Stylus (X,Y) Δq
Stylus (X, Y) Δq is the Root Mean Square Slope Along (X,Y). The Stylus X Δq and Stylus Y Δq calculations find the rms (standard deviation) of the profile slope given by:
The Δq measurements along the X and Y directions provides a quantitative assessment of the rate of change of the surface heights over the profile length. Since the slope values are squared prior to integration, the polarity (i.e. positive or negative) of the slope is lost in the calculation. The Δq measurements may be useful in applications where a machining process is producing parts with nominally correct amplitude parameters (e.g. Ra) but has other functional or process problems. For machining operations, parameters associated with the materials or machine setup may be manifested in significant changes in the surface slopes, easily measured by Δq. The wetting characteristics of a surface and the surface area of a texture may be related to Δq.
Depiction of two surfaces with similar overall roughness but different surface texture slopes along the X and Y directions as a result of the presence or absence of finer spaced features.