Design Principles For Plastic Molds

- Sep 13, 2018-

3. The wall thickness is even.


The wall thickness of plastic parts is an important structural factor, which is determined by the use requirements and process requirements, and has a great influence on the process. Therefore, it is very important to choose the wall thickness of the plastic parts reasonably. As far as the process is concerned, the wall thickness is too small, the flow resistance of the plastic in the cavity is large, and the molding is difficult.


Especially for complex shapes and large-sized plastic parts, it is easy to have a defect of filling or to increase the injection pressure; if the wall thickness is too large, it not only increases the cost, but also prolongs the cooling time, lengthens the molding cycle, and reduces the production efficiency. It is easy to produce defects such as shrinkage cavities and bubbles. The wall thickness should be based on the principle of uniformity everywhere, but it must be changed due to the structure of the plastic part or the thickness of the formed upper wall. And for economic reasons, it is necessary to make appropriate adjustments to the wall thickness.


Therefore, the following points must be considered when determining the wall thickness:


(1) Construction strength.

(2) Demoulding strength.

(3) It can evenly distribute the impact.

(4) The fitting metal part is partially prevented from cracking (the thermal expansion coefficient of the molding material and the metal material is different, and cracks are likely to occur at the time of shrinkage).

(5) The structure hinders the flow and prevents insufficient filling. The wall thickness is selected according to the type of plastic and the size of the molded part.