5.5 Cosmetic Inspection Standards (Visual Quality)

Cosmetic standardsinspection areis subjectivethe unlessmost quantified.dangerous phase of manufacturing because it is subjective. Without quantifiable physics, the production line devolves into an art critique session, driving up scrap costs without adding value. This sectionchapter definesconverts "Good"it vs.looks "Bad"bad" into binary pass/fail logic. We inspect to protect the Brand and ensure consistency, not to hunt for surfaces.microscopic anomalies that the user will never see.

Surface Zoning Logic

Do not inspect the entire unit with the same severity. Apply criteria based on the surface's function and visibility.

Zoning ClassificationsDecision Matrix:

• Zone A (Primary):If Thesurface faceis ofconstantly theviewed product always visible toby the user (e.g., Screen, Top Bezel, Primary Buttons) → Define as Zone A.
  • Standard:Action: NoTarget scratchesZero Defects. Any visible imperfection at arm's length (60cm).is Zeroa dirt/contamination.Reject.
• If surface is visible only during setup, handling, or cleaning (Back Panel, Side Vents) → Define as Zone B (Secondary): Sides or back, visible during handling but not operation..
  • Standard:Action: Max 2Allow minor scratchesimperfections (e.g., single scratch < 2mm5 long) allowed per unit.
• Zone C (Non-Visible): Bottom or Internal surfaces.
  • Standard: Scratches allowedmm) if they do not exposepenetrate rawthe metalcoating.
• If (corrosionsurface risk)is internal, bottom-facing, or affectservice-only fit.→ Define as Zone C.
  • Action: Ignore cosmetic flaws. Reject only for structural issues (corrosion, stripped threads, burrs).

The Physics of Inspection Conditions

Standardize the environment. If the lighting changes, the acceptance rate changes.

Viewing Conditions:

1. Lighting:Illuminance: CoolMaintain White Fluorescent (800 – 1000 Lux)Lux (Cool White).
   • Why: < 800 Lux hides defects; > 1200 Lux causes glare and false failures on textured plastic.
2. Distance: Inspect from 600 mm (Arm's length).
3. Time: Scan for 5 to– 10 seconds per surfaceunit.
4. Angle: (scan,View doat 45˚ – 90˚ relative to the light source.

The "Scan" Rule:

• If the defect is not stare)visible within 5 seconds of scanning → Then it is not a defect.
• If you must tilt the unit at a specific angle to "catch the light" to see the scratch → Then it is Acceptable.

Pro-Tip: Never use magnification for cosmetic inspection. Microscopes are for Root Cause Analysis (RCA), not for sorting. If a defect requires 10x magnification to be seen, it does not exist to the customer.

Defect Quantization

Replace adjectives with dimensions. A "big scratch" is an opinion; a "5 mm scratch" is data.

Scratch & Dent Logic:

• Zone A:
  • If Scratch Length > 0 mm (Visible) → Fail.
  • If Dot/Inclusion > 0.3 mm diameter → Fail.
• Zone B:
  • If Scratch Length ≤ 5 mm AND Separation > 50 mm → Pass.
  • If Dent Depth ≤ 0.1 mm → Pass.
• Texture/Molding Issues:
  • If "Knit Lines" (weld lines) are visible in Zone A → Fail (Process parameter issue).
  • Distance:If 60"Gate cm (approx. arm's length). Using microscopes for cosmetic inspectionVestige" is flush with surface (Zone B/C) → prohibitedPass as it leads to false failures..

Final Checklist

ZoneControl Point	ScratchCritical LimitRequirement	DentRisk Limit	ContaminationAvoided
Zone A (Face)	0Zero visible scratches/dents at 600 mm.	0	0Brand Reputation Damage
Zone B (Side)	Max 2 minor scratches (< 5mm5 lengthmm); Separation > 50 mm.	<Excessive 1mmScrap diam	0Cost
Zone C (Inside)	AllowedStructural integrity only (No raw metal/corrosion).	AllowedFunctional Failure
Lighting	Clean800 – 1000 Lux (Cool White) at workstation.	Inspection Variability
Distance	Fixed at 600 mm (No oil/dust)microscopy).	Over-Inspection
Timing	Max 10 sec scan time per unit.	Bottleneck Creation