Secondary injection molding device and secondary injection molding process for mobile phone case

Abstract

The present invention discloses a secondary injection molding device and a secondary injection molding process for a mobile phone case. The secondary injection molding device includes a primary injection mold and a secondary injection mold. The first upper mold of the primary injection mold is provided with at least two positioning molding cavities. The blank is injection-molded in the primary injection mold to form a primary molded part having a positioning structure that conforms to the shape of the positioning molding cavity. The secondary injection mold includes a second upper mold and a second lower mold. The primary molded part is placed in the molding cavity of the second lower mold. The second upper mold is provided with a limiting structure that matches the positioning structure. The secondary injection molding process for a mobile phone case is to form a positioning structure on the blank in the primary injection mold, and then use the positioning structure as a positioning reference to perform secondary injection molding in the secondary injection mold. Finally, the inner bottom surface is CNC-machined to obtain a finished product. The injection-molded positioning structure is used as a positioning reference during secondary injection molding to improve the injection molding quality and improve the product appearance.

Description

Technical Field

[0001] The present invention relates to the technical field of injection molds, and in particular to a secondary injection molding device and a secondary injection molding process for a mobile phone shell. Background Art

[0002] Before injection molding mobile phone cases, the blank is first CNC-machined to form positioning holes and other structures. The positioning holes are used to accurately place the blank in the injection mold. However, during CNC machining, machining errors such as jigs often cause deviations in the accuracy of the positioning holes, resulting in inaccurate positioning on the mold. This makes it difficult to maintain consistency in the size and shape of the injection-molded product, making it difficult to control quality. Another reason for the above reasons is that the CNC machining positioning datum and the injection molding positioning datum in the mold are different, which easily leads to cumulative deviations. Summary of the Invention

[0003] The present invention aims to provide a secondary injection molding device in which a positioning structure is formed in the primary injection mold of the blank. This positioning structure serves as a positioning reference during the secondary injection molding process, reducing deviations and improving positioning accuracy, thereby enhancing injection molding quality. This device solves the problem of CNC-machined positioning holes in the blank before placement in the injection mold for injection molding, which can lead to deviations in the size and shape of the injection-molded part due to insufficient positioning hole accuracy and / or different secondary positioning references, as well as the inability to shield the positioning holes, which can affect the appearance of the resulting part.

[0004] To achieve this object, the present invention adopts the following technical solutions:

[0005] The secondary injection molding device includes a primary injection mold and a secondary injection mold. The primary injection mold includes a first upper mold and a first lower mold. The first upper mold is provided with at least two positioning molding cavities; the first lower mold is provided with a first fixing cavity for placing a blank.

[0006] The blank is injection molded into a primary injection mold to form a primary molded part having a positioning structure that conforms to the shape of the positioning molding cavity;

[0007] The secondary injection mold includes a second upper mold and a second lower mold that form a secondary injection molding cavity. The primary molded part is placed in the molding cavity of the second lower mold. The second upper mold is provided with a limiting structure that cooperates with the positioning structure.

[0008] Therefore, the blank is injection molded in the primary injection mold to form a positioning structure, and then the primary molded part is placed in the secondary injection mold for a second injection molding. The secondary injection mold is provided with a limiting structure that cooperates with the positioning structure, so that the primary molded part can be accurately placed in the secondary injection mold. In this way, the positioning structure serves as a positioning reference during the secondary injection molding. The cooperation between the positioning structure and the limiting structure reduces the reference offset, so that the size and shape of the secondary molded part formed by the secondary injection molding are more accurate, which solves the problem that the blank is first CNC-machined to form a positioning hole and then placed in the injection mold for injection molding. The problem that the size and shape of the injection-molded part are deviated due to the insufficient accuracy of the added positioning holes and / or the different secondary positioning references, and the positioning holes cannot shield the appearance.

[0009] In some embodiments, the positioning structure is a positioning column, and the limiting structure is a limiting groove.

[0010] Therefore, the positioning structure can also be a positioning edge or positioning groove structure, and the positioning column structure is simpler and easier to injection mold. The corresponding limiting structure can also adopt a slot hole structure or a needle column structure, and the limiting groove and positioning column are easier to manufacture and mold.

[0011] In some embodiments, the positioning molding cavity further includes a first step groove and a second step groove, wherein the second step groove is provided at the bottom of the first step groove; the second step groove is used to form the positioning column, and the first step groove is used to form a step of the primary molded part.

[0012] Therefore, the first-step groove is arranged to form a step structure of the primary molded part, which is beneficial to strengthening the mechanical strength of the positioning column on the one hand, and also plays a certain limiting function on the other hand.

[0013] In some embodiments, the positioning molding cavity includes a first positioning molding cavity, a second positioning molding cavity, and a third positioning molding cavity. The first positioning molding cavity and the second positioning molding cavity are mirror-symmetrical with respect to the longitudinal center plane of the first upper mold; the second positioning molding cavity and the second positioning molding cavity are mirror-symmetrical with respect to the transverse center plane of the first upper mold.

[0014] Therefore, three positioning molding cavities are provided, and different lines are arranged at the three corners of the molding cavity of the primary injection mold, forming effective positioning in the left and right and up and down directions, thereby improving positioning accuracy.

[0015] In some embodiments, the first upper mold is further provided with a balancing molding cavity.

[0016] Therefore, in order to improve and enhance the injection molding process, setting up a balanced molding cavity is beneficial to balancing the pressure and flow rate of the pouring system, evenly distributing the pouring pressure during injection molding, and making the mold more evenly stressed.

[0017] In some embodiments, the balancing forming cavity is provided on a region on a side of the first positioning forming cavity that is mirrored relative to the transverse center plane.

[0018] Therefore, the balancing molding cavity and the three positioning molding cavities form a balanced pouring system with a rectangular distribution.

[0019] In some embodiments, the height of the step is no greater than the thickness of the periphery of the step formed during the overmolding process.

[0020] As a result, after secondary injection molding, the step does not protrude from the inner surface of the secondary molded part, thereby improving the aesthetics.

[0021] In some embodiments, the second step trough is connected to the pouring gate.

[0022] Thus, the second-stage trough is connected to the pouring gate, which facilitates injection molding and also helps to simplify the structure.

[0023] A secondary injection molding process for a mobile phone case includes a secondary injection molding device. The molding process includes the following steps:

[0024] Step 1: Place the blank in a primary injection mold to form a primary molded part with a positioning structure;

[0025] Step 2: Place the primary molded part in the secondary injection mold, cooperate with the positioning structure and the limiting structure, and inject to form the secondary molded part;

[0026] Step 3: CNC machine the secondary molded part, mill the inner bottom surface and make holes to form the finished product.

[0027] Therefore, a positioning structure is first formed in the blank in the primary injection mold, and then the positioning structure is used as a positioning reference. The secondary injection mold is provided with a corresponding limiting structure. The positioning structure and the limiting structure cooperate to reduce the reference offset, thereby improving the injection molding accuracy. Finally, the positioning structure is CNC cut to form the final mobile phone case product.

[0028] In some embodiments, the positioning structure in step 1 is a positioning post; and the limiting structure in step 2 is a limiting groove.

[0029] The beneficial effects of the present invention are as follows: a positioning structure such as a positioning column is formed in the blank during the primary injection molding, and the positioning structure is used to perform positioning injection molding in the secondary injection mold, thereby improving positioning accuracy, improving injection molding quality, simplifying the manufacturing process, and improving production efficiency;

[0030] In addition, there are three positioning structures such as positioning columns, which can effectively and accurately define the position of the blank and prevent position deviation from occurring.

[0031] Furthermore, a balanced molding cavity is provided to balance the pouring system, making the pouring pressure and flow rate more uniform, which is more conducive to positioning structure injection molding and improving the injection molding process;

[0032] Finally, the positioning structure is formed on the inner surface of the product and can be removed using CNC machining. The entire injection molding process will not have a negative impact on the appearance of the product. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] Figure 1 A structural diagram of a primary injection mold of a secondary injection molding device of the present invention;

[0034] Figure 2 A structural diagram of a first upper mold of a primary injection mold of a secondary injection molding device of the present invention;

[0035] Figure 3 for Figure 2 A local enlarged view of point A;

[0036] Figure 4 for Figure 2 A partial enlarged view of point B;

[0037] Figure 5 A structural diagram of a first lower mold of a primary injection mold of a secondary injection molding device of the present invention;

[0038] Figure 6 A structural diagram of a secondary injection mold of a secondary injection molding device of the present invention;

[0039] Figure 7 A structural diagram of a second upper mold of a secondary injection mold of a secondary injection molding device of the present invention;

[0040] Figure 8 A structural diagram of a second lower mold of a secondary injection mold of a secondary injection molding device of the present invention;

[0041] Figure 9 This is a diagram of the blank structure of the present invention;

[0042] Figure 10 This is a structural diagram of a primary molded part of the present invention;

[0043] Figure 11 This is a diagram of the secondary molding structure of the present invention;

[0044] Figure 12 This is a structural diagram of a finished product of the present invention;

[0045] Among them: 1-primary injection mold; 11-first upper mold; 111-positioning molding cavity; 1111-first step groove; 1112-second step groove; 10-first positioning molding cavity; 20-second positioning molding cavity; 30-third positioning molding cavity; 112-balancing molding cavity; 1121-third step groove; 1122-fourth step groove; 12-first lower mold; 21-first fixing cavity; 2-secondary injection mold; 21-second upper mold; 211-limiting groove; 22-second lower mold; 3-blank; 4-primary molded part; 41-step; 42-positioning column; 43-balancing step; 44-balancing column; 5-secondary molded part; 6-finished product. DETAILED DESCRIPTION

[0046] The present invention will be further described in detail below with reference to the accompanying drawings.

[0047] like Figures 1 to 12 As shown, the secondary injection molding device includes a primary injection mold 1 and a secondary injection mold 2. The primary injection mold 1 includes a first upper mold 11 and a first lower mold 12. The first upper mold 11 is provided with at least two positioning molding cavities 111; the first lower mold 12 is provided with a first fixing cavity 121 for placing the blank 3;

[0048] The blank 3 is injection molded in the primary injection mold 1 to form a primary molded part 4 having a positioning structure that conforms to the shape of the positioning molding cavity 111;

[0049] The secondary injection mold 2 includes a second upper mold 21 and a second lower mold 22 constituting a secondary injection molding cavity. The primary molded part 4 is placed in the molding cavity of the second lower mold 22. The second upper mold 21 is provided with a limiting structure that cooperates with the positioning structure.

[0050] To further illustrate, the positioning structure is the positioning column 42 , and the limiting structure is the limiting groove 211 .

[0051] To further illustrate, the positioning molding cavity 111 includes a first step groove 1111 and a second step groove 1112 , wherein the second step groove 1112 is provided at the bottom of the first step groove 1111 ; the second step groove 1112 is used to form the positioning column 42 , and the first step groove 1111 is used to form the step 41 of the primary molded part 4 .

[0052] Further explanation, such as Figures 2 to 4 The positioning molding cavity 111 includes a first positioning molding cavity 10, a second positioning molding cavity 20 and a third positioning molding cavity 30. The first positioning molding cavity 10 and the second positioning molding cavity 20 are mirror-symmetrical with respect to the longitudinal center plane of the first upper mold 11; the second positioning molding cavity 20111 and the second positioning molding cavity 20111 are mirror-symmetrical with respect to the transverse center plane of the first upper mold 11.

[0053] To further explain, the first upper mold 11 is further provided with a balancing molding cavity 112 .

[0054] To further explain, the balancing molding cavity 112 is provided on a region on a side of the first positioning molding cavity 10 that is mirrored relative to the transverse center plane.

[0055] To further illustrate, the height of the step 41 is not greater than the thickness of the periphery of the step 41 formed during the secondary injection molding.

[0056] To further illustrate, the second step trough 1112 is connected to the pouring gate.

[0057] A secondary injection molding process for a mobile phone case includes a secondary injection molding device. The molding process includes the following steps:

[0058] Step 1: placing the blank 3 in a primary injection mold 1 and injection molding to form a primary molded part 4 with a positioning structure;

[0059] Step 2: Place the primary molded part 4 in the secondary injection mold 2, and use the positioning structure and the limiting structure to form a secondary molded part 5 by injection molding;

[0060] Step 3: The secondary molded part 5 is CNC-processed, and the inner bottom surface is milled and holes are opened to form a finished product 6.

[0061] To further illustrate, the positioning structure in step 1 is the positioning post 42 ; and the limiting structure in step 2 is the limiting groove 211 .

[0062] Working principle:

[0063] The secondary injection molding device includes a primary injection mold 1 and a secondary injection mold 2. The first upper mold 11 of the primary injection mold 1 is provided with a positioning molding cavity 111 for molding a positioning column 42. The blank 3 is injection-molded in the primary mold to form a primary molded part 4. The positioning column 42 of the primary molded part 4 is placed in the secondary injection mold 2 as a positioning reference for a second injection molding. The second upper mold 21 of the secondary injection mold 2 is provided with a limiting groove 211 that matches the positioning column 42. Since the manufacturing precision of the mold is high, the precision of the molded positioning column 42 is also high. The molded positioning column 42 is used as a reference to reduce the deviation caused by the reference offset. Therefore, the above-mentioned high-precision structure can protect the size and shape of the product after molding.

[0064] In order to further improve the positioning accuracy and minimize the deviation in the left and right and / or up and down directions during positioning, three non-collinear positioning molding cavities 111 are provided and distributed at the three corners of the molding cavity of the first upper mold 11. The three non-collinear points can define the position of a surface. Therefore, when three positioning molding cavities 111 are set, three positioning columns 42 can be formed during injection molding, which effectively improves the positioning accuracy.

[0065] An unbalanced gating system design can lead to poor molding of injection molded parts, such as underfill, deformation, or severe shrinkage. To improve the balance of the gating system and enhance the injection molding process, a balancing molding cavity 112 is provided at the last corner of the molding cavity of the first upper mold 11. Together with the three positioning molding cavities 111, they are roughly evenly distributed at the four corners of the molding cavity. This makes the flow direction and pressure of the runner more uniform, which is more conducive to the injection molding of the positioning pillars 42. Accordingly, a balancing step 4341 and a balancing pillar 44 are injection molded on the primary molded part 4.

[0066] The primary molded part 4 is injection molded in the secondary injection mold 2 to form a secondary molded part 5. The positioning column 42 and other structures in the secondary molded part 5 are removed by CNC to form a finished mobile phone case 6. The outer surface is not processed.

[0067] Therefore, the product after secondary injection molding will not leave any manufacturing marks and processing structures on the outer surface of the product, which will affect the appearance quality of the product. The positioning column 42 formed by injection molding is used as a positioning reference to improve the injection molding accuracy and improve product quality.

[0068] This secondary injection molding process can be used for both plastic and ceramic injection molding. The positioning structure on the primary molded part 4 can be designed as a positioning edge or a positioning groove, in addition to the positioning column 42. The appropriate selection is based on the product. When designed as a positioning groove, the groove should be roughly the shape of a hollow annular column, with the slot being a blind hole. The secondary injection mold 2 is equipped with a matching limiting pin or other structure.

[0069] The above are only some embodiments of the present invention. For those skilled in the art, several modifications and improvements can be made without departing from the inventive concept of the present invention, and these all fall within the scope of protection of the invention.

Claims

1. A secondary injection molding device, characterized in that: The invention comprises a primary injection mold (1) and a secondary injection mold (2), wherein the primary injection mold (1) comprises a first upper mold (11) and a first lower mold (12), wherein the first upper mold (11) is provided with at least two positioning molding cavities (111); and the first lower mold (12) is provided with a first fixed cavity (121) for placing a blank (3); The blank (3) is injection molded in the primary injection mold (1) to form a primary molded part (4) having a positioning structure that conforms to the shape of the positioning molding cavity (111); The secondary injection mold (2) comprises a second upper mold (21) and a second lower mold (22) constituting a secondary injection molding cavity, the primary molded part (4) is placed in the molding cavity of the second lower mold (22), and the second upper mold (21) is provided with a limiting structure that cooperates with the positioning structure; The positioning structure is a positioning column (42), and the limiting structure is a limiting groove (211); The positioning molding cavity (111) comprises a first positioning molding cavity (10), a second positioning molding cavity (20) and a third positioning molding cavity (30), wherein the first positioning molding cavity (10) and the second positioning molding cavity (20) are mirror-symmetrical relative to the longitudinal center plane of the first upper mold (11); and the second positioning molding cavity (20) and the second positioning molding cavity (20) are mirror-symmetrical relative to the transverse center plane of the first upper mold (11); The first upper mold (11) is further provided with a balanced molding cavity (112); The balancing molding cavity (112) is provided on an area on a side of the first positioning molding cavity (10) that is mirrored relative to the transverse center plane; The positioning molding cavity (111) further comprises a first step groove (1111) and a second step groove (1112), wherein the second step groove (1112) is provided at the bottom of the first step groove (1111); the second step groove (1112) is used for molding the positioning column (42), and the first step groove (1111) is used for molding the step (41) of the primary molded part (4); The second-stage trough (1112) is connected to the pouring gate; The height of the step (41) is not greater than the thickness of the periphery of the step (41) formed during secondary injection molding.

2. A secondary injection molding process for a mobile phone case, comprising the secondary injection molding device according to claim 1, characterized in that: The molding process includes the following steps: Step 1: placing a blank (3) in a primary injection mold (1) and injection molding to form a primary molded part (4) having a positioning structure; Step 2: placing the primary molded part (4) in the secondary injection mold (2), cooperating with the positioning structure and the limiting structure, and injection molding to form the secondary molded part (5); Step 3: The secondary molded part (5) is CNC machined to mill the inner bottom surface and perform hole drilling to form a finished product (6).

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