What are the main performance requirements of plastic molds for automobile stamping parts?

2023-08-01 16:31:05

1. Heat resistance With the emergence of high-speed molding machinery, the production speed of plastic products is accelerated. Since the molding temperature is generally between 160 and 350 °C, some of them have poor fluidity and fast forming speed, 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, resulting in early wear or plastic deformation of the mold and failure. In order to ensure the accuracy and small deformation of the mold during use, the mold steel should have high heat resistance. In order to reduce the temperature rise, the mold steel should have good thermal conductivity and low thermal expansion coefficient.

2. Sufficient temperature at working temperature Most of the working conditions of the mold are very harsh, and some often bear a large load, which leads to brittle fracture of auto parts. 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 With the expansion of the use of plastic products, it is often necessary to add inorganic materials such as glass fiber to enhance the plasticity. Due to the addition of additives, the fluidity of the plastic is greatly reduced, resulting in wear of the mold, so The mold is required to have good wear resistance.

4. Corrosion resistance Adding flame retardant and polyvinyl chloride to ABS resin may release corrosive gas during the molding process, and sometimes the mold will be corroded and damaged at the air flow channel, so the mold steel is required to have good corrosion resistance.

5. Good machinability With the increase in size, shape and precision of plastic products, steel for molds is required to have good machinability and less work hardening during cutting. In order to avoid mold deformation and affect the accuracy, it is hoped that the machining residual stress can be controlled to a minimum.

6. Mirror polishing processability The inner surface of the mold cavity is smooth, and the molding surface is required to be polished to a mirror surface, and the surface roughness is lower than Ra0.4μm, so as to ensure the appearance of the plastic pressed parts and facilitate demoulding.

7. Dimensional accuracy The mold insert has high processing precision and high matching precision, and the cavity dimensional accuracy is generally 3~5 grades. The joint surfaces of mosaic cavities are required to be tightly sealed to prevent molten material from entering the gap and causing material leakage.

8. Photoetching performance of patterns and patterns Many plastic products have patterns added to their surfaces for beautification. In the leather industry, large-scale embossed panels are used, which requires mold steel to have good pattern photoetching.

Therefore, the mold steel of automobile stamping parts should meet the performance of strength, hardness, wear resistance, heat resistance, corrosion resistance, etc.; at the same time, it should have good polishing, dimensional stability, easy nitriding and small heat treatment deformation; good Excellent thermal conductivity and small linear expansion coefficient and other physical properties.