Measured Variables

Fig.. 1

Fig. 2

The scattered light sensor captures the roughness according to the characteristic value Aq (VDA 2009). For specific machining processes, Aq can be correlated with the well-known characteristic values Ra or Rz. However, when the profile signature changes, Aq registers the change with high sensitivity, but Ra and Rz, as pure height characteristics do not (Fig. 1).

This has the advantage amongst others, that an increased contact area is better captured. Thus, Aq should be used as an independent parameter in line with VDA 2009.

Scattered light technology also has the capability of absoute measurement of roundness and waviness of precision machined parts.

During uniform movement of the sensor or the surface, the sensor captures not only roughness changes on the surface, but also the tilt M of the light distribution cause by flatness changes of the surface. From the angle measurement and the know speed, the waviness of the surface (roundness for a round part) can be mathematically calculated.