Meaning
Verification and adjustment of measuring instruments against a traceable reference standard ensures the accuracy and reliability of dimensional data in manufacturing. Implementing regular metrology calibration allows plastic molders to confidently measure tight-tolerance features on molded parts and core pins. This action determines the deviation of the measurement tool from the true value, which is then corrected or documented.
Without this step, wear in calipers, micrometers, or coordinate measuring machines can lead to the acceptance of defective parts.
Calibration Standard
Traceability to national or international standards is maintained by using certified master artifacts such as gauge blocks or ring gauges. During metrology calibration, the technician measures these master parts at controlled temperatures to eliminate the effects of thermal expansion. The results are recorded to calculate the measurement uncertainty and to confirm that the tool remains within its specified tolerance band.
Moulding Control
Shrinkage of polymer resins after ejection from the mold must be tracked with high precision to adjust the process parameters. When metrology calibration is neglected, the measurement errors can be mistaken for actual parts drifting out of spec, causing the operator to make unnecessary and counterproductive adjustments to the molding machine. Consistent calibration keeps the measurement system from introducing artificial noise into the statistical process control charts.
Process Assurance
Compliance with quality management systems requires a documented schedule of instrument audits. A robust metrology calibration program ensures that all inspection equipment used on the factory floor provides consistent data across different shifts and operators.
