An investigation into surface integrity of AISI P20 machined under the influence of spindle forced vibrations

Abstract

Vibrations are an undesirable yet inherent aspect of conventional machining which adversely affect the surface integrity of machined components ultimately resulting into inferior quality components. This study purposely introduces spindle forced vibrations while machining AISI P20 with high-speed steel (HSS) end-mill cutter to evaluate the extent of their influence on ensuing surface integrity aspects. Taguchi L9 array has been employed for experimentation followed by analysis of variance (ANOVA) and linear regression modeling to predict the effect of spindle forced vibration together with other milling parameters (axial depth of cut and feed rate) on the machined component’s surface roughness (Ra). Additionally, micro-hardness and microstructure have been evaluated. X-ray diffraction (XRD) analysis is used to augment the findings as deduced by microstructure analysis. It is found that spindle forced vibration is most significant parameter at 95% confidence interval for surface roughness whereas the same parameter along with feed rate is mainly responsible for strain hardening of the milled part. Results are discussed in light of physical phenomenon involved. Discussion is supplemented with results of additional experimentation done at higher feed rate regime wherein catastrophic failure of tool is encountered whose reasons are sought with the help of scanning electron microscopy images.