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Design essentials of injection molding parts

Release time:2024-04-09

stayInjection moldingIn the process, due to the uneven cooling and shrinkage of plastic in the mold cavity and the unreasonable structural design of injection molded parts, it is easy to cause various defects of products: shrinkage, weld marks, pores, deformation, galling, top injury, flash.

In order to obtain high-quality injection molded products, the structural manufacturability of products must be fully considered in the design. Next, combined with the main structural characteristics of injection molding products, the methods to avoid injection molding defects are analyzed.


1、 Mold opening direction and parting line

At the beginning of each injection product design, the mold opening direction and parting line should be determined first, so as to minimize the influence of the core pulling mechanism and the parting line on the appearance. So pay attention to the key points.

1. After the mold opening direction is determined, the stiffener, buckle, bulge and other structures of the product should be designed to be consistent with the mold opening direction as far as possible, so as to avoid core pulling, reduce the suture, and extend the service life of the mold.

2. For example, the mold opening direction of the bumper is generally the body coordinates χ If the mold opening direction is designed as χ If the shafts are inconsistent, the included angle must be indicated in the product drawing.

3. After the mold opening direction is determined, the appropriate parting line can be selected to improve the appearance and performance.

2、 Demoulding slope

1. Proper demoulding slope can avoid product galling. The demoulding slope of smooth surface should be greater than 0.5 degrees, that of fine grained surface should be greater than 1 degree, and that of coarse grained surface should be greater than 1.5 degrees.

2. Proper demoulding slope can avoid damage to the top of the product.

3. When designing products with deep cavity structure, the slope of the outer surface should be less than that of the inner surface, so as to ensure that the mold core does not shift during injection molding, obtain uniform product wall thickness, and ensure the material density and strength of the opening of the product.

3、 Product wall thickness

1. All kinds of plastics have a certain wall thickness range, generally 0.5~4mm. When the wall thickness exceeds 4mm, it will cause problems such as too long cooling time and printing. We should consider changing the structure of the product.

2. Uneven wall thickness will lead to surface reduction.

3. Uneven wall thickness will cause pores and weld marks.

4、 Stiffener

1. Reasonable application of stiffeners can increase the rigidity of products and reduce deformation.

2. The thickness of the stiffener must be less than 1/3 of the product wall thickness, otherwise the surface will be reduced.

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