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Common materials and requirements for injection mold design
Commonly used plastic materials for injection molds are: ABS, AS, PC, PS, PP, PVC, etc.
Generally, there are the following requirements for commonly used injection mold materials:
1. Good polishing performance
Injection moldmaterials are generally required to have good gloss and surface condition, so the roughness of the cavity surface is required to be very small, so that the surface of the cavity must be surface processed, such as polishing, grinding, etc. Therefore, the selected steel should not contain rough impurities and pores.
2. Less affected by heat treatment
In order to improve the hardness and wear resistance, the injection mold is generally heat treated, but this treatment should make the size change small. Therefore, it is best to use pre-hardened steel that can be machined.
3. Good wear resistance
The gloss and accuracy of the surface of the injection mold material are directly related to the wear resistance of the surface of the injection mold cavity. Especially when glass fiber, inorganic fillers and certain pigments are added to some plastics, they will be combined with the plastic melt. The high-speed flow in the runner and the mold cavity causes great friction on the surface of the cavity. If the material is not wear-resistant, it will wear out quickly, which will damage the quality of the plastic part.
4. High corrosion resistance
Many resins and additives have a corrosive effect on the surface of the cavity. This corrosion causes the metal on the surface of the cavity to be corroded and peeled off, the surface condition deteriorates, and the quality of the plastic parts deteriorates. Therefore, it is best to use corrosion-resistant steel, or chromium plating, cymbal nickel treatment on the surface of the cavity.
5. Good dimensional stability
During injection molding, the temperature of the injection mold cavity must be above 300°C. For this reason, it is best to select tool steel (heat-treated steel) that has been properly tempered. Otherwise it will cause changes in the microstructure of the material, resulting in changes in the size of the injection mold.
6. Easy to process
* Most of the injection mold parts are made of metal materials, and some structural shapes are still very complicated. In order to shorten the production cycle and improve efficiency, the injection mold materials are required to be easy to process into the shape and accuracy required by the drawings.
* The shape of the parts of the injection mold is often complicated and difficult to process after quenching. Therefore, materials with good thermal stability should be selected as far as possible.
* Injection mold materials can also be divided into soft molds and hard molds.
* The soft mold is generally made of P-20 pre-hardened steel, and some backward places are made of carbon steel above 45, and the production capacity is generally about 500,000 times;
* The hard mold is made of hot work mold steel such as H-13 (chrome steel) or 420 (stainless steel). It needs to be processed by heat treatment. The material and processing cost is more than twice as expensive, and the production capacity is more than one million times.