Scattering light in bearing production: roundness, waviness, roughness in one operation

Bearings are precision machine elements with very high requirements regarding the roundness, waviness and roughness of the rolling elements as well as the bearing rings. The production processes have to meet sub-micron tolerances. To verify production quality, state of the art tactile measuring technologies are used, such as roundness and waviness measurements as well as roughness measurement according to ISO 4287. To measure roundness and waviness a special gauge is used, where as a second gauge is measuring the roughness of the surface. The measurements are mostly performed in a laboratory environment checking parts in a random sampling procedure. To meet the rising demands on quality of bearings, it is necessary to increase the sample size. On the other hand, this increases the time needed for quality inspection. The optical measuring technology SCATTERING LIGHT can help to solve these contradictory demands. The technology is based on the reflection of light from a surface. It can be used to measure roundness, waviness and roughness in one single operation. Providing a clean environment, the measurements with scattering light can be automated and integrated in production processes such as honing and grinding. Furthermore, the cycle time is shorter than from the tactile measuring procedure. Results from scattering light measurements can be calibrated. Roundness and waviness are traceable to international standards. The optical result for surface roughness “Aq” is a new parameter that does not correlate to the common known Ra and Rz values but to the occasionally used Rdq value.