① Cavity layout.
The number of cavities and their arrangement are determined according to the geometric structure characteristics of plastic parts, dimensional accuracy requirements, batch size, difficulty of mold manufacturing, and mold cost.Factors affecting the structure of the mold and the individual systems of the mold
For the injection mold, the precision of the plastic parts is grade 3 and grade 3a, the weight is 5 grams, the hardened pouring system is adopted, and the number of cavities is 4-6; the plastic parts are of general precision (4-5 grade), and the molding The material is partially crystalline material, the number of cavities can be 16-20; the weight of plastic parts is 12-16 grams, the number of cavities is 8-12; the weight of plastic parts is 50-100 grams, the number of cavities is 4-8 pieces.Factors affecting the structure of the mold and the individual systems of the mold
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 7-9 precision grades, the maximum number of cavities increases to 50% compared with the pointed 4-5 grades of precision plastics.
② 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.Plastic mold design process
③Determine the gating system (the shape, position and size of the main runner, sub-runner and gate) and the exhaust system (the method of exhaust, the position and size of the exhaust groove).
④ Select the ejection method (ejector pin, pipe ejector, push plate, combined ejector), and determine the undercut treatment method and core pulling method.
⑤Determine the cooling and heating methods, the shape and position of the heating and cooling grooves, and the installation parts of the heating elements.
⑥ 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.
⑦ Determine the structural form of the main molding parts and structural parts.
⑧ 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 naturally be solved. At this time, you should start to draw a sketch of the mold structure to prepare for the formal drawing.
⑨Draw mold diagram
It is required to draw according to the national drafting standards, but it is also required to combine the factory standards and the customary drawing methods of the factory not stipulated by the state.
Before drawing the general assembly drawing of the mold, the process drawing should be drawn, and it must meet the requirements of the part drawing and process information. The size guaranteed by the next process should be marked with the words “process size” on the drawing. If no other mechanical processing is performed after forming except for repairing burrs, then the process drawing is exactly the same as the part drawing.
It is best to mark the part number, name, material, material shrinkage rate, drawing scale, etc. under the process drawing. Usually, the process drawing is drawn on the mold assembly drawing.
Factors affecting the structure of the mold and the individual systems of the mold