Study on high-speed on-machine measurement of deep-hole accuracy

Deep-holes can be bored by using deep-hole drilling machines as well as by using large lathes, machining centers, boring machines, etc. Even in the case of holes with a relatively small L/D ratio, which are machined using machines such as lathes, it is difficult to precisely evaluate their accuracy. We developed an on-machine measurement system on a lathe and evaluated the performance of the measurement system. The system consists of a laser interferometer set behind a head stock, and a measurement unit with the pentaprism and corner cube prism. It was observed it takes 25 min to evaluate the accuracy of a hole with a diameter of 63 mm and a length of 250 mm. If the system is used for the feed-back control of NC machines, the evaluation time should be shortened. In this study, the influence of the rotational speed and feed speed on the measurement accuracy was observed using three workpieces with holes of different shapes. Through the experiments, it was confirmed that the hole accuracy can be measured within 17 s at a high feed speed of 900 mm/min.