MACHINING ECONOMETRICS Machinery's Handbook, 31st Edition
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T = 45 T = 120 T = 15
T = 15 T = 45 T = 120
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Fig. 17e. Tool Life for End-Milling Low-Alloy Steel Using Coated Carbide
Fig. 17f. Tool Life for Face-Milling SAE 1045 Steel Using Coated Carbide
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T = 15 T = 45 T = 120
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T = 30 T = 10 T = 1
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ECT , mm
Fig. 17g. Tool Life for Solid Carbide Drill Fig. 17h. Wheel Life in Grinding M4 Tool-Steel Calculation of Optimized Values of Tool Life, Feed and Cutting Speed Minimum Cost.— Global optimum is defined as the absolute minimum cost considering all alternative speeds, feeds and tool-lives, and refers to the determination of optimum tool life T O , feed f O , and cutting speed V O , for either minimum cost or maximum produc tion rate. When using the tool life equation, T = f ( V , ECT ), determine the corresponding feed, for given values of depth of cut and operation geometry, from optimum equivalent chip thickness, ECT O . Mathematically the task is to determine minimum cost, employing the cost function C TOT = cost of machining time + tool changing cost + tooling cost. Mini mum cost optima occur along the so-called G -curve, identified in Fig. 6c. Another important factor when optimizing cutting conditions involves choosing the proper cost values for cost per edge C E , replacement time per edge T RPL , and not least, the hourly rate H R that should be applied. H R is defined as the portion of the hourly shop rate that is applied to the operations and machines in question. If optimizing all operations in the portion of the shop for which H R is calculated, use the full rate; if only one machine is involved, apply a lower rate, as only a portion of the general overhead rate should be used, otherwise the optimum, and anticipated savings, are erroneous.
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