Device for detecting the start of contact between a cutting tool and a workpiece on a cutting machine tool

摘要

A Machine Tool Monitor detects the sudden increase in vibration signal level when a slowly advancing cutting tool first touches the workpiece. The delay to a tool touch decision is reduced while still avoiding false alarms on high amplitude single-peaked and multi-peaked noise spikes. Samples of the preprocessed analog vibration signal that are above a low threshold level are analyzed by digital tool touch detection logic. The signal slope polarity is determined by comparison of a new sample to the tracking mean, or by sample-to-sample amplitude comparisons, and presented to an up/down counter. A tool touch alarm is generated when the positive slope counts exceed the negative slope counts by a preset number slightly greater than occur in a time period from the start of a noise spike until its peak amplitude is passed.