Design points for injection molding parts

Design points for injection molding parts

In the injection molding process, due to the uneven cooling and uneven shrinkage of the plastic in the cavity and the unreasonable structural design of the injection molded part, it is easy to cause various defects of the product:

Shrinkage, weld marks, pores, deformation, napping, top injury, flash.

  

In order to obtain high-quality injection molding products, we must fully consider the structural processability when designing the products. The following is a combination of the main structural characteristics of the injection molding products to analyze the methods to avoid injection defects. Design points for injection molding parts

1 mold opening direction and parting line

Each injection molding product must first determine its mold opening direction and parting line at the beginning of the design to ensure that the core pulling mechanism is minimized and the influence of the parting line on the appearance is eliminated.

  1.1 After the mold opening direction is determined, the reinforcement ribs, snaps, protrusions, and other structures of the product are designed to be consistent with the mold opening direction as much as possible to avoid the core pulling to reduce the seam line and prolong the life of the mold.

1.2, For example, the direction of the mold opening of the bumper is generally the direction of the body coordinate,. If the mold opening direction is designed to be inconsistent with the χ axis, the angle must be indicated in the product drawing.

  

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

2 draft angle

2.1 Appropriate draft angle can avoid product pulling. The smooth surface should have a draft angle greater than 0.5 degrees, a fine grain surface greater than 1 degree, and a rough grain surface greater than 1.5 degrees.

2.2 Appropriate draft angle can avoid product top injury.

  

2.3 Deep cavity structure product design When the outer surface slope is required to be smaller than the inner surface slope, to ensure that the mold core is not biased during injection, to obtain a uniform product wall thickness, and to ensure the material density strength of the product opening.

3 product wall thickness

   3.1 All kinds of plastics have a certain wall thickness range, generally 0.5 ~ 4mm, when the wall thickness exceeds 4mm, it will cause the cooling time is too long, resulting in shrinkage and other issues should consider changing the product structure.

  

3.2 Uneven wall thickness will cause surface shrinkage.

3.3 Uneven wall thickness can cause pores and weld lines.

4 stiffeners

4.1 Reasonable application of ribs can increase product rigidity and reduce deformation.

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