Compression molding is also called compression molding […]
Compression molding is also called compression molding or compression molding. Compression molding (also known as compression molding or compression molding) is an operation that first puts powdered, granular or fibrous plastic into a mold cavity at the molding temperature, and then closes the mold to press to shape and solidify it. Compression molding can be used for thermosetting plastics, thermoplastics and rubber materials.
This molding method is to first put powder, granular or fiber-like plastics into the mold cavity at the molding temperature. Then the mold is closed and pressurized to form and solidify. The compression mold can be used for thermosetting plastics and thermoplastics. When the thermosetting plastic is molded, the plastic is always at a high temperature. The thermosetting placed in the physical cavity is expected to be under pressure. Under this condition, the solid becomes a half-wave body and fills the cavity in this state to obtain the shape given by the cavity. As the cross-linking reaction deepens, the viscosity of the semi-liquid gradually increases until it becomes a solid. Molded into a product. The molding of thermoplastics in the previous stage is the same as that of thermosetting plastics but because there is no cross-linking reaction. Therefore, after the cavity is filled, the mold must be cooled and solidified to be demolded into a product. Because the mold needs to be heated and cooled alternately during the molding of thermoplastics, and the production cycle is long, the molding of thermoplastic products is more economical by injection molding, and compression molding is only used when molding larger flat plastic products.
The complete compression molding process is composed of two processes: material preparation and molding. The material preparation is divided into two parts: pre-pressing and pre-heating. Pre-pressing is generally only used for thermosetting plastics, while pre-heating can be used for thermosetting and thermoplastic plastics. When molding thermosetting plastics, the two parts of pre-pressing and pre-heating can be used, or only one of the pre-heating parts can be used. It is rare to perform pre-compression without pre-heating. Pre-pressing and pre-heating can not only improve the molding efficiency, but also play a positive role in the quality of the product. If the product is not large and the quality requirements are not high, the preparation process can also be eliminated.
(1) The loss of raw materials is small and will not cause too much loss (usually 2% to 5% of the product quality).
(2) The internal stress of the product is very low, and the warpage deformation is also very small, and the mechanical properties are relatively stable.
(3) The wear of the mold cavity is small, and the maintenance cost of the mold is low.
(4) The cost of molding equipment is low, and its mold structure is simpler, and its manufacturing cost is usually lower than that of injection molds or transfer molding molds.
(5) Larger flat products can be formed. The size of the product that can be molded by molding is only determined by the clamping force of the existing molding press and the size of the template.
(6) The shrinkage of the product is small and the repeatability is good.
(7) A mold with a large number of cavities can be placed on a given template, and the productivity is high.
(8) It can be adapted to automatic feeding and automatic removal of products.
(9) High production efficiency, easy to realize specialized and automated production.
(10) The product has high dimensional accuracy and good repeatability.
(11) The surface is smooth and clean without secondary modification.
(12) Products with complex structures can be formed at one time.
(13) Mass production, relatively low price.