MEASUREMENT OF DYNAMIC CUTTING FORCE COEFFICIENTS

Abstract

<p>The dynamic behaviour of metal cutting process is investigated by measuring the various components of dynamic cutting force. For the complete description of dynamics of metal cutting it is necessary to give eight components belonging to the resultant dynamic cutting force in an orthogonal cutting process. These components originate from the two sides of chip, which under vibratory cutting conditions have undulations and are termed as inner and outer modulations respectively. The dynamic cutting forces are phase shifted with respect to their own modulations and are given respectively by real part and imaginary part of inner modulation, real part and imaginary part of outer modulation. Each of these four components are determined separately for main cutting force and thrust force and are specified as cutting force per unit amplitude of modulation per unit chip width, termed as dynamic cutting force coefficients. An experimental technique termed as the Double Modulation Method has been developed to measure the above eight coefficients for various cutting conditions of speed, feed, frequency, tool wear and work piece materials. The method is based on the Fast Fourier Transform of the measured signals of dynamic cutting forces and tool work piece relative displacement. The accuracy and reliability of the technique is established by comparing some of the results obtained from this method with those obtained from other two methods which are far simpler and conceptually more direct. These methods are termed as Kal's Method and Inner Modulation Method. The effects of various cutting conditions stipulated above on the individual coefficients have been investigated and the results are shown to be in agreement with the general practical observations. The result of stability analysis as performed by Moriwaki (21) using the coefficients measured in this work is included, to highlight the practical significance of the dynamic cutting force coefficients, for predicting the limit of stability.</p>