What are the main properties of plastic mold?
1. Heat Resistance
With the emergence of high-speed molding machinery, the manufacturing of plastic products have speeded up. As the molding temperature is generally between 160 ~ 350 ℃, the poor fluidity and fast forming speed will make part of the molding surface temperature exceed 400 ℃ in a very short period of time. When the mold temperature is high, the mould hardness and strength will reduce, which will lead to the failure of the mould due to early wear or mold plastic deformation. In order to ensure the accuracy and deformation of the mould while using, die steel should have a higher heat resistance. To reduce the temperature rise, die steel should have good thermal conductivity and low coefficient of thermal expansion.
2. The strength and toughness of the mould
The operating conditions of mould are mostly very poor, and some of them often bear larger loads, which will result in brittle fracture. The pressure of extrusion molding is big, it is generally 10 ~ 35MPa. Therefore, in order to prevent the mold parts from breaking suddenly while manufacturing, the mould should have a high strength and toughness.
3. Abrasive Resistance
With the expansion of plastic products, we often need to add inorganic materials such as glass fiber to enhance plasticity. The adding of inorganic materials have reduced the fluidity of plastic and cause wear of the mould, so the mould should have good wear resistance.
4. Corrosion Resistance
We add flame retardant and PVC in the ABS plastic resin, which may release corrosive gases in the molding process. Sometimes the mould
will be damaged because of the rust at the air flow mouth, so the die steel should have a good corrosion resistance.
5. Good Cutting Performance
With the large-scale, complex shape and sophistication of plastic products, the die steel needs to have a good cutting performance, so that we can reduce work hardening. In order to avoid the deformation of the mold and affect the accuracy, hopefully that the residual stress can be controlled at the lowest.
6. Mirror Polished
The surface of die cavity is smooth, so the forming surface should be burnished to mirror surface, its surface roughness is below Ra0.4μm so that we can ensure good appearance of plastic die cast parts and easy mold release.
7. Dimensional Accuracy
Die insert processing is done with high precision, the cavity dimensional accuracy is generally 3 level to 5 level. The joining surface of the core cavity formed by insert blocks is required to be sealed, in order to prevent the melting materials from falling into the gap and cause material leakage.
8. The light fastness of patterns
Many plastic products have patterns on their surfaces in order to beautify the products. Leather embossed plate is applied to leather industry, which requires the die steel to have good etching property. Therefore, the die steel should have performances of strength, hardness, wear resistance, heat resistance and corrosion resistance, as well as good polishing, dimensional stability, easy to nitride and heat, tiny deformation; good thermal conductivity and small linear expansion coefficient, etc. Plastic molds should choose the die steel with different quality and price based on the specific requirements of the component.