Machining precision augmented by sensors

In order to improve machining accuracy in turning, two types of on-machine measurements are conducted between successive cutting passes. The first type provides a reference position of the tool-tip using diffraction measurements. While this allows compensation for thermal deformations and tool wear by adjusting the feed of the tool, elastic deformations that are due to cutting forces remain unavailable. For this reason, the dimension of the work in progress is measured periodically so that elastic deflections expected during a subsequent tool pass can also be accounted for. This second measurement type is by the (now referenced) tool-tip acting as a probe of a 'fine touch' contact sensor that is under proximity control while approaching the part. The entire concept is illustrated in the example of cutting a groove inside a narrow hole, whereby the tool wear and thermal and elastic deformations are all significant sources of inaccuracies.