Areal Surface Texture Filtering Selection in High-Precision Micro Injection Moulding
Selecting areal surface texture filter cutoffs under ISO 25178 matches transmission bandwidth to moulding replication limits, preventing false tooling rejects.
Edge Roll-off Artifact
Meaning
When a tactile or optical profilometer scans near the perimeter of a molded polymer specimen, the measurement results can show a false rounded boundary. This distortion is recognized as an edge roll-off artifact. It arises because the steep slope of the boundary causes a loss of signal or mechanical over-travel.
Such measurement errors can lead to the incorrect rejection of precision components or wrong adjustments to the injection mold tooling.
Optical Distortion
Coherence scanning interferometry relies on backscattered light to reconstruct the surface topography. Near the steep curved perimeter of a plastic optic, the reflected rays deflect away from the objective lens. This loss of signal generates data dropouts that the software misinterprets as a sloped profile.
Boundary Error
The measurement area is restricted to a subset of the actual surface to avoid this edge roll-off artifact entirely. Technicians set a mechanical or digital mask that excludes the outer five percent of the part diameter. Removing this region ensures that the roughness metrics represent the functional area of the component.
This masking process avoids the artificial elevation of root-mean-square roughness values.
Stylus Deflection
Tactile metrology instruments experience physical inertia when the sensor traverses a steep boundary. The diamond tip loses contact with the surface at the perimeter. This mechanical bounce produces a profile that does not represent the real molded geometry.