(1) Injection molding The plastic is first added to the […]
(1) Injection molding
The plastic is first added to the heating barrel of the injection machine. The plastic is heated and melted. Under the push of the injection machine screw or plunger, the nozzle and the mold casting system enter the mold cavity, and the hardening and shaping become the injection molding due to physical and chemical action. product. Injection molding consists of a cycle consisting of injection, pressure holding (cooling) and plastic part demolding, so that injection molding has periodic characteristics. Thermoplastic injection molding has a short molding cycle, high production efficiency, and low wear of the melt on the mold. It can form large-sized plastic parts with complex shapes, clear surface patterns and high mark precision; but for plastics with large wall thickness changes. It is difficult to avoid molding defects. Plastic anisotropy is also one of the quality issues and should be minimized by taking all possible measures.
(2) compression molding
Commonly known as press molding, it is one of the first methods of molding plastic parts. Compression molding is to directly add plastic to an open mold cavity with a certain temperature, and then close the mold, and the plastic melts into a flowing state under the action of heat and pressure. Due to physical and chemical effects, the plastic is hardened into a plastic part having a constant shape and constant shape and size. Compression molding is mainly used for molding thermosetting plastics, such as phenolic molding powder, urea-formaldehyde and melamine formaldehyde molding powder, glass fiber reinforced phenolic plastic, epoxy resin, DAP resin, silicone resin, polyimide, etc. It is also possible to mold and process unsaturated polyester dough (DMC), sheet molding compound (SMC), pre-formed molding compound (BMC), and the like. Under normal circumstances, the compression mold is often divided into three types: the overflow type, the non-overflow type, and the semi-overfill type according to the matching structure of the upper and lower molds of the compression film.