Plastic box demolding method

Abstract

The invention relates to the technical field of plastic product production, and discloses a plastic box demolding method which comprises the following steps: pressing an upper mold base, a middle mold base and a lower mold base together, and injecting a plastic glue solution into a forming mold cavity; after the plastic box body in the forming die cavity is formed, the core-pulling movable plate is moved upwards to a set position, so that the plastic box body has post-shrinkage time to be cooled and shaped; the middle mold base and the lower mold base are separated from the mold, and the plastic box body is separated from the inner mold cavity through the core-pulling insert; according to the structure, the core-pulling insert is firstly pulled out, gaps are reserved in four sides, and then the mold is opened after the product is shrunk, so that a four-side slide demolding structure is not required to be used, the appearance surface of a plastic box type product is prevented from being clamped by lines, the product is more attractive, meanwhile, the contact between the slide and the grain surface of the product is avoided, and the production efficiency is improved. The grain surface of the product can be prevented from being damaged; the problem that a plastic box body product is prone to wire clamping in the demolding process is solved.

Description

Technical Field

[0001] The invention relates to the technical field of plastic product production, and in particular to a plastic box body demoulding method. Background Art

[0002] In the production of plastic box products, when the four sides of the plastic box product are straight and textured, the conventional demoulding method is to adopt a four-sided demoulding structure.

[0003] However, in this four-sided slide demolding structure, the molding cavity is formed by four mold bodies, but the gaps between adjacent mold bodies will produce clamping lines on the appearance surface of the plastic box product, greatly affecting the aesthetics of the plastic box product. The slide is easy to damage the surface of the plastic box product during the demolding process, reducing the quality of the plastic box product. Summary of the invention

[0004] The object of the present invention is to provide a plastic box body demoulding method, aiming to solve the problem in the prior art that the plastic box body product is prone to line clamping during the demoulding process.

[0005] The present invention is implemented in this way: the plastic box body demoulding method comprises the following steps:

[0006] 1) Press the upper die base, the middle die base and the lower die base together, wherein the lower die base has an inner die cavity with a top opening, and the middle die base is sealed on the top opening of the inner die cavity, and one end of the core-pulling insert passes through the middle die base and is inserted into the inner die cavity, and the other end of the core-pulling insert is connected with a core-pulling movable plate, and the core-pulling movable plate is located between the upper die base and the middle die base;

[0007] 2) The outer periphery of the core-pulling insert, the inner side wall of the inner mold cavity and the middle mold base enclose a molding cavity for injection molding of the plastic box body, and plastic glue is injected into the molding cavity;

[0008] 3) After the plastic box body in the molding cavity is formed, the upper mold base and the core-pulling movable plate are separated from the mold, and the core-pulling movable plate is moved upward to a set position. The core-pulling movable plate drives the core-pulling insert to slowly be pulled out of the plastic box body to the set position and stay there for a set time, so that the plastic box body has a post-shrinkage time to cool and finalize;

[0009] 4) Separate the middle mold base from the lower mold base, and separate the plastic box body from the inner mold cavity through the core-pulling insert.

[0010] Furthermore, in the step 1), the core-pulling insert has an injection channel for injecting plastic liquid, the injection channel is arranged to penetrate along the axial direction of the core-pulling insert, and the injection channel is connected to the molding cavity.

[0011] Furthermore, in step 2), a nozzle piece is provided on the upper mold base, the bottom of which penetrates the upper mold base from top to bottom and abuts against the top of the core-pulling movable plate, and the nozzle piece is connected to the molding cavity through an injection channel.

[0012] Furthermore, in the step 3), the core-pulling movable plate and the middle mold base are matched with each other through a stroke adjustment mechanism, and the stroke adjustment mechanism is arranged on the outer sides of the core-pulling movable plate and the middle mold base.

[0013] Furthermore, the stroke adjustment mechanism includes a fixed meson, a movable meson and a stroke adjustment plate, the stroke adjustment plate is provided with a hollow stroke groove, one end of the fixed meson passes through the stroke groove and is connected to the middle mold base, and the other end of the fixed meson is exposed outside the stroke groove;

[0014] One end of the mobile meson passes through the stroke groove and is connected to the core-pulling movable plate, and the other end of the mobile meson is engaged with the stroke adjustment plate. The mobile meson is located above the fixed meson.

[0015] Furthermore, in the step 1), the core-pulling insert comprises a connecting piece and a core-inserting piece, one end of the core-inserting piece is connected to the connecting piece, the other end of the core-inserting piece passes through the middle mold base and is inserted into the inner mold cavity, and the connecting piece is installed in the core-pulling movable plate;

[0016] A plurality of inner positioning members are arranged on the outer periphery of the core insert, and the inner positioning members are located in the inner mold cavity. The outer periphery of the core insert, the outer side walls of the inner positioning members, the inner side walls of the inner mold cavity and the middle mold base enclose the molding cavity.

[0017] Furthermore, a plurality of the inner positioning members are arranged around and spaced along the outer circumference of the core insert, the core insert is slidably matched with the inner positioning members, and the inner positioning members are extended and arranged along the length direction of the core insert;

[0018] The core insert is inwardly recessed to form a sliding groove, the sliding groove is arranged in an inclined manner, and the core insert is slidably matched with the inner position piece through the sliding groove.

[0019] Furthermore, an inserting strip is convexly provided on the sliding groove, and a slot corresponding to the inserting strip is formed inwardly concave on the inner position member, and the sliding groove and the inner position member are slidably matched through the inserting strip and the slot.

[0020] Furthermore, an inlay is protruding upward on the top of the inner position member, the inlay is exposed outside the lower mold base, and the inlay is embedded on the top of the middle mold base.

[0021] Furthermore, in the step 4), the middle die base and the lower die base are matched with each other through a limiting mechanism, and the limiting mechanism is arranged on the outer sides of the middle die base and the lower die base;

[0022] The limiting mechanism comprises an upper meson, a lower meson and a pull plate, wherein upper and lower sides of the pull plate are respectively provided with an upper slide groove and a lower slide groove which are arranged in a hollow manner, wherein the upper slide groove and the lower slide groove are arranged in a longitudinal direction with a relative spacing therebetween, wherein one end of the upper meson passes through the upper slide groove and is connected to the middle mold seat, and the other end of the upper meson is exposed outside the upper slide groove;

[0023] One end of the lower meson passes through the lower slide groove and is connected to the lower mold base, the other end of the lower meson is exposed outside the lower slide groove, and the upper meson is located above the lower meson.

[0024] Compared with the prior art, the demoulding method for a plastic box body provided by the present invention adopts a structure in which the core insert is first drawn out, gaps are left on the four sides, and then the mold is opened after the product is shrunk for production. This method does not need to use a four-sided slide demoulding structure, thereby avoiding the appearance of clamping lines on the appearance surface of plastic box products, making the product more beautiful, and at the same time avoiding the contact between the slide and the product surface, which can ensure that the product surface is not damaged; improves the competitiveness of the product in the market, simplifies the mold structure, and saves mold costs; solves the problem of clamping lines that are prone to occur during the demoulding process of plastic box body products. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 It is a schematic diagram of the process of the plastic box demoulding method provided by the present invention;

[0026] Figure 2 It is a three-dimensional schematic diagram of the upper die base, the middle die base and the lower die base provided by the present invention;

[0027] Figure 3 It is a schematic diagram of the cross-section structure of the upper die base, the middle die base and the lower die base provided by the present invention;

[0028] Figure 4 It is a three-dimensional schematic diagram of the core-pulling insert, the inner position piece and the lower die base provided by the present invention;

[0029] Figure 5 It is a three-dimensional schematic diagram of the lower die base provided by the present invention;

[0030] Figure 6 It is a three-dimensional schematic diagram of the core-pulling insert and the inner position piece provided by the present invention.

[0031] In the figure: an upper mold base 10, a middle mold base 20, a lower mold base 30, a core-pulling movable plate 40, a molding cavity 50, a nozzle piece 60, a stroke adjustment mechanism 70, a limiting mechanism 80, an inner mold cavity 31, a core-pulling insert 41, an injection runner 42, a connecting piece 411, a core insert 412, an inner positioning piece 413, a sliding groove 414, an insert strip 415, a slot 416, an inlay piece 417, an elastic block 418, a blocking block 419, a supporting block 420, a fixed meson 71, a movable meson 72, a stroke adjustment plate 73, a stroke groove 74, an upper meson 81, a lower meson 82, a pull plate 83, an upper slide groove 84, and a lower slide groove 85. DETAILED DESCRIPTION

[0032] In order to make the purpose, technical solution and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not intended to limit the present invention.

[0033] The implementation of the present invention is described in detail below in conjunction with specific embodiments.

[0034] The same or similar numbers in the drawings of this embodiment correspond to the same or similar parts; in the description of the present invention, it should be understood that if the terms "upper", "lower", "left", "right" and the like indicate directions or positional relationships based on the directions or positional relationships shown in the drawings, it is only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific direction, be constructed and operated in a specific direction. Therefore, the terms describing the positional relationship in the drawings are only used for illustrative purposes and cannot be understood as limitations on the present invention. For ordinary technicians in this field, the specific meanings of the above terms can be understood according to specific circumstances.

[0035] Reference Figure 1-6 The figure shows a preferred embodiment of the present invention.

[0036] The plastic box demoulding method comprises the following steps:

[0037] 1) Press the upper die base 10, the middle die base 20 and the lower die base 30 together, the lower die base 30 has an inner die cavity 31 with a top opening, the middle die base 20 is sealed on the top opening of the inner die cavity 31, one end of the core-pulling insert 41 passes through the middle die base 20 and is inserted into the inner die cavity 31, the other end of the core-pulling insert 41 is connected to a core-pulling movable plate 40, and the core-pulling movable plate 40 is located between the upper die base 10 and the middle die base 20;

[0038] 2) The outer periphery of the core-pulling insert 41, the inner side wall of the inner mold cavity 31 and the middle mold base 20 enclose a molding cavity 50 for injection molding of the plastic box body, and plastic glue is injected into the molding cavity 50;

[0039] 3) After the plastic box body in the molding cavity 50 is formed, the upper mold base 10 and the core-pulling movable plate 40 are separated from the mold, and the core-pulling movable plate 40 is moved upward to a set position. At the same time, the core-pulling movable plate 40 drives the core-pulling insert 41 to slowly withdraw from the plastic box body to a set position and stay there for a set time, so that the plastic box body has a post-shrinkage time to cool and finalize;

[0040] 4) Separate the middle mold base 20 from the lower mold base 30 and remove the plastic box from the inner mold cavity 31 through the core-pulling insert 41 .

[0041] The above-mentioned plastic box demoulding method adopts a structure in which the core-pulling insert 41 is first pulled out, leaving gaps on the four sides, and then the product is shrinked and then the mold is opened for production. This method does not need to use a four-sided slide demoulding structure, thereby avoiding the appearance of clamping lines on the appearance of plastic box products, making the product more beautiful, and at the same time avoiding the contact between the slide and the product surface, which can ensure that the product surface is not damaged; improves the competitiveness of the product in the market, simplifies the mold structure, saves mold costs, and solves the problem of clamping lines that are prone to appearing on plastic box products during demoulding.

[0042] The above setting time can be selected to be about 10 seconds, and the above setting position can be determined according to the size of the actual plastic box structure.

[0043] In this embodiment, in step 1), the core-pulling insert 41 has an injection channel 42 for injecting plastic liquid, and the injection channel 42 is arranged along the axial direction of the core-pulling insert 41, and the injection channel 42 is connected to the molding cavity 50. In this way, the injection molding machine nozzle can inject the injection plastic liquid into the molding cavity 50 through the injection channel 42, so that the nozzle is hidden in the box cavity of the plastic box body.

[0044] In this embodiment, in step 2), a nozzle piece 60 is provided on the upper mold base 10, the bottom of the nozzle piece 60 penetrates the upper mold base 10 from top to bottom, and abuts against the top of the core-pulling movable plate 40, and the nozzle piece 60 is connected to the molding cavity 50 through the injection flow channel 42. In this way, the injection molding machine gun nozzle can inject the injection glue from the outside into the injection flow channel 42 through the nozzle piece 60.

[0045] In this embodiment, in step 3), the core-pulling movable plate 40 and the middle mold base 20 are matched by a stroke adjustment mechanism 70, and the stroke adjustment mechanism 70 is arranged on the outer sides of the core-pulling movable plate 40 and the middle mold base 20. In this way, the distance that the core-pulling movable plate 40 drives the core-pulling insert 41 to separate from the plastic box body can be controlled by the stroke adjustment mechanism 70, so that the plastic box body has time to shrink.

[0046] The core-pulling insert 41 is fixed on the core-pulling movable plate 40. When opening the mold, the upper mold base 10 is opened first, and then the core-pulling movable plate 40 is opened. After the two actions are completed, the sprue and the injection molding machine nozzle have been separated and ejected from the core-pulling insert 41. Next, the core-pulling movable plate 40 and the middle mold base 20 are opened. Because the core-pulling insert 41 is fixed on the core-pulling movable plate 40, the core-pulling insert 41 slowly escapes from the box cavity of the plastic box body. The escape distance can be controlled by the stroke adjustment mechanism 70. After the core-pulling movable plate 40 and the middle mold base 20 are opened, the injection molding machine needs to be controlled to stay for about 10 seconds to allow the plastic box body product to have post-shrinkage time. Next, the middle mold base 20 and the lower mold base 30 are opened, and the core-pulling insert 41 brings the plastic box body product out of the lower mold base 30. In this process, because the plastic box body product has post-shrinkage, the texture surface will not be damaged in the process of being brought out from the lower mold base 30.

[0047] It is recommended to leave about 10MM of the core-pulling insert 41 in the box cavity of the plastic box body. If too much is left, the plastic box body will be difficult to remove, and if too little is left, the plastic box body will not be tightly packed enough to be taken out of the lower mold base 30. The specific stroke can be adjusted by the stroke adjustment mechanism 70 according to actual conditions; the shrinkage time after the injection molding machine stops needs to be increased or decreased accordingly based on the product's characteristic shape and size and the sample's appearance, and there is no fixed value.

[0048] In this embodiment, the stroke adjustment mechanism 70 includes a fixed meson 71, a movable meson 72 and a stroke adjustment plate 73. The stroke adjustment plate 73 is provided with a hollow stroke groove 74. One end of the fixed meson 71 passes through the stroke groove 74 and is connected to the middle mold base 20, and the other end of the fixed meson 71 is exposed outside the stroke groove 74.

[0049] One end of the moving meson 72 passes through the stroke groove 74 and is connected to the core-pulling movable plate 40 , and the other end of the moving meson 72 is engaged with the stroke adjustment plate 73 . The moving meson 72 is located above the fixed meson 71 .

[0050] The stroke adjustment mechanism 70 is positioned by using the fixed meson 71 and the middle mold base 20, so that when the core-pulling movable plate 40 drives the movable meson 72 to rise to the above-mentioned set position, the stroke adjustment plate 73 abuts against the fixed meson 71 through the stroke groove 74 to limit the core-pulling movable plate 40 from continuing to move upward.

[0051] In this embodiment, in step 1), the core-pulling insert 41 includes a connecting piece 411 and a core insert 412, one end of the core insert 412 is connected to the connecting piece 411, the other end of the core insert 412 passes through the middle mold base 20 and is inserted into the inner mold cavity 31, and the connecting piece 411 is installed in the core-pulling movable plate 40; in this way, the core-pulling insert 41 is inserted into the inner mold cavity 31 through the core insert 412, and the core insert 412 extends outside the inner mold cavity 31 through the connecting piece 411, and the core insert 412 can be pulled out of the inner mold cavity 31 through the connecting piece 411;

[0052] A plurality of inner positioning members 413 are arranged on the outer periphery of the core insert 412 , and the inner positioning members 413 are located in the inner mold cavity 31 . The outer periphery of the core insert 412 , the outer side walls of the inner positioning members 413 , the inner side walls of the inner mold cavity 31 and the middle mold base 20 enclose a molding cavity 50 .

[0053] After the plastic box product is formed in the molding cavity 50 , when the core insert 412 is pulled out of the plastic box, the core insert 412 is displaced inwardly by the plurality of inner positioning members 413 , so that the plastic box product has space to shrink and the surface of the plastic box product is not damaged.

[0054] In this embodiment, a plurality of inner positioning members 413 are arranged around the outer circumference of the core insert 412 at intervals, the core insert 412 and the inner positioning members 413 are slidably matched, and the inner positioning members 413 are extended along the length direction of the core insert 412;

[0055] The core insert 412 is recessed inward to form a sliding groove 414, which is arranged obliquely, and the core insert 412 and the inner position member 413 are slidably matched through the sliding groove 414. In this way, when the core insert 412 is pulled out of the plastic box body, the multiple inner position members 413 can automatically move inward in cooperation with the sliding groove 414, so that the plastic box body product has space to shrink, and the texture of the plastic box body product is not damaged.

[0056] In this embodiment, an inserting strip 415 is protruded from the sliding groove 414 , and a slot 416 corresponding to the inserting strip 415 is formed inwardly on the inner position member 413 , and the sliding groove 414 and the inner position member 413 are slidably engaged with each other through the inserting strip 415 and the slot 416 .

[0057] The sliding groove 414 cooperates with the slot 416 on the inner positioning member 413 by using the insert strip 415, so that when the core insert 412 is pulled out of the plastic box body, the multiple inner positioning members 413 will not swing randomly, and the core insert 412 can be pulled out smoothly without damaging the plastic box body.

[0058] In this embodiment, the top of the inner positioning member 413 is provided with an inlay 417 protruding upward, the inlay 417 is exposed outside the lower mold base 30, and the inlay 417 is embedded on the top of the middle mold base 20. In this way, the inner positioning member 413 can be driven by the inlay 417 to be pulled out of the inner mold cavity 31, and the plastic box body can also be taken out of the inner mold cavity 31, completing the demoulding work of the product.

[0059] In this embodiment, in step 4), the middle mold base 20 and the lower mold base 30 are matched with each other through a limiting mechanism 80, and the limiting mechanism 80 is arranged on the outer sides of the middle mold base 20 and the lower mold base 30;

[0060] The limiting mechanism 80 includes an upper meson 81, a lower meson 82 and a pull plate 83. The upper and lower sides of the pull plate 83 are respectively provided with an upper slide groove 84 and a lower slide groove 85 which are arranged in a hollow manner. The upper slide groove 84 and the lower slide groove 85 are arranged with a longitudinal relative spacing. One end of the upper meson 81 passes through the upper slide groove 84 and is connected to the middle mold base 20, and the other end of the upper meson 81 is exposed outside the upper slide groove 84.

[0061] One end of the lower meson 82 passes through the lower groove 85 and is connected to the lower mold base 30 , and the other end of the lower meson 82 is exposed outside the lower groove 85 . The upper meson 81 is located above the lower meson 82 .

[0062] The limit mechanism 80 is used to limit the mold opening distance between the middle mold base 20 and the lower mold base 30, so as to prevent the cumbersome assembly process between the middle mold base 20 and the lower mold base 30 after the mold opening, and also improve the work efficiency;

[0063] The limit mechanism 80 is connected to the middle mold base 20 through the upper meson 81 and the lower meson 82 is connected to the lower mold base 30, and then the length between the upper slide groove 84 and the lower slide groove 85 of the pull plate 83 is used to determine the mold opening distance between the middle mold base 20 and the lower mold base 30. In other words, the mold opening distance between the middle mold base 20 and the lower mold base 30 can be controlled by the pull plate 83.

[0064] In this embodiment, an elastic block 418 with elastic deformation is protruding outward from the insert strip 415, and the elastic block 418 is arranged relatively spaced apart from the inner position member 413. The elastic block 418 is located in the slot 416, and an elastic blocking block 419 is protruding from the inner side wall of the slot 416. The blocking block 419 and the elastic block 418 are arranged relatively spaced apart in the longitudinal direction.

[0065] When the core-pulling movable plate 40 moves upward to the set position, the elastic block 418 and the blocking block 419 are in sliding contact with each other.

[0066] When the core-pulling movable plate 40 is pulled out of the plastic box body, the insertion strip 415 drives the elastic block 418 to move upward. During the movement, the elastic block 418 collides with the blocking block 419 in the slot 416 to loosen, so that the inner position member 413 is loosened and arranged tilted, leaving gaps on the four sides of the inner side of the plastic box body, so that the plastic box body has space for post-contraction cooling; the blocking block 419 will not hinder the continued upward movement of the elastic block 418.

[0067] In this embodiment, a support block 420 is protruding from the inner wall of the slot 416. The support block 420 is located above the blocking block 419. The support block 420 and the elastic block 418 are arranged with a longitudinal relative spacing.

[0068] When the core-pulling movable plate 40 moves upward to a set position, the elastic block 418 and the supporting block 420 are movably abutted against each other.

[0069] When the elastic block 418 moves upward, the elastic block 418 pushes the support block 420 to move upward, so that the support block 420 drives the inner positioning member 413 to separate from the molding cavity 50, and the inner positioning member 413 drives the plastic box body to be demolded.

[0070] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions and improvements made within the spirit and principles of the present invention should be included in the protection scope of the present invention.

Claims

1. A method for demoulding a plastic box, characterized in that: The following steps are involved: 1) Press the upper die base, the middle die base and the lower die base together, wherein the lower die base has an inner die cavity with a top opening, and the middle die base is sealed on the top opening of the inner die cavity, and one end of the core-pulling insert passes through the middle die base and is inserted into the inner die cavity, and the other end of the core-pulling insert is connected with a core-pulling movable plate, and the core-pulling movable plate is located between the upper die base and the middle die base; 2) The outer periphery of the core-pulling insert, the inner side wall of the inner mold cavity and the middle mold base enclose a molding cavity for injection molding of the plastic box body, and plastic glue is injected into the molding cavity; 3) After the plastic box body in the molding cavity is formed, the upper mold base and the core-pulling movable plate are separated from the mold, and the core-pulling movable plate is moved upward to a set position. The core-pulling movable plate drives the core-pulling insert to slowly be pulled out of the plastic box body to the set position and stay there for a set time, so that the plastic box body has a post-shrinkage time to cool and finalize; 4) Separate the middle mold base from the lower mold base, and separate the plastic box body from the inner mold cavity through the core-pulling insert.

2. The method for demoulding a plastic box as claimed in claim 1, characterized in that: In the step 1), the core-pulling insert has an injection channel for injecting glue, the injection channel is arranged to penetrate along the axial direction of the core-pulling insert, and the injection channel is connected to the molding cavity.

3. The method for demoulding a plastic box as claimed in claim 2, characterized in that: In the step 2), a nozzle piece is provided on the upper mold base, the bottom of which penetrates the upper mold base from top to bottom and abuts against the top of the core-pulling movable plate, and the nozzle piece is connected to the molding cavity through an injection channel.

4. The method for demoulding a plastic box as claimed in claim 1, characterized in that: In the step 3), the core-pulling movable plate and the middle mold base are matched with each other through a stroke adjustment mechanism, and the stroke adjustment mechanism is arranged on the outer sides of the core-pulling movable plate and the middle mold base.

5. The method for demoulding a plastic box as claimed in claim 4, characterized in that: The stroke adjustment mechanism includes a fixed meson, a movable meson and a stroke adjustment plate, the stroke adjustment plate is provided with a hollow stroke groove, one end of the fixed meson passes through the stroke groove and is connected to the middle mold base, and the other end of the fixed meson is exposed outside the stroke groove; One end of the mobile meson passes through the stroke groove and is connected to the core-pulling movable plate, and the other end of the mobile meson is engaged with the stroke adjustment plate. The mobile meson is located above the fixed meson.

6. The method for demoulding a plastic box according to any one of claims 1 to 5, characterized in that: In the step 1), the core-pulling insert comprises a connecting piece and a core-inserting piece, one end of the core-inserting piece is connected to the connecting piece, the other end of the core-inserting piece passes through the middle mold base and is inserted into the inner mold cavity, and the connecting piece is installed in the core-pulling movable plate; A plurality of inner positioning members are arranged on the outer periphery of the core insert, and the inner positioning members are located in the inner mold cavity. The outer periphery of the core insert, the outer side walls of the inner positioning members, the inner side walls of the inner mold cavity and the middle mold base enclose the molding cavity.

7. The method for demoulding a plastic box as claimed in claim 6, characterized in that: A plurality of inner positioning members are arranged around and spaced along the outer circumference of the core insert, the core insert is slidably matched with the inner positioning members, and the inner positioning members are extended along the length direction of the core insert; The core insert is inwardly recessed to form a sliding groove, the sliding groove is arranged in an inclined manner, and the core insert is slidably matched with the inner position piece through the sliding groove.

8. The method for demoulding a plastic box as claimed in claim 7, characterized in that: The sliding groove is convexly provided with an inserting strip, and the inner position piece is inwardly recessed to form a slot corresponding to the inserting strip, and the sliding groove and the inner position piece are slidably matched through the inserting strip and the slot.

9. The method for demoulding a plastic box as claimed in claim 8, characterized in that: An inlay is protruded upwards on the top of the inner position member, the inlay is exposed outside the lower mold base, and the inlay is embedded on the top of the middle mold base.

10. The method for demoulding a plastic box according to any one of claims 1 to 5, characterized in that: In the step 4), the middle die base and the lower die base are matched with each other through a limiting mechanism, and the limiting mechanism is arranged on the outer sides of the middle die base and the lower die base; The limiting mechanism comprises an upper meson, a lower meson and a pull plate, wherein upper and lower sides of the pull plate are respectively provided with an upper slide groove and a lower slide groove which are arranged in a hollow manner, wherein the upper slide groove and the lower slide groove are arranged in a longitudinal direction with a relative spacing therebetween, one end of the upper meson passes through the upper slide groove and is connected to the middle mold seat, and the other end of the upper meson is exposed outside the upper slide groove; One end of the lower meson passes through the lower slide groove and is connected to the lower mold base, the other end of the lower meson is exposed outside the lower slide groove, and the upper meson is located above the lower meson.

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