Binder spraying 3D printing equipment and printing method for low-fluidity powder

Abstract

The invention discloses binder spraying 3D printing equipment and a printing method for low-fluidity powder, and relates to the technical field of 3D printing. The printing method comprises the steps that the powder forming module is controlled to reach an initial position; the powder forming module comprises a powder falling module and a powder spreading module which move synchronously; powder is added into the powder falling module through the powder supplementing module; the powder forming module is moved to the initial powder laying position, and powder is controlled to be scattered on a vibration plate from a powder supplementing bearing plate of the powder falling module; vibration of a vibration plate is controlled, so that the powder is transferred to the front of the powder spreading module and is spread and compacted; laying of single-layer powder is completed; the steps are repeated to complete laying of the bottom powder layer; and laying of the slice layers is completed repeatedly on the bottom powder layer, the ink jetting module is controlled to move along with the powder forming module, a binder is jetted to each slice layer, and a 3D printing product is obtained through curing. A matching scheme of layer-by-layer powder supply, independent powder spreading and independent compaction is adopted, so that high density and high uniformity of a low-fluidity powder printing breadth are ensured.

Description

Technical Field

[0001] The present invention relates to the technical field of 3D printing, and in particular to a binder jetting 3D printing device and a printing method for low-fluidity powder. Background Art

[0002] Binder Jetting (BJ, also commonly known as 3DP) is an additive manufacturing technology based on inkjet technology and a 3D printing technology based on a powder bed. It selectively sprays a binder on a powder bed and bonds the powder particles layer by layer to build a three-dimensional solid product. Using fine powder with poor fluidity as printing powder can reduce the surface roughness of the printed part, improve the dimensional accuracy and surface quality of the product, and provide better support in the powder bed to avoid damage caused by the shear force introduced during the powder laying process. From the perspective of post-processing, it can prepare products with uniform structure and fine grains, improve their mechanical properties and service life, and at the same time obtain higher sintering activity during the sintering process, achieve densification at a lower temperature, and reduce sintering energy consumption. However, fine powders with poor fluidity have small particle sizes and large specific surface areas. During the conveying process, they are easily adsorbed on the surfaces of conveying pipes, screws, valves, filters and other devices due to van der Waals forces and electrostatic forces, resulting in uneven and discontinuous powder supply, and even blockage of the conveying device. Secondly, fine powders will also adhere to the surface of the powder spreading roller, changing the effective cross-sectional area and surface roughness of the powder spreading roller, resulting in a deviation between the actual powder spreading thickness and the set value. Moreover, fine powders are prone to form powder agglomerates of different sizes during the powder spreading process, and cannot be effectively dispersed under the push of the powder spreading roller, resulting in large deviations in the uniformity of powder density in different areas. Summary of the invention

[0003] The technical problem to be solved by the present invention is to provide a binder jet 3D printing device and a printing method for low-fluidity powder, which can improve the printing accuracy of low-fluidity powder and the uniformity of powder density in the entire format, thereby improving the consistency of printed products.

[0004] In order to solve the above problems, the present invention discloses a binder jet 3D printing method for low-fluidity powder, comprising the following steps: (1) controlling the movement of the powder forming module to make it reach an initial position; wherein the powder forming module comprises a powder dropping module and a powder spreading module, and the powder dropping module and the powder spreading module move synchronously; (2) adding a preset amount of powder to the powder dropping module through the powder replenishing module, wherein the powder dropping module includes a powder replenishing receiving plate and a vibration plate; (3) moving the powder forming module to the powder spreading starting position, and controlling the powder replenishing receiving plate to cause the powder to fall onto the vibration plate; (4) by controlling the vibration of the vibration plate, the powder is transferred to a preset area in front of the powder spreading module, and then the powder spreading module is used to flatten and compact the powder in sequence; (5) moving the powder forming module to an initial position to complete the laying of a single layer of powder; (6) Repeat steps (1) to (5) until the base powder layer is laid; (7) Repeat steps (1) to (5) on the base powder layer to complete the laying of the slice layer, control the inkjet module to follow the movement of the powder forming module, spray the binder in the preset area of ​​each slice layer and solidify the powder until the printing of the model is completed to obtain a 3D printed product.

[0005] As an improvement of the above technical solution, the powder forming module also includes a bracket, the powder falling module includes a powder replenishing receiving plate and a vibration plate, and the powder spreading module includes a powder spreading roller and a compaction roller; the powder replenishing receiving plate, the vibration plate, the powder spreading roller and the compaction roller are all fixed on the bracket, the vibration plate is arranged in front of the powder spreading roller, and the compaction roller is arranged behind the powder spreading roller; there is a preset distance between the vibration plate and the powder spreading roller, forming a preset area for powder transfer.

[0006] As an improvement of the above technical solution, the powder spreading roller is used to sweep the powder scattered by the powder falling module to obtain a powder spreading layer, and the ratio of the density of the powder spreading layer to the loose density of the powder is (0.8~1.2):1; The compacting roller is used to compact the powder layer to obtain a compacted powder layer, and the ratio of the density of the compacted powder layer to the tap density of the powder is (0.8~1.2):1.

[0007] As an improvement of the above technical solution, the ratio of the thickness of the base powder layer to the thickness of each layer of the compacted powder layer is (20-40):1; The ratio of the thickness of each layer of the compacted powder layer to the D50 of the powder is (2-10):1, and / or the ratio of the thickness of each layer of the compacted powder layer to the D90 of the powder is (1.5-10):1.

[0008] As an improvement of the above technical solution, the D50 of the powder is 10 μm to 100 μm, and / or the D90 of the powder is 10 μm to 100 μm; The repose angle of the powder is 35° to 60°.

[0009] As an improvement of the above technical solution, the bottom of the vibration plate is higher than the bottom of the powder spreading roller, and the height difference between the vibration plate and the powder spreading roller is 0.5 mm to 5 mm; The compacting roller and the powder spreading roller rotate in opposite directions, the surface roughness of the compacting roller is smaller than that of the powder spreading roller; the bottom of the powder spreading roller is higher than the bottom of the compacting roller, and the height difference between the powder spreading roller and the compacting roller is 0.01 mm to 1 mm; The powder replenishing receiving plate and the vibration plate can both rotate relative to the bracket; the vibration frequency of the vibration plate is 0.1Hz~100Hz; During the process of the powder replenishing module adding powder to the powder dropping module, the powder replenishing receiving plate is located in a horizontal position; during the powder spreading process, the powder replenishing receiving plate has an angle with the horizontal direction so that the powder on the powder replenishing receiving plate falls to the vibration plate.

[0010] As an improvement of the above technical solution, the diameter of the compacting roller is 25mm~120mm, and the surface roughness is Ra0.25~Ra 3.2; the diameter of the powder spreading roller is 25mm~120mm, and the surface roughness is Ra 1.6~Ra 100.

[0011] As an improvement of the above technical solution, the preset path of movement of the inkjet module is: moving along the Y direction, spraying the binder in the preset area and curing the bonding powder, then moving a certain distance along the X direction and moving in the opposite direction along the Y direction, spraying the binder in the preset area and curing the bonding powder, and realizing inkjet printing of each slice layer in sections; The inkjet module has a moving speed of 100 mm / s to 400 mm / s in the X direction and a moving speed of 100 mm / s to 600 mm / s in the Y direction.

[0012] As an improvement of the above technical solution, during the powder spreading process, the moving speed of the powder forming module in the X direction is 50 mm / s~400 mm / s; The idle travel speed of the powder forming module from the initial position to the powder spreading starting position is 250 mm / s to 500 mm / s; The powder replenishing module is provided with a powder outlet vibrator and a powder replenishing belt. The powder replenishing powder in the powder replenishing module flows out under the action of the powder outlet vibrator. The preset amount of powder is evenly sprinkled on the powder replenishing receiving plate through the rotation of the powder replenishing belt and the movement of the powder replenishing module in the Y direction. The preset amount of powder added by the powder replenishing module to the powder falling module each time is 1 to 2 times the amount of powder required for each layer of powder laying.

[0013] Correspondingly, the present invention also discloses a binder jet 3D printing device for low-fluidity powder, which is used to perform the above-mentioned binder jet 3D printing method for low-fluidity powder, including a powder replenishing module, a powder forming module, an inkjet module and a platform module; The platform module includes a printing platform, and the printing platform is provided with a lifting mechanism, and the lifting mechanism is connected to the printing platform and is used to drive the printing platform to rise and fall in the Z direction; The powder forming module and the inkjet module are arranged above the platform module along the X direction; the powder forming module includes a powder dropping module and a powder spreading module that move synchronously; the powder dropping module includes a powder replenishing receiving plate and a vibration plate for vibrating and spreading the powder; the powder spreading module includes a powder spreading roller and a compacting roller for flattening and compacting the powder scattered by the powder dropping module; the inkjet module is used to spray adhesive on a preset area of ​​the slice layer; The powder replenishing module is arranged at one side of the platform module and is higher than the powder dropping module, and is used for replenishing powder to the powder dropping module.

[0014] The implementation of the present invention has the following beneficial effects: 1. The binder jet 3D printing method of low-fluidity powder provided by the present invention replenishes powder layer by layer through a powder dropping module before spreading each layer of powder, which can effectively avoid the cumulative error caused by excessive low-fluidity powder adhering and agglomerating on the powder dropping module and the powder spreading module, thereby improving the printing accuracy; at the same time, it avoids the reliance on precise control of the amount of replenishing powder, and reduces the difficulty of replenishing powder.

[0015] 2. The binder jet 3D printing method for low-fluidity powder provided by the present invention forms secondary destruction on the agglomeration and adhesion of powder by controlling the amplitude and vibration frequency of the vibration plate set at the powder outlet of the powder dropping module, which can improve the fluidity of the low-fluidity powder on the one hand, and improve the uniformity of powder dropping on the other hand; at the same time, the powder in the powder dropping module accumulates between the powder spreading module and the powder dropping module as the powder dropping module moves, so a large amount of powder that has not yet participated in the powder spreading can be restricted on the vibration plate, thereby avoiding damage to the printing area caused by excessive powder pile in front of the powder spreading module.

[0016] 3. The following movement of the powder spreading roller and the compacting roller can fully compact the powder continuously and timely to obtain a high stacking density, and effectively improve the uniformity of the powder density in the entire format, greatly improving the consistency of the product. At the same time, the independent working mode of the powder spreading roller and the compacting roller can give them different roughness to complete different powder sweeping and powder pressing functions. Therefore, each roller can be designed with a larger diameter to resist deformation, which is more suitable for the needs of large-format industrial-grade equipment. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 It is a schematic structural diagram of a binder jet 3D printing device for low-fluidity powder provided by the present invention; Figure 2 yes Figure 1 A magnified view of part A; Figure 3It is a schematic diagram of the top view of the structure of the binder jet 3D printing device for low-fluidity powder provided by the present invention; Figure 4 It is a schematic diagram of the working process of the powder replenishing step of laying the base powder layer of the binder jet 3D printing device of low-fluidity powder provided by the present invention; Figure 5 It is a working schematic diagram of the powder shedding preparation link of laying the bottom powder layer of the binder jet 3D printing device of low-fluidity powder provided by the present invention; Figure 6 It is a working schematic diagram of the powder dropping and powder spreading process of laying the bottom powder layer of the binder jet 3D printing device of low-fluidity powder provided by the present invention; Figure 7 It is a schematic diagram of the work of laying the bottom powder layer of the binder jet 3D printing device of low-fluidity powder provided by the present invention; Figure 8 It is a working schematic diagram of the powder dropping, powder spreading and ink jetting links in the printing stage of the binder jet 3D printing device for low-fluidity powder provided by the present invention; Fig. 9 It is a working schematic diagram of the powder replenishing link in the printing stage of the binder jet 3D printing device for low-fluidity powder provided by the present invention; Fig.10 It is a motion control logic diagram of a binder jet 3D printing device for low-fluidity powder provided by the present invention; Fig.11 It is a schematic diagram of the process of laying a base powder layer by the binder jet 3D printing method of low-fluidity powder provided by the present invention; Fig.12 It is a schematic diagram of the process of inkjet printing of the binder jet 3D printing method of low-fluidity powder provided by the present invention. DETAILED DESCRIPTION

[0018] In order to make the purpose, technical solutions and advantages of the present invention more clear, the present invention is described in further detail below.

[0019] The present invention provides a binder jet 3D printing device for low-fluidity powders, such as Figure 1~Figure 3 As shown, it includes a platform module 10, an inkjet module 20, a powder forming module, a printing powder 50 and a powder replenishing module 60, wherein the powder forming module includes a powder spreading module 30 and a powder dropping module 40 which move synchronously.

[0020] Specifically, the platform module 10 includes a base 11 and a printing platform 12. The printing platform 12 is provided with a lifting mechanism, which is connected to the bottom of the printing platform 12 and is used to drive the printing platform 12 to move up and down along the Z direction. One side of the printing platform is the starting position for spreading powder, and the other side is the initial position. In one embodiment, the platform module 10 also includes a residual powder collection device, which includes a residual powder collection box 13 and a residual powder recovery straw 14. The residual powder collection box 13 and the residual powder recovery straw 14 are arranged on one side of the printing platform 12 away from the starting position for spreading powder, and are used to recycle the residual powder 56 left after spreading powder.

[0021] The powder forming module and the inkjet module 20 are arranged on the powder spreading track 15 above the platform module 10 in the front and back directions along the X direction. It can be understood that the front and back are defined according to the movement direction of the module during the powder spreading process. The side pointing to the direction of movement from the powder spreading starting position to the initial position is the front, and the opposite direction is the rear. The powder forming module includes a powder spreading module 30 and a powder dropping module 40. The powder spreading module 30 and the powder dropping module 40 move synchronously in the X direction. The powder dropping module 40 is used to sprinkle powder onto the printing platform 12. The powder spreading module 30 is used to flatten the powder sprinkled by the powder dropping module 40 onto the printing platform 12.

[0022] In one embodiment, the powder forming module includes a bracket, a powder dropping module 40 and a powder spreading module 30. The powder dropping module 40 includes a powder replenishing receiving plate 41 and a vibration plate 44. The powder spreading module 30 includes a powder spreading roller 35 and a compacting roller 34. The powder replenishing receiving plate 41, the vibration plate 44, the powder spreading roller 35 and the compacting roller 34 are all fixed on the bracket. The vibration plate 44 is arranged in front of the powder spreading roller 35, and the compacting roller 34 is arranged behind the powder spreading roller 35. There is a preset distance between the vibration plate 44 and the powder spreading roller 34 to form a preset area for powder transfer. It can be understood that the vibration plate 44, the powder spreading roller 35 and the compacting roller 34 are arranged in sequence from front to back to form synchronous powder dropping, powder spreading and compaction.

[0023] Specifically, the bracket includes a powder dropping mounting seat 46 for fixing the powder dropping module 40 and a powder spreading mounting seat 31 for fixing the powder spreading module 30. A powder replenishing receiving plate 41, an eccentric wheel 42, a connecting rod 43, a vibration plate 44 and a powder baffle 45 are installed on the powder dropping mounting seat 46. One end of the powder replenishing receiving plate 41 is connected to the powder dropping mounting seat 46, and the powder replenishing receiving plate 41 can rotate counterclockwise. The powder replenishing receiving plate 41 rotates to a horizontal position to receive the fallen powder 52; the powder replenishing receiving plate 41 rotates to have an angle with the horizontal direction, and a powder dropping channel is reserved, and the fallen powder 52 is scattered onto the vibration plate 44. The vibration plate 44 is arranged below the powder replenishing receiving plate 41, one end of the vibration plate 44 is hinged to the powder dropping mounting seat 46, the driving mechanism 48 is fixed to the powder dropping mounting seat 46, the eccentric wheel 42 is connected to the main shaft 49 of the driving mechanism 48, one end of the connecting rod 43 is sleeved on the eccentric wheel 42, and the other end is hinged to the lower surface of the vibration plate 44; the connecting rod 43 drives the vibration plate 44 to vibrate back and forth along the vibration direction 47 under the drive of the eccentric wheel 42, and the amplitude and vibration frequency of the vibration plate 44 are adjusted by the eccentricity and rotation speed of the eccentric wheel 42. The powder baffle 45 is arranged on the side of the powder spreading module 30 close to the powder dropping module 40.

[0024] The powder spreading mounting seat 31 is provided with a powder spreading roller bracket 33 and a compacting roller bracket 32, the powder spreading roller 35 is arranged on the powder spreading roller bracket 33, and the compacting roller 34 is arranged on the compacting roller bracket 32. The powder spreading roller 35 and the compacting roller 34 are arranged front and back along the X direction, and the rotation direction 36 of the compacting roller is opposite to the rotation direction 37 of the powder spreading roller. The powder spreading roller 35 is used to sweep the powder scattered by the powder falling module 40 to obtain a powder spreading layer 53, and the compacting roller 34 is used to compact the powder spreading layer 53 to obtain a compacted powder layer 54. The vibration plate 44, the powder baffle 45 and the powder spreading roller 35 form a triangular area for carrying the falling powder 52.

[0025] The inkjet module 20 includes an integrated slide rail 21, an inkjet scanning track 22, an inkjet head integrated mechanism 23 and an inkjet head 24. The setting direction of the inkjet scanning track 22 is perpendicular to the setting direction of the powder laying track 15. The inkjet head integrated mechanism 23 scans along the inkjet scanning track 22 in the Y direction and sprays the adhesive 25 in the preset area for bonding. Then, after the inkjet module 20 moves a certain distance along the X direction, the inkjet head integrated mechanism 23 moves in the opposite direction along the inkjet scanning track 22. This combined action is repeated until the entire working plane completes inkjet printing.

[0026] The powder replenishing module 60 includes a temporary powder bin 61, a powder replenishing track 62, a powder outlet vibrator 63, a powder replenishing belt 64 and a belt driving shaft 65. The powder replenishing module 60 is arranged on the side of the platform module 10 away from the starting position of the powder spreading and moves along the Y direction. The powder replenishing module 60 is higher than the powder dropping module 40, and is used to carry the powder replenishing powder 51 and replenish the powder dropping module 40. The powder outlet vibrator 63 vibrates at a high frequency, forcing the powder replenishing powder 51 with low fluidity to obtain a certain fluidity, and under the drive of the powder replenishing belt 64, flows out from the temporary powder bin 61 of the powder replenishing module 60 along the moving direction 66 of the powder replenishing belt 64, and finally fills a certain amount of uniform powder on the powder replenishing receiving plate 41.

[0027] The present invention also provides a binder jet 3D printing method for low-fluidity powder, comprising the following steps: S1. Control the movement of the powder forming module to make it reach an initial position; wherein the powder forming module includes a powder dropping module and a powder spreading module, and the powder dropping module and the powder spreading module move synchronously.

[0028] Specifically, when the powder forming module reaches the initial position, the powder dropping module is located below the powder replenishing module.

[0029] S2. Add a preset amount of powder to the powder dropping module through the powder replenishing module. The powder dropping module includes a powder replenishing receiving plate and a vibration plate.

[0030] Specifically, the powder replenishing module moves along the Y direction, and the powder in the powder replenishing module flows out under the action of the powder outlet vibrator. Through the rotation of the powder replenishing belt, the preset amount of powder is evenly sprinkled on the powder replenishing receiving plate located in a horizontal position. In one embodiment, the preset amount of powder added by the powder replenishing module to the powder dropping module each time is 1 to 2 times the amount of powder required for each powder laying. By controlling the amount of powder added each time, excessive powder is prevented from accumulating in the powder dropping module to cause agglomeration, the laying error of each layer of powder is reduced, and the printing accuracy is improved.

[0031] It is understandable that the amount of replenishing powder added can be adjusted by the working frequency and amplitude of the vibrator, and can also be adjusted by the rotation speed and friction of the replenishing powder belt.

[0032] S3, moving the powder forming module to the powder spreading starting position, and controlling the powder replenishing receiving plate to scatter the powder onto the vibration plate.

[0033] Specifically, after the powder forming module returns to the starting position for spreading powder, the powder receiving plate flips over to sprinkle the powder onto the vibration plate. At the same time, the printing platform moves downward along the Z direction for a distance, leaving a layer of powder space. The moving speed of the printing platform in the Z direction is 5mm / s~30mm / s.

[0034] S4. By controlling the vibration of the vibration plate, the powder is transferred to a preset area in front of the powder spreading module, and then the powder spreading module is used to flatten and compact the powder in sequence.

[0035] As the powder forming module moves along the X direction, the vibration plate begins to vibrate, improving the fluidity of the low-fluidity powder and transferring the powder to the preset area in front of the powder spreading module. As the vibration plate vibrates, the low-fluidity powder that has agglomerated under gravity regains better fluidity. At this time, the fluidity of the powder is not enough to allow it to flow out completely, but it will gradually slide down with the movement of the powder spreading module and the vibration of the vibration plate. In order to avoid powder shortage or accumulation during the powder spreading process, the amplitude and / or vibration frequency of the vibration plate need to be adjusted appropriately. It is worth noting that although the vibration plate provides powder fluidity that exceeds the minimum requirement, the powder will only flow to a limited area due to the spatial limitations of the vibration plate and the powder bed. This feature avoids the formation of an excessively large powder pile in the forward direction of the powder spreading roller due to changes in powder fluidity, thereby largely avoiding the problem of pushing powder caused by excessive powder piles.

[0036] In a preferred embodiment, the amplitude and vibration frequency of the vibration plate are adjusted so that the powder in the powder falling module is accumulated between the powder spreading module and the powder falling module, and the accumulation of powder in front of the powder spreading module is controlled to avoid horizontal powder pushing and vertical crushing of the printed area. Wherein, the amplitude and vibration frequency of the vibration plate are adjusted by the eccentricity and rotation speed of the eccentric wheel. In order to avoid powder shortage or powder accumulation during the powder spreading process, the vibration frequency of the vibration plate is 0.1Hz~100Hz, exemplarily 1Hz, 5Hz, 10Hz, 30Hz or 60Hz, but not limited to this, more preferably, the vibration frequency of the vibration plate is 5Hz~20Hz. The eccentricity of the eccentric wheel is 0.1mm~5mm, exemplarily 0.4mm, 0.8mm, 1mm, 2mm or 4mm, but not limited to this, more preferably, the eccentricity of the eccentric wheel is 0.4mm~1mm, and the specific setting is related to the powder fluidity and the size of the powder outlet of the vibration plate.

[0037] While the powder dropping module completes the powder dropping, the powder spreading module flattens and compacts the powder. In one embodiment, the powder spreading speed of the powder forming module along the X direction is 50mm / s~400mm / s, and the idle stroke speed of the powder forming module after powder replenishment is 250mm / s~500mm / s. Correspondingly, the rotation speeds of the compaction roller and the powder spreading roller, as well as the vibration frequency of the vibration plate need to be changed proportionally.

[0038] In the powder spreading module, the powder spreading roller and the compacting roller are arranged front and back along the X direction, and the rotation direction of the compacting roller is opposite to that of the powder spreading roller. The powder spreading roller and the compacting roller can be independently driven by a split design, and the rotation speed and direction of both can be adjusted independently. It can be understood that the powder spreading roller is used to sweep the powder scattered by the powder falling module to obtain a powder spreading layer, and the compacting roller is used to compact the powder spreading layer to obtain a compacted powder layer. Therefore, the compacting roller is closer to the powder layer than the powder spreading roller. In one embodiment, the bottom of the powder spreading roller is higher than the bottom of the compacting roller, and the height difference is 0.01mm~1mm, and exemplarily 0.05mm, 0.1mm, 0.4mm, 0.6mm or 0.8mm, but not limited to this, which is specifically related to the compactability of the powder.

[0039] In a preferred embodiment, the diameter of the compacting roller is 25 mm to 120 mm, and the surface roughness is Ra 0.05 to Ra 3.2; the diameter of the powder spreading roller is 25 mm to 120 mm, and the surface roughness is Ra 1.6 to Ra 100; the surface of the powder spreading roller has higher visible lines or bumps; the powder spreading roller rotates counterclockwise, and the compacting roller rotates clockwise. It is understandable that the compacting roller should have a smooth surface, and the powder spreading roller should have a rough surface. The powder spreading roller with a high roughness surface generates a greater shear force when rotating counterclockwise, rolling away excess powder forward to avoid excessive downward pressure. The slightly smooth compacting roller, which is installed slightly lower than the powder spreading roller, rotates clockwise. The smooth compacting roller generates a greater downward pressure when rotating clockwise, compacting the loose powder. While compacting the powder, it avoids the horizontal shear force and horizontal displacement of the powder under high compaction, thereby avoiding problems such as pushing powder in all directions.

[0040] In one embodiment, the ratio of the density of the powder layer to the loose density of the powder is 1:(0.8~1.2), and the ratio of the density of the compacted powder layer to the tapped density of the powder is 1:(0.8~1.2), which is specifically related to the compactability of the powder. This can weaken the adhesion and mixing of the falling powder, reduce the shear force and downward pressure of the powder layer, and ensure that the powder that is not involved in the printing or the bonding area of ​​the old powder layer has sufficient support strength to avoid powder push damage.

[0041] In order to avoid excessive powder accumulation in front of the powder spreading module, in one embodiment, the bottom of the vibration plate is higher than the bottom of the powder spreading roller, and the height difference is 0.5mm~5mm, exemplarily 0.8mm, 1mm, 2mm, 3mm or 4mm, but not limited to this.

[0042] In order to achieve uniform powder laying density, in a preferred embodiment, the ratio of the thickness of the base powder layer to the thickness of each compacted powder layer is (20~40):1, that is, the compacted powder layer is laid layer by layer 20~40 times to form the base powder layer; the ratio of the thickness of each compacted powder layer to the D50 of the powder is (2~10):1, and / or the ratio of the thickness of each compacted powder layer to the D90 of the powder is (1.5~10):1.

[0043] Optionally, the D50 of the powder is 10μm~100μm, the D90 is 10μm~100μm, and the angle of repose of the powder itself or the powder after mixing with additives is 35°~60°. By controlling the performance parameters of the powder, the powder has a certain fluidity and the formation of the material arch inside the powder can be overcome. Among them, the angle of repose of the powder can be adjusted by the content of the additive liquid in the powder, the particle size of the powder, the water content and the sphericity of the powder.

[0044] S5. Move the powder forming module to the initial position to complete the laying of a single layer of powder.

[0045] In a preferred embodiment, as the powder forming module moves to the initial position, the remaining powder near the powder spreading roller that is not involved in the powder spreading falls into the remaining powder collecting device, thereby avoiding cumulative errors in the next powder replenishment and powder spreading steps. In addition, the residual powder recovery can also avoid the reliance on precise control of the amount of powder for replenishment, thereby reducing the difficulty of powder replenishment. Specifically, the negative pressure of the residual powder recovery straw is -0.4MPa~-0.6MPa.

[0046] S6. Repeat S1 to S5 until the base powder layer is laid.

[0047] The bottom powder layer is a powder layer of a certain thickness formed on the printing platform. The laying of the bottom powder layer can not only prevent the printed part from sticking to the printing platform, but also stabilize the density of each compacted powder layer through multi-layer powder laying. More importantly, the compacted bottom powder layer can provide sufficient support for the first layer of inkjet area, avoiding the problem of powder pushing caused by the loose state of natural accumulation of powder.

[0048] S7, repeating S1 to S5 on the base powder layer to complete the laying of the slice layer, controlling the inkjet module to follow the movement of the powder forming module, spraying the binder and curing the powder in the preset area of ​​each slice layer, until the printing of the model is completed to obtain a 3D printed product.

[0049] Specifically, the preset path of the inkjet module movement is: moving along the Y direction, spraying the binder in the preset area and solidifying the bonding powder, then moving a certain distance in the X direction and moving in the opposite direction in the Y direction, spraying the binder in the preset area and solidifying the bonding powder, and realizing inkjet printing of each slice layer in sections; In one embodiment, the moving speed of the inkjet module in the X direction is 100 mm / s to 400 mm / s, exemplarily 150 mm / s, 200 mm / s, 250 mm / s, 300 mm / s or 350 mm / s, but not limited thereto, and the moving speed in the Y direction is 100 mm / s to 600 mm / s, exemplarily 150 mm / s, 200 mm / s, 300 mm / s, 400 mm / s or 500 mm / s, but not limited thereto. With continuous segmented movement and scanning, the inkjet module will complete the inkjet printing of the entire printing format.

[0050] In one embodiment, according to the components of the binder, the binder can be one or more of a two-component binder, a multi-component binder, and a single-component binder; according to the solvent properties of the binder, the binder can be one or more of an aqueous binder, an oily binder, and an alcohol-based binder; according to the material of the binder, the binder can be an organic binder and / or an inorganic binder; according to the excitation source of the binder, the binder can be one or more of a dry-curing binder, a heat-curing binder, a chemical reaction-curing binder, and a UV-curing binder, and the specific selection can be based on the type of powder and the performance required for the printed product.

[0051] In general, the motion relationship and control logic of all modules are as follows: Fig.10As shown. In the entire printing system, the motion controller 100 is responsible for receiving the printing instructions of the printing software and controlling each sub-motion controller. The main modules in the system perform linear, rotational or vibration motion modes on the set degrees of freedom of motion, which are specifically controlled by each sub-motion controller, including the Z-axis linear motion controller 110, the X-axis linear motion controller 120, the Y-axis linear motion controller 130, the R rotation linear motion controller 140, the W vibration motion controller 150, and the F flip motion controller 160. Finally, each module is installed with a designed motion mode 170 to move to complete the printing behavior. Specifically, the platform module 10 performs a lifting motion Z1 in the Z-axis direction, the inkjet module 20 performs a linear reciprocating motion Y1 along the inkjet scanning track 22, and performs a scanning linear motion X1 along the powder spreading track 15 in a segmented manner. The powder spreading module 30 performs a scanning linear motion X2 along the powder spreading track 15, and the powder spreading roller 35 and the compaction roller 34 inside it perform reverse rotational motions R1 and R2 respectively. The powder dropping module 40 fixed to the powder spreading module 30 also performs a scanning linear motion X2 along the powder spreading track 15, and the powder replenishing receiving plate 41 inside it performs a flipping motion F1 to control the working position of the falling powder, and the eccentric wheel 42 performs a rotational motion R3 along the axis, driving the vibration plate 44 through the connecting rod 43 to improve the fluidity of the powder. The powder replenishing module 60 performs a powder replenishing linear motion Y2 along the powder replenishing track 62, and the powder outlet vibrator 63 inside it performs a high-frequency vibration W1, and cooperates with the rotational motion R4 of the belt drive shaft 65 to drive the powder replenishing belt 64 to bring the powder out of the temporary powder bin 61 and onto the powder replenishing receiving plate 41.

[0052] The specific process and operations are as follows.

[0053] Before inkjet printing begins, the base powder layer needs to be spread. The main function of this step is to pre-form a certain thickness of powder under the printed part, which can prevent the printed part from sticking to the printing platform, and stabilize the compaction density of each layer of powder through multi-layer spreading. More importantly, the compacted base powder layer can provide sufficient support for the first layer of inkjet area to avoid the problem of powder pushing due to the loose state of natural accumulation of powder. The schematic diagram of the base powder layer spreading process is shown below: Fig.11As shown, the action logic of the specific operation is 301~305. First, the powder replenishment waiting link 301 is carried out, the printing platform rises to the top, the powder dropping module moves to the bottom of the powder replenishment module, the vibration plate is closed, and the inkjet module returns to the starting position of powder spreading and waits. Then the link 302 is carried out, and the powder replenishment module replenishes the powder dropping module with an appropriate amount of powder. Then in link 303, the printing platform drops a layer thickness. Then in link 304, the powder spreading module and the powder dropping module return to the starting position of powder spreading and start to move horizontally to the right. The vibration plate starts to transport the powder to the front of the powder spreading roller. Through the powder sweeping of the powder spreading roller and the compaction of the compaction roller, the powder spreading action of a layer of powder is completed. Finally, in link 305, the action links of 301~304 are repeated to complete the powder spreading of the bottom powder layer. Specifically, it is explained in conjunction with the working schematic diagram.

[0054] First, if Figure 4 As shown, the inkjet module 20 moves to the left side of the platform module 10 on the powder laying track 15 along the X direction to wait, and the printing platform 12 moves downward for a distance along the Z direction to leave space for laying powder. The powder laying module 30 and the powder dropping module 40 are fixed to each other and move to the right side of the platform module 10 along the X direction to prepare for the powder replenishment action. Waiting for the powder replenishment receiving plate 41 to rotate to a horizontal position, the belt drive shaft 65 in the powder replenishment module 60 starts to rotate, driving the powder replenishment belt 64 to rotate counterclockwise. The printing powder 50 is taken away from the powder replenishment module 60 with the movement of the powder replenishment belt 64. At this time, the powder outlet vibrator 63 vibrates at a high frequency, forcing the low-fluidity powder replenishment powder 51 to obtain a certain fluidity and flow out from the temporary powder bin 61 of the powder replenishment module 60. As the powder replenishment module 60 moves in the Y direction along the powder replenishment track 62 at a certain uniform speed, a certain amount of uniform powder dropping powder 52 is finally filled on the powder replenishment receiving plate 41, and the powder replenishment module 60 stops replenishing powder and returns to the initial position.

[0055] Then, if Figure 5 As shown, the printing platform descends by a layer thickness, and then the powder spreading module 30 and the powder dropping module 40 move along the X direction to the left side of the platform module 10 to prepare for powder dropping. At this time, the powder replenishing receiving plate 41 rotates counterclockwise, and the powder 52 slides into the triangular area formed by the vibration plate 44, the powder baffle 45 and the powder spreading roller 35.

[0056] Then, if Figure 6As shown, the powder spreading module 30 and the powder dropping module 40 move to the right along the X direction. During the movement, the eccentric wheel 42 drives the connecting rod 43 and the vibration plate 44 to form a back-and-forth vibration along the vibration direction 47, and the amplitude and vibration frequency are adjusted by the eccentricity and rotation speed of the eccentric wheel 42. With the assistance of this vibration, the low-fluidity powder 52 that is reaggregated under the action of gravity regains better fluidity and slides evenly to the front of the powder spreading roller 35. The key point is that the fluidity of the powder is not enough to allow it to flow out completely at this time, and it will gradually slide down as the powder spreading module 30 and the powder dropping module 40 move to the right. In order to avoid powder shortage or powder accumulation in the powder spreading, it is necessary to appropriately adjust the amplitude and / or vibration frequency of the vibration plate 44.

[0057] As it moves to the right along the X direction, the falling powder 52 is transferred from the bottom of the powder dropping module 40 to the printing platform 12 to form a flat loose powder layer 53. The powder spreading roller 35 rotates along the rotation direction 37 of the powder spreading roller to level the powder layer. Subsequently, the powder spreading layer 53 passes through the compaction roller 34 rotating clockwise along the rotation direction 36 of the compaction roller. Since the compaction roller 34 is slightly lower than the powder spreading roller 35, the loose powder is compacted to form a compacted powder layer 54. As the powder spreading module 30 and the powder dropping module 40 move to the right, the powder spreading action of the entire format is gradually completed.

[0058] Afterwards, the powder spreading module 30 and the powder dropping module 40 move to the right side of the platform module 10 again to prepare for the next layer of powder replenishment. Figure 4~Figure 6 The steps shown in the figure are repeated until the base powder layer of the specified height is completed. Figure 7 At this time, the excess powder is collected to form residual powder 56 when passing through the residual powder collecting box 13, and the residual powder 56 is recycled through the negative pressure of the residual powder recovery suction pipe 14.

[0059] Then the inkjet printing process is carried out, and the action logic is as follows Fig.12 As shown. Similar to the powder spreading process of the base powder layer, inkjet printing requires powder replenishment, starting point preparation, and powder spreading, but the difference is that after completing the powder replenishment actions of steps 401 and 402, in the lifting step 403 of the printing platform, in addition to lowering the thickness of a layer of powder spreading layer, the printing platform also needs to drop an additional safety distance. In one embodiment, the safety distance is usually 2 to 10 times the thickness of the powder spreading layer. Its purpose is to prevent the residual powder on the surface of the powder spreading roller and the compacting roller from contacting the inkjet area of ​​the previous compacted powder layer during the movement of the powder forming module from the initial position to the powder spreading starting position, causing damage to the printed pattern and problems such as the adhesive sticking to the roller. Next, in the powder spreading step 404, the printing platform needs to rise the safety distance before spreading the powder. Then, after spreading the powder, the inkjet step 405 needs to follow, and finally, the action steps 401 to 405 are repeated in 406 until all models are printed, as shown in detail. Figure 8 and Fig. 9 shown.

[0060] Since binder jetting selectively sprays binder layer by layer on the powder bed to bond the powder and finally build a three-dimensional product, after each layer of powder is spread and compacted, the inkjet module moves horizontally in the Y direction, sprays binder in a specific area and solidifies the bonding powder. Then, the inkjet module moves horizontally in the X direction for a certain distance and moves horizontally in the Y direction in the opposite direction, sprays binder in a specific area and solidifies the bonding powder, and inkjet printing of each compacted powder layer is achieved in sections. Figure 8 As shown, at this time, the powder spreading module 30 and the powder dropping module 40 are as shown in FIG. Figure 6 The inkjet module 20 will move to the right along the X direction to the left edge of the printing platform 12. The inkjet head integrated mechanism 23 will then move to the Y direction along the inkjet scanning track 22. During this process, the inkjet head 24 sprays the adhesive 25 in the design area to form a new powder layer bonding area 55. After completing the printing of this area, the inkjet module 20 will move to the right along the X direction for a certain distance, and the inkjet head integrated mechanism 23 will then move in the opposite direction along the inkjet scanning track 22 to complete the inkjet printing of this area. With the continuous segmented movement and scanning to the right, the inkjet module 20 will complete the inkjet printing of the entire printing format.

[0061] After a layer of powder is laid and inkjet printed, the system will re-enter the process as follows: Fig. 9 The powder replenishment link shown is similar to Figure 4 As shown, the system will repeat as Figure 4~Figure 8 During the powder replenishing, powder dropping and inkjet printing processes, the new powder layer bonding area 55 will bond with the old powder layer bonding area 58, and they will be stacked layer by layer to form a three-dimensional printed body. The new compacted powder layer 54 will also be mixed with the powder 57 that did not participate in the printing before and will still maintain a non-bonded loose powder state, and will be recycled together when the printed body is taken out later for the next printing.

[0062] The present invention will be further described below with specific embodiments: Example 1 This embodiment provides a binder jet 3D printing method for low-fluidity powder, comprising the following steps: S1. Control the movement of the powder forming module to make it reach an initial position; wherein the powder forming module includes a powder dropping module and a powder spreading module, and the powder dropping module and the powder spreading module move synchronously.

[0063] The powder is non-spheroidized alumina powder, D50 is 30μm, and the powder repose angle is 45°. The size of the printing platform is 1200mm×800mm×800mm, the moving speed in the Z direction is 20mm / s, the size of the residual powder collection box is 1200mm×200mm×800mm, the diameter of the residual powder recovery straw is 50mm, and the negative pressure is -0.4MPa.

[0064] S2. Add a preset amount of powder to the powder dropping module through the powder replenishing module. The powder dropping module includes a powder replenishing receiving plate and a vibration plate.

[0065] In the powder replenishing module, the vibration frequency of the vibrator is 100 Hz, the width of the powder replenishing belt is 300 mm, the diameter of the belt driving shaft is 60 mm, and the rotation speed along the moving direction of the powder replenishing belt is 1 r / s.

[0066] In the powder dropping module, the length of the powder replenishing receiving plate is 1200 mm, the width is 100 mm, the eccentricity of the eccentric wheel is 1 mm, and the vibration frequency of the vibration plate along the vibration direction is 20 Hz.

[0067] The amount of replenishing powder filled into the powder dropping module each time is 1.5 times the amount of powder required for each powder laying layer.

[0068] S3, moving the powder forming module to the powder spreading starting position, and controlling the powder replenishing receiving plate to scatter the powder onto the vibration plate.

[0069] S4. By controlling the vibration of the vibration plate, the powder is transferred to a preset area in front of the powder spreading module, and then the powder spreading module is used to flatten and compact the powder in sequence.

[0070] In the powder spreading module, the powder spreading speed of the powder spreading module along the X direction is 200mm / s, and the idle stroke speed is 500mm / s. The powder spreading module includes a powder spreading roller and a compacting roller. The diameter of the powder spreading roller is 60mm, and the surface roughness is Ra 25. The diameter of the compacting roller is 60mm, and the surface roughness is Ra 1.0. The compacting roller rotates clockwise, and the powder spreading roller rotates counterclockwise. The height difference between the compacting roller and the powder spreading roller is 0.22mm.

[0071] S5. Move the powder forming module to the initial position to complete the laying of a single layer of powder.

[0072] S6. Repeat S1 to S5 until the base powder layer is laid.

[0073] S7, repeat S1 to S5 on the base powder layer to complete the laying of the slice layer. The powder forming module moves horizontally along the X direction, lays powder on the base powder layer and compacts it to form a slice layer with a thickness of 0.2 mm. After each slice layer is formed, the inkjet module is used to spray the binder in a specific area of ​​the layer and solidify the powder. Repeat until a 3D printed product is obtained.

[0074] In the inkjet module, the moving speed of the inkjet module in the X direction is 400 mm / s, the moving speed of the inkjet module in the Y direction is 500 mm / s, the number of inkjet heads is 8, and the adhesive is epoxy resin.

[0075] Example 2 This embodiment provides a binder jet 3D printing method for low-fluidity powder, comprising the following steps: S1. Control the movement of the powder forming module to make it reach an initial position; wherein the powder forming module includes a powder dropping module and a powder spreading module, and the powder dropping module and the powder spreading module move synchronously.

[0076] The powder is natural quartz sand powder, D50 is 70μm, and the powder repose angle is 42°. The size of the printing platform is 2500mm×1500mm×1000mm, the moving speed in the Z direction is 20mm / s, the size of the residual powder collection box is 2500mm×400mm×400mm, the diameter of the residual powder recovery straw is 80mm, and the negative pressure is -0.5MPa.

[0077] S2. Add a preset amount of powder to the powder dropping module through the powder replenishing module. The powder dropping module includes a powder replenishing receiving plate and a vibration plate.

[0078] In the powder replenishing module, the vibration frequency of the vibrator is 120 Hz, the width of the powder replenishing belt is 400 mm, the diameter of the belt driving shaft is 50 mm, and the rotation speed along the moving direction of the powder replenishing belt is 2 r / s.

[0079] In the powder dropping module, the length of the powder replenishing receiving plate is 2500 mm, the width is 120 mm, the eccentricity of the eccentric wheel is 3 mm, and the vibration frequency of the vibration plate along the vibration direction is 10 Hz.

[0080] The amount of replenishing powder filled into the powder dropping module each time is 1.8 times the amount of powder required for each powder laying layer.

[0081] S3, moving the powder forming module to the powder spreading starting position, and controlling the powder replenishing receiving plate to scatter the powder onto the vibration plate.

[0082] S4. By controlling the vibration of the vibration plate, the powder is transferred to a preset area in front of the powder spreading module, and then the powder spreading module is used to flatten and compact the powder in sequence.

[0083] In the powder spreading module, the powder spreading speed of the powder spreading module along the X direction is 300mm / s, and the idle stroke speed is 500mm / s. The powder spreading module includes a powder spreading roller and a compacting roller. The diameter of the powder spreading roller is 60mm, and the surface roughness is Ra 12.5. The diameter of the compacting roller is 120mm, and the surface roughness is Ra 0.6. The compacting roller rotates clockwise, and the powder spreading roller rotates counterclockwise. The height difference between the compacting roller and the powder spreading roller is 0.3mm.

[0084] S5. Move the powder forming module to the initial position to complete the laying of a single layer of powder.

[0085] S6. Repeat S1 to S5 until the base powder layer is laid.

[0086] S7, repeat S1 to S5 on the base powder layer to complete the laying of the slice layer. The powder forming module moves horizontally along the X direction, lays powder on the base powder layer and compacts it to form a slice layer with a thickness of 0.4 mm. After each slice layer is formed, the inkjet module is used to spray the binder in a specific area of ​​the layer and solidify the powder. Repeat until a 3D printed product is obtained.

[0087] In the inkjet module, the moving speed of the inkjet module in the X direction is 400 mm / s, the moving speed of the inkjet module in the Y direction is 600 mm / s, the number of inkjet heads is 12, and the adhesive is a silicate inorganic adhesive.

[0088] Example 3 This embodiment provides a binder jet 3D printing method for low-fluidity powder, comprising the following steps: S1. Control the movement of the powder forming module to make it reach an initial position; wherein the powder forming module includes a powder dropping module and a powder spreading module, and the powder dropping module and the powder spreading module move synchronously.

[0089] The powder is 316L stainless steel fine powder, D50 is 10μm, and the powder repose angle is 46°. The size of the printing platform is 800mm×500mm×400mm, the moving speed in the Z direction is 10mm / s, the size of the residual powder collection box is 800mm×100mm×300mm, the diameter of the residual powder recovery straw is 30mm, and the negative pressure is -0.5MPa.

[0090] S2. Add a preset amount of powder to the powder dropping module through the powder replenishing module. The powder dropping module includes a powder replenishing receiving plate and a vibration plate.

[0091] In the powder replenishing module, the vibration frequency of the vibrator is 10 Hz, the width of the powder replenishing belt is 200 mm, the diameter of the belt driving shaft is 30 mm, and the rotation speed along the moving direction of the powder replenishing belt is 3 r / s.

[0092] In the powder dropping module, the length of the powder replenishing receiving plate is 800 mm, the width is 40 mm, the eccentricity of the eccentric wheel is 1 mm, and the vibration frequency of the vibration plate along the vibration direction is 10 Hz.

[0093] The amount of replenishing powder filled into the powder dropping module each time is twice the amount of powder required for each powder laying layer.

[0094] S3, moving the powder forming module to the powder spreading starting position, and controlling the powder replenishing receiving plate to scatter the powder onto the vibration plate.

[0095] S4. By controlling the vibration of the vibration plate, the powder is transferred to a preset area in front of the powder spreading module, and then the powder spreading module is used to flatten and compact the powder in sequence.

[0096] In the powder spreading module, the powder spreading speed of the powder spreading module along the X direction is 100mm / s, and the idle stroke speed is 300mm / s. The powder spreading module includes a powder spreading roller and a compacting roller. The diameter of the powder spreading roller is 50mm, and the surface roughness is Ra 12.5. The diameter of the compacting roller is 50mm, and the surface roughness is Ra 0.25. The compacting roller rotates clockwise, and the powder spreading roller rotates counterclockwise. The height difference between the compacting roller and the powder spreading roller is 0.05mm.

[0097] S5. Move the powder forming module to the initial position to complete the laying of a single layer of powder.

[0098] S6. Repeat S1 to S5 until the base powder layer is laid.

[0099] S7, repeat S1 to S5 on the base powder layer to complete the laying of the slice layer. The powder forming module moves horizontally along the X direction, lays powder on the base powder layer and compacts it to form a slice layer with a thickness of 0.1 mm. After each slice layer is formed, the inkjet module is used to spray the binder in a specific area of ​​the layer and solidify the powder. Repeat until a 3D printed product is obtained.

[0100] In the inkjet module, the moving speed of the inkjet module in the X direction is 200 mm / s, the moving speed of the inkjet module in the Y direction is 400 mm / s, the number of inkjet heads is 12, and the adhesive is a water-based adhesive.

[0101] Embodiment 1 to embodiment 3 are tested, and the testing method is as follows: (1) Powder layer density W p : Take samples from the powder layer and calculate the density of the powder layer according to the following formula;

[0102] Among them, the sampled product is placed on the measuring table, and the weight of the sampled product in the air is measured, which is recorded as W1; the sampled product is waterproofed and placed on the measuring table, and the weight of the sampled product after waterproofing in the air is measured, which is recorded as W2; the sampled product after waterproofing is placed in water, and the weight of the sampled product after waterproofing in water is measured, which is recorded as W3.

[0103] (2) Compacted powder layer density W y : Take samples from the compacted powder layer and calculate the density of the compacted powder layer according to the following formula;

[0104] Among them, the sampling product is placed on the measuring table, and the weight of the sampling product in the air is measured, which is recorded as W4; the sampling product is waterproofed and placed on the measuring table, and the weight of the sampling product after waterproofing in the air is measured, which is recorded as W5; the sampling product after waterproofing is placed in water, and the weight of the sampling product after waterproofing in water is measured, which is recorded as W6.

[0105] (3) Printing efficiency: The printing efficiency is calculated according to the following formula;

[0106] (4) Printing space density difference RSD: Samples are taken at different positions of the printing platform (the number of samples is more than 9), the printing density at different positions is calculated, and the printing space density difference is calculated according to the following formula;

[0107] Among them, the standard deviation of the print density of the sampled products at different positions is calculated and recorded as W s ; Calculate the arithmetic mean of the print density of the sampled products at different locations, recorded as The calculation method of the printing density of the sampled products at different locations is consistent with the calculation method of the powder layer density and the compacted powder layer density.

[0108] The specific test results are as follows:

[0109] The above is a preferred embodiment of the invention. It should be pointed out that a person skilled in the art can make several improvements and modifications without departing from the principle of the invention. These improvements and modifications are also considered to be within the scope of protection of the invention.

Claims

1. A binder jet 3D printing method for low-flow powder, characterized in that: The following steps are involved: (1) controlling the movement of the powder forming module to make it reach an initial position; wherein the powder forming module comprises a powder dropping module and a powder spreading module, and the powder dropping module and the powder spreading module move synchronously; (2) adding a preset amount of powder to the powder dropping module through the powder replenishing module, wherein the powder dropping module includes a powder replenishing receiving plate and a vibration plate; (3) moving the powder forming module to the powder spreading starting position, and controlling the powder replenishing receiving plate to cause the powder to fall onto the vibration plate; (4) by controlling the vibration of the vibration plate, the powder is transferred to a preset area in front of the powder spreading module, and then the powder spreading module is used to flatten and compact the powder in sequence; (5) moving the powder forming module to an initial position to complete the laying of a single layer of powder; (6) Repeat steps (1) to (5) until the base powder layer is laid; (7) Repeat steps (1) to (5) on the base powder layer to complete the laying of the slice layer, control the inkjet module to follow the movement of the powder forming module, spray the binder in the preset area of ​​each slice layer and solidify the powder until the printing of the model is completed to obtain a 3D printed product.

2. The binder jet 3D printing method of low-fluidity powder according to claim 1, characterized in that: The powder forming module also includes a bracket, the powder falling module includes a powder replenishing receiving plate and a vibration plate, and the powder spreading module includes a powder spreading roller and a compacting roller; the powder replenishing receiving plate, the vibration plate, the powder spreading roller and the compacting roller are all fixed on the bracket, the vibration plate is arranged in front of the powder spreading roller, and the compacting roller is arranged behind the powder spreading roller; there is a preset distance between the vibration plate and the powder spreading roller, forming a preset area for powder transfer.

3. The binder jet 3D printing method of low-fluidity powder according to claim 2, characterized in that: The powder spreading roller is used to sweep the powder scattered by the powder falling module to obtain a powder spreading layer, and the ratio of the density of the powder spreading layer to the loose density of the powder is (0.8-1.2):1; The compacting roller is used to compact the powder layer to obtain a compacted powder layer, and the ratio of the density of the compacted powder layer to the tap density of the powder is (0.8~1.2):

1.

4. The binder jet 3D printing method of low-fluidity powder according to claim 3, characterized in that: The ratio of the thickness of the base powder layer to the thickness of each compacted powder layer is (20-40):1; The ratio of the thickness of each compacted powder layer to the D50 of the powder added by the powder replenishing module is (2~10):1, and / or the ratio of the thickness of each compacted powder layer to the D90 of the powder added by the powder replenishing module is (1.5~10):

1.

5. The binder jet 3D printing method of low-fluidity powder according to claim 4, characterized in that: The D50 of the powder is 10 μm to 100 μm, and / or the D90 of the powder is 10 μm to 100 μm; The repose angle of the powder is 35° to 60°.

6. The binder jet 3D printing method of low-fluidity powder according to claim 2, characterized in that: The bottom of the vibration plate is higher than the bottom of the powder spreading roller, and the height difference between the vibration plate and the powder spreading roller is 0.5 mm to 5 mm; The compacting roller and the powder spreading roller rotate in opposite directions, the surface roughness of the compacting roller is smaller than that of the powder spreading roller; the bottom of the powder spreading roller is higher than the bottom of the compacting roller, and the height difference between the powder spreading roller and the compacting roller is 0.01 mm to 1 mm; The powder replenishing receiving plate and the vibration plate can both rotate relative to the bracket; the vibration frequency of the vibration plate is 0.1Hz~100Hz; During the process of the powder replenishing module adding powder to the powder dropping module, the powder replenishing receiving plate is located in a horizontal position; during the powder spreading process, the powder replenishing receiving plate has an angle with the horizontal direction so that the powder on the powder replenishing receiving plate falls to the vibration plate.

7. The binder jet 3D printing method of low-fluidity powder according to claim 6, characterized in that: The diameter of the compacting roller is 25 mm to 120 mm, and the surface roughness is Ra 0.25 to Ra 3.2; the diameter of the powder spreading roller is 25 mm to 120 mm, and the surface roughness is Ra 1.6 to Ra 100.

8. The binder jet 3D printing method of low-fluidity powder according to claim 3, characterized in that: The preset path of movement of the inkjet module is: moving along the Y direction, spraying the binder in the preset area and curing the adhesive powder, then moving a certain distance in the X direction and moving in the opposite direction in the Y direction, spraying the binder in the preset area and curing the adhesive powder, and inkjet printing of each slice layer is achieved in sections; The inkjet module has a moving speed of 100 mm / s to 400 mm / s in the X direction and a moving speed of 100 mm / s to 600 mm / s in the Y direction.

9. The binder jet 3D printing method of low-fluidity powder according to claim 3, characterized in that: During the powder spreading process, the moving speed of the powder forming module in the X direction is 50 mm / s to 400 mm / s; The idle travel speed of the powder forming module from the initial position to the powder spreading starting position is 250 mm / s to 500 mm / s; The powder replenishing module is provided with a powder outlet vibrator and a powder replenishing belt. The powder replenishing powder in the powder replenishing module flows out under the action of the powder outlet vibrator. The preset amount of powder is evenly sprinkled on the powder replenishing receiving plate through the rotation of the powder replenishing belt and the movement of the powder replenishing module in the Y direction. The preset amount of powder added by the powder replenishing module to the powder falling module each time is 1 to 2 times the amount of powder required for each layer of powder laying.

10. A binder jetting 3D printing device for low-fluidity powder, used for executing the binder jetting 3D printing method for low-fluidity powder according to any one of claims 1 to 9, characterized in that: It includes powder replenishing module, powder forming module, inkjet module and platform module; The platform module includes a printing platform, and the printing platform is provided with a lifting mechanism, and the lifting mechanism is connected to the printing platform and is used to drive the printing platform to rise and fall in the Z direction; The powder forming module and the inkjet module are arranged above the platform module along the X direction; the powder forming module includes a powder dropping module and a powder spreading module that move synchronously; the powder dropping module includes a powder replenishing receiving plate and a vibration plate for vibrating and spreading the powder; the powder spreading module includes a powder spreading roller and a compacting roller for flattening and compacting the powder scattered by the powder dropping module; the inkjet module is used to spray adhesive on a preset area of ​​the slice layer; The powder replenishing module is arranged at one side of the platform module and is higher than the powder dropping module, and is used for replenishing powder to the powder dropping module.

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