CUTTING FLUIDS IN MICROMACHINING Machinery's Handbook, 31st Edition
1186
0.00 0.05 0.10 0.15
Dry Flood Micromist
0 10
50 60 70 20 30 40 80
Number of Facing Passes
Fig. 29. Flank Wear of Uncoated Carbide Tools in Different Cutting Fluids. Macrofacing of 4140 steel, 54 m/min, 0.1 mm/rev feed, 0.5 mm depth of cut. Comparison of Tool Wear After 75 Facing Passes
200 μ m
200 μ m
200 μ m
Mist, 75 passes
Flood, 75 passes
Dry, 75 passes Fig. 30a. Dry Machining.
Fig. 30b. Rustlick 1:15 Flood Cooling.
Fig. 30c. CL2210EP Micromist.
There is negligible nose wear for machining in micromist. Macrofacing on 4140 steel, 54 m/min, 0.1 mm/rev feed, 0.5 mm depth of cut. Microfabrication Processes and Parameters
This section discusses three major microfabrication processes: micromilling, micro drilling, and microturning. Setup, tooling, and process parameters for common engineer- ing materials are then recommended. Micromilling.— Micromilling is among the most versatile of microfabrication processes. Although alternative nontraditional processes to produce microfeatures such as laser micromachining, electrical discharge micromachining, electrochemical micromachining, chemical microetching, electron/ion beam micromachining are available, these processes are either cost prohibitive, or inferior when comparing resulting surface and subsurface integrity, anisotropic aspect ratio or feature quality. Successful micromilling requires new tool geometry, tool material, machining parameters, and machining skills. It is technically incorrect and costly to perform micromilling by just scaling down a milling cutter, or para meters from macroscale milling. Commercial micromills are available for diameters of 25 m m (0.001 inch) and up, see Table 9. • Tool material. Carbide tools should be sintered from fine grains, and ground to small cutting edge radius (see Microcutting Tools on page 1157). • Milling direction. Down milling is the preferred mode since a micromill will engage a workpiece and remove a wedge shape chip with decreasing chip thickness. In con trast, a tool in upmilling would rub on the workpiece until the effective chip thickness is greater than one-half of the cutting edge radius (see Tool Sharpness on page 1158). • Lubrication. Micromist should be used with all micromachining, but adequate venti lation and filtering are required to avoid inhalation of micromist. The nozzle should be as close as possible to the work and positioned to let the cutting flutes pull the mist into the cutting zone. Tool and workpiece should be arranged to avoid the stagnant zone (see Fig. 26a, Fig. 26b, Fig. 31a, and Fig. 31b).
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