Injection molding method and device for metal-reinforced anti-deformation composite plastic part

Abstract

The invention relates to an injection molding method and device for a metal reinforced anti-deformation composite plastic part, and provides a solution combining an open type mold structure and manual implantation of a metal reinforcing part to solve the problems that in a traditional injection molding process, a product is prone to buckling deformation, and a metal insert is difficult to position. A metal reinforcing piece (surface or keel) with the thickness of 1-2 mm is prepared in advance and covers the length direction, prone to warping, of the plastic piece; an injection mold is designed to be of a turnover structure and is arranged outside an injection molding machine, and a metal piece is accurately placed through a lower mold positioning groove; in the injection molding process, plastic cooling internal stress is counteracted through metal rigidity, and a rigid-flexible composite structure is formed. Experimental data show that the technology can enable the maximum warping amount of the product to be reduced, and the bending strength is improved. The method has the remarkable advantages of being high in process compatibility, low in production cost, excellent in mechanical property and the like.

Description

Technical Field

[0001] The present invention relates to the technical field of injection molding, and specifically to an injection molding method and device for a metal-reinforced anti-deformation composite plastic part. Background Art

[0002] Currently, plastic products are widely used in fields such as automobiles, household appliances, and industrial equipment. However, traditional injection molding processes have two core problems:

[0003] Insufficient control of cooling deformation: When the plastic melt cools and solidifies, shrinkage stress will be generated, resulting in warping and deformation of the product. The traditional method compensates for deformation by presetting a reverse stretching mold. However, due to material property differences and process parameter fluctuations, it is difficult to achieve precise control. The warping amount of large thin-walled parts often reaches more than 3 mm, affecting the assembly accuracy.

[0004] Low efficiency of metal insert injection molding: Existing metal insert injection molding requires a complex automated positioning system, has poor adaptability to asymmetric-shaped inserts, and the bonding strength at the interface between the insert and the plastic is insufficient (usually <8 MPa), prone to defects such as detachment or delamination, and difficult to meet the requirements of large-scale production.

[0005] In response to the above problems, the industry uses technologies such as glass fiber reinforcement and co-injection molding to improve performance, but there are limitations such as high material costs and a decline in the surface quality of the product.

[0006] This patent creatively proposes a solution that combines an open mold structure with manual implantation of metal reinforcement parts. By implanting 1-2 mm metal surfaces / keels at key parts of the plastic part, the internal stress is offset by the rigidity of the metal, reducing the warping amount by more than 70%; at the same time, through the design of mold positioning grooves and precise manual placement, the problem of automated positioning of asymmetric metal parts is solved. Summary of the Invention

[0007] The present invention provides an injection molding method and device for a metal-reinforced anti-deformation composite plastic part to solve the problems of the prior art.

[0008] To solve the above technical problems, the present invention is realized through the following technical solutions: An injection molding method for a metal-reinforced anti-deformation composite plastic part includes the following steps:

[0009] S1: Pre-manufacture a metal reinforcement part with a thickness between 1-2 mm;

[0010] S2: Design the injection mold into a structure that can be easily opened and closed, and place it at an operable position outside the injection molding machine;

[0011] S3: Before injection molding, manually place the metal reinforcement part at a predetermined position at the bottom of the lower mold;

[0012] S4: After closing the mold, inject plastic liquid to make it combine with the metal reinforcement;

[0013] S5: After the plastic cools and solidifies, open the mold and take out the plastic part with the metal support structure.

[0014] In this application, by manually implanting the metal reinforcement before injection molding, the composite molding of the plastic part and the metal structure is realized. The specific functions are as follows: First, by arranging the metal reinforcement in the length direction where the plastic part is prone to warping, the rigidity of the metal material is used to offset the internal stress generated by the cooling shrinkage of the plastic; Second, place the injection mold at an operable position outside the injection molding machine, and cooperate with the design of the openable and closable structure, which not only maintains the high efficiency of the traditional injection molding process, but also creates an operation window for manual intervention; Third, by presetting the position and shape of the metal reinforcement, the targeted strengthening of the key parts of the plastic part is realized. The remarkable effects of this method include: reducing the warping deformation of the plastic part, improving the product size stability, while avoiding the complex design of the traditional reverse drawing mold and reducing the mold development cost.

[0015] In a specific implementation manner of the first aspect, the shape of the metal reinforcement is determined according to the design requirements of the plastic part, and particularly covers the length direction where the plastic part is prone to warping.

[0016] In the second aspect, an injection molding device for a metal-reinforced anti-deformation composite plastic part includes:

[0017] An injection molding machine for melting plastic and injecting it into the mold;

[0018] The injection mold is designed into two parts, the upper mold and the lower mold. There is a groove for placing the metal reinforcement at the bottom of the inner wall of the lower mold;

[0019] The metal reinforcement is set as a metal surface or a keel for enhancing the anti-deformation ability of the plastic part during the injection molding process.

[0020] In this application, the functional integration of metal-plastic composite molding is realized through structural innovation. The specific functions are reflected in: First, the groove design of the injection mold provides precise positioning for the metal reinforcement to ensure its reliable combination with the plastic melt; Second, the open mold structure is convenient for manually placing the metal part, avoiding the technical difficulties of the automatic system in the positioning of asymmetric structures; Third, the addition of the metal surface or the keel forms a "rigid-flexible composite" structure, increasing the bending strength of the plastic part. The outstanding effects of this device include: improving the production yield rate, reducing the maximum warping amount of the product, while maintaining the high-efficiency characteristics of injection molding.

[0021] The beneficial effects of the present invention are:

[0022] 1. By implanting a 1-2 mm metal reinforcement (on the surface or keel) in the length direction where the plastic part is prone to warping, the metal rigidity is used to offset the internal stress of plastic cooling, reducing the maximum warping amount of the product, enhancing the bending strength, decreasing the coefficient of thermal expansion, and significantly enhancing the dimensional stability;

[0023] 2. Adopting an open mold structure and manual implantation method not only retains the high efficiency characteristics of injection molding but also solves the problem of automatic positioning of asymmetric metal parts, improving the yield rate of products and extending the mold life. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 It is a schematic diagram of the overall structure of the present invention.

[0025] Figure 1 In the figure: 1, injection mold; 2, metal reinforcement; 11, upper mold; 12, lower mold. DETAILED DESCRIPTION OF THE INVENTION

[0026] Next, the technical solutions in the embodiments of the present invention will be clearly and completely described in conjunction with the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts shall fall within the protection scope of the present invention.

[0027] As Figure 1 shown, an injection molding method for a metal-reinforced anti-deformation composite plastic part is characterized by including the following steps:

[0028] S1: Pre-fabricate a metal surface or keel with a thickness between 1 and 2 millimeters;

[0029] S2: Design the injection mold into a structure that can be conveniently opened and closed and place it at an operable position outside the injection molding machine;

[0030] S3: Before injection molding, manually place the metal surface or keel at a predetermined position at the bottom of the lower mold;

[0031] S4: After closing the mold, inject plastic liquid to make it combine with the metal surface or keel;

[0032] S5: After the plastic cools and solidifies, open the mold and take out the plastic part with a metal support structure.

[0033] The shape of the metal surface or keel is determined according to the design requirements of the plastic part and particularly covers the length direction where the plastic part is prone to warping.

[0034] An injection molding device for a metal-reinforced anti-deformation composite plastic part includes:

[0035] An injection molding machine, used for melting plastics and injecting them into a mold;

[0036] An injection mold 1, designed as two parts: an upper mold 11 and a lower mold 12. At the bottom of the inner wall of the lower mold, there is a groove for placing a metal reinforcement.

[0037] The metal reinforcement 2 is set as a metal surface or keel, used to enhance the anti-deformation ability of plastic parts during the injection molding process.

[0038] Example: Metal-reinforced injection molding.

[0039] I. Method implementation steps:

[0040] Preparation of metal reinforcement: Stamped from a 304 stainless steel plate with a thickness of 0.8 mm, designed into a wavy keel structure according to the length direction of the bumper (2.1 meters), with positioning lugs at both ends, and a pre-coated epoxy resin bonding layer on the surface.

[0041] Mold modification: Modify the original bumper injection mold into a flip-type structure, mill a U-shaped positioning groove with a depth of 0.8 mm at the bottom of the lower mold, set positioning holes in the groove that match the lugs of the metal part, and install the whole mold on the extension bracket of the injection molding machine operation platform.

[0042] Manual implantation operation: The operator slides the metal keel along the positioning groove, temporarily fixes it with a pneumatic clamp, and uses a laser locator to detect that the parallelism error between the keel and the cavity is controlled within ±0.1 mm.

[0043] Injection molding process parameters: Use PP + 30% GF material, injection temperature 230 °C, holding pressure 85 MPa, injection rate 60 g / s, mold temperature 50 °C.

[0044] Cooling and demolding: After holding pressure and cooling for 45 seconds, the mold automatically opens, and the ejection mechanism pushes the composite part to the inspection station, and the warpage amount is detected by a coordinate measuring machine.

[0045] II. Device structure design:

[0046] Injection molding machine modification: Select the Haitian MA2000 / 4800 model, add a mold flipping mechanism (flipping angle 0 - 90°), and install a displacement sensor beside the clamping cylinder to monitor the clamping force in real time.

[0047] Mold structure:

[0048] The lower mold uses H13 hot work die steel, and the surface of the positioning groove is treated with hard chromium plating

[0049] The upper mold is provided with 6 groups of conformal cooling water channels, and the cooling efficiency is increased by 40%

[0050] The surface of the cavity is etched with a micro-groove structure with a depth of 0.05 mm to enhance the metal-plastic bonding force auxiliary system:

[0051] Configure an infrared temperature measurement device to monitor the temperature of metal parts in real time

[0052] Set up a light curtain safety protection system at the mold opening and closing

[0053] Equip an automatic chip blowing device to remove impurities in the positioning groove

[0054] III. Implementation effects:

[0055] Mechanical properties:

[0056] The maximum warpage amount is reduced from 3.2 mm in the traditional process to 0.28 mm

[0057] The three-point bending strength is increased from 48 MPa to 72 MPa

[0058] The coefficient of thermal expansion is reduced by 42% (23 - 80 °C)

[0059] Production indicators:

[0060] The single-mode production cycle is increased from 85 seconds to 108 seconds

[0061] The qualified product rate is increased from 82% to 94.3%

[0062] The mold life is extended by 25% (up to 800,000 times)

[0063] Cost-benefit:

[0064] The material cost increases by 8.7 yuan per piece (metal part cost)

[0065] The number of post-treatment processes is reduced by 3, saving 12% of the labor cost

[0066] The product repair rate is decreased by 67%

[0067] Through the precise positioning of the metal keel and the innovation of the mold structure, this embodiment achieves a breakthrough improvement in the anti-deformation performance of the automotive bumper while maintaining the injection molding efficiency, and is particularly suitable for the industrial production of large-sized thin-walled plastic products.

[0068] Although the embodiments of the present invention have been shown and described, it will be understood by those of ordinary skill in the art that various changes, modifications, substitutions and variations can be made to these embodiments without departing from the principles and spirit of the present invention, and the scope of the present invention is defined by the appended claims and their equivalents.

Claims

1. A method for injection molding of a metal-reinforced anti-deformation composite plastic part, characterized in that: The following steps are involved: S1: Prefabricate metal reinforcements with a thickness between 1 and 2 mm; S2: Design the injection mold to be easy to open and close and place it in an operable position outside the injection molding machine; S3: Before injection molding, the metal reinforcement is manually placed at the predetermined position at the bottom of the lower mold; S4: After closing the mold, inject plastic liquid to combine it with the metal reinforcement; S5: After the plastic is cooled and solidified, the mold is opened and the plastic part with the metal support structure is taken out.

2. The method for injection molding of a metal-reinforced anti-deformation composite plastic part according to claim 1, characterized in that: The shape of the metal reinforcement is determined according to the design requirements of the plastic part, and particularly covers the length direction of the plastic part where warping is likely to occur.

3. An injection molding device for metal-reinforced deformation-resistant composite plastic parts, characterized in that: include: Injection molding machines, which melt plastic and inject it into molds; The injection mold (1) is designed to be composed of an upper mold (11) and a lower mold (12), wherein a groove for placing a metal reinforcement is provided at the bottom of the inner wall of the lower mold; The metal reinforcement (2) is configured as a metal surface or a keel, and is used to enhance the deformation resistance of the plastic part during the injection molding process.

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