A vertical injection molding machine and method of using the same

Abstract

The application relates to the field of injection molding, and discloses a vertical injection molding machine which comprises a rack, a connecting frame body slidably arranged on the rack in the vertical direction, an injection assembly comprising an injection cylinder arranged on the connecting frame body, a nozzle connected with a movable mold arranged at the bottom of the injection cylinder, a main piston arranged in the injection cylinder, a hollow shaft-shaped outer piston shaft and an inner piston shaft coaxially arranged on the upper surface of the main piston, the inner piston shaft being located in the outer piston shaft, a connecting hole coaxially and penetratingly arranged at the bottom of the main piston, the hole diameter of the connecting hole being smaller than the inner diameter of the nozzle, a secondary piston arranged in the inner piston shaft, a piston rod extending from the lower surface of the secondary piston, a spring arranged below the secondary piston and sleeved on the outer part of the piston rod, the piston rod comprising a smooth section with a smooth outer surface and a threaded section arranged below the smooth section and provided with threads, and initially, the bottom of the piston rod is flush with the bottom of the main piston, and the smooth section is partially sleeved in the connecting hole.

Description

Technical Field

[0001] This invention relates to the field of injection molding, and more specifically to a vertical injection molding machine and its usage method. Background Technology

[0002] A vertical injection molding machine is an injection molding device in which the injection and mold closing devices are arranged along a vertical centerline. Its core feature is the vertical opening and closing of the mold, which gives it a significant advantage in the production of products requiring inserts. It is mainly used in the production of connecting cables, power plugs (data cable plugs, USB cables, etc.), large-size or specially structurally required power plugs (such as UK and US standard plugs), and precision insert products, among other applications.

[0003] In existing injection molding machine designs, the structure of the injection nozzle mainly follows the traditional simple conical or cylindrical flow channel scheme. During the melt injection process, when the melt passes through the injection nozzle, the traditional injection nozzle only focuses on sealing and preventing spillage. Furthermore, due to the smooth inner wall and simple shape of the injection nozzle, the stirring effect of the melt in the injection nozzle has not been optimized. Therefore, how to reasonably design the internal structure of the injection nozzle so that it can generate an effective and efficient stirring effect when the molten plastic passes through, so as to improve the quality of melt mixing, has become a technical problem that urgently needs to be solved in this field.

[0004] Based on the above, the present invention proposes a vertical injection molding machine and its usage method. Summary of the Invention

[0005] To address the problems mentioned in the background above, the present invention provides a vertical injection molding machine and its usage method.

[0006] To achieve the above-mentioned technical objectives, the technical solution adopted by the present invention is as follows.

[0007] A vertical injection molding machine includes a frame, on which a mold assembly, a melting assembly and an injection assembly are arranged. The mold assembly includes a fixed mold base arranged on the frame, a movable mold base located above the fixed mold base, a fixed mold on the fixed mold base and a movable mold on the movable mold base. A connecting frame is slidably mounted on the vertical direction of the machine frame; The injection assembly includes an injection cylinder mounted on a connecting frame, with an injection nozzle at the bottom of the injection cylinder that connects to the moving mold. The syringe is fitted with a main piston. The upper surface of the main piston is coaxially fitted with an outer piston shaft and an inner piston shaft in the shape of a hollow shaft. The inner piston shaft is located inside the outer piston shaft. The bottom of the main piston is coaxially fitted with a connecting hole. The diameter of the connecting hole is smaller than the inner diameter of the injection nozzle. The inner piston shaft is fitted with a secondary piston. The lower surface of the secondary piston extends with a piston rod. The piston rod is also fitted with a spring located below the secondary piston. The piston rod includes a smooth section with a smooth outer surface and a threaded section located below the smooth section and provided with threads. Initially, the bottom of the piston rod is flush with the bottom of the main piston and the smooth section is partially fitted into the connecting hole.

[0008] As a further improvement and optimization of the present invention, when the injection barrel contains enough melt to meet the requirements of one injection molding, the distance between the main piston and the bottom of the injection barrel is h1, the distance between the bottom of the piston rod and the main piston is h2 when the compression of the spring reaches its maximum, and the axial length of the injection nozzle is h3, where h3 is greater than h2 and h1.

[0009] As a further improvement and optimization of the present invention, a horizontal pipe is connected to the outer surface of the injection nozzle, and the horizontal pipe is connected to the melting component through a connecting branch pipe. A plunger valve is installed inside the horizontal pipe, and a gate valve is also installed between the injection nozzle and the moving mold.

[0010] As a further improvement and optimization of the present invention, the plunger valve includes a plunger core sleeved in a horizontal pipe and a linear module 1 for driving the plunger core to move in the horizontal pipe. The side of the plunger core facing the injection nozzle is configured as an arc surface shape with the same diameter as the inner wall of the injection nozzle.

[0011] As a further improvement and optimization of the present invention, the gate valve includes a linear module two and a gate hole disposed on the outer circular surface of the injection nozzle and located below the horizontal pipe. A gate plate is sleeved inside the gate hole, and a bracket is connected to the outer surface of the gate plate. The bracket is connected to the linear module two. A valve hole is provided on the gate plate, and the diameter of the valve hole is consistent with the inner diameter of the injection nozzle. By driving the gate plate to move through the linear module two, the valve hole can be made coaxial with the inner wall of the injection nozzle.

[0012] As a further improvement and optimization of the present invention, an injection hydraulic cylinder is provided on the connecting frame. The output end of the injection hydraulic cylinder is coaxially connected to an outer injection shaft and an inner injection shaft in the shape of a hollow shaft. The inner injection shaft is located inside the outer injection shaft. An external step is provided at the lower end of the outer injection shaft. The area between the outer piston shaft and the inner piston shaft and the external step form a sliding fit. An internal step is provided at the upper end of the outer piston shaft. Initially, the upper surface of the external step is in contact with the lower surface of the internal step, and the bottom of the inner injection shaft is in contact with the upper surface of the auxiliary piston.

[0013] As a further improvement and optimization of the present invention, a mold-closing hydraulic cylinder is provided on the frame for driving the connecting frame to move, and a heat-insulating element is provided on the outside of the injection cylinder.

[0014] As a further improvement and optimization of the present invention, two injection components are provided and located on both sides of the melting component, and two mold components are provided and located below the two injection components.

[0015] As a further improvement and optimization of the present invention, the melting assembly includes a melting tank disposed on a connecting frame, a feed valve and an exhaust valve disposed on the tank cover of the melting tank, a hopper disposed at the upper end of the feed valve, a heating element disposed on the outside of the melting tank, a stirring element disposed inside the melting tank, and a connecting pipe connected to the bottom of the melting tank.

[0016] A method for using a vertical injection molding machine, initially, with the bottom of the main piston in contact with the bottom of the injection barrel, the plunger valve open, and the gate valve closed, the melt injection process after the mold assembly is closed via the mold-closing hydraulic cylinder includes the following steps: Step 1: The outer and inner injection shafts are moved upward by the injection hydraulic cylinder. The outer injection shaft moves upward along with the main piston through the cooperation of the external and internal steps. The main piston moves upward along with the auxiliary piston and piston rod through the spring, thereby drawing the melt into the injection barrel. Step 2: The plunger valve is closed, and the outer and inner injection shafts are driven to move downwards by the injection hydraulic cylinder. The main piston remains stationary, while the auxiliary piston and piston rod are pushed downwards by the inner injection shaft until the spring compression reaches its maximum. Step 3: The gate valve opens, and the injection hydraulic cylinder continues to drive the outer injection shaft and inner injection shaft downward. At this time, the main piston, auxiliary piston and piston rod move downward together, pushing the melt into the mold cavity of the mold assembly.

[0017] Compared with the prior art, the beneficial effects of this invention are as follows: As can be seen from step three of the working principle section at the end of the instruction manual, in this case, when the melt flows into the mold cavity of the mold assembly, the threaded section of the piston rod remains inside the injection nozzle. Therefore, during the process of the melt flowing into the mold cavity through the injection nozzle: Technical effect 1: Part of the melt flows in through the area between the threaded section and the inner wall of the injection nozzle, while another part of the melt flows through the threads of the threaded section. The two work together to create a stirring effect on the melt. Stirring can eliminate uneven temperature, improve the dispersion of components and additives, prevent retention and degradation, and stabilize injection pressure and rheological behavior, which is necessary. Technical effect 2: In this case, the melt is first quantitatively drawn into the injection cylinder, and then the melt is injected into the mold cavity. Therefore, the melt drawn in later is injected into the mold cavity first, and the melt drawn in earlier is injected into the mold cavity later. Furthermore, during the injection process, the length of the threaded section of the piston rod extending into the injection nozzle increases as the injection progresses; Therefore, there is an adaptive stirring effect on the melt. On the one hand, it ensures that the melt that is first drawn into the injection barrel but then injected into the mold cavity has an effective and good stirring effect. On the other hand, it further improves the uniformity of the melt stirring. Attached Figure Description

[0018] Figure 1This is a three-dimensional structural diagram of the present invention. Figure 1 ; Figure 2 This is a three-dimensional structural diagram of the present invention. Figure 2 ; Figure 3 This is a three-dimensional schematic diagram of the melting component, injection component, and moving mold of the present invention; Figure 4 This is a cross-sectional view of the melting assembly, injection assembly, and moving mold of the present invention. Figure 1 ; Figure 5 This is a cross-sectional view of the melting assembly, injection assembly, and moving mold of the present invention. Figure 2 ; Figure 6 This is a partial cross-sectional view of the injection assembly of the present invention. Figure 1 ; Figure 7 This is a partial cross-sectional view of the injection assembly of the present invention. Figure 2 ; Figure 8 This is a partial cross-sectional view of the injection assembly of the present invention. Figure 3 ; Figure 9 This is a partial cross-sectional view of the injection assembly of the present invention. Figure 4 .

[0019] The labels in the attached diagram are: 100. Frame; 101. Fixed mold base; 102. Moving mold base; 103. Fixed mold; 104. Moving mold; 105. Mold closing hydraulic cylinder; 106. Connecting frame; 200. Melting assembly; 201. Melting tank; 202. Heating element; 203. Feed valve; 204. Exhaust valve; 205. Stirring element; 300. Injection assembly; 301. Injection hydraulic cylinder; 302. Injection cylinder; 303. Insulation element Components; 304, Injection nozzle; 305, Horizontal pipe; 306, Connecting branch pipe; 307, Linear module one; 308, Linear module two; 309, Piston core; 310, Bracket; 311, Gate; 312, Valve hole; 313, Main piston; 314, Outer piston shaft; 315, Inner piston shaft; 316, Auxiliary piston; 317, Piston rod; 318, Spring; 319, Outer injection shaft; 320, Inner injection shaft. Detailed Implementation

[0020] To further illustrate the technical means and effects of the present invention in achieving its intended purpose, the following detailed description of the specific implementation methods, structures, features, and effects of the present invention, in conjunction with the accompanying drawings and preferred embodiments, is provided below.

[0021] A vertical injection molding machine includes a frame 100, on which a mold assembly, a melting assembly 200 and an injection assembly 300 are mounted.

[0022] Reference Figures 1-3 A connecting frame 106 is slidably mounted on the frame 100 along the vertical direction, and both the melting component 200 and the injection component 300 are mounted on the connecting frame 106.

[0023] The mold assembly includes a fixed mold base 101 disposed on the frame 100, a movable mold base 102 located above the fixed mold base 101, a fixed mold 103 disposed on the fixed mold base 101, and a movable mold 104 disposed on the movable mold base 102.

[0024] The melt output end of the injection component 300 is connected to the moving mold 104. The frame 100 is provided with a mold closing hydraulic cylinder 105 for driving the connecting frame 106 to move. Therefore, the mold assembly can be driven to perform mold closing or mold opening actions by the mold closing hydraulic cylinder 105.

[0025] Reference Figure 3 and Figure 4 The melting assembly 200 includes a melting tank 201 mounted on a connecting frame 106. The lid of the melting tank 201 is equipped with a feed valve 203 and an exhaust valve 204. A hopper is mounted on the upper end of the feed valve 203. A heating element 202 is mounted on the outside of the melting tank 201. The heating element 202 and the heat preservation element 303 mentioned later can both be implemented using existing electric heating technology, which will not be described in detail. A stirring element 205 is mounted inside the melting tank 201. The stirring element 205 can be implemented using existing blade stirring technology, which will not be described in detail.

[0026] Plastic granules enter the melting tank 201 through the hopper and are heated by the heating element 202 to melt the plastic and obtain a melt. During the melting process, the stirring element 205 stirs the plastic to improve the melting effect.

[0027] Reference Figures 4-6 The injection assembly 300 includes an injection cylinder 302 and an injection hydraulic cylinder 301 disposed on the connecting frame 106.

[0028] The bottom of the injection cylinder 302 is provided with an injection nozzle 304, and the outside of the injection cylinder 302 is provided with a heat insulation element 303. The lower end of the injection nozzle 304 is connected to the moving mold 104, and the outer surface of the injection nozzle 304 is connected with a horizontal pipe 305. The horizontal pipe 305 is connected to the melting tank 201 through a connecting branch pipe 306.

[0029] Furthermore, a plunger valve is installed inside the horizontal pipe 305. Specifically, the plunger valve includes a plunger core 309 sleeved inside the horizontal pipe 305 and a linear module 307 for driving the plunger core 309 to move within the horizontal pipe 305. Both the linear module 307 and the linear module 308 mentioned later can be implemented using existing screw linear movement technology, which will not be elaborated further. Moreover, the side of the plunger core 309 facing the injection nozzle 304 is set into an arc shape with the same diameter as the inner wall of the injection nozzle 304. Therefore, when the plunger core 309 is located on the side away from the injection nozzle 304 at the connection between the horizontal pipe 305 and the connecting branch pipe 306, the injection cylinder 302 is connected to the melting tank 201. Conversely, they are not connected. The arc surface of the plunger core 309 can keep the inner wall of the injection nozzle 304 intact.

[0030] Furthermore, a gate valve is provided between the injection nozzle 304 and the moving mold 104. Specifically, the gate valve includes a gate hole located on the outer circular surface of the injection nozzle 304 and below the horizontal pipe 305. A gate plate 311 is fitted inside the gate hole. A bracket 310 is connected to the outer surface of the gate plate 311. The bracket 310 is connected to the linear module 308. A valve hole 312 is also provided on the gate plate 311. The diameter of the valve hole 312 is the same as the inner diameter of the injection nozzle 304. The linear module 308 drives the gate plate 311 to move, thereby making the valve hole 312 coaxial with the inner wall of the injection nozzle 304, or blocking the injection nozzle 304 through the gate plate 311. The former, together with the plunger core 309, can make the inner wall of the injection nozzle 304 present a complete cylindrical inner circular surface shape.

[0031] Reference Figures 6-9 The syringe 302 is fitted with a main piston 313.

[0032] The upper surface of the main piston 313 is coaxially provided with an outer piston shaft 314 and an inner piston shaft 315, both of which are hollow shafts, and the inner piston shaft 315 is located inside the outer piston shaft 314.

[0033] The bottom of the main piston 313 is coaxially provided with a connecting hole that communicates with the inner piston shaft 315, and the diameter of the connecting hole is smaller than the inner diameter of the injection nozzle 304.

[0034] An inner piston shaft 315 is fitted with a secondary piston 316. A piston rod 317 extends coaxially from the lower surface of the secondary piston 316. A spring 318 located below the secondary piston 316 is also fitted around the piston rod 317.

[0035] Furthermore, the piston rod 317 includes a smooth section with a smooth outer surface and a threaded section located below the smooth section and provided with threads. Initially, the bottom of the piston rod 317 is flush with the bottom of the main piston 313 and the smooth section is partially fitted into the connecting hole.

[0036] Furthermore, the output end of the injection hydraulic cylinder 301 is coaxially connected to an outer injection shaft 319 and an inner injection shaft 320, both of which are hollow shafts, and the inner injection shaft 320 is located inside the outer injection shaft 319.

[0037] The lower end of the outer injection shaft 319 is provided with an external step. The area between the outer piston shaft 314 and the inner piston shaft 315 and the external step form a sliding fit. The upper end of the outer piston shaft 314 is provided with an internal step. Initially, the upper surface of the external step is in contact with the lower surface of the internal step, and the bottom of the inner injection shaft 320 is in contact with the upper surface of the auxiliary piston 316.

[0038] The working process of this invention: Initially, the bottom of the main piston 313 is in contact with the bottom of the syringe 302, the plunger valve is open, and the gate valve is closed; The mold assembly is closed by the mold-closing hydraulic cylinder 105, and then: Step 1: The injection cylinder 301 drives the outer injection shaft 319 and the inner injection shaft 320 to move upward. The outer injection shaft 319 moves upward with the outer piston shaft 314 and the main piston 313 through the cooperation of the outer step and the inner step. The main piston 313 moves upward with the auxiliary piston 316 and the piston rod 317 through the spring 318, thereby drawing the melt in the melting tank 201 into the injection cylinder 302. Step 2: The plunger valve is closed. The injection cylinder 301 drives the outer injection shaft 319 and the inner injection shaft 320 to move down. The main piston 313 remains stationary. The auxiliary piston 316 and the piston rod 317 are pushed down by the inner injection shaft 320 until the compression of the spring 318 reaches its maximum. At this time, the threaded section of the piston rod 317 extends completely out of the connecting hole and the bottom end is located inside the injection nozzle 304. The smooth section is fitted inside the connecting hole. Step 3: In this case, the products obtained by injection molding are data cables, ribbon cables, power cords, and other wire materials; The amount of melt extracted in step one is the amount required for one injection molding. After extraction is completed, the distance between the main piston 313 and the bottom of the injection barrel 302 is h1. In step two, after the compression of spring 318 reaches its maximum, the distance between the bottom of piston rod 317 and main piston 313 is h2. The axial length of the injection nozzle 304 is h3; h3 is greater than h2, which is greater than h1; When the gate valve opens, the injection hydraulic cylinder 301 continues to drive the outer injection shaft 319 and the inner injection shaft 320 to move downward. At this time, the main piston 313, the auxiliary piston 316 and the piston rod 317 move downward together, pushing the melt into the mold cavity of the mold assembly.

[0039] The technical advantage of this case lies in: As can be seen from step three above, in this case, when the melt flows into the mold cavity of the mold assembly, the threaded section of the piston rod remains inside the injection nozzle. Therefore, during the process of the melt flowing into the mold cavity through the injection nozzle: Technical effect 1: Part of the melt flows in through the area between the threaded section and the inner wall of the injection nozzle, while another part of the melt flows through the threads of the threaded section. The two work together to create a stirring effect on the melt. Stirring can eliminate uneven temperature, improve the dispersion of components and additives, prevent retention and degradation, and stabilize injection pressure and rheological behavior, which is necessary. Technical effect 2: In this case, the melt is first quantitatively drawn into the injection cylinder, and then the melt is injected into the mold cavity. Therefore, the melt drawn in later is injected into the mold cavity first, and the melt drawn in earlier is injected into the mold cavity later. Furthermore, during the injection process, the length of the threaded section of the piston rod extending into the injection nozzle increases as the injection progresses; Therefore, there is an adaptive stirring effect on the melt. On the one hand, it ensures that the melt that is first drawn into the injection barrel but then injected into the mold cavity has an effective and good stirring effect. On the other hand, it further improves the uniformity of the melt stirring.

[0040] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention in any way. Although the present invention has been disclosed above with reference to preferred embodiments, it is not intended to limit the present invention. Any person skilled in the art can make some modifications or alterations to the above-disclosed technical content to create equivalent embodiments without departing from the scope of the present invention. Any simple modifications, equivalent changes and alterations made to the above embodiments based on the technical essence of the present invention without departing from the scope of the present invention shall still fall within the scope of the present invention.

Claims

1. A vertical injection molding machine, comprising a frame (100), on which a mold assembly, a melting assembly (200), and an injection assembly (300) are disposed, characterized in that, The mold assembly includes a fixed mold base (101) disposed on the frame (100), a movable mold base (102) located above the fixed mold base (101), a fixed mold (103) disposed on the fixed mold base (101), and a movable mold (104) disposed on the movable mold base (102). A connecting frame (106) is slidably mounted on the frame (100) along the vertical direction. The injection assembly (300) includes an injection cylinder (302) disposed on a connecting frame (106), and an injection nozzle (304) connected to the moving mold (104) is disposed at the bottom of the injection cylinder (302). The syringe (302) is fitted with a main piston (313). The upper surface of the main piston (313) is coaxially fitted with an outer piston shaft (314) and an inner piston shaft (315) in the shape of a hollow shaft. The inner piston shaft (315) is located inside the outer piston shaft (314). The bottom of the main piston (313) is coaxially fitted with a connecting hole. The diameter of the connecting hole is smaller than the inner diameter of the injection nozzle (304). The inner piston shaft (315) is fitted with a secondary piston (316). The lower surface of the secondary piston (316) extends a piston rod (317). The piston rod (317) is also fitted with a spring (318) located below the secondary piston (316). The piston rod (317) includes a smooth section with a smooth outer surface and a threaded section located below the smooth section and provided with threads. Initially, the bottom of the piston rod (317) is flush with the bottom of the main piston (313) and the smooth section is partially fitted into the connecting hole.

2. A vertical injection molding machine according to claim 1, characterized in that, When the injection barrel (302) contains enough melt to meet the requirements of one injection molding, the distance between the main piston (313) and the bottom of the injection barrel (302) is h1. When the compression of the spring (318) reaches its maximum, the distance between the bottom of the piston rod (317) and the main piston (313) is h2. The axial length of the injection nozzle (304) is h3, where h3 is greater than h2 and greater than h1.

3. A vertical injection molding machine according to claim 2, characterized in that, A horizontal pipe (305) is connected to the outer surface of the injection nozzle (304). The horizontal pipe (305) is connected to the melting component (200) through a connecting branch pipe (306). A plunger valve is installed inside the horizontal pipe (305). A gate valve is also installed between the injection nozzle (304) and the moving mold (104).

4. A vertical injection molding machine according to claim 3, characterized in that, The plunger valve includes a plunger core (309) sleeved in a horizontal pipe (305) and a linear module (307) for driving the plunger core (309) to move within the horizontal pipe (305). The side of the plunger core (309) facing the injection nozzle (304) is configured as an arc-shaped surface with the same diameter as the inner wall of the injection nozzle (304).

5. A vertical injection molding machine according to claim 3, characterized in that, The gate valve includes a linear module two (308) and a gate hole located on the outer circular surface of the injection nozzle (304) and below the horizontal pipe (305). A gate plate (311) is fitted inside the gate hole. A bracket (310) is connected to the outer surface of the gate plate (311). The bracket (310) is connected to the linear module two (308). A valve hole (312) is provided on the gate plate (311). The diameter of the valve hole (312) is the same as the inner diameter of the injection nozzle (304). By driving the gate plate (311) to move through the linear module two (308), the valve hole (312) can be made coaxial with the inner wall of the injection nozzle (304).

6. A vertical injection molding machine according to claim 3, characterized in that, An injection hydraulic cylinder (301) is provided on the connecting frame (106). The output end of the injection hydraulic cylinder (301) is coaxially connected to an outer injection shaft (319) and an inner injection shaft (320) in the shape of a hollow shaft. The inner injection shaft (320) is located inside the outer injection shaft (319). An outer step is provided at the lower end of the outer injection shaft (319). The area between the outer piston shaft (314) and the inner piston shaft (315) and the outer step form a sliding fit. An inner step is provided at the upper end of the outer piston shaft (314). Initially, the upper surface of the outer step is in contact with the lower surface of the inner step, and the bottom of the inner injection shaft (320) is in contact with the upper surface of the auxiliary piston (316).

7. A vertical injection molding machine according to claim 6, characterized in that, The frame (100) is equipped with a mold-closing hydraulic cylinder (105) for driving the connecting frame (106) to move, and the outside of the injection cylinder (302) is equipped with a heat-insulating element (303).

8. A vertical injection molding machine according to claim 7, characterized in that, Two injection assemblies (300) are provided and located on both sides of the melting assembly (200), and two mold assemblies are provided and located below the two injection assemblies (300).

9. A vertical injection molding machine according to claim 7, characterized in that, The melting assembly (200) includes a melting tank (201) mounted on a connecting frame (106). The melting tank (201) has a feed valve (203) and an exhaust valve (204) on its lid. A hopper is mounted on the upper end of the feed valve (203). A heating element (202) is mounted on the outside of the melting tank (201). A stirring element (205) is mounted inside the melting tank (201). A connecting pipe (306) is connected to the bottom of the melting tank (201).

10. The method of using a vertical injection molding machine as described in claim 7, characterized in that, Initially, the bottom of the main piston (313) is in contact with the bottom of the injection cylinder (302), the plunger valve is open, and the gate valve is closed. The melt injection process after the mold assembly is closed is achieved by the mold closing hydraulic cylinder (105), which includes the following steps: Step 1: The injection cylinder (301) drives the outer injection shaft (319) and the inner injection shaft (320) to move upward. The outer injection shaft (319) moves upward with the outer piston shaft (314) and the main piston (313) through the cooperation of the outer step and the inner step. The main piston (313) moves upward with the auxiliary piston (316) and the piston rod (317) through the spring (318), thereby drawing the melt into the injection barrel (302). Step 2: The plunger valve is closed, and the outer injection shaft (319) and inner injection shaft (320) are driven to move down by the injection hydraulic cylinder (301). The main piston (313) remains stationary, while the auxiliary piston (316) and piston rod (317) are pushed down by the inner injection shaft (320) until the compression of the spring (318) reaches its maximum. Step 3: The gate valve opens, and the injection hydraulic cylinder (301) continues to drive the outer injection shaft (319) and the inner injection shaft (320) to move down. At this time, the main piston (313), the auxiliary piston (316) and the piston rod (317) move down together, pushing the melt into the mold cavity of the mold assembly.

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