Investigation of chatter in hard machining using viscoelastic damper between tool holder and insert

Abstract

The present thesis deals with the analytical and experimental investigations of chatter in hard turning. Producers of machined components are continually challenged to reduce cost, improve quality and minimize setup time in order to remain competitive. Based on the literature survey it is identified that the chatter is one of the major problems in hard turning. Machine tool chatter must be avoided to maintain machining tolerances, preserve surface finish, and prevent tool breakage. In the present work, the carbide shim is replaced with Constrained Layer Damper (CLD) shim and Poly Tetra Flora Ethylene (PTFE) coated carbide shim, cutting tests are conducted to find out the improvement in surface finish and there by chatter reduction. An analytical model is simulated using MATLAB. The stability plot for dynamic turning system is obtained during cutting process with various modes, speeds, width of cut and damping ratios. The damped tool with PTFE coated carbide shim has wide stability region, which influences the metal removal rate. In the first experiment, 24 cutting test are carried out by the combination of cutting speed, depth of cut and damping ratio at different level. It is clear from the results of ANOVA that the damping ratio is the dominant factor affecting surface finish Ra. High temperature in the tool-chip interface increases the rate of wear and lowers the tool life. The temperature distribution in the cutting tool is simulated using finite element analysis. Experiment is conducted to validate the simulated values. Results show that the temperature of the cutting tool is increased mainly due to increase in cutting speed and depth of cut. The dynamic characteristics of cutting tool system is improved with PTFE coated carbide shim and the chatter is minimized. Metal removal rate is increased with minimum cost. newline newline newline