The injection parts are short-shot. The mold temp controller reads 60 C, and the operator says the setpoint is right. You put a thermocouple in the mold and it’s at 45 C. Fifteen degrees gone in the plumbing, and that’s why the parts won’t fill.
The display isn’t the mold
The controller display shows the outlet water temperature. The mold loses heat to the shop, and there’s a temperature drop between inlet and outlet. Read 60 C and the actual mold surface might be 45 to 50 C.
Drill a thermocouple into the mold and measure. Don’t trust the controller display.
Heating and cooling are different jobs
At startup the controller heats the mold to setpoint. During production, the 200 C melt goes in and the mold needs cooling. The controller is actually in cooling mode most of the time.
Cooling capacity matters more than heating capacity. In a hot summer, the mold can’t shed heat, and you get flash and sink marks. Don’t size the controller by its heater wattage.
Keep the lines short
Five meters of hose between controller and mold means the water cools on the way. By the time it reaches the mold, it’s below setpoint. Short hoses, few bends, and run supply and return separately instead of coiled together.
Blocked water circuits
A controller running two years loses flow as scale builds in the mold channels. Heat transfer drops by half. If the parts suddenly get inconsistent, don’t blame the process first. Descale the circuit with a chemical flush and check the flow rate.
