Dynamometric cutting tool

Abstract

The aim was to develop, manufacture and test a technically simple dynamometer for monitoring the cutting process during boring and turning. An S20R-SSSCR09 right-hand cutter was selected as a research object. To register the cutting force and vibration movements of the cutter tip in tangential and radial directions, the cutter was equipped with four KF5P1-10-400-A-12 strain gauges mounted according to a half-bridge scheme. The bending stiffness of the cutter in two directions was measured by a DOU-3-01 compression dynamometer and a DDP-10A dial indicator. The cutter natural frequency was determined by a vibrogram of damped bending vibrations. The dynamometric boring tool was tested on a DMG NEF 400 turning machine by turning a workpiece made of 20X steel, 79 mm in diameter with a 200 mm extension, at a spindle rotational frequency of 600 r/min, a cutting depth of 0.8 mm and a longitudinal feed of 0.103 mm/turn. According to the conducted review of modern turning dynamometers and their designs, strain gauging of cutting tools is the simplest technical solution when carrying out boring procedures. The bending stiffness of the cutter in tangential and radial directions comprised 0.6 and 1.058 N/μm, respectively. The conversion coefficients for displacements in these directions were 3.5 and 4.2 μm/V, respectively. The mutual influence of registration of radial on tangential and tangential on radial displacements was 7.7% and 2.8%, respectively. The obtained vibrograms showed that the turning process under the given machining conditions is accompanied by distinct auto-oscillations of the cutter with a frequency of 561 Hz. Therefore, strain gauging of cutting tools provides information in the form of vibrograms about the two most important parameters of the cutting process dynamics – force and vibration displacements. The main advantages of the presented dynamometric cutting tool include its design simplicity, possibility of manufacturing in laboratory conditions, low cost and insensitivity to temperature and axial feed force variations.