How Long Does It Take to Cool Down a Hot Runner After Drying Before Start-up?

I. Normal Cooling-Down Start-up Time for Typical Case

The hot runner is complete and has been baked to specifications. Applicable Conditions: Insulation resistance after drying is steady at ≥20MΩ and the temperature rise curve is normal without any irregularities.

Total Cooling-down Start-up Time Natural cooling down below 60°C 1 to 1.5 hours. Complete wiring and installation, then heating to production temperature. After the parameters are determined to be normal, production can start promptly.

II. Start-up Time in Cooling-Down for Different Moistures

Slightly Moist Hot Runner: Cool 30 min after drying. If there is no drop, retest insulating resistance, finish wiring and heat to production temperature before start up. Total time ≤1.5 hr.

Moderately Moist Hot Runner: After drying, let cool naturally for 1 hour. Then retest the insulating resistance. If it is steady and meets the specification, heat to 100℃ and hold for 30 minutes. Then heat to production temperature before start up. Time sum ≤ 2 hrs. Severely Moisturized Hot Runner: Dried and naturally cooled for 1.5 hours. If the insulation resistance is ≥50MΩ, raise the temperature to 100℃ and hold for 1 hour. Repeat the insulation resistance tests twice. Before starting the machine, bring the temperature up gradually to the production temperature. Total time ≤3 hours.

III. Special Adjustment Rules of Cooling and Start-up Environment

In humid conditions, like the rainy season/humid season, the cooling process has to be finished in the drying chamber. The cooling time is uniformly reduced to 45 minutes to avoid the lengthy exposure and additional moisture absorption. Then boost the temperature to the production temperature and then start the machine.

For large multi-cavity hot runner plates, add further 30 minutes to the cooling period to allow the internal temperature of the runner plate to decrease evenly to below 60℃ to prevent burns to installation personnel. Then the machine can be started after heating.

Direct fan blowing and water cooling are forbidden to avoid the sudden cooling deformation of the hot runner metal components, which may cause the displacement of the sensors, leakage of the sealing surface, and delayed subsequent debugging and start-up time.

IV. Conditions for Final Confirmation Prior to Start-Up

When the hot runner reaches the production temperature, test the high-temperature insulation resistance value again ≥0.1MΩ, the temperature deviation of all sensors ≤±1℃, no abnormal warning. Then the machine can be formally put into production.