Most plastic electronic components are injection molded. Because these plastic parts have high design accuracy and are processed by using special engineering plastics. These plastic parts cannot be used conventional injection molding, but must use precision injection molding technology.
There are many related conditions for precision injection molding, and the four basic factors are plastic materials, injection molds, injection molding process and injection equipment. When it comes to "precision", it should be perfect for any product. Many things are now made through molds. What are the characteristics of precision injection molds?
The accuracy of the mold is mainly determined by the high accuracy of the mold cavity size, the accuracy of the cavity positioning or the accuracy of the parting surface. The size tolerance of general precision injection molds should be controlled below 1/3 of the product size tolerance.
Machinability and rigidity. In the design of the mold structure, the number of cavities should not be too much, and the bottom plate, support plate and cavity wall should be thicker to avoid the parts from undergoing elastic deformation under high temperature and high pressure.
The demold ability of the product, the mold should try to adopt a small number of cavities, few and short runners, and a higher finish than ordinary molds, which is conducive to mold release.
The material of precision mold is alloy steel with high mechanical strength. The materials for making the cavity and runner need to undergo strict heat treatment, and materials with high hardness (formed parts should reach about HRC52), good abrasion resistance and strong corrosion resistance are selected.
As far as plastic injection mold is concerned, the mold is one of the keys to obtaining precision plastic products that meet the quality requirements. The mold used for precision injection molding should meet the requirements for the size, accuracy and shape of the product. But even if the precision and size of the mold are consistent, the actual dimensions of the plastic products it molds will be inconsistent due to differences in shrinkage. Therefore, effectively controlling the shrinkage of plastic products is very important in precision injection molding technology.
Whether the injection mold is properly designed will directly affect the shrinkage of plastic products. Because the mold cavity size is obtained from the size of the plastic product plus the estimated shrinkage, the shrinkage is determined by the plastic manufacturer or engineering plastics manual. A value within a recommended range, which is not only related to the gate form, position and distribution of the mold, but also the crystal orientation (anisotropy) of the engineering plastic, the shape and size of the plastic product, and the distance to the gate It is related to the position and closely related to the mold cooling distribution system.
The main factors affecting plastic shrinkage are thermal shrinkage, phase change shrinkage, orientation shrinkage, compression shrinkage, and elastic recovery. These factors are related to the molding conditions or operating conditions of customized precision plastic injection mold.
Precision injection molding technology is the main and key production technology for plastic parts and the design of precision injection molds is the main part of this production technology. Reasonably designing precision injection molds is the basis and prerequisite for obtaining precision products.