TL;DR
A zone that fails to heat is usually a failed heater element, open thermocouple, or blown fuse on the TempMaster output card. Check the fuse first before testing heater resistance.
What you might see
- TempMaster shows zone temperature not rising
- zone displayed as open circuit or fault on the controller
- part quality issues in the area of the non-heating drop
- short shot or freeze-off at one gate
Likely causes
Hot runner heater element failed, open circuit
Output fuse blown on the TempMaster zone card
Thermocouple open circuit causing the controller to show an open fault
Wiring connection loose at the mold junction box
Required tools
- Multimeter
- Replacement zone output fuse (matching amperage)
- Replacement heater element or thermocouple (mold-specific)
- LOTO kit
Safety first
- Hot runner heater wiring carries line voltage. Lock out both the TempMaster and the injection press before connecting or disconnecting any hot runner wiring.
- Residual heat in the mold and hot runner manifold can cause burns. Allow cooling time or wear heat-resistant gloves.
Procedure
- 1
Note the fault displayed on the TempMaster for the affected zone. Distinguish between an open heater fault and an open thermocouple fault.
- 2
Lock out the injection molding machine and the TempMaster power before testing.
Warning: Hot runner heater wiring operates at line voltage (240V or 480V AC depending on configuration). Lock out both the TempMaster and the injection press before testing. - 3
Locate the zone output fuse in the TempMaster card rack. Check and replace if blown.[1]
- 4
Disconnect the heater cable at the mold junction box. Measure the heater element resistance with a multimeter. Open circuit indicates a failed heater element.[1]
- 5
Measure heater resistance between each heater terminal and the mold ground. A reading below 1 MOhm indicates an insulation breakdown.
- 6
Disconnect the thermocouple cable and measure thermocouple resistance. An open circuit reading means the thermocouple has failed.
- 7
Replace the failed component (fuse, heater, or thermocouple) and restore power. Confirm the zone ramps to setpoint on the TempMaster display.
- 8
Run a heat soak cycle and verify the zone temperature stabilizes before injecting parts.
Sources
Mold-Masters (Milacron) Mold-Masters TempMaster Hot Runner Controller / System general technical documentation, Mold-Masters (Milacron)
Mold-Masters TempMaster controller user guide, zone fault diagnosis and heater testing procedures (general)
More guides for Mold-Masters (Milacron) Mold-Masters TempMaster
How to fix gate drool or stringing on a Mold-Masters TempMaster hot runner system
Gate drool and stringing are nearly always caused by a gate temperature too high or insufficient decompression at end of shot. Lower the gate zone temperature by 5 C increments before adjusting decompression.
How to fix thermocouple drift on a Mold-Masters TempMaster hot runner system
A thermocouple that reads persistently above or below actual melt temperature will cause out-of-specification parts. Verify with a reference thermocouple before replacing the suspect sensor.
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