Solutions for common defects in TPE Injection molding
For the appearance of various irregular lines on the surface of TPE products, which affect the appearance quality of the products, it must be commonplace. Various texture defects appearing on the surface of TPE products are briefly divided into the following two cases according to their causes:
1. Injection flow marks
The generation of gas ray is fundamentally caused by the gas in the cavity being too fast, and the air in the tube or cavity cannot be discharged in time, generating a large gas pressure in the cavity and causing frictional shear on the surface of the product. Finally forming a sheet-like ray on the surface of the product;
Solution: Reduce the rate of fire appropriately. In addition, if the molding temperature is too high, the material will be decomposed and gas will be generated, which will also cause the formation of the ray. Solution: Control the molding temperature. If the material contains moisture, when the water is formed at a high temperature, the water evaporates to form a gas, which also causes the appearance of a ray, and if the molding temperature is low, a tinge-free pockmark is formed. Solution: Make baking treatment before molding.
2. Material flow marks
The generation of rhyolite has nothing to do with gas. It is mainly affected by material fluidity, plasticization degree, mold temperature and gate temperature. The mold and runner structure affect the material flowability. If the melt filling is not completed quickly, the melt temperature will decrease. The flow rate is reduced, and it is easy to form a flow pattern on the surface of the product;
Repalce the material with better one.
If the mold temperature and the gate temperature are too low, the frictional shear of the melt and the mold surface will be strengthened, resulting in flow pattern generation;
Appropriately increase the mold temperature and mold gate temperature. Insufficient plasticization of materials, poor melting, easy to cause obvious flow pattern on the surface of the product; Solution: Properly increase the injection temperature and screw speed to enhance plasticization.
3. Wave marks
During the melt filling process, the new melt flow is continuously laminated from the inside, pushing the front wave to stagnate and moving, while the front wave edge is continuously stretched, and the flow resistance increases the later melt pressure and the front The newly formed corrugation is flattened, causing stagnation to accumulate, thereby forming a wave pattern on the surface of the product.
1 Change the process conditions. High-pressure low-speed injection maintains the stability of the melt melt flow and prevents the appearance of wave lines.
2 Increase the mold temperature. As the mold temperature increases, the melt flowability increases, and higher temperatures favor the crystalline polymer. The uniformity of crystallization, thereby reducing the appearance of wavy lines.
3 change the cavity structure. The structure of the mold can also cause wavy lines on the surface of the product. If the edge of the mold core is more prominent, the melt flow resistance is larger, which will cause the melt flow to be unstable, thereby forming a wave pattern. Therefore, the corners of the mold core are changed to make a buffer transition, and the melt flow is kept stable, preventing the appearance of wave lines.
4 change the thickness of the product. The uneven thickness of the product will make the melt flow resistance large and small, resulting in unstable melt flow. Therefore, the thickness of the product should be designed to be uniform thickness as much as possible to prevent the appearance of wave lines.
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