Appearance quality inspection is a critical procedure to guarantee the quality of brake pad products. Systematic inspection standards and methodologies enable effective identification of cosmetic defects and ensure full compliance with quality specifications. Beyond aesthetic impacts, appearance defects can compromise product performance and driving safety, thus mandating stringent standards and scientific inspection protocols.
Core inspection items for brake pad appearance quality cover surface defects, dimensional accuracy, coating performance, and marking integrity.
1.Surface defect inspection: Examines surface irregularities including cracks, blisters, scratches, dents, foreign inclusions and other flaws. Such imperfections not only mar visual appearance but also act as stress concentration points, which may propagate during service and trigger premature product failure.
2.Dimensional accuracy inspection: Verifies whether critical dimensions (length, width, thickness, etc.) meet design specifications, alongside proper fitting tolerances between assembled components.
3.Coating quality inspection: Assesses coating uniformity, adhesion strength, film thickness and other metrics to secure superior anti-corrosion performance and long-term durability.
4.Marking integrity inspection: Confirms legible, complete and accurate product markings, including brand logos, part numbers, dimensional specifications, production dates and other technical data.
Inspection Methods
1.Visual inspection: The most fundamental and widely adopted method. Inspectors examine pad surfaces with naked eyes or 10×magnifying glasses to detect minor surface flaws. Visual inspection shall be conducted under controlled lighting with illuminance maintained between 500 and 1000 lux to guarantee clear identification of micro-defects.
2.Precision instrumental measurement: High-precision tools such as calipers, micrometers and coating thickness gauges are deployed to obtain accurate readings of component dimensions and coating film thickness.
3. Functional performance testing: Includes adhesion tests, abrasion resistance tests, corrosion resistance tests and other accelerated simulations of real-world operating conditions to evaluate coating durability and functional performance.
Applicable Standards
Brake pad appearance inspection standards are formulated based on national standards, industrial specifications or enterprise internal standards. In China, the primary governing standard is GB 5763 Brake Linings for Automobile Brakes, which stipulates mandatory appearance requirements and corresponding test procedures. Key regulatory provisions include prohibitions on surface cracks, blisters and delamination; uniform full coating without bare substrate; dimensional tolerances within specified ranges; and legible, intact permanent markings.
For export-grade products, compliance with destination market standards is additionally required, such as ECE R90 (European Union) and FMVSS 135 (United States).
Inspection Item Specification Matrix
| Inspection Item | Quality Requirement | Inspection Method | Sampling Scheme | Disposition of Nonconforming Products |
| Surface Defects | Free of cracks, blisters, delamination and other critical flaws | Visual inspection with 10× magnifier | AQL 1.0 | Rework or scrap |
| Dimensional Accuracy | Conform to drawing specifications; tolerance ±0.1 mm | Measurement via calipers & micrometers | AQL 1.0 | Rework or scrap |
| Coating Film Thickness | 20–30 μm | Coating thickness gauge measurement | AQL 1.5 | Recoat or rework |
| Coating Adhesion | Cross-hatch test grade ≥ 4 | Cross-hatch adhesion test | AQL 1.0 | Rework or scrap |
| Marking Integrity | Clear, complete and error-free markings | Visual inspection | AQL 0.65 | Re-mark or rework |
| Package Integrity | Intact packaging free of damage and contamination | Visual inspection | AQL 1.0 | Repackage |