Heater output is sensitive to supply voltage. A machine may heat correctly at idle but lose power when the oven, vacuum pump, hydraulic unit, compressor, or other plant loads operate simultaneously. Loose connections and undersized conductors can create additional local drop and heating.
Voltage should be logged at the machine input and relevant heater circuits through the production cycle. The test must capture short demand peaks and compare phases. Terminal temperature, conductor condition, breaker loading, and transformer capacity should be inspected by qualified electrical personnel.
The supply and connections must be corrected rather than offset with longer cycles or higher percentage commands. Persistent undervoltage reduces available control range; intermittent drop produces variation that recipe settings cannot remove.