Investigation workspace
NC-TOUR-001 · Anodize coating thickness below spec floor
Audit trail →
Part
PN-AL-3382
Lot
LOT-AN-42
Process
Type II sulfuric anodize
Spec
SPEC-AN-7
Measured
0.4 mil
Required
0.7–1.2 mil
D2
step
Problem description
Approved
D3
step
Interim containment
Approved
D4
step
Root cause
Approved
D4 · candidate causes & cited evidence
Machine
High confidence
Rectifier output sag took bath voltage from ~15 V to ~11 V, pulling current density to 7.9 asf and starving anodic coating growth — producing the 0.4 mil result. Mechanism matches recurrence NC-PRIOR-101.
PD-LOT-AN-42 · PD-AN-42-03 — bath_voltage_V 11.3 below setpoint
PD-LOT-AN-42 · PD-AN-42-07 — current_density_asf 7.9 (low)
NC-PRIOR-101 · root_cause — Rectifier B output sagged, lowering current density and starving growth
Environment
Low confidence
Bath-temperature excursion as a contributor — excluded by evidence; bath temp was in range.
PD-LOT-AN-42 · PD-AN-42-09 — bath_temp_F 70.0 (in range)
Measurement
Insufficient evidence
False-low eddy-current reading (probe calibration or single- vs five-point). No calibration record or full five-point dataset was retrieved.
No supporting evidence — investigate further.
D5
step
Permanent corrective action
Approved
D7
step
Prevent recurrence
Approved