Stop chasing fill drift - check temperature first

Spent a chunk of last week chasing “mystery” underfills on our 1 - 5 L weight-fill line. Operators were bumping targets a few grams at a time, checkweigher rejects spiked, and we burned hours on rework. Turned out the product temp had slid 6 - 8°C overnight. Colder, thicker product changed the valve close behavior and scale filter response, so our warm-weather tuning was cutting off late and the dribble step wasn’t cleaning it up.

Two simple changes helped more than any amount of knob‑twisting: we added an in-tank RTD and tied it to the PLC to auto-select a “cold” or “warm” recipe with different cutoff and dribble timings, and we enforced a 20-minute recirc before first fills after a long idle. We also put a small accumulator on the filler air logic to keep actuation consistent during compressor demand spikes. Cpk came back, and the setpoint creep stopped.

Curious how others handle viscosity and temperature swings on liquid lines. Do you try to hold product temp tight, or do you let it float and compensate in the filler logic? Anyone gone further and adjusted target weight based on product temp or density in real time?