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Surface Imperfections

Surface Imperfections (Glass On Surface, Mineral Bloom)
Possible Cause Suggested Remedy
Melt temperature too low Increase melt temperature
Mould temperature too cold Increase mould temperature
Insufficient packing pressure Increase packing pressure
Injection rate too slow a. Increase first stage pressure
b. Increase boost time
c. Increase injection speed
Insufficient material in mould a. Increase shot size and maintain constant cushion
b. Inspect non-return valve for wear
c. Decrease injection transfer position (thereby increasing the peak pressure)
Water on mould surface a. Increase mould temperature
b. Repair any water leaks
Excessive lubricant on mould a. Clean mould surface with solvent
b. Use mould release sparingly
Moisture in material a. Review material handling to eliminate moisture pick up
b. Dry material prior to moulding
c. Use hopper dryers
Insufficient venting Provide adequate vents