Burr size

Minimising burr size in driiling integrating response surface methodoiogy with particie swarm optimisation... 

Key words drilling burr size Box-Behnken design of experiments response surface methodology particle swarm optimisation. 

Box-Behnken design (BBD) matrix and measured vaiues of burr size... 

The multiple regression analysis was performed for constructing the RSM-based burr size mathematical models. In the present investigation, the second order burr height and burr thickness mathematical models have been developed in terms of four process parameters, namely, cutting speed (v) feed rate (/), drill diameter (d) and point angle (. The nonlinear second order response surface equation is given by ... 

Analysis of variance (ANOVA) for burr size models... 

Burr size Sum of squares Degrees of freedom Mean square F-ratio... 

The goodness of fit of the burr size mathematical models was also tested through the coefficient of determination (R ) and adjusted coefficient of determination (R adj) (Montgomery, 2003). The is the proportion of variation in the response explained by the regression model. In contrast, R dj is the coefficient of determination adjusted for the number of variables in the regression model. Unlike R, the R adj decrease if the variables are entered in the model that does not add drastically to the model fit. The coefficient of determination is given by (Montgomery, 2003) ... 

In order to validate the developed burr size models, five sets of random experiments were performed within the ranges of the process parameters selected and the burr height and burr thickness values were measured. The experimental values were then compared with the predicted values of RSM-based models and it was found that these values were close to each other, as illustrated in Table 7.5. The maximum prediction... 

Comparison of experimental and RSM-based predicted values of burr size for the validation data... 

Interaction effect of drill diameter and cutting speed on burr size (f = 0.08 mm/rev and 6= 126 degrees)... 

As seen from Figures 7.5a and 7.5b, the interaction effect of feed and drill diameter is almost the same for both the burr height and burr thickness. For a given drill diameter, increased feed results in a sharp increase in both burr height and burr thickness. This indicates that the burr size is highly sensitive to the variations in feed and it is necessary to employ lower feed to minimise the burr size. 

Optimal burr size obtained by PSO simulation for different values of drill diameter... 

It is observed from the optimisation results that for minimising burr size, the optimal cutting speed requirement is low, i.e. 8m/min irrespective of the drill diameter. On the other hand, as depicted in Figure 7.10, the requirement of optimal feed is in the low range (0.04-0.06mm/rev) and is in direct proportion to the drill diameter for the entire range specified. The reason might be that at lower feed thrust force reduces and hence forms thinner burrs. 

From the optimisation results, it is observed that the combination of optimal feed and point angle has played a key role in reducing the burr size for every drill diameter specified in the range 16-2 8mm. However, the different combinations of optimal feed and point angle are required for minimising the burr size. It is also revealed that, with the increase in drill diameter, simultaneous increase in feed and... 

---