Development and characterization of contact methods for accurate contact detection between cutting tool and workpiece in high-speed micromilling process

Cutting tool–workpiece contact detection is crucial in micromilling operation to prevent microcutting tool failure and ensure proper dimensional and geometrical accuracy of the machined part. This study analyses two methods for identifying the contact between the microcutting tool and a conductive workpiece. The first method utilizes an op-amp circuit based on a voltage comparator, while the second method employs a DC voltage applied between the cutting tool and the workpiece. Contact detection has been confirmed by the illumination of an LED connected to the output voltage generated due to contact between the cutting tool and the workpiece in both methods. Subsequently, the vibration velocity has been measured during contact using a Laser Doppler Vibrometer. The contact occurs when the voltage level ranges between 0.9 and 1.2 volts based on the first contact method using an op-amp circuit, whereas in the second method based on DC voltage supply to the cutting tool, the contact voltage ranges between 2.8 and 5 volts. Both contact methods are straightforward, cost-effective, and simple to implement, and it also ensures detection of the initial contact state between the cutting tool and the workpiece.