Machinery's Handbook, 31st Edition
1224 MACHINING ECONOMETRICS breakage, the maximum practical feed f max is used as the optimal value. The difference in costs between a global optimum and a practical minimum cost condition is negligible, as shown in Fig. 23c and Fig. 23e. A summary of the results are shown in Fig. 23a through Fig. 23e, and Table 1.
0.31
T = 120 T = 22 T = 5
0.26
0.21
0.16
0.11
0.06
0.01
0
0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9
1
fz , mm
Fig. 23c. Total Cost versus Feed/Tooth When plotting cutting time/part, t c , versus feed/tooth, f z , at T = 5, 22, 120 in Fig. 23b, tool life T = 5 minutes yields the shortest cutting time, but total cost is the highest; the min imum occurs for f z about 0.75 mm, see Fig. 23c. The minimum for T = 120 minutes is about 0.6 mm and for T O = 22 minutes around 0.7 mm.
0 0.01 0.02 0.03 0.04 0.05 0.06 0.07 0.08 0.09 0.1
T = 5 T = 22 T =120
0
0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9
1
f z , mm
Fig. 23d. Tooling Cost versus Feed/Tooth Fig. 23d shows that tooling cost drops off quickly when increasing feed from 0.1 to 0.3 to 0.4 mm, and then diminishes slowly and is almost constant up to 0.7 to 0.8 mm/tooth. It is generally very high at the short tool life 5 minutes, while tooling cost of optimal tool life 22 minutes is about three times higher than when going slow at T =120 minutes.
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