In the production process of plastic mold products, a common and troublesome appearance defect is grain, which we usually refer to as silver wire. These silver wires appear as slender silver white stripes on the surface of the product, with their opening direction often following the direction of the material flow, especially in areas where the product is not completely filled, and the fluid front end is particularly rough. The silver wire phenomenon is mainly divided into two types: degraded silver wire and water vapor silver wire, both of which are formed by the gas released from the front end of the material flow. The degradation of silver wire originates from the gas generated by the overheating degradation of the melt, while water vapor silver wire is caused by the vaporization of residual moisture in the raw material at high temperatures.
In the field of preform mold manufacturing, especially when using joint research molds for plastic processing, the silver wire problem is particularly significant. In addition to the common reason of insufficient drying of materials, design, use, and maintenance also directly affect the production of silver wire. For example, factors such as adiabatic compression, mixing of impurities, nozzle blockage, and improper design of cold material ducts may all cause silver wire phenomenon. At the same time, subtle adjustments to injection parameters such as temperature and speed are also crucial, as they are directly related to the stability and yield of the product.
1. Specific reasons and handling methods
The correlation between physical reasons and molds:
Material water absorption: Some plastics such as PA, ABS, PMMA, etc. are prone to water absorption. If storage conditions are poor, moisture can penetrate into the particles or adhere to their surfaces. When using molds for injection molding, this moisture evaporates at high temperatures, forming bubbles that ultimately lead to silver wire.
Mold design: If the cooling water channel of the mold leaks, it will directly cause cooling water to enter the mold cavity, thereby generating water vapor silver wire. Therefore, ensuring the sealing of the mold and preventing leakage from the mold cavity is the key to preventing silver wire. Meanwhile, a reasonable exhaust system design is also essential, as it can effectively exhaust gases from the melt and reduce the production of silver wire.
2. Silver wire treatment in injection molding process:
Melt temperature control: Excessive melt temperature can accelerate plastic degradation, produce gas, and form silver wire. When using the joint research mold, the melt temperature should be precisely controlled to avoid overheating.
Injection speed and holding time: Excessive injection speed and prolonged holding time can increase the risk of melt degradation, resulting in the formation of silver wire. By adjusting the injection parameters of the joint research mold, such as reducing the injection speed and shortening the holding time, the silver wire phenomenon can be effectively reduced.
3. Raw material issues and solutions:
Raw material drying: For raw materials with high moisture content, sufficient pre drying treatment must be carried out. This is not only a necessary measure to prevent water vapor silver wire, but also a prerequisite for ensuring the production efficiency and product quality of the joint research mold.
Raw material selection and processing: Choose resin with uniform particle size and stable quality, reduce the amount of recycled materials, screen out powder particles in the raw materials, and remove residual materials from the material barrel. These measures can effectively reduce the production of degraded silver wire. At the same time, pay attention to reducing the amount of mold release agent used to avoid the impact of its volatile gases on the silver wire.
In summary, Heyan Mold plays a crucial role in the production of plastic mold products. By optimizing mold design, precisely controlling injection molding process parameters, and strictly controlling raw material quality, we can effectively reduce or even eliminate the silver wire phenomenon, improve the overall quality and market competitiveness of our products.
Foshan Heyan Precision Mould Technology Co., Ltd.'s main business is preform moulds, bottle blowing moulds, bottle cap moulds and other products. It has a strong engineering, R&D, technology and sales team, advanced processing equipment and rich project experience. If you want to know more or have special needs, please call 13318345050, or add our WhatsApp.
