For the injection mold, the precision of plastic parts is grade 3 and 3a, the weight is 5g, the hardening pouring system is adopted, and the number of cavities is 4-6; The plastic parts are of general accuracy (level 4-5), the molding materials are local crystalline materials, and the number of cavities can be 16-20; The weight of plastic parts is 12-16g, and the number of cavities is 8-12; For plastic parts weighing 50 grams, the number of cavities is 4-8. For amorphous plastic parts, the recommended number of cavities is 24-48, 16-32 and 6-10. When we continue to increase the weight of plastic parts, we seldom use multi cavity mold. For plastic parts with 7-9 grade accuracy, the maximum number of cavities is 50% more than that of plastics with 4-5 grade accuracy.

2. determine the parting surface. The position of the parting surface shall be conducive to mold processing, exhaust, demoulding and molding operations, as well as the surface quality of plastic parts.

3. determine the gating system (shape, position and size of main sprue, sub sprue and gate) and exhaust system (exhaust method, exhaust slot position and size).

4. select the ejection method (ejector rod, pipe jacking, push plate, combined ejection), and determine the side concave treatment method and core pulling method.

5. determine the cooling and heating methods, the shape and position of the heating and cooling groove, and the installation position of the heating element.

6. according to the mold material, strength calculation or empirical data, determine the mold part thickness, overall dimension, overall structure and the positions of all connecting, positioning and guiding parts.

7. determine the structural form of main formed parts and structural parts.

8. considering the strength of each part of the mold, calculate the working dimensions of the formed parts.

If these problems are solved, the structural form of the mold will be solved naturally. At this time, we should draw the mold structure sketch by hand to prepare for the formal drawing.


Taizhou Yihao Mold Co., Ltd. is a professional manufacturer of precision molds and precision plastic parts in China. It is mainly engaged in the R & D, design and manufacturing of precision plastic molds, as well as injection molding and component assembly business. It is committed to providing customers with high-quality comprehensive services in mold design, injection molding plastic parts and product assembly.