Surface roughness measurement of meso-micro scale
surfaces is a challenging task, as the tactile measurement
is either infeasible or the micro probing instruments are
too expensive. On the other hand, optical measurement
technologies for surface roughness measurement have
difficulties such as longer measurement durations and
restrictions regarding the complexity of the machined
geometries, e.g. vertical walls. Also related standards
ISO 25178 were unavailable during current research, to
use standardised parameters such as cut-off length.
Mainly two surface roughness measurement methods
have been used during this work. For tactile
measurements, Talysurf from Taylor Hobson was used,
whereas Alicona Infinitefocus microscope, which is
based on focus variation technique, was used for optical
surface roughness measurement. In order to compare
reliability of the optical measurements, a comparison
study was carried out using 8 different wire-EDM
surfaces, machined on hard metal with dielectric oil, to
different surface roughness. Fig. 3 presents obtained
results indicating good repeatability of the two tactile
measurement instruments, whereas optically measured
values correlate with tactile measurement values for
Ra