A low cost, high accuracy roundness measuring system

This work presents a new architecture of a roundness measuring system in which the roundness measuring accuracy is not dependent on motion accuracy of the rotary element. In this architecture, the influence of motion errors on roundness measurement is minimized by applying a new error separation technique developed by Horikawa et. al. [1,2], the improved Reversal Method — IRM. A prototype that uses: a rotary table supported by ball bearings, non-contact gap sensors and a computer system that collects and process sensor readings has been developed. Experimental results have shown that even using a rotary table supported by ball bearings, that has non-repetitive motion errors larger than 2μm, the final measurement repeatability is better than 0.3μm of peak-to-peak value. In order to ensure the same levels of accuracy of the proposed system, a traditional roundness measuring system design must use a more precise and therefore more expensive type of bearing with a motion error no larger than 0.1μm.