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What are the performance requirements of plastic molds?

Update:19-03-2021
Summary:

When we buy plastic molds, we often have requirements f […]

When we buy plastic molds, we often have requirements for the performance of Wuhan plastic molds. The following summarizes a few points for your reference.
1. Heat resistance
With the emergence of high-speed moldingPlastic Industrial Pallet Moulds Manufacturers machinery, the production speed of plastic products has accelerated. Since the molding temperature is generally between 160-350°C, the fluidity is not good, and the forming speed is fast, which will cause the molding surface temperature of the mold part to exceed 400°C in a very short time.
When the working temperature of the mold is high, the hardness and strength of the mold will decrease, leading to early wear of the mold or plastic deformation and failure. In order to ensure the precision and small deformation of the mold in 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.
2. It has sufficient strength at working temperature
Most of the molds have very poor working conditions, and some of them are often subjected to heavy loads, which leads to brittle fracture. The extrusion molding pressure is relatively high, generally 10-35MPa. Therefore, in order to prevent sudden brittle fracture of mold parts during work, the mold must have high strength and toughness.
3. Abrasion resistance
As the use of plastic products expands, it is often necessary to add inorganic materials such as glass fiber to plastics to enhance plasticity. Because additives must be added, the fluidity of the plastic is greatly reduced, resulting in mold wear, so molds are required to have good performance. Abrasion resistance.
4. Corrosion resistance
Adding flame retardant and polyvinyl chloride to ABS resin may release corrosive gas during the molding process, and sometimes rust and damage the mold at the mouth of the air flow channel. Therefore, the mold steel is required to have good corrosion resistance.
5. Good cutting performance
As plastic products become larger, more complicated in shape, and more precise, mold steel is required to have good cutting performance and less work hardening during the cutting process. In order to avoid mold deformation and affect accuracy, it is hoped that the residual stress of machining can be controlled to a minimum.
6. Mirror polishing processability
The inner surface of the mold cavity is smooth, 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 pressing and facilitate demolding.
7. Dimensional accuracy
The mold insert has high machining accuracy and high matching accuracy, and the cavity size accuracy is generally 3-5. The joint surfaces of the mosaic cavity must be tightly closed to prevent the melted material from entering the gap and causing leakage, flashing or burrs.
8. Pattern and pattern photo-etching performance
In order to beautify many plastic products, patterns are added to the surface. For example, in the leather industry, large-scale leather embossing plates are used, which requires the mold steel to have good pattern photoetchability.
Therefore, the mold steel should meet the performance of strength, hardness, wear resistance, heat resistance, corrosion resistance, etc.; at the same time, it should also have good polishability, dimensional stability, easy nitriding and small heat treatment deformation and other process properties; good thermal conductivity Physical properties such as performance and small linear expansion coefficient.