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Industrial valves, where chemicals are used as also pump parts, are made out of PP Homo or Impact Copolymer, depending upon the impact strength requirements. H110MA and B120MA are the respective grades of Homo and Impact Copolymers used..

Moulding Problems and Suggested Remedies:

Problem Sink marks

Possible Cause Material too hot

Insufficient material into cavity Insufficient dwell time Gate freezing off too early Piece ejected too hot Insufficient effective pressure in cavity shot

Suggested remedy Reduce temperature Increase feed

cylinder

Increase cylinder heat Increase mould temperature Increase dwell time Increase mould temperature

Voids

Gas developed by too hot material

Increase cooling time in mould Increase pressure Increase cylinder heating Increase mould temperature Reduce heating

Surface defects around gate

Condensation of moisture on granules Shrinkage due to delayed solidification of the core with respect to the outside surface in thick sections Cold mould

Flash formation

Hot mould Excessive injection pressure

Material too hot Mould faces out of line Insufficient clamp pressure Foreign material of ace of mould Restriction to flow in one or

Pre-dry

Increase pressure Increase mould temperature

Increase pressure Increase injection speed Increase mould temperature Cool mould near gate

Reduce pressure, Check

sprue runners and gates Reduce heating Realign mould faces Increase clamp pressure Clean mould faces

Find and remove restriction

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