Methods to avoid defects in injection blow moulded products

In order to obtain high quality injection blow molding products, product engineers must fully consider the product structure and processability when designing products. In the following, we will share some methods to avoid the defects of injection blow molding products in combination with the main structural characteristics of injection molding products.

1. Mold opening direction and parting line

    At the beginning of the design of each injection-molded product, the mold opening direction and parting line must be determined first to minimize the core drawing mechanism and eliminate the impact of the parting line on the appearance.

    After the mold opening direction is determined, the product's reinforcing ribs, buckles, protrusions and other structures are designed to be as consistent with the mold opening direction as possible to avoid core pulling to reduce the stitching line and extend the mold life. (For example: the mold opening direction of the bumper is generally the X coordinate of the vehicle body. If the mold opening direction is designed to be inconsistent with the X axis, the included angle must be noted in the product drawing.)

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

Second, the release slope

    Appropriate demolding gradient can avoid product strain or top injury. The smooth surface should be more than 0.5 degrees, the fine-grained surface is greater than 1 degree, and the coarse-grained surface is greater than 1.5 degrees.

Product wall thickness

    Various plastics have a certain range of wall thickness, generally 0.5 ~ 4mm. When the wall thickness exceeds 4mm, it will lead to excessive cooling time, resulting in problems such as shrinkage.

    In addition to uneven wall thickness, it can cause surface shrinkage, but also cause pores and weld marks.

Fourth, stiffeners

    The thickness of the stiffener 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 theoretically be greater than 1.5 degrees to avoid top injuries. (Can be adjusted according to the actual product).

    Reasonable application of stiffeners can increase product rigidity and reduce deformation.

Five, rounded corners

    Different rounded corners may cause the parting line to move. Too small rounded corners may cause the mold cavity stress concentration (U Si Xue UG), resulting in cavity cracking. Setting a reasonable fillet can also improve the processing technology of the mold. For example, the cavity can be directly processed by R cutter milling, and low-efficiency electrical processing is avoided.

Six, holes

1. The shape of the hole should be as simple as possible, generally round.

2. The empty axial direction is the same as the mold opening direction, which can avoid core pulling.

3. When the aspect ratio of the hole is greater than 2, the draft angle should be set.

4. The aspect ratio of blind holes is generally not more than 4.

5. The distance between the hole and the edge of the product is generally greater than the size of the hole.