Compression moulding also called compression molding.
Compression Moulding is an important technical process in the molding process, has a wide range of applications in industrial production, industrial processing, in people’s lives play an important role.
A plastic or rubber compound that is molded into a product in the closed mold cavity by means of heat and pressure. In general, the powdery, granular, agglomerate, flaky, and even preformed blanks of similar shape to the product are placed in a heated mold cavity and then closed to pressurize to form and cure or vulcanize. After the release of the product, the method is particularly suitable for thermosetting plastics molding process. Disadvantages are long production cycle, low efficiency, and poor product dimensional accuracy.
Others of compression moulding:
The main equipment is presses and molds. The role of the press is to apply pressure to the plastic through the mold. In rubber processing, the press is called a plate vulcanizer. The main parameters of the press include nominal tonnage, platen size, working stroke, and plunger diameter. These specifications determine the area, height, or thickness of the molded article the press can press, and the maximum molding pressure that can be achieved. According to the characteristics of its structure, the mold can be divided into three types: overflow, non-overflow and half-overflow, of which the semi-overflow type is used most. The process is divided into feeding, mold closing, venting, curing, demolding, and mold cleaning. If the product has an insert that needs to be sealed during molding, the insert should be placed well before adding the material. The main control process conditions are pressure, mold temperature and molding time.
In addition, there is a special form of molding method, that is, the powdery plastic is compacted first, then the preform is taken out of the mold, heated in a furnace to a melting point, the plastic particles are melted into a whole, and the cooled product or semi-finished product is obtained.
This method is called sinter forming and is mainly used for forming PTFE. Applications are mainly used for the thermosetting plastic molding, such as phenolic, melamine formaldehyde, urea formaldehyde and other plastics, but also for the production of unsaturated polyester and epoxy resin plus glass fiber reinforced plastic products.
Thermoplastics are also formed using this method, such as vinyl records. However, when the thermoplastic is molded, the mold must be cooled before the product is demoulded. Before the next part is molded, the mold must be reheated, so the production efficiency is very low. Molding method is also a very important molding method in the rubber industry.
The plastic material is cut or punched into a simple shape, added into the heating mold, vulcanized at the same time as the molding, and the product is also hot-molded. Many rubber model products such as gaskets and shock-absorbing products (such as aprons, rubber sheets) are produced by this method.
