But i’m seeing small drift in image density after 5–6 hours on thermal plates baked at 240°C for 7 min, despite consistent 830 nm exposure at 130 mJ/cm² and developer at 23°C. Anyone tightened reproducibility by tweaking plate gumming or processor dwell rather than curves, or am I missing a prep variable upstream? I’m trying to keep TVI within ±2% over a full shift without babysitting.
Seeing drift after “5–6 hours” usually isn’t curves — it’s gum aging; bump your post-bake gum to a buffered 12–14% solids, lock a 20–25 s dwell, and refresh the gum bath mid-shift to stop carryover dilution. Also make sure the gum unit temp and squeegee pressure don’t creep; if you’re still drifting at “240°C for 7 min”, try 230°C/5 min to cut sensitivity to minor gum variation. What’s your gum pH at start vs end of shift?
One thing that tightened ours: we stopped gumming hot — post-bake we cool plates to under 30°C for about 3 minutes before gum; it cut mid‑shift density creep and kept TVI within ±1.5% without touching curves. @OP are you checking plate surface temp at gum entry or gumming straight out of the oven?
I’d tighten the wet end before touching curves: lock developer replenishment to 60–70 ml/m², hold the bath at 23°C ±0.3, and keep conductivity within “±5% of fresh”; also cap rinse temp at 22–24°C and swap the rinse filter halfway through to curb carry‑over — like espresso water, if it drifts, you taste it. If transport speed is fixed so dev dwell doesn’t wander, TVI usually settles. @OP what are your current rep rate and rinse‑water conductivity over a shift?
Have you logged plate temp across a run? A modest 5–10°C drift or edge‑to‑center skew in the bake oven will mimic density creep, so verify core temp with Tempilaq or a data logger across the belt and recalibrate the thermocouple/airflow if needed, @sophieM_73.
And happens a lot after 5–6 hours as the processor warms up. @mikeJ34’s oven check is solid, but also time your developer dwell at 23°C at start vs hour 6; if it’s shortened by about 1–2 s from roller swell, recal speed/nip to hold dwell within ±0.5 s and you’ll keep TVI inside ±2%.
@Liam_f56 at 240°C/7 min, lock gum 12–14°Bx, 2–3 g/m²; Brix hourly?