Machinery's Handbook, 31st Edition
MACHINING ECONOMETRICS 1231 Depending on the starting f z value, and on the combination of cutter grade and work material, the location of the H -curve plays an important role when selecting high-speed end milling data. Feed Rate and Tool Life in High-Speed Milling, Effect of ECT and Number of Teeth.— Calculation of feed rate is done using the formulas previously given: Feed Rate: F R = z 3 f z 3 rpm, where z 3 f z = f (feed/rev of cutter). Feed is measured along the feeding direction. rpm = 1000 3 V ⁄3.1416/ D , where D is diameter of cutter.
10000
T = 5 T = 15 T = 45 T = 180
10000
T = 5 T = 15 T = 45 T = 180
1000
H-CURVE
1000
T = 5 T = 15 T = 45 T = 180
T = 5 T = 15 T = 45 T= 180
100
0.01
0.1
ECT , mm
100
0.01
0.1
1
Fig. 26c. High-Speed Feed Rate and Cutting Speed versus ECT, ar / D Plotted at T = 5, 15, 45, and 180 Minutes
ar/D
Fig. 26b. High-Speed Feed Rate and Cutting Speed versus ar / D at T = 5, 15, 45, and 180 Minutes
Fig. 26b shows the variation of feed rate F R plotted versus ar / D for tool-lives 5, 15, 45 and 180 minutes with a 25 mm diameter cutter and 2 teeth. Fig. 26c shows the variation of feed rate F R when plotted versus ECT . In both graphs the corresponding cutting speeds are also plotted. The values for ar / D = 0.03 in Fig. 26b correspond to ECT = 0.011 in Fig. 26c. Feed rates have a minimum around values of ar / D = 0.8 and ECT = 0.75 and not along the H -curve. This is due to the fact that the f z / f z 0 ratio to maintain a mean chip thickness = 0.108 mm changes F R in a different proportion than the cutting speed.
100000
T = 45, SL T = 45 T = 45, HS
H-CURVE
HS6
HS4
10000
HS2
SL6
SL4
SL2
1000
0.01
0.1
1
ECT , mm
Fig. 26d. Feed Rate versus ECT Comparison of Slot Milling ( ar / D = 1) and High-Speed Milling at ( ar / D = 0.03) for 2, 4, and 6 Teeth at T = 45 Minutes
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