ISO 25178 Areal Surface Texture Parameters for Optical Inspection
ISO 25178 defines 3D areal surface parameters like Sa and Sdr, replacing 2D profiles to qualify optical non-contact inspection on textured tool steel and mouldings.
Mould Micro Infill
Meaning
Micro-cavity replication during the filling phase of injection molding determines how accurately polymer melt fills micro-scale tool surface features. When producing textured cosmetic parts or diffractive optics, mould micro infill measures the percentage of tool feature height achieved by the solidified resin. The boundary of micro filling analysis ends when macro-scale part dimensions solidify and melt flow ceases.
Melt Rheology
Shear rates inside micro-structured cavity features reach extreme levels during injection. Achieving complete mould micro infill requires high melt temperatures and rapid injection speeds to lower polymer viscosity before a frozen layer forms. High cavity pressure forces the polymer melt into sub-micron recesses, but entrapped air can cause incomplete filling if vent channels are absent.
Amorphous polymers like polycarbonate replicate fine tool details more faithfully than semi-crystalline resins due to post-mold volumetric shrinkage differences. Variothermal tool heating improves micro-feature replication measurably.
Thermal Solidification
Mold wall temperature governs the rate at which skin layers freeze during injection. Adequate mould micro infill depends on keeping the polymer interface above its glass transition temperature until filling completes.
Quality Boundary
Incomplete feature replication alters surface gloss and light diffraction performance of molded components. Moulders adjust holding pressure and pack time when mould micro infill falls short of target specifications. Tool wear over long production runs gradually reduces feature sharpness, requiring routine cavity re-polishing.
Quantitative replication audits validate tooling performance prior to commercial part release.