Plastic bottle cap molds often show many phenomena and problems during processing. Today, let's analyze the specific causes of these problems!
Problem 1: There are weld marks on the plastic bottle cap
Cause Analysis
1. Process elements: the temperature of the barrel or the hot runner is too low, and the melt is not completely plasticized; the temperature of the mold is too low, which causes the melting flow rate to slow down, the cooling is too fast, and the two streams cannot be effectively fused when they meet; The wall thickness of the plastic bottle cap is too thin and it is difficult to fill the mold, which increases the temperature difference of the melt in the mold.
2. Data element: If there is water in the material, it will affect the fusion effect of the material flow if it is converted into gas during the injection process.
3. Mould elements: unreasonable gate planning, and gate orientation should be avoided as far as possible around inserts and holes; trapped air in the mould prevents the gas in the cavity from being discharged. When the two streams merge, they will be affected. Fusion effect.
Problem 2: Bubbles and vacuum bubbles are formed on the surface of the plastic bottle cap
Cause Analysis
1. Process elements: the injection speed is too fast, the molten plastic will be differentiated by the large shearing effect, and gas will be generated; the lack of injection pressure and holding pressure makes the molten material not closely adhere to the surface of the cavity, which is not conducive to the discharge of air; part of the product Cooling is too fast and the shrinkage is uneven, especially when the wall thickness of the plastic bottle cap is large, the surface cooling speed is faster than the center part. Therefore, during the cooling process, the plastic edge at the center part shrinks and expands outward, which is lack of filling. When, it simply forms a real bubble.
2. Data element: If the material has moisture, it will cause bubbles and vacuum bubbles to form on the surface of the plastic bottle cap.
3. Mould elements: There may be air trapped in the mould, the mould should be maintained or an exhaust groove should be added.
Problem 3: The gate of the plastic bottle cap is expected and has a stinging feeling
Cause Analysis
1. Process elements: The mold temperature is too low, which causes the product to cool too fast, and the melt in the runner is forcibly taken out during demolding; the holding pressure is too large and the holding time is too long, which may cause damage to the gate and the runner. The cold material is injected into the plastic bottle cap to make the gate position appear cold; the gate may be blocked.
2. Mould elements: due to unreasonable gate planning, this kind of problem should be changed appropriately.