Machinery's Handbook, 31st Edition
CUTTING FLUIDS IN MICROMACHINING 1185 compared in Fig. 27. Large scattering of data and low machinability is observed when dry micromilling of 316L stainless steel. The machinability improves with flood cooling, spray mist, and micromist respectively. Fig. 27 shows the data points start at lower left corner for dry machining then shift to the upper right corner of the graph for micromilling in MQL, i.e., a tool can be used at higher speed for longer time to reach the same flank wear of 50 μ m. Scanning electron microscopy examination indicates significant built-up edges and attrition failure of dry cutting tools (Fig. 28a ). In contrast, a well-defined abrasive tool wear is observed on a long lasting tool after micromilling with spray mist or in MQL conditions (Fig. 28b). Micromilling in MQL condition using CL2210EP extends tool life significantly over dry machining of 316L stainless steel.
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Dry Flood, Blasocut Spray mist, Blasocut Micromist, 2210EP
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10 0
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Machining Time (min)
Fig. 27. Effect of Cutting Fluid Conditions on Micromilling of 316L Stainless Steel. 10 m m/tooth chip load, 0.348 mm axial depth, 0.558 mm radial depth, Ø1 mm uncoated carbide tool.
10.0 μ m
10.0 μ m
Fig. 28a. Built-Up Edge (Lower Right) and Adhesion Wear (Upper Left) on a Carbide Tool. (dry cutting, 1.4 min @ 18 m/min) Fig. 28b. Uniform Abrasive Flank Wear on a Carbide Tool. (micromist, 21.7 min @ 15 m/min) Micromill Ø1 mm, 10 m m/tooth chip load, 0.348 mm axial depth, 0.558 mm radial depth. Use of Micromist in Macrofacing of 4140 Steel: Bars of 4140 steel, 2 inch (50 mm) dia meter, 6 inch (150 mm) long were faced at 54 m/min (177 ft/min) maximum surface cutting speed, 0.1 mm/rev feed (0.004 in/rev), and 0.5 mm (0.020 in.) depth of cut. Uncoated carbide inserts TNG431 were used in the study. The operation was in dry condition, flood with Rustlick 1:15 water soluble water-based coolant, and CL2210EP oil micromist. Periodic interruption of the operation was made to remove a tool for wear assessment on a toolmaker’s microscope. Fig. 29 plots flank wear of all tools and Fig. 30a, Fig. 30b, and Fig. 30c compare the tool tip conditions after 75 passes. At identical machining con ditions, crater, flank and nose wear are worst for dry machining. Flood cooling improves the tool wear but nose wear is still substantial. Micromist provides the best tool protection with reduced flank and crater wear, and negligible nose wear.
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