Dimensional instability means that the size of the Pet Bottle Preform changes beyond the tolerance limit, possibly due to the injection molding machine, the mold or the injection molding process.
(1) Injection molding machine
1 The application of different types of injection molding machines leads to differences in injection molding conditions;
2 melt temperature fluctuations - check the failure of the thermocouple or temperature controller;
3 screw speed is unstable - check the hydraulic system;
4 Insulation pressure is unstable - check whether there is consistent buffering in each cycle, or whether the plastic check valve leaks, repair or replace if necessary;
1 Check if the gate is blocked by residue;
2 Check whether the mold temperature is stable, whether the coolant flow is smooth, and whether the cooling circuit connection is correct;
3 Check if the molded part is invalid;
(3) Injection molding process
1 mold temperature unevenness or unreasonable cooling circuit will lead to improper mold temperature control - adjust accordingly;
2 injection pressure is too low - increase the injection pressure;
3 appropriately increase the injection time and retention time;
4 barrel temperature or nozzle temperature is too high - adjust accordingly;
5 Filling speed is too low - increase the injection speed, or use multi-stage injection.
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