Under-Cure (Powder Not Fully Melted)

high
cure
powder
adhesion

Grainy feel, chalky edges, or powder shedding—temperature/time too low or oven uneven.

Likely Causes

  1. Low tunnel temp or short dwell: Insufficient melt.

  2. Oven cold zones: Uneven heat yields inconsistent fusion.

  3. Excess powder thickness: Bulk layer resists full melt.

  4. High line speed: Reduces dwell below spec.

  5. Incorrect powder type: Using a high-temp powder with a low-temp setting.

Quick Checks

  • Place temp strips L/C/R and profile belt.
  • Add +15–30 s dwell and retest.
  • Reduce powder feed/vibration 10–20%.
  • Slow belt by one increment.
  • Check that the powder type matches the curing profile.

Step-by-Step Fix

  1. Raise oven setpoint 10–15°F — Achieves melt window reliably.

  2. Balance IR/air zones — Eliminates cold lanes.

  3. Trim powder feed or sieve clumps — Ensures uniform thin layer.

  4. Slow belt speed — Restores target dwell time.

  5. Confirm film surface temp 240–248°F — Verifies actual heat, not just setpoint.

Acceptance Criteria
  • Smooth, non-grainy surface; no powder shed on rub test.