本帖最后由 梦舞 于 2009-3-10 22:59 编辑
Tool-wear rate is a ‘lower-the-better’ type of characteristic, and therefore the lower values ofTWR are considered to be optimal. It is clear from Fig. 2 (raw data) that tool-wear rate (TWR) islowest at the fourth level of tool material parameter (A4), first level ofabrasive material parameter (B1), third level of the grit size (C3), firstlevel of power rating (D1) and second level of slurry concentration (E2). Themain effects of the S/N ratio are also highest at these levels of theparameters that result in lowest tool-wear rate, except for slurryconcentration factor. To establish the relativesignificance of the individual factors, ANOVA was performed on the S/N data. Asper the ANOVA of S/N data (Table 6), it is clear that all the individual factors exceptslurry concentration have a significant effect on the TWR. Tool material wasfound to be the most significant parameter with a mean percent contribution of31.20% in the variation of TWR, followed by power rating parameter (30.31%).The type the abrasive used is third in significance (19.16% contribution) whilethe slurry concentration has the least contribution (1.90%) and also it is theonly insignificant factor among all factors for TWR as response. A low value ofcontribution (5.47%) has been recorded for the experimental error thusindicating the high accuracy level of the results obtained. The percent contributionof various factors towards the variation of TWR is plotted in Fig. 3. The ANOVA of S/N data coupled with raw data concludes that the order ofsignificance of the various parameters for their effects on TWR can be put as:tool, power rating, abrasive material, grit size and slurry concentration. Theanalysis of both types of results (Avg. and S/N) depicted in Table 5 indicates that the factor levels thatcontribute most to the variation (reduction) in TWR are: level 4 for toolfactor, level 1 for abrasive, level 3 for grit size and also level 1 for powerrating. Hence, A4B1C3D1represents the optimum settings for TWR. As slurry concentration is aninsignificant factor from the point of view of TWR, any level of this factorcan be chosen for optimum results. As level 3 for slurry concentration (30% slurryconcentration) contains the highest S/N response among the three levels, it wasselected for the macro-model. The same information has been presented in theform of a macro-model as detailed in Table 7. Three conformation runs were conducted at the optimumsetting as defined above to testify the results for TWR. From the conformation experiments,the optimized value of TWR was found to be 0.09 cubic mm/min, which indicates aconsiderable improvement in process efficiency as far as the TWR is concerned. | 
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