Meaning
Areal surface texture parameters defining the absolute height difference between the single highest peak and single deepest valley within a defined measurement area quantify extreme surface height variations. Monitoring surface roughness sz allows quality technicians to catch deep isolated scratches or high burrs on injection mould cavities and plastic sealing surfaces. Optical surface profilers compute this parameter across 3D height maps as specified in ISO 25178 metrology standards.
Large values indicate severe isolated surface flaws regardless of average roughness trends.
Peak To Valley
Extreme value analysis isolates localized topographical flaws that average parameters like Sa completely hide. Evaluating surface roughness sz ensures that individual micro-gouge marks on polished mould inserts do not transfer as raised cosmetic flaws onto moulded parts. Scanning high-resolution height grids exposes isolated peak heights.
Strict threshold limits reject parts with deep surface defects.
Scratch Detection
Automated surface inspection systems scan critical sealing regions on micro-moulded medical fluidic devices for isolated surface cuts. Tracking surface roughness sz flags microscopic scratches that cause fluid leakage across gasket mating faces. Optical profilometers highlight localized height spikes above baseline levels.
Early detection prevents leaking elastomeric seals.
Sealing Surface
Gasket contact zones on moulded housings demand strict peak-to-valley limits to prevent fluid bypass under operating pressures. Excessive surface roughness sz along O-ring sealing channels creates leak paths that low-durometer gaskets cannot fill. Polishing cavity sealing areas reduces peak-to-valley heights below maximum tolerance thresholds.
Smooth sealing surfaces ensure leak-tight pressure seals.
