Multi-layer injection molding method for thick-walled plastic parts

Abstract

The present invention provides a multi-layer injection molding method for thick-walled plastic parts, comprising the following steps: layer structure division step: dividing the thick-walled plastic part into 2n + 1 layer structures, namely the first layer structure to the (2n + 1)-th layer structure, the first layer structure being located in the central area of the thick-walled plastic part, and the second layer structure to the (2n + 1)-th layer structure being evenly distributed on both sides of the first layer structure; n is a natural number; multi-layer injection step: setting 2n injection molding stations, and sequentially injecting through the 2n injection molding stations to form the first layer structure to the (2n + 1)-th layer structure of the thick-walled plastic part; injecting through the first injection molding station to form the first layer structure. The present invention injects and forms a thick-walled plastic part divided into an odd number of layers with an even number of injection stations, greatly improving the forming efficiency of the thick-walled plastic part, and achieving the purpose of accurately controlling the dimensions of important shaped surfaces by simultaneously injecting the outermost layer from both the front and back at the last station.

Description

Technical Field

[0001] The present invention relates to the technical field of injection molding, and specifically, to a multi-layer injection molding method for thick-walled plastic parts, and in particular, to a 2n + 1 layer high-efficiency and high-quality injection molding device for thick-walled lenses. Background Art

[0002] Common materials for thick-walled plastic parts are transparent PMMA or PC. Taking a product with a wall thickness of 25 mm made of PMMA material as an example, if the ordinary single-layer injection molding method is used, the injection molding cycle can be as long as 1300 - 1500 seconds. The condensation sequence of the plastic part is from the outside to the inside, and the resin closest to the core of the product requires the longest cooling time. For thick-walled plastic parts, the outer shell, gate, and runner of the product will condense earlier than the material in the core of the product, and thermal cutting-off will be achieved at the early stage of the molding cycle. After thermal cutting-off, the material in the core of the product will not stop shrinking, but will continue to shrink for a long time and cannot be compensated by pressure holding. This will cause the shrinkage rate of the product to be too large, and the surface shape of the product to deviate greatly from the design. For optical plastic parts with high-precision requirements, a large number of scraps and defects will be caused. The dimension h refers to the maximum value of the wall thickness, and the thickness of an optical lens used in a typical headlight can reach 20 - 35 mm. Summary of the Invention

[0003] Aiming at the defects in the prior art, the purpose of the present invention is to provide a multi-layer injection molding method for thick-walled plastic parts.

[0004] According to a multi-layer injection molding method for thick-walled plastic parts provided by the present invention, the following steps are included:

[0005] Layer structure division step: Divide the thick-walled plastic part into 2n + 1 layer structures, namely the first layer structure to the 2n + 1 layer structure. The first layer structure is located in the central area of the thick-walled plastic part, and the second layer structure to the 2n + 1 layer structure are evenly distributed on both sides of the first layer structure; n is a natural number;

[0006] Multi-layer injection molding step: Set 2n injection molding stations, and sequentially inject through the 2n injection molding stations to form the first layer structure to the 2n + 1 layer structure of the thick-walled plastic part; Inject through the first injection molding station to form the first layer structure;

[0007] When n is equal to 1, inject through the second injection molding station to form the second layer structure and the third layer structure respectively located on both sides of the first layer structure;

[0008] When n is greater than 1, when injecting through the second injection molding station to the (2n - 1)-th injection molding station, the second layer structure to the (2n - 1)-th layer structure are successively and alternately formed on both sides of the first layer structure; the previous injection molding station injects and forms a layer structure on one side of the first layer structure, and the next injection molding station injects and forms another layer structure at the relative position on the other side of the first layer structure;

[0009] Through the 2n-th injection molding station, the 2n-th layer structure and the (2n + 1)-th layer structure are injection molded, and the 2n-th layer structure and the (2n + 1)-th layer structure form the surface layer structure of the thick-walled plastic part.

[0010] Preferably, for the second layer structure to the (2n + 1)-th layer structure, the even-numbered layer structures and the odd-numbered layer structures are successively and alternately formed on both sides of the first layer structure;

[0011] The next even-numbered layer structure covers the previous even-numbered layer structure, and the next odd-numbered layer structure covers the previous odd-numbered layer structure.

[0012] Preferably, for the second layer structure to the (2n + 1)-th layer structure, the even-numbered layer structures are formed on the movable side of the injection molding station, and the odd-numbered layer structures are formed on the fixed side of the injection molding station.

[0013] Preferably, the multi-layer injection molding steps specifically include the following steps:

[0014] Step S1: Set up a moving component and 2n injection molding stations, arrange the 2n injection molding stations so that the moving component can successively reach the first injection molding station to the 2n-th injection molding station;

[0015] Step S2: Make the moving component reach the first injection molding station, close the fixed station and the movable station of the first injection molding station, and injection mold the first layer structure;

[0016] Wherein, a connecting structure on the moving component can be located in the cavity of the first injection molding station, the first layer structure can be fixed on the connecting structure, and the moving component can drive the first layer structure to move;

[0017] Step S3: Open the fixed station and the movable station of the first injection molding station, eject the first layer structure from the movable station of the first injection molding station through the moving component, and then move the first layer structure to the movable station of the second injection molding station through the moving component;

[0018] Step S4: Close the fixed station and the movable station of the second injection molding station, and injection mold the second layer structure connected to the first layer structure on one side of the first layer structure;

[0019] Step S5: Open the mold of the fixed station and the movable station of the second injection molding station, eject the combination of the first layer structure and the second layer structure from the movable station of the second injection molding station through the moving component, and then move the combination of the first layer structure and the second layer structure to the movable station of the third injection molding station through the moving component;

[0020] Step S6: Close the mold of the fixed station and the movable station of the third injection molding station, and inject and form the third layer structure connected to the first layer structure on the other side of the first layer structure;

[0021] Step S7: Open the mold of the fixed station and the movable station of the third injection molding station, eject the combination of the first layer structure, the second layer structure and the third layer structure from the movable station of the third injection molding station through the moving component, and then move the combination of the first layer structure, the second layer structure and the third layer structure to the movable station of the fourth injection molding station through the moving component;

[0022] Among them, if n is greater than 2, then step S8 and step S9 are carried out in sequence; if n is equal to 2, then directly go to step S9;

[0023] Step S8: Close the mold of the fixed station and the movable station of the a-th injection molding station, and inject and form the a-th layer structure connected to the (a - 2)-th layer structure on one side of the first layer structure;

[0024] Open the mold of the fixed station and the movable station of the a-th injection molding station, eject the combination injected and formed at the a-th injection molding station from the movable station of the a-th injection molding station through the moving component, and then move the combination injected and formed at the a-th injection molding station to the movable station of the (a + 1)-th injection molding station through the moving component;

[0025] Close the mold of the fixed station and the movable station of the (a + 1)-th injection molding station, and inject and form the (a + 1)-th layer structure connected to the (a - 1)-th layer structure on the other side of the first layer structure;

[0026] Open the mold of the fixed station and the movable station of the (a + 1)-th injection molding station, eject the combination injected and formed at the (a + 1)-th injection molding station from the movable station of the (a + 1)-th injection molding station through the moving component, and then move the combination injected and formed at the (a + 1)-th injection molding station to the movable station of the (a + 2)-th injection molding station through the moving component;

[0027] a is an even number greater than or equal to 4 and less than 2n, and the fourth layer structure to the (2n - 1)-th layer structure are formed in sequence through the above steps;

[0028] Step S9: Close the mold of the fixed station and the movable station of the 2n-th injection molding station, inject on one side of the first-layer structure to form the 2n-th layer structure connected to the 2n - 2-th layer structure, and inject on the other side of the first-layer structure to form the 2n + 1-th layer structure connected to the 2n - 1-th layer structure;

[0029] Step 10: Open the mold of the fixed station and the movable station of the 2n-th injection molding station, and take out the formed thick-walled plastic part.

[0030] Preferably, in step S2, when injecting the first-layer structure, the cavity for injecting the first-layer structure is partially located on the fixed station and partially on the movable station, and both sides of the first-layer structure can be in contact with the fixed station and the movable station respectively for heat conduction.

[0031] Preferably, in step S4, when injecting the second-layer structure, the cavity for injecting the second-layer structure is located on the movable station, and the other side of the first-layer structure can be in contact with the fixed station for heat conduction.

[0032] Preferably, in step S6, when injecting the third-layer structure, the cavity for injecting the third-layer structure is located on the fixed station, and the second-layer structure can be in contact with the movable station for heat conduction.

[0033] Preferably, in step S8, when injecting the a-th layer structure, the cavity for injecting the a-th layer structure is located on the movable station, and the a - 1-th layer structure can be in contact with the fixed station for heat conduction;

[0034] When injecting the a + 1-th layer structure, the cavity for injecting the a + 1-th layer structure is located on the fixed station, and the a-th layer structure can be in contact with the movable station for heat conduction.

[0035] Preferably, in step S9, when injecting the 2n-th layer structure and the 2n + 1-th layer structure, the cavity for injecting the 2n-th layer structure is located on the movable station, and the cavity for injecting the 2n + 1-th layer structure is located on the fixed station.

[0036] Preferably, the moving component is connected to the first-layer structure through a rotatable arm built in the movable side, and the rotatable arm built in the movable side can move the workpiece formed by the previous injection molding station to the next injection molding station;

[0037] During the entire injection process of the thick-walled plastic part, the rotatable arm built in the movable side can always conduct out the heat accumulated on the first-layer structure.

[0038] Compared with the prior art, the present invention has the following beneficial effects:

[0039] 1. Through multi-layer injection molding, the present invention first injects the core part of the product and then injects and forms the two sides of the product in multiple layers in a divided manner, enabling the resin of each layer to be cooled most sufficiently and solving the problem of long molding cycle. Through multi-layer injection molding, on the basis of the part of the product that has been sufficiently cooled previously, the next layer is injected, so that the shrinkage generated by the previous layer of the product is compensated during the injection of the next layer. Through the injection compensation of multiple stations, the lens shape deviation caused by the shrinkage naturally possessed by the resin can be minimized to the greatest extent.

[0040] 2. Through layer-by-layer injection molding, the light-emitting surface of the lens is formed at the last station. For the existing light-emitting surface of the lens, it is usually necessary to process complex and expensive micro-structured patterns on the molded product. The present invention only forms the last layer of the front and back surfaces of the product at the last station, so only an optical micro-structured insert needs to be set at the last station.

[0041] 3. By cleverly dividing the injection molding layers of the thick-walled lens and selecting the injection molding sequence that most conforms to the law of heat transfer, the present invention achieves the goal of low equipment investment and high-efficiency production of high-quality lenses. Both PC and PMMA are poor conductors of heat. The thermal conductivity of typical die steel is about 29 w / m2C. Generally speaking, the thermal conductivity of plastic PMMA and PC is not higher than 0.29 w / m2C, and the former is 100 times that of the latter. Only by allowing the injected resin to contact the steel more can the heat of the plastic be discharged faster. The present invention first injects the core part of the product to allow the core part of the product to be sufficiently cooled first, and then sequentially superimposes the high-temperature resin on the formed part on the front or back of the formed part. This way can keep one side of the product in contact with the steel in the 2nd to 5th stations for the product formed by the previous injection molding, continuously taking out the heat of the product. One side of the newly injection-molded part will continuously contact the die steel in the next station, continuously taking out the heat of the product.

[0042] 4. Due to the optical requirements of the lens, there are extremely high requirements for the shape accuracy of the light-incident surface and the light-emitting surface. Through clever design, the present invention places the two surfaces with the highest requirements at the last station for forming. At this time, most of the core material of the lens has been sufficiently cooled, and the resin shrinkage has also been relatively sufficiently compensated during the forming of the first layer. On this basis, the 2nd to 2n + 1st layers are sequentially injection-molded layer by layer, preferably injecting the 2nth and 2n + 1st layers simultaneously. The shrinkage of the resin injected in the previous layer will also be compensated during the injection and pressure holding of the next layer. This makes the forming process stronger, with strong anti-interference ability of the forming process, maximized forming window, and at the same time forming the light-incident surface and the light-emitting surface of the product, converting the thick-wall injection molding into general thin-wall injection molding, greatly improving the shape accuracy of the optical lens. Even if it is necessary to adjust the cavity shape of the light-incident surface and the light-emitting surface for some reason, only the corresponding insert at the last station needs to be adjusted.

[0043] 5. The present invention can achieve multi-layer injection molding of thick-walled plastic parts. First, the first fixed station and the first movable station are used to form the first layer structure in the central area of the thick-walled plastic part. Then, the subsequent fixed stations and movable stations are alternately used to form multi-layer structures on both sides of the first layer structure in sequence, thereby realizing the multi-layer injection molding of the thick-walled plastic part. This can greatly reduce the injection molding cycle of the thick-walled plastic part. Taking the product with a wall thickness of 25 mm mentioned above as an example, when it is divided into 7 layers, its molding cycle can be reduced to one-eighth to one-twelfth of the cycle required for single-layer injection molding. At the same time, the present invention optimizes the setting method of the runner, greatly improving the product quality of multi-layer injection molding and achieving synchronous improvement in efficiency and quality. BRIEF DESCRIPTION OF THE DRAWINGS

[0044] Other features, objects, and advantages of the present invention will become more apparent by reading the following detailed description of non-limiting embodiments with reference to the accompanying drawings:

[0045] Figure 1 Schematic diagram highlighting the structure of the fixed station on the fixed mold;

[0046] Figure 2 Schematic diagram highlighting the structure of the movable station on the movable mold;

[0047] Figure 3 Schematic diagram highlighting the structure of the swing arm on the movable mold;

[0048] Figure 4 Schematic diagram highlighting the rotation direction of the swing arm;

[0049] Figure 5 Schematic diagram highlighting the formation of the first layer structure;

[0050] Figure 6 Schematic diagram highlighting the formation of the second layer structure;

[0051] Figure 7 Schematic diagram highlighting the formation of the third layer structure;

[0052] Figure 8 Schematic diagram highlighting the formation of the fourth layer structure;

[0053] Figure 9 Schematic diagram highlighting the formation of the fifth layer structure;

[0054] Figure 10 Schematic diagram highlighting the formation of the sixth layer structure and the seventh layer structure;

[0055] Figure 11 Schematic diagram highlighting the structure of the movable station;

[0056] Figure 12Schematic three-dimensional structure diagram of a thick-walled plastic part;

[0057] Figure 13 Schematic plan structure diagram of a thick-walled plastic part;

[0058] Figure 14 is Figure 13 Schematic sectional structure diagram along lines B-B and A-A;

[0059] Figure 15 Schematic three-dimensional structure diagram of a thick-walled plastic part with an injection structure in the runner;

[0060] Figure 16 Schematic plan structure diagram of a thick-walled plastic part with an injection structure in the runner;

[0061] Figure 17 is Figure 16 Schematic sectional structure diagram along line C-C;

[0062] Figure 18 is Figure 16 Schematic sectional structure diagram along line D-D;

[0063] Figure 19 is Figure 16 Schematic sectional structure diagram along line E-E;

[0064] Figure 20 is Figure 16 Schematic sectional structure diagram along line F-F;

[0065] Figure 21 Schematic distribution diagram of a runner injection structure with three runners in each layer;

[0066] Figure 22 Schematic distribution diagram of a runner injection structure with two runners in each layer;

[0067] Figure 23 Schematic injection process diagram;

[0068] Figure 24 Schematic step flow diagram of a multi-layer injection molding method for a thick-walled plastic part;

[0069] Figure 25 Schematic structure diagram showing the thickness h of each layer structure;

[0070] Figure 26 Schematic diagram of simultaneously injecting the second layer structure and the third layer structure.

[0071] The figure shows:

[0072] Specific implementation manner

[0073] The present invention will be described in detail below in conjunction with specific embodiments. The following embodiments will help those skilled in the art to further understand the present invention, but do not limit the present invention in any form. It should be noted that for those of ordinary skill in the art, without departing from the concept of the present invention, several changes and improvements can still be made. These all fall within the protection scope of the present invention.

[0074] Example 1:

[0075] As Figures 1 to 26 shown, this embodiment provides a multi-layer injection molding method for thick-walled plastic parts, including the following steps:

[0076] Layer structure division step: Divide the thick-walled plastic part into 2n + 1 layer structures, namely the first layer structure to the (2n + 1)-th layer structure. The first layer structure is located in the central area of the thick-walled plastic part, and the second layer structure to the (2n + 1)-th layer structure are equally distributed on both sides of the first layer structure; n is a natural number;

[0077] Multi-layer injection molding step: Set 2n injection molding stations, and sequentially inject through the 2n injection molding stations to form the first layer structure to the (2n + 1)-th layer structure of the thick-walled plastic part; inject through the first injection molding station to form the first layer structure;

[0078] When n is equal to 1, inject through the second injection molding station to form the second layer structure and the third layer structure respectively located on both sides of the first layer structure;

[0079] When n is greater than 1, when injecting through the second injection molding station to the (2n - 1)-th injection molding station, sequentially and alternately form the second layer structure to the (2n - 1)-th layer structure on both sides of the first layer structure; the previous injection molding station injects to form a layer structure on one side of the first layer structure, and the next injection molding station injects to form another layer structure at the relative position on the other side of the first layer structure; inject through the 2n-th injection molding station to form the 2n-th layer structure and the (2n + 1)-th layer structure, and the 2n-th layer structure and the (2n + 1)-th layer structure form the surface layer structure of the thick-walled plastic part.

[0080] For the second layer structure to the (2n + 1)-th layer structure, the even-numbered layer structures and the odd-numbered layer structures are sequentially and alternately formed on both sides of the first layer structure; the next even-numbered layer structure covers the previous even-numbered layer structure, and the next odd-numbered layer structure covers the previous odd-numbered layer structure. For the second layer structure to the (2n + 1)-th layer structure, the even-numbered layer structures are formed on the movable side of the injection molding station, and the odd-numbered layer structures are formed on the fixed side of the injection molding station.

[0081] The multi-layer injection molding step specifically includes the following steps:

[0082] Step S1: Set up a moving component and 2n injection molding stations, arrange the 2n injection molding stations so that the moving component can reach the first injection molding station to the 2nth injection molding station in sequence;

[0083] Step S2: Make the moving component reach the first injection molding station, close the mold of the fixed station and the movable station of the first injection molding station, and inject to form the first layer structure;

[0084] Among them, a connecting structure on the moving component can be located in the cavity of the first injection molding station, the first layer structure can be fixed on the connecting structure, and the moving component can drive the first layer structure to move;

[0085] In Step S2, when injecting the first layer structure, the cavity for injecting the first layer structure is partly located on the fixed station and partly on the movable station, and both sides of the first layer structure can be in contact with the fixed station and the movable station respectively for heat conduction;

[0086] Step S3: Open the mold of the fixed station and the movable station of the first injection molding station, eject the first layer structure from the movable station of the first injection molding station through the moving component, and then move the first layer structure to the movable station of the second injection molding station through the moving component;

[0087] Step S4: Close the mold of the fixed station and the movable station of the second injection molding station, and inject and form the second layer structure connected to the first layer structure on one side of the first layer structure;

[0088] In Step S4, when injecting the second layer structure, the cavity for injecting the second layer structure is located on the movable station, and the other side of the first layer structure can be in contact with the fixed station for heat conduction;

[0089] Step S5: Open the mold of the fixed station and the movable station of the second injection molding station, eject the combination of the first layer structure and the second layer structure from the movable station of the second injection molding station through the moving component, and then move the combination of the first layer structure and the second layer structure to the movable station of the third injection molding station through the moving component;

[0090] Step S6: Close the mold of the fixed station and the movable station of the third injection molding station, and inject and form the third layer structure connected to the first layer structure on the other side of the first layer structure;

[0091] In Step S6, when injecting the third layer structure, the cavity for injecting the third layer structure is located on the fixed station, and the second layer structure can be in contact with the movable station for heat conduction;

[0092] Step S7: Open the mold of the fixed station and the movable station of the third injection molding station. Use the moving component to eject the combination of the first-layer structure, the second-layer structure, and the third-layer structure from the movable station of the third injection molding station, and then use the moving component to move the combination of the first-layer structure, the second-layer structure, and the third-layer structure to the movable station of the fourth injection molding station;

[0093] Wherein, if n is greater than 2, then step S8 and step S9 are performed sequentially; if n is equal to 2, then directly proceed to step S9;

[0094] Step S8: Close the mold of the fixed station and the movable station of the a-th injection molding station, and inject and form the a-th layer structure connected to the (a - 2)-th layer structure on one side of the first-layer structure;

[0095] Open the mold of the fixed station and the movable station of the a-th injection molding station. Use the moving component to eject the combination formed by injection molding at the a-th injection molding station from the movable station of the a-th injection molding station, and then use the moving component to move the combination formed by injection molding at the a-th injection molding station to the movable station of the (a + 1)-th injection molding station;

[0096] Close the mold of the fixed station and the movable station of the (a + 1)-th injection molding station, and inject and form the (a + 1)-th layer structure connected to the (a - 1)-th layer structure on the other side of the first-layer structure;

[0097] Open the mold of the fixed station and the movable station of the (a + 1)-th injection molding station. Use the moving component to eject the combination formed by injection molding at the (a + 1)-th injection molding station from the movable station of the (a + 1)-th injection molding station, and then use the moving component to move the combination formed by injection molding at the (a + 1)-th injection molding station to the movable station of the (a + 2)-th injection molding station;

[0098] a is an even number greater than or equal to 4 and less than 2n. The fourth-layer structure to the (2n - 1)-th layer structure are sequentially formed through the above steps;

[0099] In step S8, when injecting the a-th layer structure, the cavity for injecting the a-th layer structure is located on the movable station, and the (a - 1)-th layer structure can contact and conduct heat with the fixed station;

[0100] When injecting the (a + 1)-th layer structure, the cavity for injecting the (a + 1)-th layer structure is located on the fixed station, and the a-th layer structure can contact and conduct heat with the movable station;

[0101] Step S9: Close the mold of the fixed station and the movable station of the 2n-th injection molding station, inject on one side of the first layer structure to form the 2n-th layer structure connected to the 2n - 2-th layer structure, and inject on the other side of the first layer structure to form the 2n + 1-th layer structure connected to the 2n - 1-th layer structure;

[0102] In step S9, when injecting the 2n-th layer structure and the 2n + 1-th layer structure, the cavity for injecting the 2n-th layer structure is located on the movable station, and the cavity for injecting the 2n + 1-th layer structure is located on the fixed station;

[0103] Step 10: Open the mold of the fixed station and the movable station of the 2n-th injection molding station, and take out the formed thick-walled plastic part.

[0104] The moving component is connected to the first layer structure through a rotatable arm built inside the movable side. The rotatable arm built inside the movable side can move the workpiece formed by the previous injection molding station to the next injection molding station; during the entire injection process of the thick-walled plastic part, the rotatable arm built inside the movable side can always conduct the heat accumulated on the first layer structure.

[0105] In this embodiment, n = 3, and the thick-walled plastic part is divided into 7 layer structures, namely the first layer structure 4, the second layer structure 6, the third layer structure 8, the fourth layer structure 10, the fifth layer structure 12, the sixth layer structure 14, and the seventh layer structure 16. Three layer structures are divided on both sides of the first layer structure. On one side are the second layer structure 6, the fourth layer structure 10, and the sixth layer structure 14, and on the other side are the third layer structure 8, the fifth layer structure 12, and the seventh layer structure 16;

[0106] In other embodiments, if n = 4, it is divided into 9 layers. There are 4 layer structures on both sides of the first layer structure. On one side are the second layer structure, the fourth layer structure, the sixth layer structure, and the tenth layer structure, and on the other side are the third layer structure, the fifth layer structure, the seventh layer structure, and the ninth layer structure, and so on;

[0107] In this embodiment, 6 injection molding stations are set. The first layer structure to the seventh layer structure of the thick-walled plastic part are sequentially injected through 6 injection molding stations. When injecting at the 2nd to 5th injection molding stations, the second layer structure to the fifth layer structure are alternately formed on both sides of the first layer structure. After the first injection molding station injects the first layer structure, the second injection molding station injects the second layer structure on one side of the first layer structure, the third injection molding station injects the third layer structure at the relative position on the other side of the first layer structure, the fourth injection molding station injects the fourth layer structure connected to the second layer structure on one side of the first layer structure, and the fifth injection molding station injects the fifth layer structure connected to the third layer structure at the relative position on the other side of the first layer structure;

[0108] In this embodiment, the sixth injection molding station injects and forms the sixth layer structure and the seventh layer structure, and the sixth layer structure and the seventh layer structure form the surface layer structure of the thick-walled plastic part. The sixth layer structure and the seventh layer structure form the most important structure of the surface layer. In the scenario of a lens, they correspond to the light incident surface and the light exiting surface, which are the two surfaces with the highest requirements for the mating surfaces.

[0109] In this embodiment, the six injection molding stations are arranged so that the moving component can sequentially reach the first injection molding station to the sixth injection molding station.

[0110] In this embodiment, if n is 3, then a is 4. Then, the fixed station and the movable station of the fourth injection molding station are closed for molding, and the fourth layer structure connected to the second layer structure is injected and formed on one side of the first layer structure.

[0111] The fixed station and the movable station of the fourth injection molding station are opened. The combination injected and formed at the fourth injection molding station is ejected from the movable station of the fourth injection molding station through the moving component, and then the combination injected and formed at the fourth injection molding station is moved to the movable station of the fifth injection molding station through the moving component. The combination is the combination of the first layer structure, the second layer structure, the third layer structure, and the fourth layer structure.

[0112] The fixed station and the movable station of the fifth injection molding station are closed for molding, and the fifth layer structure connected to the third layer structure is injected and formed on the other side of the first layer structure.

[0113] The fixed station and the movable station of the fifth injection molding station are opened. The combination injected and formed at the fifth injection molding station is ejected from the movable station of the fifth injection molding station through the moving component, and then the combination injected and formed at the fifth injection molding station is moved to the movable station of the sixth injection molding station through the moving component. The combination is the combination of the first layer structure, the second layer structure, the third layer structure, the fourth layer structure, and the fifth layer structure.

[0114] In other embodiments, if n is 4, then a are 4 and 6 in sequence, and the fourth layer structure to the seventh layer structure are formed in sequence. If n is 5, then a are 4, 6, and 8 in sequence, and the fourth layer structure to the ninth layer structure are formed in sequence, and so on.

[0115] When injecting the fourth layer structure, the cavity for injecting the fourth layer structure is located on the movable station, and the third layer structure can contact and conduct heat with the fixed station. When injecting the fifth layer structure, the cavity for injecting the fifth layer structure is located on the fixed station, and the fourth layer structure can contact and conduct heat with the movable station.

[0116] In this embodiment, the fixed station and the movable station of the sixth injection molding station are closed for mold clamping. The sixth layer structure connected to the fourth layer structure is injection molded on one side of the first layer structure, and the seventh layer structure connected to the fifth layer structure is injection molded on the other side of the first layer structure.

[0117] When injecting the sixth layer structure and the seventh layer structure, the cavity for injecting the sixth layer structure is located on the movable station, and the cavity for injecting the seventh layer structure is located on the fixed station.

[0118] The fixed station and the movable station of the sixth injection molding station are opened for mold release, and the formed thick-walled plastic part is taken out.

[0119] On the fixed mold, 2n fixed stations are arranged circumferentially; on the movable mold, 2n movable stations are arranged circumferentially; the fixed stations and the movable stations are arranged in one-to-one correspondence, and the 2n fixed stations and the 2n movable stations form 2n injection molding stations; the moving component includes a driving component and a movable-side built-in rotating arm arranged on the movable mold. The driving component and the movable-side built-in rotating arm are located in the annular area formed by the 2n movable stations; the driving component drives the movable-side built-in rotating arm to rotate, and one end of the movable-side built-in rotating arm can reach the first injection molding station to the 2nth injection molding station in sequence; one end of the movable-side built-in rotating arm forms a connecting structure for fixing the first layer structure and can drive the first layer structure to rotate; the movable-side built-in rotating arm can move the injection molded part of the previous injection molding station to the next injection molding station through rotation. During the entire injection molding process of the thick-walled plastic part, the movable-side built-in rotating arm can always export the heat accumulated on the first layer structure. The connecting structure is provided with pins for fixing the first layer structure.

[0120] In this embodiment, 6 fixed stations are arranged circumferentially on the fixed mold; 6 movable stations are arranged circumferentially on the movable mold; the fixed stations and the movable stations are arranged in one-to-one correspondence, and the 6 fixed stations and the 6 movable stations form 6 injection molding stations.

[0121] Example 2:

[0122] Those skilled in the art can understand this embodiment as a more specific description of Embodiment 1.

[0123] This embodiment provides an efficient and high-quality injection molding device and method for a thick-walled lens with 2n + 1 (odd) layers.

[0124] In this embodiment, the thick-walled plastic part is divided into 7 layer structures, and 6 injection molding stations are set. In other embodiments, it is not limited to 7 layer structures and 6 injection molding stations.

[0125] Figure 1This is the fixed side view, which is the view of the fixed side parting surface of a monochromatic six-station injection molding die. The figure shows the outer shape of the fixed side of the die, and the positions of the first-layer injection point gate 5, the second-layer injection point gate 7, the third-layer injection point gate 9, the fourth-layer injection point gate 11, the fifth-layer injection point gate 13, and the seventh-layer injection point gate 17 are marked in the figure.

[0126] Among them, the first-layer injection point gate 5, the second-layer injection point gate 7, the third-layer injection point gate 9, the fourth-layer injection point gate 11, the fifth-layer injection point gate 13, and the seventh-layer injection point gate 17 all inject the plastic required for forming by the screw on the fixed side.

[0127] Figure 2 This is the movable side view, which shows the view of the movable side parting surface of the die. It is the movable side of the injection mold, which is the outer shape of the movable side of the die, and the position of the sixth-layer injection point gate 15 is marked in the figure.

[0128] In this embodiment, the plastic required for forming is injected by the screw on the movable side of the molding machine. However, it is also possible to inject the plastic required for the sixth injection by the screw on the fixed side through appropriate runner design. To ensure the pressure balance of the sixth station, the sixth injection and the seventh injection should be carried out simultaneously. This can prevent the parts formed in the first to fifth stations from deforming under the action of a single force.

[0129] Figure 3 This is the movable side view showing the rotating arm. Figure 4 This is the movable side view showing the moving direction of the rotating arm.

[0130] As Figures 5 to 10 shown, it describes the product parts and shapes corresponding to the forming of each station.

[0131] Figure 6 This is the movable side view showing product layer two. Figure 7 This is the movable side view showing product layer three. Figure 8 This is the movable side view showing product layer four. Figure 9 This is the movable side view showing product layer five. Figure 10 This is the movable side view showing product layer six. Figure 11 This is the movable side view showing product layer seven.

[0132] As Figure 5 shown, this is the movable side view showing product layer one, which shows the position of the first-layer injection point gate 5. The first-layer structure 4 in the figure is the shape formed in the first station. Both sides of the product are in contact with the steel. The SEC A-A view in the upper left corner of the figure is the schematic cross-sectional view of the right structure along the A-A line.

[0133] As Figure 6As shown, it is a movable side view showing the product layer two, showing the position of the injection point gate 7 of the second layer. The second layer structure 6 in the figure is the shape formed at the second station, and the cavity is located on the movable side. The SEC B-B view in the lower left corner of the figure is a schematic cross-sectional view of the right structure along the B-B line.

[0134] As Figure 7 shown, it is a movable side view showing the product layer three, showing the position of the injection point gate 9 of the third layer. The third layer structure 8 in the figure is the shape formed at the third station, and the cavity is located on the fixed side. The SEC C-C view below the figure is a schematic cross-sectional view of the upper structure along the C-C line.

[0135] As Figure 8 shown, it is a movable side view showing the product layer four, showing the position of the injection point gate 11 of the fourth layer. The fourth layer structure 10 in the figure is the shape formed at the fourth station, and the cavity is located on the movable side. The SEC D-D view in the lower right corner of the figure is a schematic cross-sectional view of the left structure along the D-D line.

[0136] As Figure 9 shown, it is a movable side view showing the product layer five, showing the position of the injection point gate 13 of the fifth layer. The fifth layer structure 12 in the figure is the shape formed at the fifth station, and the cavity is located on the fixed side. The SEC E-E view in the upper right corner of the figure is a schematic cross-sectional view of the left structure along the E-E line.

[0137] As Figure 10 shown, it is a movable side view showing the product layer six and the product layer seven, showing the positions of the injection point gate 15 of the sixth layer and the injection point gate 17 of the seventh layer. The sixth layer structure 14 and the seventh layer structure 16 in the figure correspond to the shapes formed at the sixth station, where the cavity of the sixth layer structure 14 is on the movable side and the cavity of the seventh layer structure 16 is on the fixed side. The SEC F-F view in the upper right corner of the figure is a schematic cross-sectional view of the lower structure along the E-E line.

[0138] Figure 11 It is a movable side view showing the product removal schematic. Figure 12 It is a three-dimensional structure schematic of the thick-walled plastic part 25. Figure 13 It is a planar structure schematic of the thick-walled plastic part 25.

[0139] Figure 14 The SEC B-B view on the left in the figure is Figure 13 a schematic cross-sectional view along the B-B line. Figure 14 The SEC A-A view on the right in the figure is Figure 13 a schematic cross-sectional view along the A-A line.

[0140] Figure 15 It is a three-dimensional structure schematic of the thick-walled plastic part 25 with the runner injection structure 26 formed by the runner in the injection structure.Figure 16 It is a schematic plan view of a thick-walled plastic part 25 with a runner injection structure 26 formed by a runner in an injection structure.

[0141] Figure 17 The SEC C-C view in Figure 16 is a schematic cross-sectional view along the C-C line. The figure shows the first injection molding runner 24, the sixth injection molding runner 22, and the seventh injection molding runner 23.

[0142] Figure 18 The SEC D-D view in Figure 16 is a schematic cross-sectional view along the D-D line. The figure shows the second injection molding runner 18 and the third injection molding runner 19.

[0143] Figure 19 The SEC E-E view in Figure 16 is a schematic cross-sectional view along the E-E line. The figure shows the fourth injection molding runner 20 and the fifth injection molding runner 21.

[0144] As Figure 20 shown, it demonstrates a cleverly designed gate / runner stacking method to achieve the above molding sequence. The first injection molding runner 24 in the figure is the cross-section of the runner formed in the first station. Its thickness is about 3 - 6 mm and its width is 8 - 15 mm. The second injection molding runner 18 in the figure is the cross-section of the runner formed in the second station. The main part of the cold runner has a thickness of about 2 - 5 mm and a width of about 3 - 5 mm.

[0145] Since the second injection cavity is located on the movable side, the main part of the cold runner is also on the movable side. To enable injection from the fixed side, a cold runner located on the fixed side is designed beside the first injection runner, and a part of the second injection runner on the movable side is extended so that the two partially overlap, achieving the connection between the fixed-side hot gate and the movable-side cold runner.

[0146] A new side runner structure is added on one side of the structure for forming the runner. By forming a side runner in the side runner structure, the runner on the movable side is connected, and the gate is led to the fixed side.

[0147] The third injection molding runner 19 in the figure is the cross-section of the runner formed in the third station. Its thickness is about 2 - 5 mm and its width is about 3 - 5 mm. The fourth injection molding runner 20 in the figure is the cross-section of the runner formed in the fourth station. The main part of the cold runner has a thickness of about 2 - 5 mm and a width of about 3 - 5 mm.

[0148] Since the fourth injection cavity is located on the movable side, the main part of the cold runner is also on the movable side. To enable injection from the fixed side, a cold runner on the fixed side is designed beside the first injection runner, and a part of the fourth injection runner on the movable side is extended so that the two partially overlap, achieving the connection between the hot runner on the fixed side and the cold runner on the movable side.

[0149] A new side runner structure is added to one side of the structure for forming the runner. By forming a side runner in the side runner structure, the runner on the movable side is connected, and the gate is directed to the fixed side.

[0150] The fifth injection molding runner 21 in the figure is the cross-section of the runner formed at the fifth station. The thickness is about 2 - 5 mm, and the width is about 3 - 5 mm. The sixth injection molding runner 22 and the seventh injection molding runner 23 in the figure are the cross-sections of the runners formed at the sixth station. The main part has a thickness of about 2 - 5 mm and a width of about 3 - 5 mm.

[0151] Among them, the sixth injection molding runner 22 is formed by injection molding with a screw on the movable side, and the hot gate is directly set in the middle of the runner. The seventh injection molding runner 23 is formed by injection molding with a screw on the fixed side, and the hot gate is directly set in the middle of the runner.

[0152] Figure 20 is the cross-sectional shape of the main part of the cold runner. The first injection molding runner 24 is the runner corresponding to the first-layer structure 4. The second injection molding runner 18 is the runner corresponding to the second-layer structure 6. The third injection molding runner 19 is the runner corresponding to the third-layer structure 8. The fourth injection molding runner 20 is the runner corresponding to the fourth-layer structure 10. The fifth injection molding runner 21 is the runner corresponding to the fifth-layer structure 12. The sixth injection molding runner 22 is the runner corresponding to the sixth-layer structure 14. The seventh injection molding runner 23 is the runner corresponding to the seventh-layer structure 16.

[0153] Figure 3 and Figure 4 shows the design of the swing arm fork for ejecting the product formed at the first station and bringing it to the next station. The rotational power is driven by a motor installed on the movable side of the mold. The ejection power is provided by the ejector rod of the molding machine. At one end of the rotating arm 3 built in the movable side near the product, two or more pins are set and extend into the cavity beside the main body of the first-shot formed runner. The plastic injected at the first station will wrap around the pins. Under the action of the resin shrinkage force, the formed product will tightly hold the swing arm. So that the product is firmly fixed on the swing arm and does not loosen during the process from the first station to the sixth station. After the injection is completed at the sixth station and the product is ejected, the complete product is taken out from the swing arm by a manipulator or manually.

[0154] In this embodiment, through multi-layer injection molding, the core of the product is injected first, and then the two sides of the product are formed by multi-layer injection in multiple steps, so that the resin of each layer can be cooled most sufficiently, solving the problem of long molding cycle.

[0155] In this embodiment, through multi-layer injection molding, the next layer is injected on the basis of the part of the product that has been sufficiently cooled before, so that the shrinkage generated by the previous layer of the product can be compensated during the injection molding of the next layer. Through the injection compensation of multiple stations, the lens shape deviation caused by the natural shrinkage of the resin can be minimized.

[0156] In this embodiment, the light-emitting surface of the lens usually needs to be provided with complex and expensive micro-structured patterns. This design only forms the last layer of the front and back of the product at the last station. Therefore, only an optical micro-structured insert needs to be set at the last station.

[0157] In this embodiment, both PC and PMMA are poor conductors of heat. The thermal conductivity of typical die steel is about 29 w / m2C. Generally speaking, the thermal conductivity of plastic PMMA and PC is not higher than 0.29 w / m2C, and the former is more than 100 times that of the latter. Only by allowing the injected resin to contact the steel more can the heat of the plastic be discharged faster. This design first injects the core of the product to cool the core of the product sufficiently first, and then sequentially stacks the high-temperature resin on the formed part on the front or back of the formed part. In this way, the product formed by the previous injection can still keep one side of the product in contact with the steel in the 2nd to 5th stations, continuously taking out the heat of the product. One side of the newly formed part will continuously contact the die steel in the next station, continuously taking out the heat of the product.

[0158] In this embodiment, due to the optical requirements of the lens, there are extremely high requirements for the shape accuracy of the light-incident surface and the light-emitting surface. Through a clever design, this design places the two surfaces with the highest requirements at the last station for forming. At this time, most of the core material of the lens has been sufficiently cooled, and the resin shrinkage has also been fully compensated during the forming of the first layer. On this basis, the light-incident surface and the light-emitting surface of the product are formed simultaneously, converting the thick-wall injection molding into general thin-wall injection molding, greatly improving the shape accuracy of the optical lens. Even if it is necessary to adjust the cavity shape of the light-incident surface and the light-emitting surface for some reason, only the corresponding insert at the last station needs to be adjusted.

[0159] The forming challenge of thick-wall injection molded parts lies in the extremely long molding cycle and the shrinkage that is difficult to be compensated. This embodiment cleverly divides the injection molding layers of the thick-wall parts, designs the injection molding sequence that most conforms to the heat transfer law, and combines the multi-layer injection molding method to achieve the goal of efficiently producing thick-wall injection molded parts with low shrinkage and high precision.

[0160] To address the problems encountered by thick-walled plastic parts in injection molding as mentioned in the prior art, in this embodiment, the entire product is divided into an odd number of layers. Figure 14 shows the cross-sections of the product in two perpendicular directions when divided into 7 layers. Figure 23 The process of shows the possible injection sequence for this layered design. The first layer structure 4 is injected first, and the second layer structure 6 and the third layer structure 8 can be injected simultaneously or sequentially. The fourth layer structure 10 and the fifth layer structure 12 can also be injected simultaneously or sequentially. The sixth layer structure 14 and the seventh layer structure 16 can also be injected simultaneously or sequentially. Specifically, the most suitable method can be selected according to the conditions of the equipment.

[0161] The second layer structure 6 and the third layer structure 8 cover the first layer structure. When choosing to inject the second layer structure 6 or the third layer structure 8 first, this is free, as long as the corresponding runners and gates are provided. In the case where the corresponding runners and gates are opened, the second layer structure 6 and the third layer structure 8 can be injected simultaneously. As Figure 26 shown, in the case where the molding machine has injection barrels on both the fixed side and the movable side, two hot runners can be used to inject simultaneously from A and B. In the case where the molding machine only has an injection barrel on the fixed side, a runner cavity C can be opened to connect the injection runner cavities of the second layer structure 6 and the third layer structure 8, so that only injecting from A can achieve the purpose of simultaneously injecting the second layer structure 6 and the third layer structure 8.

[0162] As Figure 25 shown, the dimension h refers to the maximum value of the wall thickness of a single-layer structure. The thickness of an optical lens for a typical headlight can reach 20 - 35 mm. h1 is the thickness of the first layer, h2 is the thickness of the second layer, h3 is the thickness of the third layer, h4 is the thickness of the fourth layer, h5 is the thickness of the fifth layer, h6 is the thickness of the sixth layer, and h7 is the thickness of the seventh layer.

[0163] Among them, the wall thickness of the first layer structure 4 needs to be larger than that of other layers in order to achieve higher injection molding efficiency. In a preferred embodiment, the wall thickness ratio is such that the maximum wall thickness of the first layer structure 4 is 2 times the maximum wall thickness of the second layer structure 6. For the intermediate layers of the second layer structure 6, the third layer structure 8, the fourth layer structure 10, and the fifth layer structure 12, their maximum wall thicknesses are kept equal or at least close. This can make the cooling curves of the intermediate injection layers almost the same or similar. For the sixth layer structure 14 and the seventh layer structure 16, which are the surface layers of the product, the wall thickness is kept uniform and less than that of the intermediate layers. The typical range of the sixth layer structure 14 and the seventh layer structure 16 is 1.5 - 5 mm.

[0164] Taking the product with a wall thickness of 25 mm made of PMMA material as an example, by using the above seven-layer injection molding method, the molding cycle can be shortened to 100 - 150 seconds.

[0165] In this embodiment, through the odd-layer injection molding method, the molding cycle can be greatly reduced, the surface quality of the plastic part can be improved, and strict optical requirements can be met.

[0166] The thick-walled injection molded part in this embodiment is innovatively divided into odd layers, and requires an appropriate gate design. A clever gate design can maximize the advantages of short molding cycle and full compensation for plastic part shrinkage in multi-layer injection molding. In this embodiment, through a clever stacked runner design, the injection molding of plastic parts divided into odd layers becomes possible. At the same time, the compactness of the gate is taken into account, and the gates are maximally concentrated in one place. The subsequent laser cutting of the gate is very convenient, minimizing the residual marks of the gate after cutting.

[0167] Figure 12 Shown is a thick-walled plastic part of a product. Taking the lens of an automotive headlight mold as an example, the thickness is often 25 - 35 mm. If a single-layer molding method is used for injecting plastic parts of this thickness, the molding cycle can be as long as 20 - 30 minutes or even longer. As an alternative to single-layer injection molding, multi-layer injection molding can greatly reduce the molding cycle.

[0168] Taking seven-layer injection molding as an example, the molding cycle can be reduced by about 90%, and the product quality is higher and the optical performance is more excellent. For the 2n + 1 (odd) layer scenario developed for multi-layer injection molding, this embodiment cleverly designs the gates and runners that can adapt to the thick-walled plastic parts injected layer by layer from the inside out. By using the thickest first injection molding runner 24 as the basis of the stack, the corresponding gates and runners of the subsequent forming layers are superimposed on the front and back of the first injection molding runner, corresponding to the second injection molding runner 18, the third injection molding runner 19, the fourth injection molding runner 20, the fifth injection molding runner 21, the sixth injection molding runner 22, and the seventh injection molding runner 23 in sequence.

[0169] By setting the first injection molding runner 24 to be the widest and thickest, taking the example of injection molding in seven layers with a maximum thickness of 25 mm, the gate thickness of the first layer is 3 - 6 mm, and the runner width has a relatively large selection range depending on the product size. The goal is to ensure that the product of the first layer receives sufficient pressure holding and shrinkage compensation. By setting the second injection molding runner 18, the third injection molding runner 19, the fourth injection molding runner 20, and the fifth injection molding runner 21 in the middle layer to be of similar sizes, the middle layer, which already has a similar thickness, can obtain almost the same pressure holding and shrinkage compensation windows. In the case of seven - layer injection molding, by setting the sixth injection molding runner 22 and the seventh injection molding runner 23 at the center of the already - formed gate runner, since three sides of the runner are plastic at this time, the heat dissipation speed is much slower than that of direct contact with steel, which delays the thermal cut - off time of the runner as much as possible. Taking the scenario of seven - layer injection molding with a thickness of 25 mm as an example, placing the sixth injection molding runner 22 and the seventh injection molding runner 23 in the middle can extend the available pressure holding window by more than double. The longer pressure holding and feeding time windows enable the entire plastic part injection molding to be within a wider molding window, making the injection molding process stronger and more robust. While the quality of the plastic part is more excellent, it also makes industrial production more stable.

[0170] Figure 21 and Figure 22 shows the extended situation of the gate runner stack design. Figure 21 shows the adaptation to injection molding scenarios with 7 - layer, 13 - layer, 19 - layer, etc. Figure 11 shows the adaptation to injection molding scenarios with 5 - layer, 9 - layer, 13 - layer, etc. for plastic parts.

[0171] In this embodiment, by cleverly adopting the structure of the gate runner stack design, the problem of sufficient filling balance and pressure holding for each layer of odd - layer plastic parts is solved, minimizing the shrinkage of the final product.

[0172] In this embodiment, by integrating the gates of multi - layer injection molding in one place, the subsequent gate removal process is simplified, the gate residual marks are minimized, and the impact on the appearance is minimized.

[0173] In this embodiment, by setting the gates and runners of the last two formed layers in the middle of the existing runner, the formed pressure holding window is widened as much as possible, achieving stable and robust injection molding process, and higher and more stable product quality.

[0174] Example 3:

[0175] Those skilled in the art can understand this embodiment as a more specific illustration of Embodiment 1.

[0176] In this embodiment, by cleverly dividing the injection molding levels of the thick-walled lens and selecting the injection molding sequence that best conforms to the heat transfer law, the goal of low equipment investment and efficient production of high-quality lenses is achieved. In this embodiment, a thick-walled plastic part divided into 2n + 1 layers is injection molded at 2n stations, greatly improving the molding efficiency of the thick-walled plastic part. In the last station, the outermost layer is injection molded on both the front and back sides simultaneously to achieve the purpose of accurately controlling the important surface dimensions, which is particularly suitable for controlling the shapes of the light incident surface and the light exit surface of the thick-walled lens.

[0177] Taking the mold of a thick-walled plastic part divided into 7 layers injection molded at 6 stations in this embodiment as an example, the 6 stations for 7 layers are only an example of the preferred solution and are not limited to 7 layers.

[0178] The fixed mold 1 is the fixed side of the mold for injection molding.

[0179] The movable mold 2 is the movable side of the mold for injection molding. The built-in rotating arm 3 on the movable side is an electric rotating arm built into the movable mold 2. As Figure 4 shown, the arrow indicates the schematic rotation direction of the rotating arm.

[0180] The first-layer structure 4 is the product and the runner injection molded at the first station. The first-layer injection point gate 5 is the point gate of the first-layer structure 4.

[0181] Since the fork needle of the built-in rotating arm 3 on the movable side is cleverly inserted into the runner cavity of the first-layer structure 4, after the first-layer structure 4 is injection molded and cooled, the first-layer structure 4 will be tightly clamped on the fork needle of the built-in rotating arm 3 on the movable side. When the molding machine opens the mold, the built-in rotating arm 3 on the movable side will be ejected from the movable mold and rotate 60 degrees, bringing the first-layer structure 4 above the second station. Then, the ejected built-in rotating arm 3 on the movable side retracts back into the movable mold 2, and at the same time, the first-layer structure 4 is brought into the cavity of the second station. At the second station, the first-layer structure 4 will remain in contact with the steel of the fixed mold 1 after the mold is closed, which can allow the plastic part to dissipate heat continuously and efficiently. The cavity of the second layer is mainly on the movable side of the mold. The second-layer structure 6 is superimposed on the first-layer structure 4 by injection molding. The second-layer injection point gate 7 is where the gate of the second-layer structure 6 is located. In this example, the second-layer injection point gate 7 is on the fixed side, but if the injection molding machine supports it, the second-layer injection point gate 7 may also be set on the movable side.

[0182] After the injection molding and cooling of the second-layer structure 6 are completed, the molding machine opens the mold. The rotatable arm 3 built into the movable side ejects again and rotates 60 degrees backward and returns to the movable mold 2, while bringing the second-layer structure 6 into the third station. At the third station, after the mold is closed, the second-layer structure 6 remains in contact with the steel of the movable mold 2, which allows the second-layer structure 6 to dissipate heat continuously and efficiently. The cavity of the third layer is mainly on the fixed side of the mold. The third-layer structure 8 is stacked on the combination of the first-layer structure 4 and the second-layer structure 6 by injection molding. The third-layer injection point gate 9 is where the gate of the third-layer structure 8 is located. In this example, the third-layer injection point gate 9 is on the fixed side, but if the injection molding machine supports it, the third-layer injection point gate 9 may also be set on the movable side.

[0183] After the injection molding and cooling of the third-layer structure 8 are completed, the molding machine opens the mold. The rotatable arm 3 built into the movable side ejects again and rotates 60 degrees backward and returns to the movable mold 2, while bringing the third-layer structure 8 into the fourth station. At the fourth station, after the mold is closed, the third-layer structure 8 remains in contact with the steel of 1, which allows the third-layer structure 8 to dissipate heat continuously and efficiently. The cavity of the fourth layer is mainly on the movable side of the mold. The fourth-layer structure 10 is stacked on the combination of the first-layer structure 4, the second-layer structure 6, and the third-layer structure 8 by injection molding. The fourth-layer injection point gate 11 is where the gate of the fourth-layer structure 10 is located. In this example, the fourth-layer injection point gate 11 is on the fixed side, but if the injection molding machine supports it, the fourth-layer injection point gate 11 may also be set on the movable side.

[0184] After the injection molding and cooling of the fourth-layer structure 10 are completed, the molding machine opens the mold. The rotatable arm 3 built into the movable side ejects again and rotates 60 degrees backward and returns to the movable mold 2, while bringing the fourth-layer structure 10 into the fifth station. At the fifth station, after the mold is closed, the fourth-layer structure 10 remains in contact with the steel of the movable mold 2, which allows the fourth-layer structure 10 to dissipate heat continuously and efficiently. The cavity of the fifth layer is mainly on the fixed side of the mold. The fifth-layer structure 12 is stacked on the combination of the first-layer structure 4, the second-layer structure 6, the third-layer structure 8, and the fourth-layer structure 10 by injection molding. The fifth-layer injection point gate 13 is where the gate of the fifth-layer structure 12 is located. In this example, the fifth-layer injection point gate 13 is on the fixed side, but if the injection molding machine supports it, the fifth-layer injection point gate 13 may also be set on the movable side.

[0185] After the injection molding and cooling of the fifth-layer structure 12 are completed, the molding machine opens the mold. The rotatable arm 3 built into the movable side ejects again and rotates backward by 60 degrees and returns to the movable mold 2, while bringing the fifth-layer structure 12 into the sixth station. At the sixth station, the fifth-layer structure 12 will remain suspended after the mold is closed because it is necessary to simultaneously injection mold the front and back sides of the outermost layer of the product at this station. The cavity of the sixth layer is mainly on the fixed side of the mold, and the cavity of the seventh layer is mainly on the fixed side of the mold. To prevent the suspended plastic part from deflecting to one side under the pressure of the fluid, the sixth-layer structure 14 and the seventh-layer structure 16 should be stacked on the combined body of the first-layer structure 4, the second-layer structure 6, the third-layer structure 8, the fourth-layer structure 10, and the fifth-layer structure 12 by simultaneous injection molding. The gate of the sixth-layer injection point 15 is where the gate of the sixth-layer structure 14 is located. The gate of the seventh-layer injection point 17 is where the gate of the seventh-layer structure 16 is located. In this example, the gate of the sixth-layer injection point 15 is located on the movable side, and the gate of the seventh-layer injection point 17 is on the fixed side. Such a runner is the simplest and shortest, which has obvious benefits for improving the pressure holding quality of the plastic part. However, if the position of the injection machine barrel does not support it, the gate of the sixth-layer injection point 15 and the gate of the seventh-layer injection point 17 may also be set on the movable side of the molding machine.

[0186] After the injection molding and cooling of the sixth-layer structure 14 and the seventh-layer structure 16 are completed, the molding machine opens the mold, and the rotatable arm 3 built into the movable side ejects again. The completed product is taken out from the 3 by a manipulator, and the runner is removed in the next process to obtain the product. The rotatable arm then continues to rotate and enters the next molding cycle.

[0187] The above molding steps can be extended to the case of molding a thick-walled plastic part with 2n (even) layers at 2n (even) stations. In this embodiment, a thick-walled plastic part divided into 2n + 1 (odd) layers is injection molded at 2n (even) stations, which greatly improves the molding efficiency of the thick-walled plastic part. In the last station, the outermost layer is injection molded simultaneously on the front and back sides to achieve the purpose of accurately controlling the important surface dimensions, which is especially suitable for the shape control of the light incident surface and the light exit surface of a thick-walled lens.

[0188] In this embodiment, through a clever mold design, it is possible to set the shell that has the greatest influence on the product surface in the last station, and it is possible to control the injection molding parameters of the front and back sides of the product by two different screws (in the case of a lens, respectively control the molding parameters of the light incident surface layer and the light exit surface layer). The goal of producing thick-walled parts with low shrinkage and high precision is achieved.

[0189] In this embodiment, by first injection molding the center of the product and then successively stacking and injecting on the front and back sides, the problems of difficult heat dissipation in the core of a single-color injection molded product, long cooling time, and large product shrinkage are solved. The benefit of more efficiently using the mold steel to cool the plastic part is achieved, which greatly reduces the molding cycle of the plastic part, and the benefit of large-scale mass production is very obvious.

[0190] In this embodiment, by arranging the outer shell that has the greatest impact on the product surface in the last station, the processing accuracy requirements for the product cavities in the previous stations are greatly alleviated. If there are scratches or roughness on the cavities in the previous stations, they can be fully melted by the high-temperature resin formed by the next-layer stacking. This greatly reduces the pressure on mold maintenance.

[0191] In this embodiment, by arranging the outer shell that has the greatest impact on the product surface in the last station, only the cavity of the last station needs to be processed with high precision, which greatly reduces the processing cost of the mold and the possible subsequent design change cost.

[0192] In this embodiment, by first injection-molding the center of the product and then layer-by-layer injection-molding on the front and back sides, the problems of short holding pressure window time and large product shrinkage of single-color injection-molded products are solved. It achieves sufficient holding pressure for the plastic parts at each layer and creates a forming condition that allows the next station to compensate for the shrinkage of the plastic parts in the previous station, resulting in a low shrinkage of the final product and being suitable for large-scale production of plastic parts with strict precision requirements (such as optical lenses).

[0193] Example 4:

[0194] Those skilled in the art can understand this embodiment as a more specific description of Embodiment 1.

[0195] As Figures 1 to 26 shown, this embodiment provides a multi-layer injection molding device for thick-walled plastic parts, which is used to injection-mold thick-walled plastic parts divided into 2n + 1 layers, including: a fixed mold 1 and a movable mold 2; 2n fixed stations are arranged along the circumferential direction of the fixed mold 1, and 2n movable stations are arranged along the circumferential direction of the movable mold 2; n is a natural number; the 2n fixed stations and the 2n movable stations form 2n injection molding stations, and a moving component is arranged on the movable mold 2, and the moving component can move the workpiece formed by the previous injection molding station to the next injection molding station; the first injection molding station injection-molds the first-layer structure located in the central area of the thick-walled plastic part; when n is equal to 1, the second injection molding station injection-molds the second-layer structure and the third-layer structure respectively located on both sides of the first-layer structure; when n is greater than 1, the second injection molding station to the (2n - 1)th injection molding station alternately injection-mold the second-layer structure to the (2n - 1)th layer structure on both sides of the first-layer structure in sequence, and the 2nth injection molding station injection-molds the 2nth layer structure and the (2n + 1)th layer structure; for the second-layer structure to the (2n + 1)th layer structure, the cavities for forming the even-layer structures are located on the movable mold 2, and the cavities for forming the odd-layer structures are located on the fixed mold 1.

[0196] The moving component includes: a driving component and a rotatable arm 3 built inside the movable side; the driving component and the rotatable arm 3 built inside the movable side are located within the area surrounded by 2n workable positions, and the driving component drives the rotatable arm 3 built inside the movable side to rotate; one end of the rotatable arm 3 built inside the movable side is connected to the driving component, and the other end of the rotatable arm 3 built inside the movable side can move the workpiece formed by injection molding at the previous injection molding position to the next injection molding position.

[0197] When the rotatable arm 3 built inside the movable side reaches the first fixed position and the first workable position, the other end of the rotatable arm 3 built inside the movable side can be located within the injection cavity formed by the first fixed position and the first workable position; the first layer structure formed by injection molding at the first fixed position and the first workable position can be fixed on the rotatable arm 3 built inside the movable side. A pin is provided at the other end of the rotatable arm 3 built inside the movable side, and the pin is used to fix the first layer structure; the heat of the first layer structure can be transferred out through the rotatable arm 3 built inside the movable side.

[0198] When n is equal to 1, the first fixed position and the first workable position injection mold the first layer structure located in the central area of the thick-walled plastic part; the second fixed position and the second workable position injection mold the second layer structure connected to one side of the first layer structure, and also injection mold the third layer structure connected to the other side of the first layer structure.

[0199] When n is equal to 2, the first fixed position and the first workable position injection mold the first layer structure located in the central area of the thick-walled plastic part; the second fixed position and the second workable position injection mold the second layer structure connected to one side of the first layer structure; the third fixed position and the third workable position injection mold the third layer structure connected to the other side of the first layer structure; the fourth fixed position and the fourth workable position injection mold the fourth layer structure covering the second layer structure, and also injection mold the fifth layer structure covering the third layer structure.

[0200] When n is greater than 2, the first fixed position and the first workable position injection mold the first layer structure located in the central area of the thick-walled plastic part; the second fixed position and the second workable position injection mold the second layer structure connected to one side of the first layer structure; the third fixed position and the third workable position injection mold the third layer structure connected to the other side of the first layer structure; the mth fixed position and the mth workable position injection mold the mth layer structure covering the m - 2th layer structure; the (m + 1)th fixed position and the (m + 1)th workable position injection mold the (m + 1)th layer structure covering the m - 1th layer structure; m is an even number greater than or equal to 4 and less than 2n; the 2nth fixed position and the 2nth workable position injection mold the 2nth layer structure covering the 2n - 2th layer structure, and also injection mold the (2n + 1)th layer structure covering the 2n - 1th layer structure.

[0201] The cavity for forming the second-layer structure is located at the movable station; the cavity for forming the third-layer structure is located at the fixed station; the cavity for forming the m-th layer structure is located at the movable station; the cavity for forming the (m + 1)-th layer structure is located at the fixed station; the cavity for forming the 2n-th layer structure is located at the movable station, and the cavity for forming the (2n + 1)-th layer structure is located at the fixed station.

[0202] The injection runner for injection molding the first-layer structure is the first runner; the injection runner for injection molding the (j + 1)-th layer structure is the (j + 1)-th runner, and the injection runner for injection molding the (j + 2)-th layer structure is the (j + 2)-th runner. The (j + 1)-th runner and the (j + 2)-th runner are respectively arranged on both sides of the first runner. The (j + 1)-th runner is located on the movable side, and the (j + 2)-th runner is located on the fixed side; j is an odd number greater than or equal to 1 and less than 2n + 1; all the even-numbered runners are arranged in one or more layers on the movable side of the first runner. Each layer contains at least two even-numbered runners, and the multiple even-numbered runners in each layer are arranged along the width direction of the first runner. The width of the first runner can cover the widths of the multiple even-numbered runners in each layer; when arranged in multiple layers, the multiple layers of even-numbered runners are arranged in sequence along the movable side direction; all the odd-numbered runners are arranged in one or more layers on the fixed side of the first runner. Each layer contains at least two odd-numbered runners, and the multiple odd-numbered runners in each layer are arranged along the width direction of the first runner. The width of the first runner can cover the widths of the multiple odd-numbered runners in each layer; when arranged in multiple layers, the multiple layers of odd-numbered runners are arranged in sequence along the fixed side direction.

[0203] The width and thickness of the first runner are the largest among all the runners. The multiple runners in each layer are distributed from both sides to the center in sequence along the width direction of the first runner;

[0204] When n is odd, the number of runners arranged in each layer is odd; when n is even and its factors do not include odd numbers greater than 1, then the number of runners arranged in each layer is even; when n is even and its factors include odd numbers greater than 1, then the number of runners arranged in each layer is even or odd.

[0205] In this embodiment, through 2n stations, the injection molding of the thick-walled plastic part in 2n + 1 layers is completed.

[0206] In this embodiment, n is 3. Six fixed stations are arranged along the circumferential direction of the fixed mold 1, and six movable stations are arranged along the circumferential direction of the movable mold 2. m is an even number greater than or equal to 4 and less than 2n, so m is 4.

[0207] When m is 4, the fourth fixed station and the fourth movable station are injection molded to form the fourth-layer structure connected to the second-layer structure; the fifth fixed station and the fifth movable station are injection molded to form the fifth-layer structure connected to the third-layer structure.

[0208] The sixth fixed station and the sixth movable station are injection molded to form a sixth layer structure and a seventh layer structure respectively connected to the fourth layer structure and the fifth layer structure.

[0209] In other embodiments, if n is 4, then m is successively 4 and 6; if n is 5, then m is successively 4, 6, and 8; if n is 6, then m is successively 4, 6, 8, and 10, and so on.

[0210] One fixed station and one corresponding movable station form an injection molding station, and a total of 2n injection molding stations are formed, namely the first injection molding station, the second injection molding station,..., the (2n - 1)th injection molding station, and the 2nth injection molding station.

[0211] In this embodiment, the cavity for forming the first layer structure is located on the fixed station of the first injection molding station, and the cavity for forming the second layer structure is located on the movable station of the second injection molding station; the cavity for forming the third layer structure is located on the fixed station of the third injection molding station; the cavity for forming the fourth layer structure is located on the movable station of the fourth injection molding station; the cavity for forming the fifth layer structure is located on the fixed station of the fifth injection molding station; the cavity for forming the sixth layer structure is located on the movable station of the sixth injection molding station, and the cavity for forming the seventh layer structure is located on the fixed station of the seventh injection molding station.

[0212] The cavity for forming an even - numbered layer structure is on the movable station of its corresponding injection molding station, and the cavity for forming an odd - numbered layer structure is on the fixed station of its corresponding injection molding station.

[0213] In other embodiments, if n is 4, then the cavity for forming the eighth layer structure is located on the movable station of the eighth injection molding station, and the cavity for forming the ninth layer structure is located on the fixed station of the ninth injection molding station; if n is 5, then the cavity for forming the tenth layer structure is located on the movable station of the tenth injection molding station, and the cavity for forming the eleventh layer structure is located on the fixed station of the eleventh injection molding station; if n is 6, then the cavity for forming the twelfth layer structure is located on the movable station of the twelfth injection molding station, and the cavity for forming the thirteenth layer structure is located on the fixed station of the twelfth injection molding station, and so on.

[0214] A plurality of movable - side built - in rotating arms 3 are arranged in sequence along the circumferential direction, and each movable - side built - in rotating arm 3 can successively move to the first injection molding station, the second injection molding station,..., the (2n - 1)th injection molding station, and the 2nth injection molding station.

[0215] In this embodiment, the number of the movable-side built-in rotating arms 3 is set to be the same as the number of the injection molding stations. During injection molding, the movable-side built-in rotating arms 3 correspond to the injection molding stations one by one. A plurality of movable-side built-in rotating arms 3 are radially arranged on the driving component, and the driving component drives the plurality of movable-side built-in rotating arms 3 to rotate simultaneously. In this embodiment, the number of the movable-side built-in rotating arms 3 is six.

[0216] During injection molding, a plurality of thick-walled plastic parts are injection molded simultaneously:

[0217] After the first movable-side built-in rotating arm 3 completes the injection molding of the first-layer structure at the first injection molding station, it drives the first-layer structure to move to the second injection molding station. At the same time, the second movable-side built-in rotating arm 3 moves to the first injection molding station to perform the injection molding of the first-layer structure;

[0218] After the first movable-side built-in rotating arm 3 completes the injection molding of the second-layer structure at the second injection molding station, it drives the combination of the first-layer structure and the second-layer structure to move to the third injection molding station to perform the injection molding of the third-layer structure. At the same time, the second movable-side built-in rotating arm 3 drives the first-layer structure to move to the second injection molding station to perform the injection molding of the second-layer structure, and the third movable-side built-in rotating arm 3 moves to the first injection molding station to perform the injection molding of the first-layer structure;

[0219] After the first movable-side built-in rotating arm 3 completes the injection molding of the third-layer structure at the third injection molding station, it drives the combination of the first-layer structure, the second-layer structure, and the third-layer structure to move to the fourth injection molding station to perform the injection molding of the fourth-layer structure. At the same time, the second movable-side built-in rotating arm 3 drives the combination of the first-layer structure and the second-layer structure to move to the third injection molding station to perform the injection molding of the third-layer structure, the third movable-side built-in rotating arm 3 drives the first-layer structure to move to the second injection molding station to perform the injection molding of the second-layer structure, and the fourth movable-side built-in rotating arm 3 moves to the first injection molding station to perform the injection molding of the first-layer structure;

[0220] And so on.

[0221] In this embodiment, a plastic is injected into the mold clamping of the fixed station and the movable station through an injection structure, and a runner for injecting the plastic is arranged in the injection structure.

[0222] The injection runner for injection molding the first-layer structure is the first runner. The first runner is located in the middle area of the connecting body structure in the thickness direction. The width direction and the length direction of the first runner are the same as the length direction of the connecting body structure, and the width of the first runner is the same as the width of the connecting body structure.

[0223] In this embodiment, j is an odd number greater than or equal to 1 and less than 2n + 1. When n is 3, there are 7 layers of structures. Therefore, j is 1, 3, and 5 in sequence.

[0224] When j is 1, the injection runner for injection molding of the second-layer structure is the second runner, and the injection runner for injection molding of the third-layer structure is the third runner. The third runner and the second runner are respectively arranged on both sides of the first runner. The second runner is located on the movable side, and the third runner is located on the fixed side.

[0225] When j is 3, the injection runner for injection molding of the fourth-layer structure is the fourth runner, and the injection runner for injection molding of the fifth-layer structure is the fifth runner. The fifth runner and the fourth runner are respectively arranged on both sides of the first runner. The fourth runner is located on the movable side, and the fifth runner is located on the fixed side.

[0226] When j is 5, the injection runner for injection molding of the sixth-layer structure is the sixth runner, and the injection runner for injection molding of the seventh-layer structure is the seventh runner. The seventh runner and the sixth runner are respectively arranged on both sides of the first runner. The sixth runner is located on the movable side, and the seventh runner is located on the fixed side.

[0227] The injection structure is formed by the clamping of the movable injection structure and the fixed injection structure. The movable injection structure is connected to the movable working position, and the fixed injection structure is connected to the fixed working position. The even-numbered runners are all arranged on the movable injection structure, and the odd-numbered runners are all arranged on the fixed injection structure.

[0228] All the even-numbered runners are arranged in one layer or multiple layers. For multiple runners in a single layer, they are distributed from both sides to the middle in the width direction in sequence. For multiple layers, they are distributed from the middle to one side in the thickness direction in sequence.

[0229] All the odd-numbered runners are arranged in one layer or multiple layers. For multiple runners in a single layer, they are distributed from both sides to the middle in the width direction in sequence. For multiple layers, they are distributed from the middle to one side in the thickness direction in sequence.

[0230] In this embodiment, the second runner, the fourth runner, and the sixth runner are arranged in one layer, and the third runner, the fifth runner, and the seventh runner are arranged in one layer.

[0231] As Figure 20 shown, the second runner is arranged at the leftmost side of the area on one side of the first runner, the third runner is correspondingly arranged at the leftmost side of the area on the other side of the first runner, the fourth runner is arranged at the rightmost side of the area on one side of the first runner, the fifth runner is correspondingly arranged at the rightmost side of the area on the other side of the first runner, the sixth runner is arranged between the second runner and the fourth runner, and the seventh runner is correspondingly arranged between the third runner and the fifth runner.

[0232] The relationship between the number of layers of the thick-walled plastic part and n is that the number of layers is 2n + 1, and the number of runners is the same as the number of layers.

[0233] When n is odd, the number of flow channels arranged in a single layer on one side of the first flow channel is odd. For example, when n = 3, 3 flow channels are arranged in a single layer; when n = 5, 5 flow channels are arranged in a single layer; when n = 7, 7 flow channels are arranged in a single layer, and so on.

[0234] When n is even and its factors do not include odd numbers greater than 1, the number of flow channels arranged in each layer is even. For example, when n = 2, 2 flow channels are arranged in a single layer; when n = 4, 2 or 4 flow channels are arranged in a single layer; when n = 8, 2 or 4 or 8 flow channels are arranged in a single layer, and so on.

[0235] When n is even and its factors include odd numbers greater than 1, the number of flow channels arranged in each layer is even or odd. For example, when n = 6, 2 or 3 flow channels are arranged in a single layer; when n = 10, 2 or 5 flow channels are arranged in a single layer, and so on.

[0236] The present invention divides a thick-walled plastic part formed by injection molding with an even number of injection molding stations into an odd number of layers, greatly improving the forming efficiency of the thick-walled plastic part. In the last station, the outermost layer is injection molded simultaneously on the front and back sides to achieve the purpose of accurately controlling the important surface dimensions.

[0237] In the description of the present application, it should be understood that the orientation or positional relationship indicated by the terms "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", etc. is based on the orientation or positional relationship shown in the drawings. It is only for the convenience of describing the present application and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be construed as a limitation to the present application.

[0238] The specific embodiments of the present invention have been described above. It should be understood that the present invention is not limited to the above specific embodiments, and those skilled in the art can make various changes or modifications within the scope of the claims, which do not affect the essence of the present invention. Without conflict, the embodiments of the present application and the features in the embodiments can be combined arbitrarily with each other.

Claims

1. A multi-layer injection molding method for thick-walled plastic parts, characterized in that, It includes the following steps: Layer structure division step: Divide the thick-walled plastic part into 2n + 1 layer structures, namely the first layer structure to the (2n + 1)-th layer structure. The first layer structure is located in the central area of the thick-walled plastic part, and the second layer structure to the (2n + 1)-th layer structure are evenly distributed on both sides of the first layer structure; n is a natural number; Multi-layer injection molding step: Set 2n injection molding stations, and sequentially inject through the 2n injection molding stations to form the first layer structure to the (2n + 1)-th layer structure of the thick-walled plastic part; Inject through the first injection molding station to form the first layer structure; When n equals 1, inject through the second injection molding station to form the second layer structure and the third layer structure respectively located on both sides of the first layer structure; When n is greater than 1, when injecting through the second injection molding station to the (2n - 1)-th injection molding station, sequentially and alternately form the second layer structure to the (2n - 1)-th layer structure on both sides of the first layer structure; The previous injection molding station injects to form a layer structure on one side of the first layer structure, and the next injection molding station immediately injects to form another layer structure at the relative position on the other side of the first layer structure; Inject through the 2n-th injection molding station to form the 2n-th layer structure and the (2n + 1)-th layer structure. The 2n-th layer structure and the (2n + 1)-th layer structure form the surface layer structure of the thick-walled plastic part; For the second layer structure to the (2n + 1)-th layer structure, the even-numbered layer structures and the odd-numbered layer structures are sequentially and alternately formed on both sides of the first layer structure; The next even-numbered layer structure covers the previous even-numbered layer structure, and the next odd-numbered layer structure covers the previous odd-numbered layer structure; For the second layer structure to the (2n + 1)-th layer structure, the even-numbered layer structures are formed on the movable side of the injection molding station, and the odd-numbered layer structures are formed on the fixed side of the injection molding station; The multi-layer injection molding step specifically includes the following steps: Step S1: Set a moving component and 2n injection molding stations, arrange the 2n injection molding stations so that the moving component can sequentially reach the first injection molding station to the 2n-th injection molding station; Step S2: Make the moving component reach the first injection molding station, close the fixed station and the movable station of the first injection molding station, and inject to form the first layer structure; Wherein, a connecting structure on the moving component can be located in the cavity of the first injection molding station, the first layer structure can be fixed on the connecting structure, and the moving component can drive the first layer structure to move; Step S3: Open the fixed station and the movable station of the first injection molding station, eject the first layer structure from the movable station of the first injection molding station through the moving component, and then move the first layer structure to the movable station of the second injection molding station through the moving component; Step S4: Close the fixed station and the movable station of the second injection molding station, and inject on one side of the first layer structure to form the second layer structure connected to the first layer structure; Step S5: Open the mold of the fixed station and the movable station of the second injection molding station. Use the moving component to eject the combination of the first layer structure and the second layer structure from the movable station of the second injection molding station, and then use the moving component to move the combination of the first layer structure and the second layer structure to the movable station of the third injection molding station; Step S6: Close the mold of the fixed station and the movable station of the third injection molding station. Inject and form the third layer structure connected to the first layer structure on the other side of the first layer structure; Step S7: Open the mold of the fixed station and the movable station of the third injection molding station. Use the moving component to eject the combination of the first layer structure, the second layer structure, and the third layer structure from the movable station of the third injection molding station, and then use the moving component to move the combination of the first layer structure, the second layer structure, and the third layer structure to the movable station of the fourth injection molding station; Among them, if n is greater than 2, then step S8 and step S9 are performed in sequence. If n is equal to 2, then directly perform step S9; Step S8: Close the mold of the fixed station and the movable station of the a-th injection molding station. Inject and form the a-th layer structure connected to the (a - 2)-th layer structure on one side of the first layer structure; Open the mold of the fixed station and the movable station of the a-th injection molding station. Use the moving component to eject the combination formed by injection molding at the a-th injection molding station from the movable station of the a-th injection molding station, and then use the moving component to move the combination formed by injection molding at the a-th injection molding station to the movable station of the (a + 1)-th injection molding station; Close the mold of the fixed station and the movable station of the (a + 1)-th injection molding station. Inject and form the (a + 1)-th layer structure connected to the (a - 1)-th layer structure on the other side of the first layer structure; Open the mold of the fixed station and the movable station of the (a + 1)-th injection molding station. Use the moving component to eject the combination formed by injection molding at the (a + 1)-th injection molding station from the movable station of the (a + 1)-th injection molding station, and then use the moving component to move the combination formed by injection molding at the (a + 1)-th injection molding station to the movable station of the (a + 2)-th injection molding station; a is an even number greater than or equal to 4 and less than 2n. The fourth layer structure to the (2n - 1)-th layer structure are formed in sequence through the above steps; Step S9: Close the mold of the fixed station and the movable station of the 2n-th injection molding station. Inject and form the 2n-th layer structure connected to the (2n - 2)-th layer structure on one side of the first layer structure, and inject and form the (2n + 1)-th layer structure connected to the (2n - 1)-th layer structure on the other side of the first layer structure; Step 10: Open the mold of the fixed station and the movable station of the 2n-th injection molding station, and take out the formed thick-walled plastic part; In the above step S2, when injecting the first layer structure, the cavity for injecting the first layer structure, a part is located on the fixed station, and the other part is located on the movable station. Both sides of the first layer structure can be in contact with the fixed station and the movable station respectively for heat conduction; In step S4, when injecting the second layer structure, the cavity for injecting the second layer structure is located at the workable position, and the other side of the first layer structure can contact and conduct heat with the fixed position; In step S6, when injecting the third layer structure, the cavity for injecting the third layer structure is located at the fixed position, and the second layer structure can contact and conduct heat with the workable position; In step S8, when injecting the a-th layer structure, the cavity for injecting the a-th layer structure is located at the workable position, and the (a - 1)-th layer structure can contact and conduct heat with the fixed position; When injecting the (a + 1)-th layer structure, the cavity for injecting the (a + 1)-th layer structure is located at the fixed position, and the a-th layer structure can contact and conduct heat with the workable position; In step S9, when injecting the 2n-th layer structure and the (2n + 1)-th layer structure, the cavity for injecting the 2n-th layer structure is located at the workable position, and the cavity for injecting the (2n + 1)-th layer structure is located at the fixed position.

2. The multi-layer injection molding method for thick-walled plastic parts according to claim 1, characterized in that The moving component is connected to the first layer structure through a rotatable arm built inside the movable side, and the rotatable arm built inside the movable side can move the workpiece formed by injection molding at the previous injection molding position to the next injection molding position; During the entire injection molding process of the thick-walled plastic part, the rotatable arm built inside the movable side can always conduct out the heat accumulated on the first layer structure.

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