Molds & Tooling
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PPO burnt marks
Problem Phenomenon
Burnt marks and brown streaks appear at fixed positions of PPO products, mostly at flow ends and material convergence areas; they improve briefly after machine purging and then recur.
Cause Analysis
When mold venting is poor, the compressed air heats up adiabatically and burns the melt; stagnant material dead spots in the barrel and nozzle decompose under long-term heating and are carried into the product; excessive melt temperature aggravates the heat damage risk.
Solution
①For fixed-position burning, prioritize checking venting and adding vent grooves; ②clean the stagnant material dead spots of the barrel and nozzle; ③appropriately reduce the melt and mold temperatures; ④adjust the filling rate to prevent trapped gas.
Key Takeaway
For PPO burning, first distinguish the two causes of venting trapped gas and equipment stagnant material; fixed positions are characteristic of venting problems; random distribution points to equipment dead spots.; after confirming effectiveness, solidify the parameters and practices into the work instruction to prevent recurrence
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