A comparison of the performance of tool pre-setting optical systems: On- and offmachine tool assessment

Tool geometry can be determined off-machine using tool pre-setters by mounting the cutting tool on the tool holder; however, such arrangement introduces the unquantified clamping errors associated with the interface between the tool holder and the machine tool spindle and affecting the precision of machining processes. Thus, on-machine integrated tool pre-setting systems are important to accomplish reliable and accurate tool measurements and attaining the desired accuracies in the machining operations. These days, machine tools are normally equipped with tool pre-setting optical systems such as laser beam interruption systems or camera-based systems; however, the traceability of such optical sensors is not guaranteed due to the lack of a specific international standard. In this work, we have evaluated the performance of camera-based tool pre-setting optical systems for on- and off-machine scenarios. The measurement procedure resides on the guidelines specified in ISO 15530 part-3 which provides a method of uncertainty evaluation using calibrated artefacts or standards. For this purpose, a reference artefact with a square cross-section is designed from a cylindrical gauge pin (Ø6 mm ± 1 μm) and machined into a square end by wire EDM. The reference artefact is mounted on a tool holder and calibrated using a coordinate measuring machine by repeating measurements twenty times and the task-specific uncertainty is determined. The calibrated artefact is later employed to evaluate the performance of the tool pre-setting optical systems for on- and off-machine instances. Experiments have shown the implication of the developed approach for the characterisation of tool pre-setting optical systems for tool geometry assessment.