CN202291409U - Selective laser melting rapid molding equipment for directly fabricating large-sized parts - Google Patents

Abstract

The utility model discloses an area-selective laser melting rapid prototyping equipment for directly manufacturing large parts, which mainly includes a laser array, an optical system array, a forming cylinder, a three-dimensional segmented heating and heat preservation structure for the forming cylinder, a weight balance system for the forming cylinder, and a substrate adjustment system. Leveling device, double recovery cylinder, double powder storage box, double quantitative powder feeding and powder dropping device, powder spreading device, protective atmosphere hood, gas purification system, and control system. The adopted optical system is constructed by multiple optical system units and a mechanical moving platform, which can arbitrarily expand or reduce the coverage of the optical system. The size of the parts manufactured by the utility model is much larger than the parts that can be manufactured by the current selective laser melting technology at home and abroad, and the molding efficiency is doubled without changing the molding accuracy, the complexity of the parts and the mechanical properties.

Description

Selective laser melting rapid prototyping equipment for direct manufacturing of large parts

technical field

The utility model belongs to the field of laser rapid manufacturing, and specifically relates to a selective laser melting rapid prototyping device for large-size, high-precision and complex-structured parts. The parts can be metal, non-metal or composite materials of metal and non-metal.

Background technique

At present, there are two ways of direct and rapid laser manufacturing of parts: one is the laser cladding direct manufacturing technology (Direct Laser Fabrication-DLF) based on synchronous powder feeding or wire feeding process, which fixes the laser processing head on the machine tool and can move in the Z direction On the movement axis of the machine, the metal powder or metal wire fed in synchronously is melted by the focused laser beam, and the single-layer manufacturing of parts is realized by controlling the movement of the worktable on the XY plane according to the planned trajectory. After completing the manufacturing of one layer, Z goes up for a certain distance, and then repeats the previous process, layer by layer until the three-dimensional molding of the parts is realized; the second is the selective laser melting rapid prototyping technology based on powder coating SLM), its basic working principle is to flatten a certain thickness of powder in the working cylinder, according to the control of the computer, the laser beam scans through the galvanometer to selectively melt the preset powder layer according to the slice processing results of the three-dimensional parts graphics . Then the working cylinder descends a certain distance and spreads the powder again, and the laser beam is driven by the galvanometer to complete the next layer of manufacturing of the parts according to the three-dimensional graphics of the parts. The process of powder spreading, scanning and working cylinder lowering is repeated in this way to realize the manufacture of three-dimensional parts.

The size of parts that can be processed by laser cladding direct manufacturing technology based on automatic powder feeding and wire feeding process is closely related to the size that can be processed by machine tools. This processing method generally uses Nd:YAG, CO ₂ or fiber lasers with a power of more than 1 kilowatts. After the laser is focused, a large molten pool is formed on the surface of the workpiece, and alloy powder or wire is fed into the molten pool. The added materials The height and width of the single-pass cladding layer formed after melting are relatively large, and the dimensional accuracy of the formed parts is not high, requiring subsequent mechanical processing. At the same time, the overall moving speed of the machine tool is not high, and cannot provide a fast processing speed . In addition, due to the large mass, large inertia and small acceleration of the machine tool, it not only affects the processing efficiency, but also has a great impact on the processing quality of the corner, start and stop position, etc. Due to the limitations of the technical principles of the laser cladding direct manufacturing process based on automatic powder feeding and wire feeding, this method cannot be used to form parts with relatively complex shapes (such as complex inner cavities and suspended structures, etc.).

Selective laser melting rapid prototyping technology can realize the molding of parts with arbitrary complex shapes, and several related patents have been published at home and abroad. The US patent "PROCESS AND DEVICE FOR PRODUCING A SHAPED BODYBY SELECTIVE LASER MELTING" (patent number: US7047098) describes in detail a selective laser melting forming method and equipment for manufacturing dense parts using a three-dimensional digital model. In the equipment, the powder falls into the powder hopper from the upper powder storage cavity, and a powder spreading device is installed under the powder hopper, which spreads the powder to the forming cylinder and sends the excess powder into the recovery cavity. The galvanometer scanning system is used to control the trajectory of the laser on the processing plane, and the focused laser beam completes the melting and solidification of the parts in the graphics layer based on the processing trajectory formed by the slice data of the three-dimensional model of the metal parts. Then, the Z-axis of the forming cylinder is lowered to a certain height, and the process of powder spreading and laser selective melting is repeated, and finally a three-dimensional part is obtained. The advantage of the selective laser melting rapid prototyping equipment involved in this patent is that the powder spreading device has a unique brush-type avoidance structure and a mechanical structure with automatic control of powder feeding volume, which corrects or avoids the insufficient flatness of the previous layer during the forming process. impact on precision. The disadvantage is that although the falling powder feeding structure is adopted to improve the processing efficiency to a certain extent, the one-way powder feeding itself has certain efficiency defects.

The domestic patent document "A method and device for selective laser melting rapid prototyping of metal parts" (patent publication number: CN 1603031A) discloses a selective laser melting rapid prototyping device. It adopts the top-powder powder feeding method in which the powder feeding cylinder is placed below the working plane, which improves the loose packing density of the powder to be processed in the forming cylinder, but is not conducive to the improvement of forming efficiency. It also uses a powder spreading roller for powder spreading, which is prone to powder sticking and shaking, and it is difficult to obtain a thin and uniform high-quality powder spreading effect, which ultimately affects the performance and quality of the parts. The Chinese patent document "A Rapid Prototyping System for Direct Manufacturing of Metal Parts" (Patent Publication No.: CN 1631582A) also describes in detail a selective laser rapid prototyping system. It adopts a relatively efficient two-way powder falling and spreading structure, and uses a hard scraper as a powder spreading tool to improve the quality of powder spreading. However, the selected open powder falling structure has caused relatively large dust pollution to the entire processing environment, reducing the effective power of the laser, and the selected laser motion control structure is composed of upper and lower polarizers, sliders and guide rails. The upper and lower polarizers move on the guide rail with the slider to realize the movement of the laser focus spot on the processing surface. This structure has defects such as slow movement speed and unstable movement process, which makes it difficult to meet the precision and performance of the processed parts. In addition, the first two patents also have a common disadvantage. The optical system used in the equipment only includes a laser scanning galvanometer and an optical focusing mirror system, so not only the size of the parts that can be processed is very limited, but the processing efficiency is also low. .

In addition to the published patent documents, a number of foreign equipment manufacturers have developed selective laser melting rapid prototyping equipment, mainly represented by EOS, CONCEPT Laser in Germany and DTM in the United States. The selective laser melting rapid prototyping they designed and manufactured The equipment is relatively mature. Among them, the equipment of EOS company adopts a scanning galvanometer with small moment of inertia and fast response speed to realize high-speed and accurate scanning up to 7m/s. High dimensional accuracy, low surface roughness, and thin-walled structures with a minimum thickness of about 0.08mm can be formed. DTM uses laser melting resin and other non-metallic powder or mixed powder to realize the bonding between powder particles and complete the manufacture of non-metallic parts. However, the size of the processing parts of the above-mentioned equipment is limited by optical devices such as laser galvanometers and f-theta combination lenses. At present, the maximum processing format of the company's equipment is 250mm×250mm, which cannot process larger-sized parts. The CONCEPT Laser company uses a mechanical mobile platform equipped with a laser scanning galvanometer, which greatly expands the processing area that the laser can cover, and significantly increases the size of the parts that can be processed by the selective laser melting rapid prototyping equipment. The maximum processing format of the company's equipment is 800mm×500mm. The disadvantage is that the processing efficiency is low, and a low-power laser can produce large-size parts that cannot meet the important requirements of rapid prototyping technology for the production cycle.

It can be seen that there are mainly three problems in the direct and rapid manufacturing of parts by laser:

(1) The size of the machined parts is inconsistent with the dimensional accuracy. Laser cladding direct manufacturing parts technology based on automatic powder feeding can realize the direct manufacturing of "meter" level large-size parts, but its dimensional accuracy can only reach "millimeter" level; the processing that can be realized by selective laser melting rapid prototyping technology The precision can reach the "micron" level, but its processing size is limited by the existing optical devices. Without the use of mechanical structures to move the optical devices, the maximum processing format can only reach 250mm×250mm. If a mechanical structure is used to move the optical system, the processing efficiency will be greatly reduced.

(2) The shape complexity of the machinable parts is inconsistent with the size of the parts. The laser cladding direct manufacturing parts technology based on automatic powder feeding can only directly form large-sized, simple-shaped blanks; although the selective laser melting rapid prototyping technology is not affected by the complexity of the parts, the size of the parts is far from smaller than the former.

(3) There is a contradiction between the dimensional accuracy of the machined parts and the machining efficiency. The processing efficiency of high-precision selective laser melting rapid prototyping technology is only 2-20mm ³ /s, which is one-fifth or even lower than that of low processing precision automatic powder feeding laser cladding rapid manufacturing technology.

In short, the existing laser rapid and direct manufacturing of parts cannot achieve the organic unity of large-scale, high-efficiency, high-precision and high-complexity manufacturing.

In addition, no matter from domestic and foreign patents or from the existing industrial application equipment abroad, the existing equipment is either not high in precision, poor in performance, low in forming efficiency, or unable to process large-sized parts. Therefore, it is of great significance to invent a selective laser melting forming equipment that can efficiently manufacture large-sized parts with high precision and excellent performance.

Contents of the invention

Aiming at the various deficiencies in the existing technology, the utility model proposes a selective laser melting rapid prototyping equipment for directly manufacturing large parts, which can manufacture large complex shapes with a maximum size of "meter" level with high efficiency and high precision parts, and the surface finish of the parts is very high.

The utility model discloses an area-selective laser melting rapid prototyping equipment for directly manufacturing large-scale components. The equipment includes a base plate, a lifting motion mechanism for the base plate, a forming cylinder, a first recovery cylinder, a powder spreading device and a control system. It is characterized in that the The equipment includes laser group, optical system, molding cylinder weight balance mechanism, and the first powder feeding mechanism;

The first recovery cylinder is located on one side of the molding cylinder, and the two surfaces are the same plane as the processing plane, and the powder spreading device moves on the processing plane; the first powder feeding mechanism is located on the side of the optical system; the optical system is located above the molding cylinder , the laser group consists of at least one laser, and the laser beam emitted by the laser is focused on the surface of the molding cylinder through the optical system;

The forming cylinder is equipped with a base plate, and the base plate is connected with a lifting motion mechanism. The lifting motion mechanism drives the base plate to move up and down in the forming cylinder. The weight balance mechanism of the forming cylinder is located at the bottom of the equipment and acts on the lifting motion mechanism.

The utility model has the following technical effects:

(1) The utility model arranges one or several or even dozens of lasers and corresponding optical systems in a fixed array distribution mode, a mobile platform mode or a mixed mode of the above two, and only needs to increase or decrease the number of lasers and optical systems The number, or the size and number of mobile platforms can meet the processing requirements of parts of any size and shape.

(2) The utility model can optimize the construction mode of the optical system according to different requirements such as processing efficiency and platform construction cost. Among them, the fixed array distribution mode has the highest processing efficiency, while the mobile platform mode and the mixed mode can sacrifice certain efficiency. Reducing the number of lasers and optical systems significantly reduces platform construction costs.

(3) The quantitative closed powder-falling type two-way powder feeding structure is adopted to realize the two-way powder spreading on the molding cylinder, which simplifies the structure of the rapid prototyping equipment and improves the efficiency of laser melting molding, and reduces the manufacturing cost of the molding equipment and the cost of parts. Processing costs.

(4) The utility model adopts the weight balance mechanism of the forming cylinder to keep the load of the driving motor of the forming cylinder unchanged during the whole laser forming process, thereby ensuring the long-term stable operation of the equipment and the processing accuracy in the height direction.

The improved technical solution of the utility model has the following technical effects:

(5) The utility model adopts the method of parallel scanning to form the parts in partitions, which greatly improves the forming efficiency under the premise of maintaining high dimensional accuracy, and can effectively reduce the thermal stress generated during the laser forming process.

(6) The segmented heating and heat preservation system of the forming cylinder performs a whole-process heat treatment on the formed parts, which greatly reduces the internal thermal stress of the parts and ensures the dimensional accuracy and performance of the formed parts.

(7) The protection cover for the processing area designed by the utility model can meet the requirement of water and oxygen content for laser forming in a short time, and quickly remove the smoke and dust generated during the laser forming process.

Description of drawings

Fig. 1 is the structural representation of the first embodiment of the selective laser melting rapid prototyping equipment of the present invention;

Fig. 2 is the structural representation of the second embodiment of the selective laser melting rapid prototyping equipment of the present invention;

Fig. 3 is a schematic structural view of an optical system unit of the present invention;

4 is a schematic diagram of a first specific implementation of a fixed array distributed mode optical system;

5 is a schematic diagram of a second specific implementation of a fixed array distributed mode optical system;

6 is a schematic diagram of a first specific implementation of the mobile platform mode optical system;

7 is a schematic diagram of a second specific implementation of the mobile platform mode optical system;

8 is a schematic diagram of a first specific implementation of a mixed-mode optical system;

FIG. 9 is a schematic diagram of a second specific implementation of a mixed-mode optical system;

FIG. 10 is a schematic diagram of a third specific implementation of a mixed-mode optical system;

FIG. 11 is a schematic diagram of a fourth specific implementation of a mixed-mode optical system;

Fig. 12 is a structural schematic diagram of the substrate lifting movement mechanism, segmented heating and heat preservation system, and forming cylinder weight balance mechanism of the present invention;

Fig. 13 is a structural schematic diagram of the second form of the molding cylinder weight balance mechanism of the present invention;

Fig. 14 is a structural schematic diagram of the first quantitative powder feeding mechanism and powder spreading device of the present utility model;

Fig. 15 is a structural schematic diagram of the first substrate leveling mechanism of the present invention;

Fig. 16 is a schematic diagram of the first specific implementation of the protection lens on the cover plate of the protective atmosphere cover of the present invention;

Fig. 17 is a schematic diagram of a second specific implementation of the protection lens on the cover plate of the protective atmosphere cover of the present invention;

Fig. 18 is a schematic structural view of the second quantitative powder feeding mechanism and powder spreading device of the present invention;

Fig. 19 is a partial structural schematic diagram of the second substrate leveling mechanism of the present invention;

Fig. 20 is a schematic structural view of an embodiment of the built-in optical system of the present invention;

Fig. 21 is a structural schematic diagram of an optical system unit equipped with a sealing structure of the present invention;

Fig. 22 is a structural schematic diagram of the third form of the forming cylinder weight balance mechanism of the present invention.

Detailed ways

The utility model is described in more detail below by means of examples, but the following examples are only illustrative, and the protection scope of the utility model is not limited by these examples.

As shown in Figure 1, a specific embodiment of the selective laser melting rapid prototyping equipment involved in the utility model includes a laser group 1, an optical system 3, a substrate 8, a substrate lifting mechanism 13, a molding cylinder 7, and a weight balance of the molding cylinder Mechanism 15, recovery cylinder 6, quantitative powder feeding mechanism 2, powder spreading device 12 and control system 14.

The surface of forming cylinder 7 and the surface of recovery cylinder 6 are the same plane, that is, the processing plane, and the powder spreading device 12 can move left and right on the processing plane. The optical system 3 is located directly above the molding cylinder 7 , and the quantitative powder feeding mechanism 2 is located on one side of the optical system 3 . The multiple laser beams emitted by the laser group 1 are focused on the surface of the molding cylinder 7 via the optical system 3 .

The molding cylinder 7 is equipped with a substrate 8, which is the growth base of the molding parts, and above it is the powder and the parts to be molded 9. The substrate 8 is driven by the lifting movement mechanism 13 below it to move up and down in the molding cylinder 7, and the weight of the molding cylinder is balanced. The mechanism 15 is located at the bottom of the device and acts on the lifting motion mechanism 13 .

In the above structure, at least one of the second recovery cylinder 6', the second powder feeding mechanism 2', the protective atmosphere cover 5, the gas purification system 4, the substrate leveling mechanism 11 and the heating and heat preservation system 10 can be added, wherein the first The second recovery cylinder 6' and the second powder feeding mechanism 2' must be added simultaneously. The protective atmosphere cover 5 and the gas purification system 4 must be added simultaneously. When the above components are added at the same time, its structure is shown in Figure 2.

The second recovery cylinder 6' and the first recovery cylinder 6 are respectively located on both sides of the molding cylinder 7. The surfaces of the three are the same plane, that is, the processing plane. The powder spreading device 12 can move left and right on the processing plane. The processing plane and the powder spreading device The occupied space of 12 etc. is enveloped by protective atmosphere cover 5, and protective atmosphere cover 5 is respectively communicated with gas purification system 4 by air inlet and exhaust port (in Fig. part). Above the protective atmosphere cover 5 are the optical system 3 and the quantitative powder feeding mechanism 2, 2', wherein the optical system 3 is located in the middle, and there is a quantitative powder feeding mechanism on the left and right sides. The multiple laser beams emitted by the laser group 1 pass through the optical system 3 Focus on the forming cylinder 7 surface.

The added substrate leveling mechanism 11 is installed above the substrate 8 .

The added heating and heat preservation system 10 is located in the molding cylinder 7. The heating and heat preservation system 10 is segmented and consists of the heating structure between the base plate 8 and the lifting motion mechanism 13 and the heating structure of the inner wall of the molding cylinder 7. The heating structure can be various heating forms such as resistance wire, heating plate, induction heating or far-infrared heating.

Taking the structure shown in Fig. 2 as an example, the control system 14 with the industrial control computer and the motion control card as the main body controls the coordinated movement of various mechanisms. The basic working process is as follows:

(1) Open the protective atmosphere cover 5, place the substrate 8 on the heating structure in the molding cylinder 7, and adjust the substrate 8 to the level through the substrate leveling mechanism 11. Seal the protective atmosphere cover 5 and open the gas purification system 4, fill the cover with inert gas from the air inlet, and maintain the circulation, so that the gas atmosphere in the cover is controlled within the range required for processing.

(2) Import the STL file of the part to be formed into the industrial control computer and obtain the slice data of the part, and generate the laser processing trajectory of each layer.

(3) Quantitative powder feeder 2' sends the powder to the right side of the surface of the molding cylinder 7 according to the set amount, the substrate 8 is lowered by a section height, and the powder spreading device 12 moves from right to left to the recovery cylinder 6, and the powder is ready Tiled on the substrate 8, the laser group 1 emits laser light, and the optical system 3 controls the focused spot to move on the processing plane according to the processing track to realize the processing of the current layer.

(4) The quantitative powder feeder 2 sends the powder to the left side of the surface of the forming cylinder 7 according to the set amount, the base plate 8 is lowered by a section height, and the powder spreading device 12 moves from left to right to the recovery cylinder 6'. A new layer of powder is evenly spread on the deposited metal layer, the laser group 1 emits laser light, and the optical system 3 controls the focused spot to move on the processing plane according to the processing track to realize the processing of the current layer.

(5) Steps (3) and (4) are repeated continuously to finally realize the expansion of parts from two-dimensional molding to three-dimensional molding, and obtain solid parts.

(6) During the processing, the heating and heat preservation system 10 is opened in stages as the substrate 8 continues to descend, so as to ensure that only the powder and parts above the substrate 8 are heated all the time. At the same time, each time a layer is added, the control system 14 calculates the increased weight of the molding cylinder according to the slice thickness of the parts and the bulk density of the powder, and controls the weight balance mechanism 15 of the molding cylinder to provide the real-time force of the same weight for balancing, so that the lifting movement The weight borne by the mechanism 13 is always kept constant to ensure the smooth movement of the substrate 8 .

The following examples illustrate several specific implementations of each component.

The laser group of the selective laser melting rapid prototyping equipment involved in the utility model is composed of one or several or even tens of lasers, and the lasers can be medium and high power _CO2 lasers, Nd:YAG lasers, fiber lasers and semiconductor lasers etc., the number of which is determined by the design structure of the optical system.

The optical system involved in the utility model is one of the key technologies for realizing the high-precision and excellent-performance large-size parts manufactured by the selective laser melting rapid prototyping equipment efficiently. The optical system involved in the utility model can adopt a fixed array distribution mode, a mobile platform mode or a mixed mode of the above two. The basic composition structure in various modes is an optical system unit, as shown in Figure 3, each optical system unit includes a beam expander 17, an XY laser scanning galvanometer 18, and an f-θ combination lens 19, and the laser is emitted from the light outlet 16 , successively through the beam expander 17, the XY laser scanning vibrating mirror 18 and the f-θ combination lens 19 to focus on the processing plane. Protective lens 20 is installed between. The optical system unit can also be composed of a beam expander and an XYZ three-dimensional dynamic focusing scanning galvanometer. The laser light is emitted from the light outlet 16 and focused on the processing plane through the beam expander 17 and the XYZ three-dimensional dynamic focusing scanning galvanometer. According to different modes adopted, the optical system involved in the present invention also includes related mechanical structures that can move the optical system unit in two-dimensional or three-dimensional space. The optical system unit can also adopt any other optical device capable of focusing laser beams for laser processing in the prior art.

Figures 4 to 11 respectively show the schematic diagrams of optical path design in the fixed array distribution mode, mobile platform mode, and mixed mode, but the utility model is not limited to the optical systems described in these schematic diagrams. The actions of different optical systems are only different in the laser scanning process of each layer, and have no effect on the movement process of other structures of the device, which will not be repeated here.

Depending on the size of the processed parts, the fixed array distribution mode can be composed of several or dozens of lasers and corresponding optical system units arranged in an array, which can be used for molding parts of any shape. One laser can correspond to one optical system unit, or can correspond to multiple optical system units through light splitting. Figure 4 shows the first specific implementation of the fixed array distributed mode optical system. Several optical system units 21 are arranged in a rectangular array and fixed on the positioning plate 22. In practical applications, the positioning plate 22 only needs to be placed on the position shown in Figure 2. The position of the optical system shown is sufficient, and the optical system unit 21 has the structure shown in FIG. 3 . The processing area planning method corresponding to the optical system unit 21 is as follows: the substrate is divided into several identical or different areas, and there are a small amount of overlapping parts between adjacent areas, and the scanning field of each optical system unit covers an area on the substrate. The size and shape of this area are determined by the devices used in the optical system (such as XY laser scanning galvanometer and f-θ combination lens or XYZ three-dimensional dynamic focusing scanning galvanometer, etc.). The computer decomposes the XY plane of the three-dimensional model of the part into several areas, which correspond to the areas divided on the substrate in shape, size, and position one by one. During laser scanning, each optical system unit is sliced according to the area corresponding to the unit assigned by the computer. Graphical data selection melting powder. During laser processing, all optical system units work at the same time. For the processing of overlapping areas, one optical system unit can be selected to scan the other optical system unit without scanning, or two optical system units can be selected to scan separately or alternately. To ensure The processing quality of the joint part shall prevail.

FIG. 5 shows the second specific implementation of the fixed array distributed mode optical system. Several optical system units 21 are arranged in a circular array and fixed on the positioning plate 22, which can be used for processing large ring-shaped parts. Each circular dotted line in the figure represents the center line of the arrangement of optical system units in a circular array, and is arranged layer by layer according to the range that the optical system units can cover from the inside to the outside, so as to ensure that the combined processing area of all optical system units covers the entire Component. The processing area planning method corresponding to the optical system unit 21 is similar to the first implementation mode, except that each area needs to be arranged in a circular array according to the shape and size of the ring part.

Two optical systems with fixed array distribution patterns in Figure 4 and Figure 5 are used to process metal parts of different shapes respectively. Their common advantage is that all lasers and optical system units work at the same time during the scanning process, and the selected area of each layer is melted and formed. The time depends on the group of lasers and optical system units with the longest scanning time. The single-layer processing time is short and the processing efficiency is high. The disadvantage is that the coverage of the entire processing area requires many optical system units and corresponding lasers, and the cost of equipment construction is relatively high.

The optical system unit 21 may be arranged in a rectangular, circular or other arbitrary array.

Fig. 6 shows the first specific implementation of the optical system in the mobile platform mode, the optical system uses an XY ball screw to carry the optical system unit. In the XY ball screw moving platform mode optical system, the optical system unit 21 is directly installed on the moving platform composed of the X-direction screw 23 and the Y-direction screw 24, and the computer moves the optical system unit by controlling the XY ball screw moving platform. 21 so that its processing area covers the entire substrate. The processing area planning method of the optical system unit 21 is as follows: the projection figures of the parts on the XY plane are assembled from several areas with the same shape and size or different areas, and there are a small number of overlapping parts in adjacent areas. device decision. During laser scanning processing, the computer moves the optical system unit 21 to the top of each area in a certain order by controlling the XY ball screw moving platform, and completes the laser scanning process in these areas in sequence.

FIG. 7 shows the second specific implementation of the optical system in the mobile platform mode. The optical system unit 21 is mounted on the mobile platform around the circumference, and the division method of the processing area refers to the optical system in the circular array distribution mode shown in FIG. 5 . During laser processing, the optical system unit 21 sequentially moves above each area on the circular slide rail 25 to complete the laser scanning process of the graphics in these areas.

This mode expands the size of parts that can be processed by a single laser and a single optical system unit with the help of a mobile platform, so that the size of parts that can be formed by selective laser melting equipment is no longer limited by optical components. However, the selective laser of each layer The scanning tasks are all completed by this laser and optical system unit, and the time required for processing is much longer than that of the fixed array distribution mode, and the efficiency is very low.

The optical system unit 21 can be mounted on any form of two-dimensional and three-dimensional moving stages other than XY ball screws and circular slide rails.

Fig. 8 to Fig. 11 are the implementation manners of the given four mixed-mode optical systems. Fig. 8 is the first implementation of the mixed-mode optical system, which adopts XY ball screw to carry the rectangular array mode optical system 26; the second realization of the mixed-mode optical system in Fig. Array mode optical system 26 . The rectangular array mode optical system 26 is the rectangular array mode optical system as shown in FIG. 4 , and the rectangular array mode optical system 26 respectively replaces the XY ball screw moving platform mode optical system in FIG. 6 and the circumferential orbiting moving platform mode optical system in FIG. 7 The optical system unit 21 constitutes the first and second implementations of the mixed-mode optical system. According to the processing area covered by the rectangular array mode optical system 26 and the shape and motion characteristics of the mobile platform, the projected graphics of the parts on the XY plane are combined. During laser scanning processing, the rectangular array mode optical system 26 moves sequentially to the top of different processing areas. The optical system units 21, 21'... simultaneously process this area.

A third implementation of the mixed-mode optical system shown in FIG. 10 . It takes the mobile platform mode optical system 27 shown in FIG. 6 as a basic unit, and is installed on the positioning plate 22 in the form of a rectangular array. The division method of the processing area of each basic component unit is the same as the first realization of the mixed mode, and the laser scanning processing of each basic component unit is performed simultaneously.

The fourth implementation of the mixed-mode optical system shown in FIG. 11 adopts a mobile platform around the circumference to carry multiple rectangular array optical systems 26, and all the rectangular array optical systems 26 are evenly distributed and arranged, and can move on the mobile platform. The optical system in this mode is the same as the area distribution of the optical system shown in Figure 9 in the distribution of the processing area. Each rectangular array optical system 26 and 26' needs to perform laser scanning processing in several areas. During the processing, each rectangular array optical system The systems 26 and 26' scan and move simultaneously to complete the laser processing task of each layer.

The hybrid mode is a comprehensive application of the fixed array mode and the mobile platform mode. It uses multiple lasers and multiple optical system units to scan simultaneously. The processing efficiency is between the above two modes, and it can be controlled by an optimized algorithm according to the different shapes of the parts. The order and position of different optical system units or arrays composed of optical system units move successively on the mobile platform, so as to further improve the utilization efficiency of lasers and optical systems, and obtain the optimal efficiency and cost ratio.

As shown in Figure 12, the segmented heating and heat preservation system of the present utility model is composed of two parts, one part is the resistance wire 32 located on the inner wall of the forming cylinder 7, and the resistance wire 32 is divided into several sections from top to bottom, and the As the base plate 8 descends, it is opened in sequence; the other part is fixed under the base plate 8, which are the heating plate 28, the ceramic fiber plate 29 for heat insulation and the cooling plate 30 with cooling channels. In the molding process of the parts, it is decided according to the material of the parts whether to use the heating and heat preservation function, the temperature of the heat preservation and the timing of the heat preservation are set. The purpose of the segmented resistance wire is to improve the utilization efficiency of heat, and the heat shield and cooling plate are mainly used to prevent the heat generated by heating from spreading to the substrate lifting movement mechanism and other functional mechanisms, which will affect the stability of the equipment. This heating system can also adopt different heating forms such as induction heating and far-infrared heating, and the specific scheme shall prevail to obtain the highest heating efficiency.

As shown in FIG. 12 , the substrate lifting mechanism includes a piston 31 , a circular connecting plate 33 , a first ball screw 35 , a worm gear reducer 36 and a first motor 37 . The upper end of the piston 31 is connected with the cooling plate 30, and the lower end is connected with the circular connecting plate 33. One end of the ball screw 35 is located at the center of the circular connecting plate 33 and fixed thereto, and the other end is connected with the worm gear reducer 36, and the worm gear reduces the speed. The device 36 is connected with the first motor 37. When working, the first motor 37 drives the worm gear reducer 36 to rotate, thereby driving the ball screw 35 to rotate, and drives the circular connecting plate 33 and the piston 31 connected to it to move synchronously, and then the base plate 8 moves up and down.

The base plate lifting movement mechanism can also add multiple sets of motors and worm gear reducer structures to act on the circular connecting plate according to the different loads required; the rack and pinion structure can also be used to replace the ball screw, and the motor drives the gear to rotate. The up and down movement of the strip drives the piston, the circular connecting plate and the base plate fixed on its upper end to move up and down in unison; the servo hydraulic transmission mechanism can also be used to directly act on the base plate or the lower part of the heating and heat preservation system to drive the base plate to move up and down.

As shown in Figure 12, the forming cylinder weight balance mechanism is composed of at least two hydraulic mechanisms 38 and a connecting mechanism 34 formed by steel wire ropes and pulleys. When the base plate 8 descends, each hydraulic mechanism 38 acts on the circle through the steel wire rope of the connecting mechanism 34. On the connecting plate 33, real-time force is provided to balance the huge load produced by the continuous accumulation of powder in the molding cylinder 7 and the continuous growth of parts, so that the weight borne by the lifting motion mechanism 13 is always kept constant. The form of this mechanism is not limited to the connection structure that adopts steel wire rope and pulley to form, can also adopt the form as shown in Figure 13 according to the difference of equipment size, promptly hydraulic mechanism 38 acts on the circular connecting plate 33 directly.

This equipment can adopt a single powder feeding mechanism or two powder feeding mechanisms. The powder feeding mechanism can be quantitative or non-quantitative. The specific structure of the powder feeding mechanism can adopt various existing structures or the one provided in this example. structure. The structure of a specific embodiment of the quantitative powder feeding mechanism is described below. As shown in Figure 14, the quantitative powder feeding mechanism mainly includes a powder storage box 41, a sleeve 42, a roller 43, a powder delivery pipe 44, a second motor 49, and the like. The sleeve 42 is placed horizontally, and the tube wall is provided with a powder inlet groove and a powder outlet groove. The drum 43 is installed in the sleeve 42 , and its periphery is in close contact with the inner wall of the sleeve 42 , and at least one powder storage groove 40 is formed along the circumference. The second motor 49 drives the drum 43 to rotate in the sleeve 42 . It should be noted that the cross-section of the groove 40, the cross-section of the powder inlet groove and the powder outlet groove of the sleeve 42, the outlet 39 and the mouth of the powder delivery pipe 44 are matched in shape, preferably all are narrow. rectangle. When feeding powder, the second motor 49 drives the drum 43 to rotate, and when one groove of the powder storage groove 40 is aligned with the outlet 39, the powder enters the powder storage groove 40, while the other groove opposite to it is aligned with the powder delivery pipe 44 upper nozzle, powder in it falls with powder delivery pipe 44, and cylinder 43 every rotation certain angle, can send out a certain amount of powder.

According to different parts manufacturing requirements, the powder feeding mechanism can be an open or closed structure. When the parts need to be manufactured in a protective atmosphere, a closed powder feeding mechanism must be used. This closed powder feeding mechanism means that the powder storage box 41 is closed, and the powder is only fed externally through the powder delivery pipe 44.

The quantitative powder feeding mechanism adopted in the utility model can also adopt a translational quantitative powder feeding mechanism in addition to the aforementioned rotary type quantitative powder feeding mechanism. As shown in FIG. 18 , the translational quantitative powder feeding mechanism includes a powder storage box 41 , a bracket 60 , a powder inlet tank 59 , a powder outlet tank 61 , a powder feeding plate 62 , a moving mechanism 63 and a powder delivery pipe 44 . The upper part and the lower part of the support 60 are respectively provided with horizontally staggered powder inlet groove 59 and powder outlet groove 61. A powder feeding plate 62 with a powder storage hole 64 is installed horizontally in the bracket 60, and the right end of the powder feeding plate 62 is connected to a moving mechanism 63, and the moving mechanism 63 can be combined by a motor and a lead screw, or can be combined by a high-pressure air flow and a relay, or It is other structural forms that can push the powder feeding plate 62 to move left and right. Similar to the rotary quantitative powder feeding mechanism, the shapes of the powder inlet trough 59, the powder outlet trough 61, the cross section of the powder storage hole 64, the outlet 39 and the mouth of the powder delivery pipe 44 are matched, preferably all narrow. rectangle. When feeding powder, the movement mechanism 63 drives the powder feeding plate 62 to move so that the powder storage hole 64 is aligned with the powder inlet groove 59, and the powder in the powder storage box 41 enters the powder storage hole 64 by gravity, and the powder feeding plate moves to the left to make the powder storage hole 64 Align the powder outlet trough 61, and the powder in the powder storage hole 64 falls freely along the powder delivery pipe 44, and a certain amount of powder can be sent out, and the quantitative powder delivery can be realized by the number of times of moving left and right.

When two powder feeding mechanisms are used, the structures of the two can be the same or different.

As shown in Figure 22, the weight balance mechanism of the forming cylinder can also be composed of at least two sets of quantitative powder feeding assemblies, each quantitative powder feeding assembly includes a third quantitative powder feeding mechanism 69, a powder holding box 70, a directional guide rail 71, a steel wire rope, and a pulley The formed connecting structure 34 is composed. Orientation guide rail 71 is vertically installed on the bottom of the equipment, powder holding box 70 is movably installed on the orientation guide rail 71, and can move up and down along the orientation guide rail 71, and the powder outlets of the third quantitative powder feeding mechanism 69 are respectively located on the top of powder storage box 70. During the descending process of the base plate 8, the third quantitative powder feeding mechanism 69 continuously feeds powder into the powder holding box 70. The weight of the fed powder is the same as the weight produced by the accumulation of powder in the molding cylinder 7 and the growth of parts, so as to ensure that the base plate 8 is accurate. , Stable up and down movement. The third quantitative powder feeding mechanism 69 can adopt the same structure as the first and second quantitative powder feeding mechanisms, or can adopt the currently widely used belt pulley powder feeding structure and cladding powder feeder structure.

As shown in FIG. 14 , the powder spreading device includes a T-shaped beam 45 , powder guide pipes 46 located on both sides of the beam 45 , a scraper 48 , a pressing block 47 and a transmission mechanism. The upper mouth of the powder guide pipe 46 is at the same height as the lower mouth of the powder conveying pipe 44 to ensure that the powder will not pollute the processing cavity during the free fall process. The material of the scraper 48 can be ceramics, hard metal alloys or organic materials, etc., and is fastened in the groove at the lower end of the T-shaped beam 45 by the pressing block 47. The lower surface of the scraper 48 is a smooth plane and is close to the processing plane, T A profile beam 45 is located above the base plate 8 . Before powder feeding, the T-shaped beam 45 is driven by the transmission mechanism to move to the bottom of the right quantitative powder feeding mechanism, and the upper nozzle of the left powder guide pipe 46 is aligned with the nozzle of the powder delivery pipe 44. After the powder falls completely, , the T-shaped beam moves horizontally to the left recovery cylinder to complete the powder spreading action of the current layer, and the same is applicable to the powder spreading process of the symmetrical left structure, thereby realizing the two-way powder spreading function of this equipment and greatly improving the powder spreading process. powder efficiency. The transmission mechanism of the T-shaped beam 45 can adopt a ball screw transmission mechanism driven by a motor, a belt pulley transmission mechanism driven by a motor, or other types of linear transmission mechanisms.

Under the condition that the accuracy requirement is not high, the powder spreading device can also adopt the roller powder spreading mechanism.

As shown in FIG. 15 , the substrate leveling mechanism includes a guide rail 52 and a leveling bracket 54 . The guide rail 52 is installed on the T-shaped beam 45 along the Y-axis direction of the forming cylinder, and is parallel to the processing plane. The leveling bracket 54 is installed on the guide rail 52. The front end of the horizontal part of the bracket has a circular hole 55 up and down, which is used for clamping. Sub-table, in addition, the screw 53 of vertical circular hole is fastened. In order to achieve a better leveling effect, the base plate 8 is installed on the heating plate 28 through the positioning screws 50 and the leveling screws 51, and the positioning screws 50 and the leveling screws 51 are evenly distributed, not limited to the three groups shown in Figure 15 screw. The specific leveling method is as follows: take the processing plane as a benchmark, drive the leveling bracket 54 equipped with a dial indicator to move left and right along the X-axis direction through the T-shaped crossbeam 45, and the leveling bracket 54 can move back and forth along the Y guide rail 52 simultaneously, thereby The height value of each position of the substrate 8 is displayed, and the upper surface of the substrate 8 coincides with the processing plane by adjusting the height of the leveling screw 51 .

Due to the heavy weight of the large-sized substrate, it is difficult to meet the use requirements due to poor accuracy or limited by human strength during the leveling process using positioning screws and leveling screws. For this reason, the utility model can also adopt another kind of mechanism to replace the positioning screw and the leveling screw. 67 , 67 ′, second and third ball screw 65 , 65 ′, as shown in FIG. 19 , wherein one end of the fixed rod 68 is fixed on the piston 31 , and the other end is directly connected under the cooling plate 30 . First and second support frames 66, 66 ' are fixed on the piston 31, the second ball screw 65 is vertically installed on the first support frame 66, its upper end is fixed with the cooling plate 30, and its lower end is connected with the third motor 67. Similarly, the second support frame 66', the fourth motor 67', and the third ball screw 65' are connected with the same structure, that is, the third ball screw 65' is vertically installed on the second support frame 66', and the upper end is connected with the cooling The board 30 is fixed, and its lower end is connected with the fourth motor 67'. For the convenience of adjustment, the triangle formed by the connection between the fixed rod 68 and the first and second support frames 66, 66' is preferably an equilateral triangle. During the leveling process, rely on the third and fourth motors 67, 67' to drive the screw to rotate, thereby driving the cooling plate 30 to move, and the principle of determining a plane by three points is used to realize and maintain the level of the base plate 8.

While the protective atmosphere cover seals the processing chamber, it must ensure sufficient light-transmitting area to ensure that the laser beam can be completely focused on the processing plane after being deflected by the galvanometer. Therefore, a protective lens must be added on the cover plate of the protective atmosphere cover. Figures 16 and 17 are top views of protective atmosphere covers with different types of protective lenses, in which Figure 16 shows that a plurality of protective lenses 57 distributed in an array are embedded on the cover plate 56 of the protective atmosphere cover, mainly matching with the optical system of the array distribution mode , each protective lens corresponds to an optical system unit in the array distribution mode. Figure 17 shows that a single large protective lens 58 is embedded on the cover plate 56 of the protective atmosphere cover, which is mainly matched with the optical system of the mobile platform mode and the mixed mode. The former does not have high requirements on the material and production of the protective lens, and the protective lens that fails can be replaced at any time, which is economical; although the latter is expensive, it can meet the use of random positioning of the optical system unit in the mobile platform mode and hybrid mode Requirements, complete penetration of the laser beam can be achieved at any position.

The gas purification system forms a closed cycle through the air inlet and exhaust port and the protective atmosphere hood to ensure that the water and oxygen content in the protective atmosphere hood meet the use requirements. Both the air inlet and the exhaust port are equipped with dust filter devices to prevent the micro and nano dust generated during the processing from polluting the internal and external environment.

The processing and manufacturing of the large protective lens is relatively difficult. In order to better realize the mobile platform mode optical system and the hybrid mode optical system, the optical system 3 can also be integrated into the gas shield 5 . The specific arrangement method is shown in Figure 20, the optical system 3 is fixed under the cover plate of the gas shield 5, and the positions of other components and structures remain basically unchanged. As shown in Figure 21, with this structure, it is necessary to install a sealing cover 69 separately for each open optical system unit to protect the optical device from dust and smoke pollution in the cavity. The arrangement and scanning mode of the optical system units are the same as The external optical system is consistent.

The utility model is not limited to the above-mentioned specific implementation methods, and those skilled in the art can implement the utility model by adopting other various specific implementation modes according to the disclosed content of the utility model. Do some simple changes or modified designs, all fall into the protection scope of the present utility model.

Claims (18)

1. A selective area laser melting rapid prototyping equipment for directly manufacturing large parts, the equipment includes a substrate (8), a substrate lifting mechanism (13), a molding cylinder (7), a first recovery cylinder (6), and a powder spreading device (12) and control system (14), it is characterized in that, this equipment comprises laser group (1), optical system (3), forming cylinder weight balance mechanism (15), and the first powder feeding mechanism; The first recovery cylinder (6) is located on one side of the molding cylinder (7), and the surfaces of both are the same plane as the processing plane, and the powder spreading device (12) moves on the processing plane; the first powder feeding mechanism is respectively located in the optical system (3) one side; the optical system (3) is located above the molding cylinder (7), the laser group (1) is composed of at least one laser, and the laser beam emitted by the laser is focused on the surface of the molding cylinder (7) through the optical system (3) ; The forming cylinder (7) is equipped with a base plate (8), and the bottom of the base plate (8) is connected with a lifting motion mechanism (13). The lifting motion mechanism (13) drives the base plate (8) to move up and down in the forming cylinder (7), and the forming cylinder The weight balancing mechanism (15) is located at the bottom of the equipment and acts on the lifting motion mechanism (13). 2. The selective laser melting rapid prototyping equipment according to claim 1, characterized in that, a substrate leveling mechanism (11) is also provided above the substrate (8). 3. The selective area laser melting rapid prototyping equipment according to claim 1, characterized in that a heating and heat preservation system (10) is arranged in the forming cylinder (7). 4. The selective area laser melting rapid prototyping equipment according to claim 3, characterized in that, the heating and heat preservation system (10) is segmented, and the heating structure and molding between the substrate (8) and the lifting motion mechanism (13) The heating structure of cylinder (7) inner wall forms jointly. 5. The selective laser melting rapid prototyping equipment according to claim 3, characterized in that the equipment also includes a second powder feeding mechanism and a second recovery cylinder (6'), the second powder feeding mechanism and the first powder feeding mechanism The structure is the same, it is located on the other side of the optical system, and the second recovery cylinder (6') is located on the other side of the molding cylinder (7), and its surface is located in the processing plane. 6. The selective laser melting rapid prototyping equipment according to claim 1, characterized in that the equipment also includes a gas purification system (4) and a protective atmosphere cover (5), and the processing plane and the powder spreading device (12) are located in the protective atmosphere Inside the cover (5), the protective atmosphere cover (5) communicates with the gas purification system (4) through the air inlet and the exhaust port respectively. 7. The selective laser melting rapid prototyping device according to claim 1, wherein the optical system is composed of at least one optical system unit, and each optical system unit (21) is arranged in an array and fixed on the positioning plate (22), The laser beam emitted by the laser is scanned in parallel partitions after passing through the optical system unit (21), so that the processing area covers the entire substrate. 8. The selective laser melting rapid prototyping device according to claim 1, wherein the optical system is composed of one or a plurality of optical subsystems distributed in an array, and the optical subsystem is installed on the X-direction screw (23 ) and at least one optical system unit (21) on the mobile platform formed by the Y-direction lead screw (24), the control system (14) drives the optical system unit (21) by controlling the mobile platform, and the laser beam emitted by the laser passes through the learning system After the unit (21), parallel partition scanning is performed, so that the processing area covers the entire substrate. 9. The selective laser melting rapid prototyping equipment according to claim 1, characterized in that the optical system consists of at least one optical subsystem installed on the circular slide rail (25), and the optical subsystem consists of one or in an array form It is composed of a plurality of distributed optical system units (21), and the laser beam emitted by the laser passes through the optical system unit (21) to perform parallel partition scanning, so that the processing area covers the entire substrate. 10. The selective laser melting rapid prototyping equipment according to claim 1, characterized in that the weight balance mechanism of the molding cylinder is composed of two to four sets of powder feeding components, and each powder feeding component includes a quantitative powder feeding mechanism, a powder holding box, Orientation guide rail and connection structure, the orientation guide rail is vertically installed at the bottom of the equipment, the powder box is movably installed on the orientation guide rail, moves up and down along the orientation guide rail, and the powder outlet of the quantitative powder feeding mechanism is located above the powder storage box. 11. The selective laser melting rapid prototyping equipment according to any one of claims 1 to 10, characterized in that the first powder feeding mechanism is a quantitative powder feeding mechanism, which includes a powder storage box (41), a sleeve (42) , drum (43), powder delivery pipe (44) and second motor (49); sleeve (42) is placed horizontally, and there are powder inlet groove and powder outlet groove on the cylinder wall, the position of powder inlet groove and powder storage box The outlet (39) of (41) corresponds, and the powder outlet is connected with the powder delivery pipe (44); the cylinder (43) is installed in the sleeve (42), and its periphery is closely attached to the inner wall of the sleeve (42). And at least one powder storage groove (40) is opened along the circumference, and the second motor (49) is connected with the drum (43). 12. The selective laser melting rapid prototyping equipment according to any one of claims 1 to 10, characterized in that the first powder feeding mechanism is a quantitative powder feeding mechanism, which includes a powder storage box (41), a bracket (60), Powder inlet slot (59), powder outlet slot (61), powder feeding plate (62), movement mechanism (63) and powder delivery pipe (44); the upper and lower parts of the support (60) are respectively provided with horizontally staggered powder inlet slots (59) and the powder outlet groove (61), the position of the powder inlet groove (59) is corresponding to the outlet (40) of the powder storage box (41), and the powder outlet groove (61) is connected with the powder delivery pipe (44), A powder feeding plate (62) having a powder storage hole (64) is horizontally installed in the support (60), and the end of the powder feeding plate (62) is connected with a motion mechanism (63). 13. The selective laser melting rapid prototyping equipment according to any one of claims 1 to 10, characterized in that the powder spreading device comprises a T-shaped beam (45), powder guide pipes (46) located on both sides of the beam (45) , scraper (48), briquetting block (47) and the transmission mechanism; the upper nozzle of the powder guide pipe (46) is at the same height as the powder outlet of the quantitative powder feeding mechanism, and the scraper (48) is tightened by the briquetting block (47) Fixed in the groove at the lower end of the T-shaped crossbeam (45), the lower surface of the scraper (48) is a smooth plane and is close to the processing plane. The T-shaped crossbeam (45) is located above the base plate (8), and the T-shaped crossbeam (45) and The transmission mechanism is connected, and the T-shaped beam (45) moves under the drive of the transmission mechanism. 14. The selective laser melting rapid prototyping equipment according to claim 3, characterized in that, the segmented heating and heat preservation system is composed of two parts, one part is the resistance wire (32) positioned at the inner wall of the forming cylinder (7), and the resistance wire ( 32) It is divided into several sections from top to bottom, and the other part includes a heating plate (28), a ceramic fiber board (29) for heat insulation, and a cooling plate (30) with cooling channels connected sequentially from top to bottom, and the heating plate (28) ) is located under the substrate (8) and is fixedly connected to the substrate (8). 15. The selective laser melting rapid prototyping equipment according to any one of claims 1 to 10, characterized in that the substrate lifting mechanism includes a piston (31), a circular connecting plate (33), a first ball screw (35 ), the worm gear reducer (36) and the first motor (37); the upper end of the piston (31) is connected with the base plate (8) or the heating and heat preservation system (10), the lower end is connected with the circular connecting plate (33), and the first ball Leading screw (35) one end is positioned at the central position of circular connecting plate (33) and is fixed with it, and the other end links to each other with worm gear reducer (36), and worm gear reducer (36) links to each other with first motor (37). 16. The selective laser melting rapid prototyping equipment according to any one of claims 1 to 10, characterized in that the forming cylinder weight balance mechanism is composed of at least two hydraulic mechanisms (38) and connecting mechanisms (34), and the hydraulic mechanism ( 38) Act on the substrate lifting movement mechanism through the connection mechanism (34). 17. The selective area laser melting rapid prototyping equipment according to claim 2, characterized in that, the substrate leveling mechanism comprises a guide rail (52) and a leveling bracket (54); the guide rail (52) is installed on the T On the type beam (45), and parallel to the processing plane, the leveling bracket (54) is installed on the guide rail (52), and the front end of the horizontal part of the leveling bracket is provided with upper and lower through holes (55) for clamping the dial gauge. . 18. The selective laser melting rapid prototyping equipment according to claim 15, characterized in that a fixed rod (68) is arranged between the cooling plate (30) and the piston (31), and the first and second support frames (66 , 66'), the third and fourth motors (67, 67'), and the second and third ball screws (65, 65'); one end of the fixed rod (68) is fixed on the piston (31), and the other One end is directly connected under the cooling plate (30), the first and second support frames (66, 66') are fixed on the piston (31), and the second ball screw (65) is vertically installed on the first support frame (66 '). ), one end of which is connected and fixed with the cooling plate (30), and the other end is connected with the third motor (67); the third ball screw (65') is installed vertically on the second support frame (66'), and one end It is connected and fixed with the cooling plate (30), and the other end is connected with the fourth motor (67').

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