A traceless injection molding method for automobile plastic ornaments

Abstract

This invention relates to the field of injection molding and intelligent mold control technology, specifically disclosing a method for seamless injection molding of automotive plastic trim parts. This method uses a dedicated mold whose cavity is formed by a fixed mold, a moving mold, and a movable insert. The front end face of the movable insert has a waste material sub-cavity. The method includes: after mold closing, sliding the movable insert to the molding position; plasticizing the first plastic component into a skin layer melt and the second plastic component into a core layer melt, injecting them in the order of skin layer first, then core layer; by matching the injection speed with the size parameters of the waste material sub-cavity, the melt front and the confluence interface are both confined within the waste material sub-cavity; after holding pressure and cooling, driving the movable insert to slide under a certain holding pressure to cut and separate the waste material from the product body; and opening the mold and removing the part. This invention solves the problems of difficult elimination of cold material defects and the inability to seamlessly cut the end of the product in reverse co-injection processes, achieving a smooth and seamless end face of the product.

Description

Technical Field

[0001] This invention relates to the fields of injection molding and intelligent mold control, and in particular to a method for seamless injection molding of automotive plastic trim parts. Background Technology

[0002] Currently, double-layer co-injection molding is widely used in automotive interior and exterior parts. The conventional solution adopts a forward process of injecting the high-temperature skin layer first and the low-temperature glass fiber core layer later. It relies on the overflow sub-cavity at the end of the cavity to collect the melt weld interface, and uses the sliding slider to remove the overflow in the mold by hot cutting, thus eliminating the weld marks on the end face of the product.

[0003] Due to production limitations such as matte polypropylene raw materials, thin-walled molding, and color difference control, some decorative parts must employ a reverse co-injection process: first injecting a low-melting-point skin layer, followed by injecting a high-temperature glass fiber reinforced core layer. Existing forward injection molding processes and molds are incompatible with this reverse process, exhibiting several inherent defects. 1. The low-temperature skin layer quickly forms a semi-cured cold film upon contact with the mold wall, and the high-temperature core layer cannot fully fuse with it. The cold material front and the interface between layers are prone to flow back to the product area, resulting in cold material spots and interface delamination. Conventional overflow channels do not have precise melt limit control methods, and it is difficult to stably retain the cold defect layer by relying solely on empirical parameters.

[0004] 2. Traditional hot cutting dies do not have a zoned independent cooling structure. The product and the overflow are cooled at the same time. Shearing at the same temperature is prone to stringing, burrs and end face tearing. If the whole is fully cooled before shearing, the production cycle will be greatly reduced.

[0005] 3. The general-purpose shearing slider lacks a matching clamping structure and an independent waste cooling circuit. The servo drive is not matched to the short-stroke shearing condition under high pressure holding. Under high pressure filling state, shearing deviation and incomplete cutting are prone to occur, making it impossible to achieve seamless forming of the product end face.

[0006] Existing two-layer injection molding systems are only suitable for forward molding conditions and lack a complete process that can adapt to reverse co-injection, stably eliminate cold material defects, and achieve traceless shearing.

[0007] To address the aforementioned issues, we propose a traceless injection molding method for automotive plastic trim parts. Summary of the Invention

[0008] This invention aims to solve the problems of cold material defects being difficult to eliminate stably and the inability to achieve seamless shearing at the end of the product in the reverse co-injection process of the prior art. It proposes a seamless injection molding method for automotive plastic trim parts and a special mold.

[0009] To achieve the above objectives, the technical solution adopted by the present invention is as follows.

[0010] A method for seamless injection molding of automotive plastic trim parts includes general injection molding steps such as mold closing, plasticizing, injection, holding pressure and cooling, and mold opening and ejection. Its unique feature is that: The method uses a special injection mold, the cavity of which is formed by a fixed mold, a moving mold and at least one movable insert; the movable insert is embedded in the fixed mold or the moving mold and can slide back and forth in a direction perpendicular to the mold opening and closing direction; the front end face of the movable insert is the end forming face of the product body cavity, and an inwardly recessed waste material sub-cavity is formed thereon. The method includes the following steps: S1: Mold closing and positioning: In the mold closing state, slide the movable insert to the forming position so that its front end face is flush with the forming surfaces of the fixed mold and the moving mold, and the waste material sub-cavity is connected to the end of the product body cavity; S2: Layered plasticizing and sequential injection: The first plastic component is plasticized into a skin melt at a first plasticizing temperature T1, and the second plastic component is plasticized into a core melt at a second plasticizing temperature T2, which is higher than T1. The skin melt and core melt are fed into the mold cavity through separate gates, in the order of skin melt first and core melt second. The skin melt is injected through the gate located at the front of the product body cavity, and the core melt is injected through the gate located behind the skin melt gate. The linear velocity of the skin layer melt as it passes through the gate is 20~40 mm / s, and the linear velocity of the core layer melt as it passes through the gate is 45~60 mm / s. During the filling process, the flow distance Lg from the gate outlet of the skin melt to the inlet of the scrap cavity, the opening width Wf of the scrap cavity perpendicular to the flow direction, and the injection speed Vp of the skin melt satisfy the following: Vp≥Lg / (Wf / k), where k is the melt flow time correction coefficient, which characterizes the melt filling rheological resistance and takes a value of 0.05~0.2s / mm, so that the leading edge of the skin melt and all the interfaces where the skin and core melts meet are restricted and remain in the scrap cavity; S3: Pressure Holding and Cooling: After injection, pressure holding and cooling are performed; S4: Mechanical shear separation: After cooling, the movable insert is driven to slide away from the product body cavity, with a sliding stroke of 3~8mm and a sliding speed of 10~20mm / s; throughout the entire process from the start of sliding to the completion of the entire sliding stroke, the internal pressure of the cavity is maintained at 30~50MPa. By utilizing the relative shearing motion generated between the sidewall of the waste material sub-cavity and the end face of the product body cavity, all the waste material remaining in the waste material sub-cavity in step S2 is cut off and separated from the product body; S5: Mold opening and part removal: Then open the mold, eject the product body and waste material, and obtain an automotive plastic trim part without any weld lines or breakage marks at the end face of the product body cavity.

[0011] Furthermore, in S2, the opening width Wf of the waste material secondary cavity is 1.5~2.5mm larger than the maximum melting convergence and diffusion width perpendicular to the melt flow direction at the moment of filling completion.

[0012] Furthermore, in S2, the first plastic component is polypropylene, and the second plastic component is glass fiber reinforced polypropylene with a glass fiber content of 20% to 40%.

[0013] Furthermore, in S2, the complete injection time of the skin melt, starting from the moment its gate is opened, is 2 to 5 seconds; the core melt is injected within 0.3 to 1 second after the skin melt is injected, and the injection pressure of the core melt is 10% to 20% higher than the peak injection pressure of the skin melt.

[0014] Furthermore, in S4, the timing for driving the movable insert to slide is when the temperature at the center point of the waste material sub-cavity cools down to below 80°C, and the surface temperature of the product at the end of the product body cavity is maintained at 100~120°C.

[0015] This invention also provides a dedicated injection mold suitable for any of the above-described methods for seamless injection molding of automotive plastic trim parts, comprising a fixed mold, a moving mold, and a product body cavity formed between the fixed mold and the moving mold, characterized in that it further comprises: A movable insert is embedded in the fixed mold or the moving mold, with its front end facing the mold cavity; the fixed mold or the moving mold has a guide groove that matches the movable insert, the guide groove extends perpendicular to the mold opening and closing direction, and has limit blocks at both ends; the movable insert slides in the guide groove, and its extreme sliding position is limited by rigid contact with the limit blocks, and the maximum retraction stroke corresponding to the extreme position is greater than the depth of the waste material secondary cavity; when the mold is closed and forming, the front end face of the movable insert constitutes the end forming surface of the product body cavity; A waste material auxiliary cavity is formed on the front end face of the movable insert and is recessed inward; in the forming position, the waste material auxiliary cavity is connected to the end of the product body cavity; A servo linear drive module is fixedly installed on the outside of the fixed mold or moving mold, and its output end is rigidly connected to the tail of the movable insert; the maximum output speed of the servo linear drive module is not less than 20 mm / s, and its rated thrust is sufficient to overcome the injection molding pressure resistance borne by the movable insert within a sliding stroke of 3~8 mm and a cavity pressure of 30~50 MPa; Two sets of independent inlet gates and runners are provided on the fixed mold or the moving mold; the skin melt gate is located at the front end of the product body cavity, and the core melt gate is located behind the skin melt gate, and the distance between the core melt gate and the end of the product body cavity is 1 / 3 to 1 / 2 of the total length of the product body cavity; the total length of the product body cavity is defined as the distance from the inner wall surface of the inlet end of the product body cavity to its end face.

[0016] Furthermore, the angle between the inner side molding surface of the waste material sub-cavity and the inner side molding surface of the front end face is 30°~60°.

[0017] Furthermore, on the front end face of the movable insert, along the edge of the side of the waste material secondary cavity opening facing the product body cavity, there is a continuously raised pressure strip; the raised height of the pressure strip is 0.8~1.5mm, the width is 1~2mm, and it is arranged along the entire length of the edge.

[0018] Furthermore, the movable insert is equipped with an independent cooling circuit. The pipes of the cooling circuit are arranged around the bottom and side walls of the waste sub-cavity, and are equipped with independent cooling medium inlets and outlets.

[0019] Furthermore, the bottom or side wall of the waste material sub-cavity is provided with an independently ejectable ejector rod, which is ejected after the movable insert has completed its shearing and retraction.

[0020] As can be seen from the above technical solution, the beneficial technical effects of the present invention are as follows: 1. This invention combines the waste material sub-cavity on the movable insert with a precise melt flow control formula to forcibly restrict and retain all cold material fronts and skin-core interface generated during the reverse co-injection process within the waste material sub-cavity, thereby fundamentally solving the appearance defects such as cold material spots and interface delamination in the reverse co-injection process.

[0021] 2. This invention achieves waste separation by utilizing the relative shearing motion between the movable insert and the end face of the product body cavity under pressure. It also incorporates an independent cooling circuit for the movable insert to differentiate the temperature control of the product and the waste, ensuring that the waste is fully cooled and brittle during shearing while the product surface remains tough. This results in a smooth cut at the end face of the product without stringing, burrs, or breakage marks.

[0022] 3. The method and mold of the present invention are specifically designed for the reverse co-injection process of low melting point skin and high temperature core layer, filling the gap in the existing technology in this field and expanding the application scope of two-component injection molding process in automotive trim parts. Attached Figure Description

[0023] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0024] Figure 1 This is a flowchart of the steps of a method for seamless injection molding of automotive plastic trim parts according to the present invention; Figure 2 This is the present invention. Figure 1 Detailed flowchart of S2 Figure 3 This is a schematic diagram of the structure of a special injection mold in this invention; Figure 4 This is a top view of a special injection mold used in this invention; Figure 5 This is a structural assembly diagram of the movable insert and servo linear drive module in this invention.

[0025] Figure label: 1-Fixed mold, 2-Moving mold, 3-Moving insert, 31-Front end face, 32-Scrap sub-cavity, 33-Pressure bar, 34-Independent cooling circuit, 35-Ejector rod, 4-Product body cavity, 5-Guide slide, 6-Servo linear drive module, 7-Skin layer melt gate, 8-Core layer melt gate. Detailed Implementation

[0026] The embodiments of the technical solution of the present invention will now be described in detail with reference to the accompanying drawings. These embodiments are merely illustrative of the technical solution of the present invention and are therefore intended to limit the scope of protection of the present invention.

[0027] It should be noted that, unless otherwise stated, the technical or scientific terms used in this application should have the ordinary meaning as understood by one of ordinary skill in the art to which this invention pertains.

[0028] In the description of this application, it should be understood that the terms "center", "longitudinal", "lateral", "length", "width", "thickness", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings, and are only for the convenience of describing the present invention and simplifying the description, and are not intended to indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of the present invention.

[0029] Furthermore, the terms "first," "second," etc., are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. In the description of this invention, "a plurality of" means two or more, unless otherwise explicitly defined.

[0030] In this application, unless otherwise expressly specified and limited, the terms "installation," "connection," "joining," and "fixing," etc., should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral part; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; they can refer to the internal communication of two components or the interaction between two components. Those skilled in the art can understand the specific meaning of the above terms in this invention according to the specific circumstances.

[0031] Molding method embodiment like Figures 1 to 5 As shown in the figure, this embodiment provides a method for seamless injection molding of automotive plastic trim parts, which is specifically designed for reverse co-injection conditions, i.e., the production scenario in which a low-melting-point skin material is injected first and a high-temperature core material is injected later. This method solves the problems of the difficulty in stable elimination of cold material defects and the inability to achieve seamless shearing at the end of the product under this condition.

[0032] S1: Mold closing and positioning.

[0033] The dedicated injection mold is closed. In the closed state, the movable insert 3 is pushed into the guide groove 5 and locked in the molding position by the servo linear drive module 6. At this time, the front end face 31 of the movable insert 3 is flush with the molding surfaces of the fixed mold 1 and the moving mold 2, and the waste material sub-cavity 32 is connected to the end of the product body cavity 4, forming a closed space to be filled.

[0034] S2: Layered plasticizing and sequential injection.

[0035] In two independent plasticizing units, the first plastic component, serving as the skin layer, is plasticized into a skin melt at a first plasticizing temperature T1, while the second plastic component, serving as the core layer, is plasticized into a core melt at a second plasticizing temperature T2, which is higher than T1. The first plastic component is polypropylene, and the second plastic component is glass fiber reinforced polypropylene with a glass fiber content of 20% to 40%. This temperature setting is consistent with the reverse co-injection process.

[0036] At the start of injection, the skin melt is injected first through gate 7 at the front end of the product body cavity. The linear velocity when passing through the gate is in the range of 20~40mm / s, and the complete injection time is 2~5s. The skin melt leading edge contacts the low temperature mold wall to form a semi-solidified cold film. This part of the melt leading edge with defects, along with the skin-core interface generated during the subsequent core layer injection, must be completely captured.

[0037] Within 0.3 to 1 second after the skin layer melt injection is completed, the core layer melt is injected through the gate 8 located behind the skin layer gate. The injection pressure is 10% to 20% higher than the peak injection pressure of the skin layer, and the linear velocity through the gate is in the range of 45 to 60 mm / s. Throughout the filling process, the flow distance Lg from the skin layer melt gate outlet to the inlet of the scrap cavity, the opening width Wf of the scrap cavity perpendicular to the flow direction, and the skin layer melt injection speed Vp strictly satisfy the relationship defined in claim 1: Vp ≥ Lg / (Wf / k), where k is the melt flow time correction coefficient, with a value of 0.05 to 0.2 s / mm. This relationship ensures that the melt front has sufficient filling speed to rush into the scrap cavity 32, so that all cold material fronts and the skin-core layer interface are reliably confined and remain in the scrap cavity 32, and do not flow back into the product body cavity 4.

[0038] S3: Pressure holding cooling.

[0039] After injection, the pressure is switched to holding pressure to compensate for shrinkage and cool the cavity.

[0040] S4: Mechanical shear separation.

[0041] During the cooling process, the waste material sub-cavity 32 area is cooled by the independent cooling circuit 34 inside the movable insert 3, so that the cooling rate of the waste material sub-cavity area is higher than that of the product body cavity area. When the temperature of the center point of the waste material sub-cavity 32 is cooled to below 80°C, and the surface temperature of the product at the end of the product body cavity 4 is still maintained at 100~120°C, the shearing action is performed.

[0042] At this point, the cavity maintains a holding pressure of 30-50 MPa. Under this high pressure, the servo linear drive module 6 is activated, driving the movable insert 3 to slide smoothly away from the product body cavity 4 at a speed of 10-20 mm / s, with a sliding stroke of 3-8 mm. Because the product inside the product body cavity 4 is firmly pressed against the mold wall and remains stationary under the holding pressure, while the waste material in the waste material sub-cavity 32 moves along with the movable insert 3, the strong relative shearing force generated between the side wall of the waste material sub-cavity 32 and the end face of the product body cavity 4 achieves instantaneous, flush cutting at the connection point. At this point, the waste material is brittle due to the low temperature, while the product end remains tough due to the high temperature, resulting in a clean and neat cross-section without fraying, burrs, or tears.

[0043] S5: Mold opening and part removal.

[0044] After shearing, the holding pressure is released and the mold is opened. The product body is ejected, resulting in an automotive plastic trim part without any weld lines or breakage marks at the end face; subsequently, the ejector rod 35 on the movable insert 3 moves to eject the waste material, completing one molding cycle.

[0045] Special mold examples Combination Figures 3 to 5 As shown, this embodiment provides a seamless injection mold for automotive plastic trim parts to implement the above method, including a fixed mold 1, a moving mold 2, and a product body cavity 4 formed between the two. Its core improvement lies in the addition of an end-effector that integrates a waste material auxiliary cavity.

[0046] A movable insert 3 is embedded in the moving mold 2, with its front end face 31 facing the mold cavity. The moving mold 2 has a guide groove 5 that matches the movable insert 3. The guide groove 5 extends perpendicular to the mold opening and closing direction and has limit stops at both ends. The movable insert 3 slides within the guide groove 5, and its extreme sliding retraction position is limited by rigid contact with the limit stops. The maximum retraction stroke corresponding to this extreme position is greater than the depth of the scrap cavity 32. In the mold closing and forming position, the front end face 31 of the movable insert 3 forms the end forming surface of the product body cavity 4.

[0047] A scrap material auxiliary cavity 32 is formed on the front end face 31 of the movable insert 3 and is recessed inward. In the forming position, the scrap material auxiliary cavity 32 is connected to the end of the product body cavity 4. The angle between the inner forming surface of the side wall of the scrap material auxiliary cavity 32 and the inner forming surface of the front end face 31 is in the range of 30° to 60°. This draft angle facilitates the smooth ejection of scrap. On the front end face 31 of the movable insert 3, along the edge of the scrap material auxiliary cavity 32 facing the product body cavity 4, a continuously raised pressure strip 33 is provided. The height of the pressure strip is 0.8 to 1.5 mm and the width is 1 to 2 mm. During shearing, it can play a role in local pressure increase and precise guiding cutting.

[0048] A servo linear drive module 6 is fixedly installed on the outside of the moving mold 2, and its output end is rigidly connected to the tail of the movable insert 3. The maximum output speed of the servo linear drive module is not less than 20 mm / s, and its rated thrust is sufficient to overcome the injection molding pressure resistance borne by the movable insert 3 within a sliding stroke of 3~8 mm and a cavity pressure of 30~50 MPa.

[0049] Two independent inlet gates and runners are located on the mold. The skin melt gate 7 is located at the front end of the product body cavity 4, and the core melt gate 8 is located behind the skin melt gate 7. The distance between the core melt gate 8 and the end of the product body cavity 4 is 1 / 3 to 1 / 2 of the total length of the product body cavity. This design ensures that the skin melt has fully filled the end area when the core melt is injected.

[0050] In addition, the movable insert 3 has an independent cooling circuit 34 inside, with pipes surrounding the bottom and side walls of the waste material sub-cavity 32, and equipped with independent cooling medium inlets and outlets. The bottom wall of the waste material sub-cavity 32 is provided with an independently ejectable ejector rod 35, which is ejected only after the movable insert 3 has completed its shearing and retraction.

[0051] It should be noted that the temperature sensor, servo linear drive module, etc. involved in this invention are all commercially available and mature components in the prior art, and are not improvements of this invention; those skilled in the art can select and adapt them according to actual usage needs.

[0052] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention, and they should all be covered within the scope of the claims and specification of the present invention.

Claims

1. A method for seamless injection molding of automotive plastic trim parts, comprising general injection molding steps including mold closing, plasticizing, injection, pressure holding and cooling, and mold opening and ejection, characterized in that: The method uses a special injection mold, the cavity of which is formed by a fixed mold, a moving mold and at least one movable insert; the movable insert is embedded in the fixed mold or the moving mold and can slide back and forth in a direction perpendicular to the mold opening and closing direction; the front end face of the movable insert is the end forming surface of the product body cavity, and an inwardly recessed waste material sub-cavity is formed thereon. The method includes the following steps: S1: Mold closing and positioning: In the mold closing state, slide the movable insert to the forming position so that its front end face is flush with the forming surfaces of the fixed mold and the moving mold, and the waste material sub-cavity is connected to the end of the product body cavity; S2: Layered plasticizing and sequential injection: The first plastic component is plasticized into a skin melt at a first plasticizing temperature T1, and the second plastic component is plasticized into a core melt at a second plasticizing temperature T2, which is higher than T1. The skin melt and core melt are fed into the mold cavity through separate gates, in the order of skin melt first and core melt second. The skin melt is injected through the gate located at the front of the product body cavity, and the core melt is injected through the gate located behind the skin melt gate. The linear velocity of the skin layer melt as it passes through the gate is 20~40 mm / s, and the linear velocity of the core layer melt as it passes through the gate is 45~60 mm / s. During the filling process, the flow distance Lg from the gate outlet of the skin melt to the inlet of the scrap cavity, the opening width Wf of the scrap cavity perpendicular to the flow direction, and the injection speed Vp of the skin melt satisfy the following: Vp≥Lg / (Wf / k), where k is the melt flow time correction coefficient, which characterizes the melt filling rheological resistance and takes a value of 0.05~0.2s / mm, so that the leading edge of the skin melt and all the interfaces where the skin and core melts meet are restricted and remain in the scrap cavity; S3: Pressure Holding and Cooling: After injection, pressure holding and cooling are performed; S4: Mechanical shear separation: After cooling, the movable insert is driven to slide away from the product body cavity, with a sliding stroke of 3~8mm and a sliding speed of 10~20mm / s; throughout the entire process from the start of sliding to the completion of the entire sliding stroke, the internal pressure of the cavity is maintained at 30~50MPa. By utilizing the relative shearing motion generated between the sidewall of the waste material sub-cavity and the end face of the product body cavity, all the waste material remaining in the waste material sub-cavity in step S2 is cut off and separated from the product body; Step S5, Mold Opening and Part Removal: Then open the mold, eject the product body and waste material, and obtain an automotive plastic trim part without any weld lines or breakage marks at the end face of the product body cavity.

2. The method of claim 1, wherein, In step S2, the opening width Wf of the waste material sub-cavity is 1.5~2.5mm larger than the maximum melting diffusion width perpendicular to the melt flow direction at the moment of filling completion.

3. The method of claim 1, wherein, In step S2, the first plastic component is polypropylene, and the second plastic component is glass fiber reinforced polypropylene with a glass fiber content of 20% to 40%.

4. The method of claim 1, wherein, In step S2, the complete injection time of the skin melt, starting from the opening of its gate, is 25 seconds; the core melt is injected within 0.3 to 1 second after the skin melt injection is completed, and the injection pressure of the core melt is 10% to 20% higher than the peak injection pressure of the skin melt.

5. The method of claim 1, wherein, In step S4, the timing for driving the movable insert to slide is when the temperature at the center point of the waste material sub-cavity cools down to below 80°C, and the surface temperature of the product at the end of the product body cavity is maintained at 100~120°C.

6. A special injection mold suitable for the traceless injection molding method of the automotive plastic trim part according to any one of claims 1 to 5, comprising a fixed mold, a movable mold, a product body cavity formed between the fixed mold and the movable mold, characterized in that, Also includes: A movable insert is embedded in the fixed mold, with its front end facing the mold cavity. The fixed mold has a guide groove that matches the movable insert. The guide groove extends perpendicular to the mold opening and closing direction and has limit blocks at both ends. The movable insert slides within the guide groove, and its extreme sliding position is limited by rigid contact with the limit blocks. The maximum retraction stroke corresponding to this extreme position is greater than the depth of the waste material secondary cavity. In the mold closing and forming position, the front end of the movable insert forms the end forming surface of the product body cavity. The waste material auxiliary cavity is formed on the front end face of the movable insert and is recessed inward; in the forming position, the waste material auxiliary cavity is connected to the end of the product body cavity; A servo linear drive module is fixedly installed on the outside of the fixed mold or moving mold, and its output end is rigidly connected to the tail of the movable insert; the maximum output speed of the servo linear drive module is not less than 20 mm / s, and its rated thrust is sufficient to overcome the injection molding pressure resistance borne by the movable insert within a sliding stroke of 3~8 mm and a cavity pressure of 30~50 MPa; A skin melt gate and a core melt gate are provided on the moving mold; the skin melt gate is located at the front end of the product body cavity, and the core melt gate is located behind the skin melt gate, and the distance between the core melt gate and the end of the product body cavity is 1 / 3 to 1 / 2 of the total length of the product body cavity; the total length of the product body cavity is defined as the distance from the inner wall surface of the feed end of the product body cavity to its end face.

7. The application master as claimed in claim 6, characterized in that The angle between the inner forming surface of the side wall of the waste material auxiliary cavity and the inner forming surface of the front end face is 30°~60°.

8. The special mold according to claim 6, characterized in that, On the front end face of the movable insert, along the edge of the side of the waste material secondary cavity opening facing the product body cavity, there is a continuously raised pressure strip; the height of the raised strip is 0.8~1.5mm, the width is 1~2mm, and it is arranged along the entire length of the edge.

9. The special mold according to claim 6, characterized in that, The movable insert has an independent cooling circuit inside. The pipes of the cooling circuit are arranged around the bottom and side walls of the waste sub-cavity, and have independent cooling medium inlets and outlets.

10. The special mold according to claim 6, characterized in that, The waste material auxiliary cavity is provided with an independently ejectable ejector rod on its bottom or side wall. The ejection action of the ejector rod is performed after the movable insert completes its shearing and retraction.

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