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What are the material requirements for plastic molds?
Release time:2023-10-24
What are the material requirements for plastic molds?
Plastic mold working conditions and cold punching molds are different, generally in 150 ° C - 200 ° C to work, in addition to a certain pressure, but also to withstand the effects of temperature. Now according to the plastic molding mold conditions, processing methods will be different from the basic performance requirements of plastic mold steel is generally summarized below:
1 sufficient surface hardness and wear resistance
Plastic mold hardness is usually below 50-60HRC, after heat treatment of the mold should have sufficient surface hardness to ensure that the mold has sufficient rigidity. Mold in the work due to the filling and flow of plastic to withstand greater compressive stress and friction, the mold is required to maintain the shape of the precision and dimensional accuracy of the stability of the mold to ensure that the mold has sufficient service life. The wear resistance of the mold depends on the chemical composition of the steel and heat treatment hardness, so improve the hardness of the mold is conducive to improve its wear resistance.
2 excellent cutting and processing
Most of the plastic molding molds, in addition to EMD processing also need to carry out a certain amount of cutting processing and clamp repair. In order to extend the service life of cutting tools, improve cutting performance, reduce surface roughness, plastic mold steel hardness must be appropriate.
3 good polishing performance
High-quality plastic products, the requirements of the cavity surface roughness value is small. For example, the injection mold cavity surface roughness value is required to be less than Ra0.1 ~ 0.25 level, the optical surface is required to Ra <0.01nm, the cavity must be polished, reduce the surface roughness value. For this reason, the choice of steel requires less impurities in the material, the organization of fine uniformity, no fiber orientation, polishing should not appear pitting or orange peel defects.
4 good thermal stability
Plastic injection mold parts are often complex shape, hard to process after quenching, so we should try to use a good thermal stability, when the mold mold molding process after heat treatment due to the coefficient of linear expansion is small, heat treatment deformation is small, the temperature difference caused by the rate of change of the size of the small, the metallurgical organization and mold dimensional stability can be reduced or no longer be processed to ensure that the mold dimensional accuracy and surface roughness requirements.
45, 50 grades of carbon steel has a certain strength and wear resistance, after tempering treatment is used for mold materials. High-carbon tool steel, low alloy tool steel after heat treatment with high strength and wear resistance, more for molding parts. But high carbon tool steel because of its heat treatment deformation, only for the manufacture of small size, simple shape molding parts.
With the development of the plastics industry, the complexity of plastic products, precision and other requirements are getting higher and higher requirements for mold materials. For the manufacture of complex, precision and corrosion-resistant plastic mold, can be used pre-hardened steel (such as PMS), corrosion-resistant steel (such as PCR) and low-carbon martensitic aging steel (such as 18Ni-250), have a better cutting and processing, heat treatment and polishing performance and high strength.
In addition, in the selection of materials must also be considered to prevent abrasion and gluing, such as the existence of two surfaces of the relative movement of the situation, try to avoid the selection of the same organizational structure of the material, special conditions can be one side of the plating or nitriding, so that the two sides of the surface with a different structure.
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