The surface topography of the workpiece is the result of the contour of the tool being mapped onto the workpiece. Therefore, the surface roughness of the machining is determined by the accuracy of the relative motion between the tool and the workpiece and the shape of the cutting edge of the tool. In fine cutting, since the depth of cut is often smaller than the grain diameter of the material, it is equivalent to cutting one by one. This microscopic intermittent cutting and the dynamic characteristics of the machine tool can cause micro-vibration during the cutting process. The influence of microvibration in micro-cutting on the quality of the machined surface cannot be ignored.
 Figure 3 Effect of cutting speed V on the height of built-up edge |
 Figure 4 Effect of feed rate f on the height of built-up edge |
When ultra-fine cutting, the influence of built-up edge can not be ignored. The built-up edge affects the cutting force and the cutting deformation, and the built-up edge of the cold welding on the cutting edge also affects the surface roughness of the machined surface. In addition to the microscopic defects of the blade have a direct impact on the formation of built-up edge, the impact of cutting speed and feed on the built-up edge is also obvious. In micro-cutting, there is a built-up edge in all cutting speed ranges, but the cutting speed will affect the height of the built-up edge: the lower the cutting speed, the higher the built-up edge (cutting speed V is the height of the built-up edge) The effect is shown in Figure 3); the smaller the feed, the higher the built-up edge (the effect of feed rate f on the height of built-up edge is shown in Figure 4).
4 Measures and methodsTo solve the above technical difficulties in ultrafine machining, the following technical measures and methods should be taken during processing:
Reasonable material selectionIn order to improve the surface quality of ultra-fine processing, the workpiece material should be selected reasonably. Selecting a workpiece material with a good micro-machining property (such as an amorphous material or a material having a fine grain structure) can obtain a surface of a workpiece having a good surface integrity.
Reduce the radius of the cutting edgeUltra-precision machining of non-ferrous metals and non-metallic materials with diamond tools enables the acquisition of mirrors with a Ra of 0.02 to 0.002 μm. After fine grinding, the chips can be cut to a thickness of 1 nm. At present, the cutting edge quality of the diamond tool is mainly obtained by finely grinding and polishing the diamond cutting edge on the rotating cast iron plate, and the ion beam processing and the chemical polishing process can make the processed tool have submicron shape accuracy.
Bevel cuttingBevel cutting can increase the actual pre-cutting angle, reduce the cutting edge arc radius and the minimum minimum cutting thickness, thus achieving ultra-thin cutting and fine cutting. For fine cutting, the choice of the edge angle of the blade needs to take into account the choice of the diamond tool face and the sharpening.
Select the appropriate tool front and back flankNatural diamond has a series of excellent properties such as high hardness, high wear resistance, high temperature strength, good thermal conductivity, low friction coefficient with non-ferrous metals, and the ability to sharpen sharp edges. Therefore, although natural diamonds are expensive, natural diamonds are expensive. Still an irreplaceable ultra-fine cutting tool material.
Diamond crystals have strong anisotropy, so the choice of crystal faces on the front and back flank of diamond tools is particularly important. The diamond crystal faces normally used as the front and back flank of the tool are (100) crystal faces and (11 0) crystal faces. The use of a small coefficient of friction (100) crystal plane as the front and back flank of the tool can reduce the cutting deformation, reduce the friction between the tool flank and the machined surface and the residual stress on the machined surface. At the same time, the (1 0 0) crystal plane is used as the front and back flank of the tool, the wear resistance is good, the micro-strength of the blade is high, and the micro-cracking is not easy to occur, which is very beneficial for maintaining the sharpness of the blade and prolonging the service life of the tool.Stable machine dynamics and machining environment
To achieve ultra-fine cutting, it is also important to choose the dynamic characteristics of the machine and to maintain the stability of the machining environment. The processing machine should be equipped with a high-precision micro-feed device to achieve accurate, stable, reliable and fast micro-displacement. At the same time, the processing should have an ultra-stable processing environment to ensure strict temperature, constant humidity and vibration resistance during processing. Under ultra-clean conditions, the effect of micro-vibration on the quality of the machined surface is minimized.Reduce cutting temperature
Since the amount of cutting affects the height of the cutting edge of the tool by the change of the cutting temperature, using the cutting fluid to reduce the cutting temperature is an effective measure to suppress the built-up edge and reduce tool wear.5 Conclusion
Ultra-fine cutting is a kind of micro-interrupted cutting, the unit cutting force is large, the surface quality of the workpiece is subject to many factors, and the cutting process is complicated. In this paper, by quantifying the relationship between the minimum cutting thickness and the radius of the cutting edge of the tool during ultra-fine cutting, it is proposed to select the workpiece material with good micro-machining, use the bevel cutting, fine grinding tool, reduce the radius of the cutting edge of the tool. Selecting the appropriate diamond crystal face as the front and back flank of the tool and reducing the cutting temperature to achieve ultra-fine cutting technology, and pointed out that high-precision machine tools and ultra-stable machining environment are also important for ultra-fine cutting. condition.
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