Surface Finish Definitions:

1. Ra: Ra is the arithmetic average of the absolute values of the roughness profile ordinates. Also known as Arithmetic Average (AA), Center Line Average (CLA). The average roughness is the area between the roughness profile and its mean line, or the integral of the absolute value of the roughness profile height over the evaluation length
2. Rz: Rz is the arithmetic mean value of the single roughness depths of consecutive sampling lengths. Z is the sum of the height of the highest peaks and the lowest valley depth within a sampling length.
3. Cutoff λc: of a profile filter determines which wavelengths belong to roughness and which ones to waviness.
4. Sampling Length: is the reference for roughness evaluation. Its length is equal to the cutoff wavelength.
5. Traversing Length: is the overall length traveled by the stylus when acquiring the traced profile. It is the total of Pre-travel, evaluation length and post travel
6. Evaluation Length: is the part of the traversing length from where the values of the surface parameters are determined.
7. Pre-Travel: the first part of the traversing length.
8. Post-Travel: The last part of the traversing length

Selection of Cutoff λc