· KAIPU Engineering · glossary · 1 min read

undefined — Industry Glossary Entry

Definition of surface roughness (Ra) in industrial blade measurement: the arithmetic average of the absolute deviations of the surface profile from the mean, and the typical Ra targets for slitter and shear blades.

undefined is the arithmetic average of the absolute deviations of the surface profile from the mean, expressed in micrometres (µm) and denoted Ra. A lower Ra means a smoother surface.

Typical Ra by application

  • Precision slitter (film, foil): Ra ≤ 0.2 µm
  • Standard slitter (paper): Ra ≤ 0.4 µm
  • Tissue slitter: Ra ≤ 0.4 µm
  • Granulator: Ra ≤ 0.8 µm (less critical)
  • Plate shear: Ra ≤ 0.4 µm on the cutting face

How to measure

  • Contact profilometer: most accurate, trace over 4–12 mm
  • Optical profilometer: non-contact, suitable for soft coatings
  • Stylus profilometer: classic, contact-based
  • Compare to a calibrated roughness specimen for spot checks

See also: Hone (micro-hone), PVD Coating Comparison Table.

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