Surface Roughness

Surface roughness is a measure of the texture of a manufactured surface.   Although there are many definitions of surface roughness, all of them are based on a statistical representation of the high frequency surface deviations (peaks and values) from the local mean surface height.    Filtering is used to separate the high frequency texture data from lower frequency machining features.

Surface roughness can be measured using contact methods involving dragging a stylus across the part, or using non-contact optical methods.  CiDRA® Precision Serivces, LLC uses both measurement methods.

Ra, the most commonly used surface roughness definition, is expressed mathematically by

where n is the total number of data points used in the calculation and Y is the vertical surface position measure from the average surface height. To be applied properly, this line measurement should be made perpendicular to machining lay marks. Visit http:/Wikipedia.org/wikiw/roughness for a more in-depth explanation of surface roughness.