1. Cavity layout.

Determine the number of cavities and their arrangement according to the geometric structure characteristics of the plastic parts, dimensional accuracy requirements, batch size, mold manufacturing difficulty, mold cost, etc.

For injection molds, the precision of plastic parts is 3 and 3a, and the weight is 5 grams. The hardening casting system is adopted, and the number of cavities is 4-6; the plastic parts are general precision (4-5), and the molding The material is a partially crystalline material, and the number of cavities can be 16-20; the weight of plastic parts is 12-16 grams, and the number of cavities is 8-12; and the weight of plastic parts is 50-100 grams, the number of cavities is selected 4-8.

The recommended number of cavities for amorphous plastic parts is 24-48, 16-32 and 6-10. When the weight of plastic parts continues to increase, multi-cavity molds are rarely used. For plastic parts with 7-9 accuracy, the maximum number of cavities is increased to 50% compared with the indicated plastic with 4-5 accuracy.

2. Determine the parting surface.

The position of the parting surface should be conducive to mold processing, venting, demolding and molding operations, and the surface quality of plastic parts.

3. Determine the pouring system (the shape, location and size of the main runner, sub-runner and gate) and exhaust system (exhaust method, exhaust slot location, size).

4. Select the ejection method (ejector, pipe, push plate, combined ejector), determine the undercut treatment method and core pulling method.

5. Determine the cooling and heating method, the shape and location of the heating and cooling groove, and the installation location of the heating element.

6. According to the mold material, strength calculation or empirical data, determine the thickness and dimensions of the mold parts, the shape structure and all connections, positioning, and guide positions.

7. Determine the structure of the main forming parts and structural parts.

8. Consider the strength of each part of the mold, calculate the working size of the molded part. If these problems are solved, the structure of the mold will naturally be solved. At this time, we should start to draw the mold structure sketch to prepare for the formal drawing.