Meaning
Calculated numerical distance formulas quantify the total perceptible colour difference between a target production sample and a master reference standard. Spectrophotometric measurements evaluate colorimetric shifts across three axes to produce a single value known as cie l a b delta e. In polymer processing, this metric governs quality control approval for masterbatch additions and finished injection moulded parts.
The calculation sets boundary conditions for acceptable visual variation, stopping batch shipment when colorimetric drift exceeds agreed customer tolerances.
Colour Space
Three-dimensional coordinates define lightness alongside red-green and yellow-blue coordinates within the CIELAB colour space. A calculated cie l a b delta e combines differences across all three axes into a single scalar value.
Process Drift
Thermal degradation during extrusion and injection moulding frequently alters colorimetric values without changing mechanical properties. Fluctuations in barrel residence time or processing temperature alter the colorimetric distance, causing batch-to-batch variation. Moulders track cie l a b delta e to detect pigment degradation caused by excessive shear inside the screw assembly.
Colorant metering pumps are adjusted immediately when numerical readings cross target control thresholds.
Tolerance Boundary
Automotive and packaging applications enforce tight statistical limits on acceptable colour variation across production runs. A cie l a b delta e value below zero point five remains imperceptible to the human eye under standard lighting conditions. Commercial supply contracts define upper acceptance thresholds, often rejecting parts that exceed one point zero.
Regrind integration introduces shade variations that shift colorimetric distance away from virgin resin baselines.
