Method for eliminating flashing of PVC products

April 26, 2019

Method for eliminating flashing of PVC products
 

1. The cause of the flash
1-1 mold parting surface (PL) sliding surface does not match. 1-2 Injection pressure is too high; 1-3 Injection machine offset; 1-4 Locking force is insufficient

 

2. Associated knowledge
2-1 Parting surface PL of the mold, sliding mating surface, demoulding pin, spacer and so on. The gap between the various grooves of the mold is formed, and if the PVC compound material flows, it becomes a flash. The flash edge is a wedge block. There is a tendency to gradually increase. 2-2 Eliminating the flash of the product is generally based on the principle of repairing the mold. Due to the poor setting conditions, the flash edge should be used to reduce the temperature of the barrel. The direction in which the mold temperature is lowered and the injection speed is lowered causes the pvc compound material fluidity to decrease. However, it should be noted that this will cause residual internal stress in the product.

 

3. The solution
  3-1 Instant: Reduce the injection pressure and lower the temperature of the heating cylinder. Reduce the injection speed. 3-2 Short-term: Grinding the surface where the mold has a flash.
  3-3 Long-term: The mold uses hard steel materials.

 

4. Due to PVC compound material differences
  4-1 Because of the fluidity of the pvc compound material, it is easy to produce flash, so the mold parting surface should be done strictly.
  4-2 Crystalline materials have low viscosity due to melting. In particular, the tightness of the mold parting surface is required.

 

5. Reference matter
  5-1 It should be noted that excessive pressure on the mold will also produce flash edges. Between the parting surfaces, foreign objects will damage the mold and produce flash.
  5-2 Mold materials are usually made of materials such as S50C (Japan JJS standard is equivalent to domestic 50# steel). HRC30 pre-hardened special steel is used, and it is difficult to produce flash on the parting surface.

 

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