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.
Vmp Parameter
Meaning
Peak material volume measurements calculate the actual substance present in the highest portions of a surface topography. The vmp parameter quantifies how much polymer will make initial contact with an opposing surface or how much sacrificial material exists to be worn away. This metric is used to evaluate the potential for rapid change in gloss as the finest tips of the texture are abraded.
Friction Initiation
Small volumes at the peak lead to quick changes in tactile feel during the first few uses of a product. A high vmp parameter indicates that the top level of the texture is substantial and may resist crushing. Designers track this to ensure the part looks new for as long as possible.
Wear Behavior
Erosion starts at these locations since they bear the majority of the incoming load. Evaluating the vmp parameter tells a quality engineer how quickly a texture will lose its original matte appearance. Thin peaks disappear fast under common handling forces.
Process Fidelity
Incomplete filling of the mould shows up as a low peak volume because the resin did not reach the full depth of the master texture. High levels of vmp parameter results confirm that the moulding press successfully packed the resin into the sharpest features of the steel. This number serves as an identity check for the replication quality.