1 Introduction Microfabrication technology refers to the manufacturing and processing technology of small-sized parts. With the development of aerospace, defense industry, modern medicine, and bioengineering technology, more and more miniaturized, miniaturized equipment, and micro-sized parts have emerged. Various micro-machineries manufactured using micro-machining technology such as micro-motors, micro Sensors, micro-pumps, etc. have increasingly broad application prospects. The requirements for microfabrication in modern manufacturing technologies are also increasing. They have developed into ultra-fine micromachining. They have challenged the processing limits of existing manufacturing technologies, and have developed super-precision machining, ultra-fine processing and nano-machining technologies, which have become modern manufacturing technologies. A direction of development. The micro-machining technology not only includes various conventional precision machining methods, but also includes special processing methods such as electron beam processing, ion beam processing, and chemical processing. These special processing methods are currently well applied in the micro-fabrication field. However, there are some technical difficulties in the micro- and ultra-fine micro-scale machining, which limits its wide application. Because even the traditional mechanical processing, the processing mechanism and method are not the same for the micro size and the normal size. This paper analyzes the mechanism of ultra-fine processing, analyzes the technical difficulties in ultra-fine processing and its impact on the processing process, and proposes solutions. 2 Mechanism of Ultrafine Machining Machining and fine cutting differ in the machining mechanism. In normal cutting, the allowable depth of cut and feed are large due to the large size of the workpiece. In the case of micro-cutting, due to the small size of the workpiece, large depths of cut and advances in strength and stiffness are not allowed. To give the quantity, at the same time to ensure the workpiece size accuracy requirements, the final finish of the surface cut-off layer thickness must be less than the precision value, so the amount of cutting must be very small. The general metal material is composed of crystal grains having a diameter of several micrometers to several hundred micrometers. Due to the very small cutting depth of fine cutting, especially submicron and nanometer ultrafine cutting, the depth of cut is usually smaller than the grain diameter of the material, so that the cutting can only be performed within the grains, and the cutting is equivalent to one at a time. Discontinuities are cut, so fine cutting is an interrupted cut. Due to the presence of micro-defects in the material and non-uniform material distribution, the cutting force of the cutting tool changes greatly, and the cutting edge will be subject to greater impact and vibration. Cutting force characteristics of micro-cutting Micro-cutting machining is an ultra-micro separation technology. The cutting force near the cutting edge of diamond cutting tools is sub-Newtonian or even smaller. The cutting force can clearly reflect the removal process of the chips. Therefore, it is helpful to study the cutting force model to understand the chip cutting characteristics. The cutting force characteristics in fine cutting are: the cutting force is small, the unit cutting force is large, and the cutting depth resistance is greater than the main cutting force; the cutting force increases with the decrease of the cutting depth, and the cutting force sharply increases when the cutting depth is small Big. This is the size effect of the cutting force. The physical model of the cutting force during fine cutting is closely related to the submicron structure of the cutting edge. Due to the presence of the arc radius of the cutting edge edge, the cutting edge has a large negative rake angle at the nanometer cutting stage, which increases the cutting deformation, so the unit cutting force during cutting is large; at the same time, fine cutting is often performed. Within the grain, the cutting force must be greater than the molecular and atomic bonding forces inside the crystal, and thus the cutting force on the unit cutting area increases sharply. The cutting force increases with the increase of the cutting depth when compared with the ordinary cutting, and the depth of cut and the feed amount during the fine cutting are very small. Due to the presence of the arc radius of the tool tip and the radius of the arc of the cutting edge, the cutting deformation is significantly increased. When the depth of cut is small, the additional deformation caused by the radius of the tool tip arc accounts for a large proportion of the total cutting distortion. Due to the size effect of the cutting force, the smaller the depth of cut, the greater the cutting force (the influence of the depth of cut on the cutting force at the time of fine cutting is shown in Fig. 1).
hDmin=r(1-cosq) (1) Where: r—cutting edge radius of the cutting edge is known from Fig. 2, q+w+b=90°, ie q=90°-(w+b) ( 2) Where: b—the friction angle between the tool and the workpiece material, tgb=μ(friction coefficient), the friction coefficient is approximately 0.12 to 0.26 w when cutting the aluminum alloy with a diamond tool—the clamp of the normal stress direction and the cutting speed direction The angle, w value is related to the strength of the workpiece material, elongation, friction coefficient, and the position of the point A. According to the experience w=38° to 45°, substituting formula (2) into formula (1) can be simplified:
Fig. 1 Effect of cutting depth on cutting force
Fig. 2 Effect of the minimum cutting thickness on the arc radius of the blade
hDmin=r(1-cosq) (1) Where: r—cutting edge radius of the cutting edge is known from Fig. 2, q+w+b=90°, ie q=90°-(w+b) ( 2) Where: b—the friction angle between the tool and the workpiece material, tgb=μ(friction coefficient), the friction coefficient is approximately 0.12 to 0.26 w when cutting the aluminum alloy with a diamond tool—the clamp of the normal stress direction and the cutting speed direction The angle, w value is related to the strength of the workpiece material, elongation, friction coefficient, and the position of the point A. According to the experience w=38° to 45°, substituting formula (2) into formula (1) can be simplified:
Fig. 3 Effect of cutting speed V on the height of BUE
Fig. 4 Effect of feed f on the height of BUE
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