What Are The Basic Material Requirements For Injection Molds?

Reasonable selection of molding materials is the primary task of mold designers. Generally, the basic requirements for mold materials are as follows.

1. Easy to process, mold parts are mostly made of metal materials, and some structural shapes are still very complicated. In order to shorten the production cycle and improve efficiency, the mold materials are required to be easily processed into the shape and precision required by the drawings.

2. Good wear resistance The gloss and precision of the surface of the plastic part are directly related to the wear resistance of the surface of the mold cavity, especially when some plastics are added with glass fiber, inorganic filler and some pigments, they are plastic. The melt flows together in the flow channel and the cavity, and the friction on the surface of the cavity is very large. If the material is not wear-resistant, it will wear quickly and the quality of the plastic part will be damaged.

3. High Corrosion Resistance Many resins and additives have corrosive effects on the surface of the cavity. This corrosion causes the surface of the cavity to corrode and peel off, the surface condition deteriorates, and the quality of the molded part deteriorates. Therefore, it is best to use corrosion-resistant steel or chrome-plated or nickel-plated surfaces.

4. Good dimensional stability During injection molding, the temperature of the mold cavity should reach 300 °C or higher. For this reason, it is preferable to use a suitably tempered tool steel (heat treated steel). Otherwise it will cause a change in the microstructure of the material, resulting in a change in the size of the mold.

5. Small effect by heat treatment In order to improve the hardness and wear resistance, the mold is generally subjected to heat treatment, but this treatment should be such that the dimensional change is small. Therefore, it is preferable to use a pre-hardenable steel that can be machined.

6. Polishing performance Good plastic parts usually require good gloss and surface condition. Therefore, the surface roughness of the cavity is required to be very small. Therefore, the surface of the cavity must be surface-processed, such as polishing and grinding. Therefore, the selected steel should not contain rough impurities and pores.