Key points in the design of injection molded plastic parts

- Aug 14, 2018-

  The choice of injection molded plastic parts depends mainly on the type of plastic (thermoplastic or thermoset), the starting form, and the shape and size of the product. Injection molded parts are generally molded, transfer molded, and injection molded. Lamination, molding, and thermoforming are the shaping of plastic on a flat surface. The above methods can be used for rubber processing. In addition, there are castings using liquid monomers or polymers as raw materials. Among these methods, extrusion and injection molding are used most and are the most basic molding methods.

1. Opening direction and parting line

  Each injection molded 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. After the mold opening direction is determined, the reinforcing ribs, snaps, protrusions and the like of the product are designed to be in the same direction as the mold opening direction, so as to avoid the core pulling to reduce the seam line and prolong the life of the mold. After the mold opening direction is determined, an appropriate parting line can be selected to improve the appearance and performance.

2. Demoulding slope

  Appropriate draft angle prevents product from being pulled. 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. The design of the deep cavity structure product requires that the slope of the outer surface is smaller than the slope of the inner surface 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 opening portion of the product.

3. Product wall thickness

  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. Uneven wall thickness can cause surface shrinkage. Uneven wall thickness can cause pores and weld lines.