What are the main performance requirements of plastic molds

Update: 02-04-2021

With the advent flip cap mould of high-speed molding ma […]

With the advent flip cap mould of high-speed molding machinery, the production speed of plastic products is getting faster and faster. Since the molding temperature is generally between 160~350°C, some have poor fluidity, and the molding speed is fast. A part of the molding die will soon exceed the surface temperature of 400°C. When the mold temperature increases, the hardness and strength of the mold will decrease, leading to early failure, mold wear or plastic deformation. In order to ensure the accuracy and small deformation of the mold, the tool steel should have high heat resistance when in use. In order to reduce the temperature, the die steel should have good thermal conductivity and a low coefficient of thermal expansion.


The working conditions of the molds are usually very poor, and some often bear a large load, which leads to brittle fracture. The larger extrusion pressure is generally 10~35MPa. Therefore, in order to prevent sudden brittle fracture of mold parts at work, the mold should have high strength and toughness. With the expansion of the use of plastic products, it is often necessary to add inorganic materials to the plastic, such as glass fiber reinforced materials. Due to the addition of additives, the plastic flow is greatly reduced, leading to mold wear. Therefore, the mold is required to have good wear resistance. Adding flame retardants such as polyvinyl chloride to the ABS resin may release corrosive gases during the molding process, and sometimes corrode and damage the mold in the airflow at the intersection.


Therefore, the mold needs to have good corrosion resistance. For plastic products that require large-scale, complex shapes and precision, the mold steel should have good cutting performance during the machining and hardening process. In order to prevent mold deformation and affect accuracy, we hope that the machining residual stress can be controlled to a minimum. The surface of the mold cavity is smooth, and the surface formed by the mirror surface needs to be polished. Its surface roughness is less than Ra0.4μm to ensure the appearance of the plastic molded product and promote the demolding of the molded product. The mold insert has high precision and high precision, and the cavity size accuracy is generally three to five.


Strive for the adhesion of the mating surface required to insert the cavity to prevent the molten material from entering the gap and causing material leakage. Many plastic products beautify their surface patterns by engraving. The application of large-bar embossed plates requires mold steel to have good pattern light corrosion resistance. Therefore, plastic mold steel should meet the performance of strength, hardness, wear, heat resistance, corrosion resistance, etc.; it should also have good polishing resistance, dimensional stability, easy nitrogen and thermal deformation and other process properties; good thermal conductivity, linear expansion coefficient Small physical properties. Plastic molds should choose different levels of quality and price according to the specific requirements of the molded parts.