Quality Control in Manufacturing - QC Methods and Standards

Manufacturing quality control methods: inspection levels, CMM, SPC, ISO standards. How to ensure part quality from suppliers.

Quality Control Overview

Manufacturing QC ensures parts meet specifications before shipment.

Inspection Levels

• First Article Inspection (FAI): Full dimensional check of first parts
• In-Process Inspection: Regular checks during production
• Final Inspection: AQL sampling per ISO 2859
• Pre-Shipment Inspection: Third-party QC review

Measurement Tools

• CMM: Touch probe or laser. Accuracy +/-0.001 mm
• Optical Comparators: Project profile onto screen for 2D checks
• Calipers & Micrometers: +/-0.01 mm for shop-floor checks
• Go/No-Go Gauges: Pass/fail for threads and holes
• Surface Roughness Tester: Ra, Rz measurement

Statistical Process Control (SPC)

SPC uses control charts to monitor production. Cp and Cpk indicate process capability. Cp over 1.33 is acceptable, over 1.67 is excellent.

ISO Standards

• ISO 9001: Quality management system
• ISO 13485: Medical device quality
• IATF 16949: Automotive quality
• AS9100: Aerospace quality

QC Tips for Overseas Suppliers

• Request full FAI report with CMM data
• Specify AQL sampling (1.0 critical, 2.5 major, 4.0 minor)
• Use third-party inspection (SGS, Bureau Veritas, TUV)
• Include QC checkpoints in purchase orders