EFFECT OF PROCESS FACTORS ON SURFACE ROUGHNESS IN DIP CRYOGENIC MACHINING OF AISI 1040 STEEL USING TAGUCHI’S APPROACH

Abstract

Surface roughness is the most prominent factor in machining of any metal. The efficacy of a machining process is largely dependant on quality of surface roughness obtained for the workpiece. This experiment involves turning of AISI 1040 steel under dry, conventional cutting fluid (wet) and cryogenic condition using high speed steel cutting tool. The surface roughness values for each of the trials were measured and recorded.Taguchi's signal-to-noise (S/N) ratio was introduced to this experiment inorder to determine the significant control factor (cutting speed, feed rate or depth of cut) for all three machining processes along with the optimal control factor combination. The control factors were set in an orthogonal array (L27). MINITAB 16 was used to determine the S/N ratio valuesfor all the different interactions by incorporating "smaller the better" characteristic. The analysis concluded that the significant control factor for dry machining was feed rate, depth of cut for conventional cutting fluid (wet) machining and feed rate for cryogenic machining. Feed rate of 0.10mm/rev,depth of cut of 0.25mm and cutting speed of 43.73m/minare the optimumcontrol factor combination to be set to procure minimum surface roughness in each of the machining process. Even though the optimum combinations were observed to be same for all the machining process, there was an improvement of 53.57% in cryogenic machining observed in analogous to dry machining and an improvement of 33.92% in cryogenic machining was observed in correspondent to wet machiningfor S/N ratio values of optimum control factor combinations. It was also observed that the S/N ratio values for optimum combination (minimum surface roughness) in cryogenic machining were the least in analogous to other forms of machining. Thus this developed model concludes that the dip cryogenic machining should be adapted in order to procure minimum surface roughness.