There are significant fluctuations in the injection end-point value from shot to shot, resulting in unstable product weight and dimensions; issues such as short shots and flash occur intermittently, and the position where plasticizing concludes drifts.
Establish standardized machine setup parameter templates; directly recall baseline parameters during mold or material changes to minimize trial-run waste caused by repeated mold testing.
Optimize parameters for holding pressure, injection, temperature, and cooling to reduce cosmetic defects such as short shots, flash, sink marks, burn marks, and stress cracking.
Minimize unnecessary air shots and repeated injections; lower the barrel temperature during machine downtime or standby periods to reduce material decomposition and carbonization, thereby minimizing waste.
Perform regular mold maintenance to reduce product scrap caused by mold sticking, scoring, flash, stress marks, and drag marks; optimize venting to alleviate defects such as burning and gas entrapment.
Conduct regular equipment inspections-covering non-return rings, screw and barrel assemblies, thermocouples, linear transducers, toggle mechanisms, etc.-to prevent batch defects caused by equipment malfunctions.
Optimize runner and gate designs, reduce runner dimensions, and lower the proportion of runner and gate scrap to minimize waste generation at the source.
Properly dry raw materials to prevent defects such as bubbles and silver streaks caused by moisture; store different grades and colors of raw materials separately to eliminate material mixing and subsequent scrapping.
Sprues and runners are collected and sorted by category, distinguishing between acceptable material, carbonized material, and contaminated waste. Acceptable sprues and runners are blended back into production at a fixed ratio; this mixing ratio is strictly controlled to prevent secondary defects.
Prevent batch waste caused by spilled raw materials, agglomeration in the hopper, and residual carbonized materials in the material tube.
Set scrap rate targets for machines and track scrap quantities by machine, categorizing the waste into scrap resulting from machine setup, equipment issues, mold issues, and human error.
Standardize mold, color, and material changeover operations to shorten machine cleaning time and reduce waste generated during cleaning.
Conduct training for operators and machine setters to minimize batch scrap caused by human error; mandate first-article inspection to prevent batch defects.
Address unexpected shutdowns promptly; empty the barrel during prolonged shutdowns to prevent material degradation and waste.
High scrap rates during the mold change and machine setup phase: Optimize baseline parameters and standardize mold change operations.
Persistent defects during mass production: investigate mold issues, equipment malfunctions, and process parameters.
Excessive proportion of sprue/runner scrap: Optimize the mold runner system and properly reuse qualified regrind.
Track scrap rates for each machine; maintain a categorized log of defect causes; prioritize resolving high-frequency scrap issues; and ensure compliant reuse of qualified sprue/runner material while strictly prohibiting the indiscriminate disposal of scrap.
