What are the main performance requirements for medical plastic molds?
Time: October 16, 2024
The main performance requirements for plastic molds are that the quality of the mold plays a crucial role in ensuring product quality during plastic film forming and processing. Different types of plastic products and molding processes have different requirements for the material, performance, and shape of molds.
With the emergence of high-speed molding machinery, the production speed of plastic products has accelerated in terms of heat resistance. Due to the molding temperature generally ranging from 160~350 ℃, some have poor fluidity and fast molding speed, which can cause the surface temperature of the mold to exceed 400 ℃ in a very short period of time. When the working temperature of the mold is high, it will cause a decrease in the hardness and strength of the mold, leading to early wear or plastic deformation and failure of the mold. To ensure the accuracy and minimal deformation of the mold during use, the mold steel should have high heat resistance. To reduce temperature rise, mold steel should have good thermal conductivity and a low coefficient of thermal expansion.
2. The working conditions of molds with sufficient temperature at working temperature are mostly very harsh, and some often bear large loads, leading to brittle fracture. The extrusion molding pressure is relatively high, generally ranging from 10 to 35 MPa. Therefore, in order to prevent sudden brittle fracture of mold parts during operation, the mold should have high strength and toughness.
3. Wear resistance: With the expansion of the use of plastic products, inorganic materials such as glass fiber are often added to plastics to enhance plasticity. Due to the addition of additives, the flowability of plastics is greatly reduced, leading to mold wear. Therefore, molds are required to have good wear resistance.
4. Corrosion resistance: Adding flame retardants and polyvinyl chloride to ABS resin may release corrosive gases during the molding process, sometimes causing mold corrosion and damage at the air flow channel. Therefore, it is required that the mold steel has good corrosion resistance.
5. With the increasing size, complexity, and precision of plastic products, mold steel is required to have good cutting performance and minimal work hardening during the cutting process. To avoid mold deformation affecting accuracy, it is hoped that residual stresses during processing can be controlled to a minimum.
6. Mirror polishing processing: The surface inside the mold cavity is smooth, and the forming surface is required to be polished into a mirror surface with a surface roughness of less than Ra0.4 μ m to ensure the appearance of the plastic pressing parts and facilitate demolding.
7. The dimensional accuracy of mold inserts is high, and the fitting accuracy is high. The dimensional accuracy of the mold cavity is generally 3-5 levels. The joint surface of the splicing cavity requires a tight fit to prevent melted materials from entering the gap and causing material leakage.
Many plastic products have added patterned patterns on their surfaces for beautification purposes. In the leather industry, large embossed leather plates are used, which requires mold steel to have good pattern etching properties.
Therefore, mold steel should meet performance requirements such as strength, hardness, wear resistance, heat resistance, and corrosion resistance; At the same time, it should also have good polishing properties, dimensional stability, ease of nitriding, and minimal deformation during heat treatment; Good thermal conductivity and small coefficient of linear expansion, among other physical properties. Plastic molds should be made of mold steel of different quality and price levels according to the specific requirements of the parts.
