Ways to Avoid Defects in Injection Blow Molded Products

2023/04/23

Author: MULAN -Plastic Molding Manufacturer

In order to obtain high-quality injection blow molding products, product engineers must fully consider the product structure and manufacturability when designing products. Combining with the main structural characteristics of injection molding products, we will share with you some methods to avoid defects of injection blow molding products. 1. Mold opening direction and parting line At the beginning of the design of each injection molding product, its mold opening direction and parting line must be determined first, so as to reduce the core-pulling mechanism and eliminate the influence of the parting line on the appearance as much as possible. After the mold opening direction is determined, the product's ribs, buckles, protrusions and other structures are designed to be consistent with the mold opening direction as much as possible, so as to avoid core pulling and reduce stitching lines, prolonging the life of the mold. (For example: the mold opening direction of the bumper is generally the X direction of the body coordinates. If the mold opening direction is designed to be inconsistent with the X axis, the included angle must be indicated in the product drawing.) After the mold opening direction is determined, an appropriate parting line can be selected to improve appearance and performance. 2. Drafting slope Appropriate demoulding slope can avoid product strain or top injury. The demoulding slope of the smooth surface should be greater than 0.5 degrees, the surface of the fine skin texture should be greater than 1 degree, and the surface of the rough skin texture should be greater than 1.5 degrees. 3. Product wall thickness All kinds of plastics have a certain range of wall thickness, generally 0.5 ~ 4mm, when the wall thickness exceeds 4mm, it will lead to too long cooling time, resulting in shrinkage and other problems. In addition to causing surface shrinkage, uneven wall thickness can also cause pores and weld lines. 4. Reinforcing ribs The thickness of the rib should be less than 2/3 of the wall thickness of the product, otherwise it will cause surface shrinkage, and its single-sided slope should be greater than 1.5 degrees in theory to avoid top damage. (It can be adjusted according to the actual product). Reasonable application of ribs can increase product rigidity and reduce deformation. 5. Fillet Different fillets may cause the parting line to move, too small fillets may cause stress concentration in the mold cavity (Wu Si Xue UG), resulting in cavity cracking. Setting reasonable rounded corners can also improve the processing technology of the mold. For example, the cavity can be directly milled with R cutter to avoid low-efficiency electric machining. Six, hole 1. The shape of the hole should be as simple as possible, generally round. 2. The hollow axis is consistent with the mold opening direction, which can avoid core pulling. 3. When the aspect ratio of the hole is greater than 2, the draft should be set. 4. The length-to-diameter ratio of blind holes generally does not exceed 4. 5. The distance between the hole and the edge of the product is generally greater than the hole size.

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