MACHINING ECONOMETRICS Machinery's Handbook, 31st Edition
1225
0.3
0.25
0.2
0.15
0.1
0.05
T = 120 T = 22 T = 5
0
0
50 100 150 200 250 300 350 400 450 500
V, m/min
Fig. 23e. Total Cost versus Cutting Speed at 3 Constant Tool-Lives, Feed Varies The total cost curves in Fig. 23e were obtained by varying feed and cutting speed in order to maintain constant tool-lives at 5, 22 and 120 minutes. Cost is plotted as a function of speed V instead of feed/tooth. Approximate optimum speeds are V = 150 m/min at T = 5 minutes, V = 180 m/min at T = 120 minutes, and the global optimum speed is V O = 110 m/min for T O = 22 minutes. Table 1 displays the exact numerical values of cutting speed, tooling cost and total cost for the selected tool-lives of 5, 22, and 120 minutes, obtained from the software program. Table 1. Face Milling, Total and Tooling Cost versus ECT , Feed/tooth fz , and Cutting Speed V , at Tool-lives 5, 22, and 120 minutes
T = 5 minutes
T = 22 minutes
T = 120 minutes
f z C TOOL 0.03 0.08 489 0.72891 0.39759 416 0.49650 0.10667 344 0.49378 0.02351 0.08 0.21 492 0.27196 0.14834 397 0.19489 0.04187 311 0.20534 0.00978 0.10 0.26 469 0.22834 0.12455 374 0.16553 0.03556 289 0.17674 0.00842 0.17 0.44 388 0.16218 0.08846 301 0.12084 0.02596 225 0.13316 0.00634 0.20 0.51 359 0.14911 0.08133 276 0.11204 0.02407 205 0.12466 0.00594 0.40 1.03 230 0.11622 0.06339 171 0.09051 0.01945 122 0.10495 0.00500 0.60 1.54 164 0.10904 0.05948 119 0.08672 0.01863 83 0.10301 0.00491 0.70 1.80 141 0.10802 0.05892 102 0.08665 0.01862 70 0.10393 0.00495 0.80 2.06 124 0.10800 0.05891 89 0.08723 0.01874 60 0.10547 0.00502 1.00 2.57 98 0.10968 0.05982 69 0.08957 0.01924 47 0.10967 0.00522 High-Speed Machining Econometrics ECT V C TOT C TOOL V C TOT C TOOL V C TOT High-Speed Machining, No Mystery.— This section describes the theory and gives the basic formulas for any milling operation and high-speed milling in particular, followed by several examples on high-speed milling econometrics. These rules constitute the basis on which selection of milling feed factors is done. Selection of cutting speeds for general milling is done using the Handbook Table 10 through Table 14, starting on page 1112. High-speed machining is no mystery to those who understand metal cutting. Machining materials with good machinability, such as low-alloyed aluminum, has for ages been performed at cutting speeds well below the speed values at which these materials should be cut. Operating at such low speeds often results in built-up edges and poor surface finish, because the operating conditions selected are on the wrong side of the Taylor curve, i.e. to the left of the H- curve representing maximum tool life (see Fig. 4 on page 1199).
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