# How to improve the precision of plastic molds

Update:02-09-2022
Summary:

For injection molds, the precision of plastic parts is […]

For injection molds, the precision of plastic parts is grade 3 and grade 3a, the weight is 5 grams, the hardening gating system is used, and the number of cavities is 4-6; the plastic parts are general precision (grade 4-5), forming The material is a partially crystalline material, and the number of cavities can be 16-20; the weight of the plastic part is 12-16 grams, and the number of cavities is 8-12; and the plastic part with a weight of 50-gram, 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 the weight of plastic parts continues to increase, multi-cavity molds are rarely used. For plastic parts with grades 7-9, the maximum number of cavities is increased by 50% compared to the plastics with grades 4-5 indicated.
Determine the parting surface. The position of the parting surface should be conducive to mold processing, exhaust, demoulding and molding operations, and the surface quality of plastic parts.
Determine the gating system (shape, location and size of main runner, sub-runner and gate) and exhaust system (exhaust method, location and size of exhaust groove).
Select the ejection method (ejector rod, ejector tube, push plate, combined ejector), and determine the undercut treatment method and core pulling method.
Determine the cooling and heating method, the shape and position of the heating and cooling groove, and the installation position of the heating element.
According to the mold material, strength calculation or empirical data, determine the thickness and external dimensions of the mold parts, the external structure and the positions of all connections, positioning, and guides.
Determine the main auto parts mould, the structural form of the structural parts.
Considering the strength of each part of the mold, calculate the working size of the molded part.
If the above problems are solved, the structural form of the mold will be solved naturally. At this time, you should start to draw the mold structure sketch to prepare for the formal drawing.