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Part Sticking in Mould

Part Sticking in Mould
Possible Cause Suggested Remedy
Overpacking material in mould a. Decrease first stage injection pressure
b. Decrease boost time
c. Decrease injection forward time
d. Decrease packing pressure
e. Increase injection transfer position (to lower injection peak pressure)
Improper finish on mould Draw polish mould to proper finish
Insufficient draft on cavities and sprue Polish and provide maximum allowable draft
Knockout system poorly designed a. Redesign knockout system for balanced ejection forces
b. Review operation of knockout system, plates not opening in proper sequence
Core shifting and cavity misalignment a. Realign cavities and cores
b. Add interlocks to mould halves
Undercuts in mould and possible surface imperfections a. Repair and polish
b. If undercut is intentional, redesign or reduce
Non-uniform cavity pressure in multi-cavity mould Redesign runners and gates for balanced filling of cavities
Moulded parts too hot for ejection a. Increase cooling time
b. Decrease melt temperature
c. Decrease mould temperature
Moulded parts sticking to stationary half of mould a. Redesign sprue puller
b. Apply mould release
c. Increase nozzle temperature
d. If parts remain on wrong side of mould, undercut other side or try differential mould temperatures