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What are the main performance requirements for plastic molds?

update:05-01-2019
abstract:

1. Heat-resistance function With the advent of high-spe […]

1. Heat-resistance function With the advent of high-speed molding machinery, the production speed of plastic products is accelerating. Because the molding temperature of Jiangxi plastic mold is usually between 160~350 °C, some fluidity is not good, and the forming speed is fast, which will make the mold part molding surface temperature exceed 400 °C in a very short time. When the working temperature of the mold is high, the hardness and strength of the mold are lowered, causing the mold to wear out or plastically deform and fail. In order to ensure the accuracy and deformation of the mold during use, the mold steel should have a high heat resistance. In order to reduce the temperature rise, the mold steel should have excellent thermal conductivity and a low coefficient of thermal expansion.

2. Satisfactory temperature at the operating temperature Most of the working conditions of the mold are very bad, and some often accept a large load, and then cause brittle fracture. The extrusion molding pressure is large, usually 10 to 35 MPa. Therefore, in order to prevent the mold parts from being brittle during operation, the plastic molds of the Jiangxi Province must have high strength and durability.

3. Wear resistance follows the expansion of the use of plastic products. In plastic guessing, it is usually necessary to increase inorganic materials such as glass fiber to enhance plasticity. Because the increase of the participation of the plastics, the fluidity of the plastic is greatly reduced, resulting in wear of the mold. The mold is requested to have excellent wear resistance.

4. Corrosion resistance In the ABS resin, the addition of flame retardant and polyvinyl chloride, etc., may release corrosive gas during the molding process, and sometimes the mold is rusted and damaged at the air flow passage, so the mold steel is required to have excellent corrosion resistance.

5. Outstanding cutting processing function With the enlargement of plastic products and the complicated shape and refinement of the plastic products, the steel for the mold is requested to have an excellent cutting function, and the work hardening is small during the cutting process. In order to prevent the deformation of the mold from affecting the accuracy, it is desirable to limit the residual stress of the machining to a minimum.

6. Mirror surface finishability The inner and outer surfaces of the cavity are lubricated, and the molding surface is required to be polished into a mirror surface. The surface roughness is lower than Ra 0.4 μm to ensure the appearance of the plastic pressed part and facilitate demolding.

7. Scale accuracy The precision of the mold insert is high and the cooperation precision is high. The accuracy of the cavity scale is usually 3~5. The joint surface of the mosaic cavity is requested to be tight to prevent the molten material from entering the gap and forming a leak.

8. Photo-etching function of zebra pattern Many plastic products have added a zebra pattern to their appearance for the sake of beautification. In the leather industry, large-scale embossed embossed sheets are used, which all require mold steel to have good picture photo-etching properties. Therefore, the mold steel should meet the functions of strength, hardness, wear resistance, heat resistance, corrosion resistance, etc.; together with outstanding polishing properties, dimensional stability, easy nitriding and heat treatment deformation, etc.; outstanding thermal conductivity Physical functions such as small linear expansion coefficients. Plastic molds should be selected according to the specific requirements of the parts of the mold steel of different quality and quotation level