The plastic mold is a combined plastic mold for compression molding, extrusion molding, injection molding, blow molding and low foam molding, which mainly comprises a combination of a die assembly substrate, a die assembly and a die combination card. A concave mold of a variable cavity, a punch having a variable core composed of a punch combination substrate, a punch assembly, a punch combination card, a cavity cutting assembly, and a side cut combination plate. Coordinated changes in the die, die and auxiliary forming systems. It can process series of plastic parts of different shapes and sizes.
Material requirements for plastic molds
1. Sufficient surface hardness and wear resistance
The hardness of the plastic mold is usually below 50-60HRC, and the heat-treated mold should have sufficient surface hardness to ensure sufficient rigidity of the mold. In the work, the mold is subjected to large compressive stress and friction due to the filling and flowing of the plastic. The mold is required to maintain the accuracy of the shape and the stability of the dimensional accuracy to ensure the mold has a sufficient service life. The wear resistance of the mold depends on the chemical composition of the steel and the heat treatment hardness, so increasing the hardness of the mold is beneficial to improve its wear resistance.
2. Excellent machinability
Most plastic molding dies require a certain amount of cutting and trimming in addition to EMD processing. In order to prolong the service life of the cutting tool, improve the cutting performance, and reduce the surface roughness, the hardness of the steel for the plastic mold must be appropriate.
3. Good polishing performance
High-quality plastic products require a small roughness value on the surface of the cavity. For example, the surface roughness value of the injection molding cavity is required to be less than Ra 0.1 to 0.25, and the optical surface is required to be Ra < 0.01 nm. The cavity must be polished to reduce the surface roughness value. The steel material selected for this purpose requires less material impurities, fine uniformity of the structure, no fiber orientation, and no pitting or orange peel defects during polishing.
4. Good thermal stability
The shape of the parts of the plastic injection mold is often complicated, and it is difficult to process after quenching. Therefore, it should be selected with good thermal stability. When the mold is formed by heat treatment, the linear expansion coefficient is small, the heat treatment deformation is small, and the dimensional difference caused by the temperature difference The rate is small, the metallographic structure and the mold size are stable, and the processing can be reduced or no longer processed to ensure the dimensional accuracy and surface roughness of the mold.
45, 50 grade carbon steel has a certain strength and wear resistance, and is mostly used for formwork materials after quenching and tempering treatment. High carbon tool steel and low alloy tool steel have high strength and wear resistance after heat treatment, and are mostly used for forming parts. However, high carbon tool steel is only suitable for the manufacture of molded parts with small size and simple shape due to its large heat treatment deformation.
With the development of the plastics industry, the complexity and precision of plastic products are becoming more and more demanding, and higher requirements are also placed on the mold materials. For the production of complex, precise and corrosion-resistant plastic molds, pre-hardened steel (such as PMS), corrosion-resistant steel (such as PCR) and low-carbon maraging steel (such as 18Ni-250) can be used. Machining, heat treatment and polishing performance and high strength.
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Plastic Mold Materials: What Are The Requirements?
原文：https://www.cnblogs.com/kristamedicalmould/p/11764327.html