The quality of plastic part mould depends on the material it chooses. A plastic part mould is an indispensable tool in plastic molding processing, and its proportion in the total mould output is increasing year by year. According to statistics, plastic part mould is about It accounts for 33% of the total amount of forming molds. Therefore, the application of plastic part mould is becoming more and more important in the national economy. The main factors that affect the life of plastic parts are mold structure, mold material, mold processing quality, mold working status, product parts condition, etc. Among them, the characteristics of the mold material itself and the heat treatment play a vital role.
Choose plastic part mould materials and requirements
1. Good thermal stability
The shape of the parts of the plastic injection mold is often complicated to process after quenching. Therefore, materials with good thermal stability should be selected as far as possible. After the plastic mold is formed by heat treatment, the linear expansion coefficient is small, the heat treatment deformation is small, and the dimensional change rate caused by the temperature difference is small. The metallographic structure and the mold size are stable. It can be reduced or no longer processed to ensure the size of the plastic mold. Precision and surface roughness requirements.
2. Good polishing performance
High-quality injection molded products require a small roughness value on the surface of the cavity. For example, the surface roughness value of the injection mold cavity is required to be less than Ra0.1-0.25, and the optical surface requires Ra<0.01nm. The cavity must be polished to reduce the surface roughness value. For this reason, the selected steel requires fewer material impurities, a fine and uniform structure, no fiber directionality, and no pitting or orange peel defects during polishing.
3. Sufficient surface hardness and wear resistance
The hardness of the plastic mold is usually below 50-60HRC, and the heat-treated mold should have sufficient surface hardness to ensure that the mold has sufficient rigidity. When the mold is in operation, because the filling and flow of the plastic have to withstand greater compressive stress and friction, the mold is required to maintain the stability of shape accuracy and dimensional accuracy to ensure that the mold has sufficient service life. The wear resistance of the mold depends on the chemical composition and heat treatment hardness of the steel. Therefore, increasing the hardness of the mold is beneficial to enhance its wear resistance.
4. Excellent machinability
In addition to EMD processing, most plastic molding molds require certain cutting processing and fitter repairs. To extend the service life of cutting tools, enhance cutting performance, and reduce surface roughness, the hardness of the steel used for plastic molds must be appropriate.
Pre-hardened plastic part mould steel is the specified hardness used in the treatment of steel. This type of steel has good cutting performance and can be directly processed into the cavity. Usually used in a large number of plastic products, such as the processing of mirror molds, the hardness range of 32 ~ 40HRC is used. Now, most carbon steel mold steel is widely used because of its low price, convenient use, and certain mechanical properties. In addition to plastic part mould steel, it also includes pre-hardened plastic part mould steel and other mould steels. There are many mould sheets of steel. At present, the more commonly used mould steels include pre-hardened plastic part mould steel and carburized plastic part mould steel, and age-hardened plastic part mould steel.