Abstract:
Following an extensive literature review on the vibrations in machining
operations, experimental work is undertaken in two main phases on the investigation and
optimization of effects of machine vibrations on dimensional surface quality in milling
operations. In Phase IA, forced vibrations are induced in the spindle of CNC machining center comparable to the older machines used in industry. This has been done using external
weights with the help of purpose built gripper. Effects of external weight and spindle
speed are found significant on vibration amplitudes. In Phase IB, industrial machines are
selected to benchmark the vibration amplitudes induced in the machine under study. The
selected vibration amplitude levels are used in Phase II to investigate the effects of
spindle forced vibrations during milling operations. Phase IIA and Phase IIB are aimed to carry out experimentation using high speed steel (HSS)and solid carbide end mill cutters in order to investigate the effects of spindle
forced vibrations along feed rate and axial depth of cut on dependent parameters
including surface roughness and dimensional accuracy. Cutting speed, radial depth of cut,
spindle speed, number of flutes and tool hang are taken as fixed parameters. A L9
Taguchi orthogonal array is used for design of experiments. The signal to noise ratio
(S/N) analysis followed by analysis of variance (ANOVA) is used for analysis. It is
revealed by ANOVA that spindle forced vibrations have strong effects on surface
roughness in case of solid carbide end mill cutter.
In Phase IIC, different tool wear patterns are evaluated for HSS and solid carbide
end mills. It is found that higher levels of vibration amplitude and feed rate accelerate the
propagation of tool wear. A tool failure is also observed at high vibration amplitudes in
case of solid carbide end mill cutter. Based on the results obtained in Phase IIB, optimization is done on the basis of ANOVA and recommends preferred operating parameters for finishing operations using solid carbide end mill cutter.
