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What are the main performance requirements of plastic molds?

Update:15-01-2022
Summary:

The main function of the plastic mold requires that in […]

The main function of the plastic mold requires that in the plastic film forming process, the quality of the mold plays an obvious role in ensuring the quality of the product. Different types of plastic products and the molding process of different products have different requirements for the material, function and shape of the Helmet Mould. With the emergence of high-speed molding machines, the production speed of plastic products has accelerated. Because the molding temperature is generally between 160 and 350 ℃, some of them have poor fluidity, and the forming speed is fast, which will make the molding surface temperature of the mold part exceed 400 ℃ in a very short time. When the working temperature of the mold is high, the hardness and strength of the mold will decrease, resulting in early wear of the mold or plastic deformation and failure. In order to ensure the precision and small deformation of the mold during use, the mold steel should have high heat resistance. In order to reduce the temperature rise, the die steel should have good thermal conductivity and low thermal expansion coefficient.


With sufficient temperature at the working temperature, most of the working conditions of the mold are very harsh, and some often undergo large loads, which then lead to brittle fracture. The extrusion molding pressure is relatively large, generally 10~35MPa. Therefore, in order to avoid sudden brittle fracture of mold parts during operation, the mold must have high strength and toughness. With the expansion of the use of plastic products, the wear resistance often needs to add inorganic materials such as glass fiber to enhance the plasticity. Because of the addition of the additives, the fluidity of the plastic is greatly reduced, resulting in the wear of the mold, so the mold is required to be used. Has outstanding wear resistance. Corrosion resistance Adding flame retardants to ABS resin may release corrosive gas during the molding process, and sometimes the mold is rusted and damaged at the air runner mouth, so the mold steel is required to have excellent corrosion resistance.

Excellent cutting performance With the large-scale, complex and refined shape of plastic products, mold steel is required to have excellent cutting performance and less work hardening during the cutting process. In order to avoid the deformation of the mold and affect the accuracy, it is hoped that the residual stress of the machining can be controlled to a small limit. Mirror polishing processability The inner and outer surfaces of the mold cavity are lubricated, and the molding surface needs to be polished into a mirror surface, and the surface roughness is lower than Ra0.4μm to ensure the appearance of the plastic pressed parts and facilitate demoulding. Scale precision mold inserts have high machining precision and high matching precision, and the cavity scale precision is generally 3 to 5 grades. The joint surface of the mosaic cavity is required to be tightly closed to prevent the molten material from entering the gap and causing material leakage. The pattern is added to its surface. In the leather industry, large-scale leather embossed plates are used, which all require mold steel to have good pattern photoerosion.

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