of the middle airway and the bottom length L3 of the contraction airway is: L1:L2:L3=(7-10):1:(1.8-2.3).

5. A rapid powder cleaning forming cylinder device according to claim 3 or 4, characterized in that: The outward expansion angle α1 of the top wall of the expansion airway directly opposite to its bottom satisfies 8°≤α1≤15°, and the outward expansion angle α2 of the two side walls of the expansion airway satisfies 30°≤α2≤40°.

6. A rapid powder cleaning forming cylinder device according to claim 5, characterized in that: The relationship between the inclination angle β of the plane where the bottom of the air distribution channel is located compared to the side wall of the cylinder liner and the outward expansion angle α1 of the top wall of the expansion channel satisfies the following formula: β=-3.46α1+81.9, where the angle β is in degrees.

7. A rapid powder cleaning forming cylinder device according to claim 6, characterized in that: The gap D1 between the inner wall of the cylinder sleeve and the side wall of the piston satisfies 2 mm ≤ D1 ≤ 3.5 mm; the relationship between the spacing S between the outlet ends of the upper and lower adjacent gas distribution channels, the gap D1 and the inclination angle β of the gas distribution channels satisfies the following formula: The unit of spacing S is mm.

8. The rapid powder cleaning forming cylinder device according to claim 1 is characterized in that: The powder receiving part includes a powder receiving trough, a powder conveying pipe, and a plurality of guide pipes equidistantly distributed along the axis of the powder conveying pipe. One end of the powder conveying pipe is connected to an inert gas source as a gas conveying end, and the other end is connected to a metal powder collecting mechanism as a powder outlet end. The powder receiving trough is connected below the powder cleaning flow channel. One end of the guide pipe is connected to the powder receiving trough, and the other end is connected to the powder conveying pipe. The angle γ between the axis of the guide pipe and the axis of the powder conveying pipe satisfies 50°≤γ≤70°.

9. A 3D printing device, characterized in that: It comprises a forming cylinder device as described in any one of claims 1 to 8, and also comprises a printing cabin for accommodating the forming cylinder device, and a powder cleaning device, a laser printing device and a powder spreading device arranged inside the cabin and above the printing platform for cleaning residual metal powder into the powder cleaning gap between the cylinder liner and the piston.

10. An operating method, which is applied to the forming cylinder device according to any one of claims 1 to 8, characterized in that: include: S1, driving the piston downward until its bottom abuts against the boss; S2, inflating the inflatable sealing ring disposed in the groove until the inflatable sealing ring is in close contact with the bottom of the piston; S3, evacuating the inflatable sealing ring embedded circumferentially of the piston, and retracting the inflatable sealing ring into the sealing ring groove; S4, the metal powder flows downward through the gap between the inner wall of the cylinder sleeve and the side wall of the piston, passes through the powder cleaning channel and enters the powder conveying pipe; S5, the powder blowing part is connected to an inert gas source, and an inert gas with a pressure of 0.25Mpa-0.4Mpa is introduced; S6, the powder conveying pipe is connected to an inert gas source, and the flow rate of the inert gas flow in the powder conveying pipe is adjusted to be higher than the flow rate of the inert gas flow blown into the cylinder sleeve through the powder blowing part, and the metal powder enters the metal powder collecting mechanism along the powder conveying pipe; S7, after the powder cleaning is completed, inflate the inflatable sealing ring embedded in the circumference of the piston until the inflatable sealing ring is in close contact with the inner wall of the cylinder sleeve; S8, driving the piston upward to the printing station; S9, evacuating the inflatable sealing ring disposed in the groove, and retracting the inflatable sealing ring into the groove.

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