⑴ suction hole design: Vacuum suction hole design is the key to mold design, suction holes should be located in the final mold affixed to the film, such as the molding die in the mold around the bottom and a concave place, when the punch molding in the bottom of the punch Around, etc., the specific circumstances depending on the shape of plastic parts and size may be.
For complex plastic parts, suction holes should be concentrated, for large flat plastic parts, exhaust holes need to be uniform. Hole spacing can be determined by the size of plastic parts, for small plastic parts, hole spacing can be selected in the 20 ~ 30mm, large plastic parts should be appropriate to increase the distance. Usually shaped plastic flow is good, the molding temperature is high, the smaller the suction hole; bad material plate thickness, the suction hole larger; billet plate thickness is small, smaller by the suction hole. In short, the size of the suction hole is required both in a short period of time between the blank material and the molding surface of the mold out of the air, without leaving traces of the vent on the plastic parts. General suction hole diameter is 0.5 ~ 1mm, the maximum suction hole diameter size does not exceed 50% of the thickness of the sheet is appropriate, but for less than 0.2mm plate, too small suction hole can not be processed.
⑵ cavity size: The cavity size of the vacuum forming mold should also consider the plastic shrinkage, the calculation method and injection cavity size calculation the same. The shrinkage of vacuum forming plastic parts, about 50% is generated after the plastic parts, 25% is maintained at room temperature within 1h after the mold release, the remaining 25% is generated in the next 8 ~ 24h of. Plastic parts molded with concave mold than the use of plastic mold shrinkage to 25% to 50%. Many factors affect the dimensional accuracy of plastic parts, reducing the dimensional accuracy of the cavity, but also with the molding temperature, mold temperature and plastic parts varieties and so on, so to accurately predict the shrinkage rate is very difficult. If the production volume is relatively large, high dimensional accuracy requirements, it is best to use gypsum mold making trial products, measured the shrinkage, the above is the basis for the design of the mold cavity.