Several Key Points in the Design of Injection Molding Parts


  1. Opening Direction and Parting Line

In order to minimize the influence of core-pulling slider mechanism and parting line on appearance, the opening direction and parting line of each injection product should be determined at the beginning of design.

  1. After the direction of die opening is determined, the structure of reinforcing rib, buckle and bulge of the product is designed to be consistent with the direction of die opening as far as possible, so as to avoid core pulling, reduce the sewing line and prolong the life of the die.
  2. After the opening direction is determined, the proper parting line can be selected to avoid the buckling in the opening direction, so as to improve the appearance and performance.
  3. Slope of demoulding
  4. Proper demoulding slope can avoid the product brushing (broaching). The demoulding slope of smooth surface should be more than 0.5 degree, the surface of fine grain (sand surface) should be more than 1 degree, and the surface of coarse grain should be more than 1.5 degree.
  5. Proper demoulding slope can avoid product top injury, such as whitening, deformation and breaking.
  6. When designing deep cavity structure products, the slope of outer surface should be greater than that of inner surface, so as to ensure that the core of the mould is not offset during injection molding, to obtain uniform product wall thickness, and to ensure the material strength of the open part of the product.

Thickness of product wall

  1. All kinds of plastics have a certain wall thickness range, generally 0.5-4 mm. When the wall thickness is more than 4 mm, it will cause long cooling time and shrinkage printing, so we should consider changing the product structure.
  2. The uneven wall thickness will cause surface shrinkage.
  3. Non-uniform wall thickness will cause gas holes and weld marks.
  4. Reinforcing tendons
  5. Reasonable application of reinforcing bars can increase product rigidity and reduce deformation.
  6. The thickness of reinforcing bars must be less than (0.5-0.7) T product wall thickness, otherwise the surface will shrink. 3. The one-sided inclination of reinforcing tendon should be greater than 1.5 degrees to avoid top injury.

Five, fillet

  1. Too small fillets may cause stress concentration and cracking of products. 2. Too small fillet may cause stress concentration in the die cavity, leading to cavity cracking.
  2. Setting reasonable rounded corners can also improve the processing technology of the die, such as the cavity can be directly milling with R cutter, and avoid inefficient electrical processing.
  3. Different rounded corners may cause the movement of parting lines. Different rounded corners or clearing corners should be selected according to the actual situation.

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