Standard ISO 25178 Parameters for Optical Profilometry Inspection
ISO 25178 areal optical profilometry replaces subjective 2D stylus traces with quantitative 3D parameters that accurately govern tool wear and part demoulding.
Sdq
Meaning
Hybrid areal parameters calculate the root mean square slope across all points within a measured surface topography. Quality engineers utilize Sdq to quantify surface steepness on textured mould cavities and moulded plastic components. A completely flat surface has an Sdq value of zero, whereas steep micro-peaks yield high numerical slope values.
Datasheet roughness average parameters ignore local surface inclinations that govern fluid contact angles.
Slope Calculation
Spatial differentiation algorithms evaluate local height gradients along orthogonal X and Y axes across the sampling grid. Root mean square averaging combines individual slope vectors into a single representative surface inclination angle. High Sdq values correlate with steep feature sidewalls that increase mechanical demoulding resistance.
Polycarbonate resin processing requires controlled mould slopes to prevent drag marks during part ejection.
Wetting Dynamics
Surface slope influences liquid spreading, seal performance and light reflection behavior on moulded parts. High slope textures increase hydrophobic contact angles on medical fluid handling components. Laser micro-machining adjusts surface slope to modify mechanical bonding strength without chemical primers.
Regrind resin contaminants fill micro-valleys, reducing average surface slope across reused material runs.
Measurement Sensitivity
High frequency noise elevates calculated slope parameters if inappropriate filtering is applied during data processing. Spatial sampling resolution determines the maximum detectable slope gradient across fine micro-structures. Process standards specify exact filtering protocol before reporting slope values for tool certification.