Micro-fine powder low-interference powder feeding and spreading mechanism

Abstract

The invention discloses a fine powder low-interference powder feeding and spreading mechanism which comprises a powder feeding cylinder and a powder recycling cylinder, a forming cylinder is arranged between the powder feeding cylinder and the powder recycling cylinder, a powder spreading and scraping pressing plate is arranged above the forming cylinder and fixedly connected to a vertical shaft, the vertical shaft is connected with a driving motor, and the driving motor is connected with the forming cylinder. A scraping blade used for scraping powder and a powder pressing part are arranged on the bottom face of the powder laying scraping and pressing plate, and the powder pressing part can be pressed on the surface of the forming cylinder. According to the invention, the powder spreading interference force is obviously reduced, the problem of transverse movement of the spread powder is fundamentally solved, the continuous and large-amplitude jumping of the powder spreading interference force can be effectively avoided, and the uniformity requirement of the powder layer before bonding can be easily and quickly met; procedures of accurately controlling the rotating speed of the roller body and the distance between the roller body and the surface of the powder layer in a traditional scheme are omitted, and the operation difficulty is low.

Description

Technical Field

[0001] The invention relates to a binder jetting additive forming device, and in particular to a fine powder low-interference powder feeding and spreading mechanism used for the device. Background Art

[0002] The powder feeding methods of the powder feeding and spreading mechanism of the existing binder jetting additive forming equipment are mainly divided into two methods: powder feeding by powder feeding cylinder and powder dropping by funnel trough. Under the condition of the same additive format, the upper powder dropping method saves cylinder space and reduces the floor space of the whole machine compared with the lower powder feeding method. The powder spreading mechanism adopting the upper powder dropping method generally has the powder spreading mechanism parked at one end of the forming working surface, and the additive structure parked at the other end of the forming working surface. When in use, the powder spreading mechanism starts to sprinkle and spread powder from the left to the right (the particle size of the powder material does not exceed 100μm), and after spreading the powder, it moves an empty stroke back to the parking position on the left. The powder spreading mechanism gives up the forming working space, and the additive structure starts to work again; the additive structure starts to spray liquid binder from the right to the left, and after the single-pass spraying is completed, it also needs to move an empty stroke back to the parking position on the right; it is repeated in the above manner until the workpiece blank is formed.

[0003] The existing document CN114226762B discloses a single scraper bidirectional powder spreading device for additive manufacturing equipment, including a powder falling transition connector, a scraper powder equalizing mechanism, a scraper frame connecting plate, a powder collecting plate, a side limit plate, a scraper frame, a scraper leveling mechanism, and a scraper reversing mechanism. The powder falling transition connector is used to transition the powder to the scraper powder equalizing mechanism. The scraper powder equalizing mechanism is used to divide the powder falling into it into two equal parts and flow to the powder storage tanks on both sides of the scraper frame connecting plate. The scraper leveling mechanism is located above the scraper frame connecting plate and is connected to the scraper frame through a connecting shaft; the scraper reversing mechanism is located at the front and rear reversing positions of the powder spreading device to realize the reciprocating motion of the powder spreading device. Although this scheme can achieve the same amount of powder spreading as much as possible, the density of the powder layer laid is poor and needs to be further improved.

[0004] The scraping and pressing composite powder spreading device disclosed in document CN207916051U includes a powder storage hopper, a powder pressing roller, a scraper and a vertically liftable working platform, a powder supply platform for holding the powder falling from the powder outlet and powder guide plates symmetrically arranged on the left and right sides of the powder supply platform, the powder pressing roller is arranged directly below the powder supply platform, and the number of the scrapers is two and they are symmetrically arranged on the left and right sides of the powder pressing roller. This scheme adopts a scheme combining a scraper and a powder pressing roller. After the powder is scraped flat, the powder layer is compacted with the help of the powder pressing roller. Although this scheme solves the problem of poor powder layer density to a certain extent, it is easy to cause the powder in the molding area to move laterally, and the powder spreading interference force is large and will continue to jump significantly. The powder spreading interference force refers to the lateral compressive stress on the laid powder layer.

[0005] In addition, the powder feeding and laying mechanism of existing binder jetting additive manufacturing equipment almost all uses a rotating roller to compact the laid powder. It is necessary not only to accurately control the roller speed during operation, but also to accurately control the distance between the roller and the surface of the powder layer. Otherwise, the uniformity requirements of the powder layer before bonding cannot be met. Summary of the invention

[0006] At least in view of the problems mentioned in the background technology, the present invention aims to provide a low-interference powder feeding and spreading mechanism for fine powder.

[0007] The present invention adopts the following technical solution.

[0008] A low-interference powder feeding and spreading mechanism for fine powder comprises a powder feeding cylinder and a powder recovery cylinder, a forming cylinder is arranged between the powder feeding cylinder and the powder recovery cylinder, a powder spreading and scraping plate is arranged above the forming cylinder, the powder spreading and scraping plate is fixedly connected to a vertical shaft, the vertical shaft is connected to a driving motor, the bottom surface of the powder spreading and scraping plate has a scraping blade for scraping powder and a powder pressing part, and the powder pressing part can be pressed on the surface of the forming cylinder.

[0009] Furthermore, a workbench is provided in the molding cylinder, the workbench is installed on the lifting mechanism, a cylindrical boss is provided on the workbench, a spring and a loop are provided on the outer wall of the cylindrical boss, the inner cavity of the loop is used to accommodate powder material, the lower end of the spring is against the workbench, and the upper end of the spring is against the bottom of the loop. This solution fundamentally solves the problem of lateral movement of powder, and significantly reduces the interference force of powder spreading, which can effectively avoid the continuous and large fluctuation of the interference force of powder spreading, and more importantly, it can easily meet the uniformity requirements before the powder layer is bonded.

[0010] Furthermore, when the spring is in a free state, the top wall of the loop and the scraping edge of the powder spreading and scraping plate are in the same horizontal plane; when the spring is in a compressed state, the top surface of the powder material and the bottom surface of the powder pressing part are in the same horizontal plane.

[0011] As a preferred solution, the lifting mechanism adopts a ball screw lifting mechanism.

[0012] As a preferred solution, the fitting clearance between the slip-on and the cylindrical boss is no more than 0.05 mm.

[0013] Furthermore, the drive motor of the vertical axis and the power system of the lifting mechanism are connected to the controller, and the processor of the controller implements the following functions when executing the program: a. In the set period 1, control the drive motor to operate so that the vertical axis rotates at a constant speed; b. After the end of the set period 1, in the set period 2, the driving motor is controlled to pause, so that the vertical shaft stops rotating; at the same time, the power system of the lifting mechanism is controlled to operate, so that the top end of the looper is fixedly pressed on the powder pressing part; c. In set period 2, control the lifting mechanism and the vertical axis to reset.

[0014] Furthermore, the outer wall near the top of the loop has a slope, and the role of the slope in the present invention is mainly to improve the density of the laid powder layer and to facilitate the laying of powder and the recovery of excess powder.

[0015] As a preferred solution, the powder spreading and scraping plate is provided with a plurality of scraping blades arranged at intervals, and the powder spreading and scraping plate is a fan-shaped plate.

[0016] As a preferred solution, the surface roughness of the lower end surface of the powder pressing part is not greater than 0.03 microns.

[0017] Beneficial effect: The scheme of the present invention not only significantly reduces the interference force of powder spreading, but also can reduce the interference force of powder spreading from the existing thousands of Pa to less than 50 Pa, fundamentally solves the problem of lateral stringing of laid powder, can effectively avoid continuous and large fluctuations of the interference force of powder spreading, and can easily and quickly meet the uniformity requirements of the powder layer before bonding, eliminating the processes of precisely controlling the roller rotation speed, the distance between the roller and the powder layer surface, etc. in the traditional scheme, and the operation difficulty is small; the powder layer laid by the present invention has good density and uniformity, and a wide range of applications. The porosity of the powder layer before bonding can be controlled at 11~17%, and the optional range of the single-layer powder laying thickness is 0.5~3mm. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 Schematic diagram of the low-interference powder feeding and spreading mechanism for fine powder in Example 1 (initial state); Figure 2 Schematic diagram of the low-interference powder feeding and spreading mechanism for fine powder in Example 1 (powder spreading state); Figure 3 It is a partial schematic diagram of the forming cylinder in Example 1; Figure 4 This is a cross-sectional schematic diagram of the low-interference powder feeding and spreading mechanism for fine powder in Example 1; Figure 5 This is a schematic diagram of the powder spreading and scraping plate in Example 1; Figure 6 This is a schematic diagram of the powder spreading state in Comparative Example 1; Figure 7 This is a schematic diagram of the powder spreading state in Comparative Example 2. DETAILED DESCRIPTION

[0019] The technical solution of the present invention is described clearly and completely below in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention. Example 1

[0020] Combination Figures 1 to 5 As shown, a low-interference powder feeding and spreading mechanism for fine powder includes a powder feeding cylinder 1 and a powder recovery cylinder 2, a forming cylinder is arranged between the powder feeding cylinder 1 and the powder recovery cylinder 2, a powder spreading scraper and pressing plate 4 is arranged above the forming cylinder, the powder spreading scraper and pressing plate 4 is fixedly connected to the vertical shaft 5, the vertical shaft 5 is connected to the driving motor, the bottom surface of the powder spreading scraper and pressing plate 6 has a scraping blade 15 for scraping powder and a powder pressing part 4, the powder pressing part 13 can be pressed on the surface of the forming cylinder, and the surface roughness of the lower end face of the powder pressing part 4 is not more than 0.03 microns.

[0021] In this embodiment, a workbench 7 is provided in the molding cylinder (below the inner cavity of the molding cylinder), and the workbench 7 is mounted on a lifting mechanism, and the lifting mechanism adopts a ball screw lifting mechanism 11. A cylindrical boss 8 is provided on the workbench 7, and a spring 9 and a loop 10 are provided on the outer wall of the cylindrical boss 8. The loop 10 is fixedly mounted on the shell through a connecting plate, and the matching clearance between the loop 10 and the cylindrical boss 8 is not greater than 0.05mm. The inner cavity of the loop 10 (that is, the inner cavity of the molding cylinder) is used to accommodate powder materials, and the lower end of the spring 9 abuts on the workbench 7, and the upper end of the spring 9 abuts on the bottom end of the loop 10. When the spring 9 is in a free state, the top wall of the loop 10 and the scraping blade 15 of the powder spreading and scraping plate 4 are in the same horizontal plane; when the spring 9 is in a compressed state, the top surface of the powder material and the bottom surface of the powder pressing part 4 are in the same horizontal plane.

[0022] In this embodiment, the outer wall near the top of the looper 10 has a slope 14, and the powder spreading and scraping plate 6 has a plurality of scraping blades 15 arranged at intervals, and the powder spreading and scraping plate 6 is a fan-shaped plate.

[0023] In this embodiment, the drive motor 13 of the vertical axis 5 and the power system of the lifting mechanism 11 are connected to the controller, and the processor of the controller implements the following functions when executing the program: a. In the set period 1, the driving motor 13 is controlled to operate so that the vertical shaft 5 rotates at a constant speed; b. After the end of the set period 1, in the set period 2, the driving motor 13 is controlled to pause, so that the vertical shaft 5 stops rotating; then, the power system of the lifting mechanism 11 is controlled to operate, so that the top end of the looper 10 presses against the powder pressing part 4; c. In the set time period 2, the lifting mechanism 11 and the vertical axis 5 are controlled to reset.

[0024] When using, combine Figure 4As shown, first add a sufficient amount of powder material into the powder feeding cylinder 1, and then feed the powder material 11 into the forming cylinder in a quantitative manner (the powder can be spread in the forming cylinder by falling powder, or the powder material can be scraped in and out of the forming cylinder by means of a scraper); then control the drive motor 13 to operate, so that the vertical shaft 5 rotates at a constant speed, thereby driving the powder spreading scraper plate 4 to scrape from the top of the loop 10, so as to achieve smooth laying of the powder material. When the scraper blade 15 of the powder spreading scraper plate 4 is completely separated from the top of the loop 10, control the drive motor 13 to pause and stop the vertical shaft 5 from rotating. Then, control the power system of the lifting mechanism 11 to operate, so that the top of the loop 10 is fixedly pressed on the powder pressing part 4. In this process, the loop 10 presses down the spring 9, and the powder in the inner cavity of the loop 10 is pressed tightly and flattened; thereafter, control the lifting mechanism 11 and the vertical shaft 5 to reset, and the spring 9 will also reset under the action of the spring.

[0025] Comparative Example 1: Combination Figure 6 As shown, after the powder is laid, it is compacted directly using a conventional roller 12 .

[0026] Comparative Example 2: Combination Figure 7 As shown, the paving scraper is first used to flatten the paved powder, and then a common roller 12 is used to compact it. The roller and paving scraper in the comparative embodiment and the matching equipment (commercially available powder bonding printing equipment can be used) are all prior art, and a simple roller that can roll at a uniform speed and can adjust the position can also be made by yourself, and a simple scraper that can scrape evenly and can adjust the position can also be made by yourself.

[0027] Comparative Example 3 refers to Example 1, and the difference between Example 3 and Example 1 is that the top end of the looper 10 is a planar structure.

[0028] Taking a titanium alloy powder (particle size 45-105μm) as an example, the single-layer laying thickness of the powder material is 1mm, and the porosity of the powder layer after scraping and pressing using the scheme in Example 1 (the porosity between powder particles) is 14.7%, the porosity of the powder layer after scraping and pressing using the scheme in Comparative Example 1 is 22.3%, the porosity of the powder layer after scraping and pressing using the scheme in Comparative Example 2 is 20.1%, and the porosity of the powder layer after scraping and pressing using the scheme in Comparative Example 3 is 21.3% (analysis shows that the larger porosity of this scheme is mainly attributed to the powder remaining at the top of the loop 10 interfering with the top pressing effect).

[0029] During implementation, Figure 4 As shown, the solution in Example 1 only needs to apply force in the vertical direction. During the top pressing process, the powder 11 is almost not subjected to lateral compressive stress (powder spreading interference force), and the powder spreading interference force is within 50pa and can be ignored. Figure 6As shown, in the scheme of comparative embodiment 1, the powder 11 is subjected to not only vertical downward stress, but also large lateral compressive stress (i.e., powder spreading interference force) up to 2000-3000 Pa, and the lateral compressive stress continues to fluctuate greatly. Figure 7 As shown, in the scheme of comparative embodiment 2, in addition to the vertical downward stress, the powder 11 is also subjected to a slightly larger lateral compressive stress of about 400-600 Pa, and it also continues to fluctuate significantly. It can be seen that the scheme of the present invention not only significantly reduces the interference force of powder spreading, but also can reduce the interference force of powder spreading from the existing thousands of Pa to less than 50 Pa, fundamentally solves the problem of lateral stringing of laid powder, effectively avoids the continuous and large fluctuation of the interference force of powder spreading, and can easily and quickly meet the uniformity requirements before the powder layer is bonded, eliminating the process of accurately controlling the roller speed and the distance between the roller and the powder layer surface in the traditional scheme, and the operation difficulty is small.

Claims

1. A low-interference powder feeding and spreading mechanism for fine powders, comprising a powder feeding cylinder (1) and a powder recovery cylinder (2), a forming cylinder being arranged between the powder feeding cylinder (1) and the powder recovery cylinder (2), the forming cylinder being located directly below an adhesive nozzle, and a powder spreading and scraping plate (6) being arranged above the forming cylinder, characterized in that: The powder spreading and scraping plate (6) is fixedly connected to the vertical shaft (5), the vertical shaft (5) is connected to the driving motor, and the bottom surface of the powder spreading and scraping plate (6) has a scraping blade for scraping powder and a powder pressing portion (4), and the powder pressing portion (13) can be pressed on the surface of the forming cylinder.

2. The powder feeding mechanism according to claim 1 is characterized in that: A workbench (7) is arranged in the molding cylinder. The workbench (7) is mounted on the lifting mechanism. A columnar boss (8) is arranged on the workbench (7). A spring (9) and a looper (10) are sleeved on the outer wall of the columnar boss (8). The inner cavity of the looper (10) is used to accommodate powder material. The lower end of the spring (9) abuts against the workbench (7), and the upper end of the spring (9) abuts against the bottom end of the looper (10).

3. The powder feeding mechanism according to claim 2 is characterized in that: When the spring (9) is in a free state, the top wall of the looper (10) and the scraping edge of the powder spreading and scraping plate (6) are in the same horizontal plane; when the spring (9) is in a compressed state, the top surface of the powder material and the bottom surface of the powder pressing portion (4) are in the same horizontal plane.

4. The powder feeding mechanism according to claim 3 is characterized in that: The lifting mechanism (11) adopts a ball screw lifting mechanism.

5. The powder feeding mechanism according to claim 4 is characterized in that: The matching clearance between the looper (10) and the cylindrical boss (8) is not greater than 0.05 mm.

6. The powder feeding mechanism according to claim 5, characterized in that: The drive motor (13) of the vertical shaft (5) and the power system of the lifting mechanism (11) are connected to the controller, and the processor of the controller implements the following functions when executing the program: a. In a set time period 1, controlling the driving motor (13) to operate so that the vertical shaft (5) rotates at a constant speed; b. After the end of the set period 1, during the set period 2, the driving motor (13) is controlled to pause, so that the vertical shaft (5) stops rotating; at the same time, the power system of the lifting mechanism (11) is controlled to operate, so that the top end of the looper (10) is fixedly pressed on the powder pressing part (4); c. In the set time period 2, the lifting mechanism (11) and the vertical axis (5) are controlled to reset.

7. The powder feeding mechanism according to any one of claims 2 to 6, characterized in that: An outer wall close to the top end of the looper (10) is provided with a slope surface (14).

8. The powder feeding mechanism according to claim 7 is characterized in that: The powder spreading and scraping plate (6) has a plurality of scraping blades arranged at intervals, and the powder spreading and scraping plate (6) is a fan-shaped plate.

9. The powder feeding mechanism according to claim 8, characterized in that: The surface roughness of the lower end surface of the powder pressing portion (4) is not greater than 0.03 micrometers.

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