Quality Control (QC) refers to the operational techniques and inspection activities used to verify that products, materials, or processes meet specified requirements and identify defects before they reach customers. Whilst quality assurance (QA) focuses on preventing defects through process design, quality control focuses on detecting defects through measurement, testing, and inspection. QC activities occur throughout manufacturing: incoming inspection verifies purchased materials meet specifications before entering production, in-process inspection catches problems during manufacturing before value is added to defective work, and final inspection validates finished products before shipment. The goal is protecting customers from receiving defective products whilst providing feedback that drives process improvement and prevents future defects.
QC methods vary by product and industry. Dimensional inspection uses measuring instruments (callipers, micrometres, coordinate measuring machines) to verify parts meet drawing specifications. Functional testing confirms products operate correctly under specified conditions. Visual inspection checks surface finish, colour, assembly correctness, and other attributes difficult to measure numerically. Non-destructive testing (x-ray, ultrasonic, magnetic particle) reveals internal defects without damaging products. Statistical process control (SPC) monitors process outputs over time, using control charts to detect when processes drift out of acceptable ranges before producing defects. Acceptance sampling applies statistical methods to inspect samples from lots rather than every item, balancing inspection cost against risk of accepting defective batches. Automated inspection using vision systems and sensors provides fast, consistent checking for high-volume production where manual inspection is impractical.
Modern QC systems integrate with MES and ERP platforms, capturing inspection results electronically rather than on paper forms. Digital checklists guide inspectors through procedures ensuring consistency. Measurement data feeds directly from inspection equipment into quality databases, eliminating transcription errors. Statistical analysis identifies trends requiring attention before processes exceed limits. When defects are found, integration with non-conformance reporting systems ensures proper disposition (scrap, rework, use-as-is) and triggers corrective action investigations. Mobile quality apps allow inspectors to record results, capture photos, and access specifications anywhere on the shop floor. While automation and process improvement reduce the need for traditional inspection, QC remains essential for validating that quality systems work as intended, providing early warning of process problems, and ensuring defective products never reach customers. The most effective quality strategies combine QA’s preventive approach with QC’s verification activities, building quality into processes whilst maintaining vigilant oversight.
