Meaning
Optical metrology provides non-destructive evaluation for injection-moulded polymer components through glancing angle reflection measurements. Incident light strikes a semi-crystalline or amorphous surface at near-grazing incidence to map micro-roughness variations across the component face. Small angular shifts reveal molecular orientation differences induced during the filling stage of thermoplastic injection moulding.
Production engineers use these interference patterns to verify that tool temperatures remain uniform within narrow processing windows. Surface gloss anomalies and weld line weaknesses disappear when operators tune the injection speed to eliminate shear-induced birefringence.
Optical Setup
Laser diodes emit polarized beams toward precision goniometer stages holding the moulded plaque. Photodetectors record intensity profiles as the collection angle sweeps across the specular reflection boundary. Small deviations in local polymer density alter the refractive index near the skin layer.
Automated software algorithms convert scatter signatures into quantitative roughness metrics without contacting the part.
Moulding Parameter
Thermal control circuits inside the cavity walls determine how polymer chains relax before final solidification occurs. Melt temperature fluctuations during high-speed injection alter the crystalline morphology at the extreme boundary. Cycle time reductions force shorter cooling phases, which subsequently increase residual stresses detectable by surface scatter analysis.
Processing technicians adjust coolant flow rates to stabilize the refractive index profile across consecutive production lots.
Resin Specifying
Polycarbonate and polymethyl methacrylate resins exhibit distinct scattering thresholds due to inherent differences in molecular polarizability. Virgin feedstock maintains consistent refractive indices across repeated thermal cycles, whereas excessive regrind blending broadens the angular reflection distribution. Material suppliers publish baseline scatter limits to separate acceptable batch variations from compounding contamination errors.
Part designers specify maximum allowable surface haze values to ensure structural integrity under sustained mechanical loads.
