To evaluate the quality of diamond tools, first of all, they must be able to process high-quality ultra-smooth surfaces, and secondly, it is required that the tool can keep the cutting edge sharp for a long time, that is, it has a long working life.
In general cutting, the cutting part of the tool mainly includes the cutter face, the main cutting edge, the secondary cutting edge, and the geometry of the tooltip. In ultra-precision cutting, the amount of material removal is extremely small (generally below the micron level), and the tooltip part interacts with the workpiece during cutting. At this time, the cutting part of the tool refers to the geometric shape part of the tooltip that actually participates in cutting.
At present, single-crystal diamond tools are widely used in ultra-precision cutting, and the geometry of the tip of the single-crystal diamond tools used is often made into two forms: straight cutting edge and arc cutting edge.
Under ultra-precision cutting conditions, the length of the straight cutting edge, the arc radius of the arc cutting edge, and the sharpness of the cutting edge all have a great influence on the physical phenomena in the process.
Influence of Tool Nose Geometry on Machining Quality
Commonly used natural diamond tools have sharp edges, multi-edged edges, straight cutting edges, curved cutting edges (mainly arc cutting edges), and so on.
In ultra-precision cutting, the straight cutting edge is the straight wiper edge, and the arc cutting edge is the arc wiper edge.
Among these diamond tools with different tip geometries, it is difficult to process ultra-precision surfaces for sharp-edged tools and multi-edged tools. Although the machining residual area of circular-arc cutting-edge tools is small, it is difficult to sharpen. On the premise of precise installation, the machining residual area of the linear cutting-edge tool is the smallest, and the machined surface quality is the highest.
Straight cutting edge
The linear cutting edge has less cutting resistance than the arc cutting edge and is easy to control the dimensional accuracy and surface roughness, and it is easy to manufacture and grind. Its advantages in high-quality and high-precision machining are difficult to replace with other cutting edges.
The straight cutting edge should not be too long, otherwise, the radial cutting force will increase, and excessive friction between the cutting edge and the workpiece surface will increase the roughness of the machined surface and accelerate tool wear.
Arc cutting edge
The diamond tool with an arc cutting edge is easy to set and use, but it is difficult to manufacture and grind the tool, and the price is relatively high. The recommended arc radius of the cutting edge is rε=0.15~3mm or less. The feed rate during ultra-precision cutting is very small. Generally, the feed rate is f <0.102mm /r.
Under the condition of the same depth of cut, the surface roughness of the workpiece increases with the decrease of the radius of the tool nose arc. This is because the residual area left when the arc cutting edge is machined changes with the radius of the arc of the tool nose. When the radius of the tool nose arc decreases, the cutting edge becomes smaller and smaller, and the residual area of the workpiece is larger and larger.
Influence of Blunt Radius of Cutting Edge on Machining Quality
Since the cutting edge cannot be made into a sharp geometric line, there is always a dull rounding of the cutting edge. The smaller the radius of the blunt circle of the cutting edge, the sharper the cutting edge, and the larger the radius of the blunt circle of the cutting edge, the blunter the cutting edge. The degree of extrusion and friction of the blunt cutting edge on the machined surface is related to the sharpness of the cutting edge. The blunter the cutting edge, the greater the deformation of the machined surface, the greater the machining error, and the worse the machining quality.
From this point of view, to achieve ultra-precision cutting, a very small amount of removal must be carried out, that is, the cutting edge of the tool must be extremely sharp or the radius of the blunt circle of the cutting edge must be extremely small, so as to ensure that the removed cutting thickness is small enough.
Therefore, the minimum cutting thickness that can ensure stable ultra-precision cutting has a certain relationship with the radius of the blunt circle of the cutting edge of the diamond tool.
When the parameters such as depth of cut, feed rate, cutting speed, and cutting edge change within the range of ultra-precision cutting conditions, the sharper the cutting edge (that is, the smaller the radius of the blunt circle of the cutting edge), the better the quality of the processed surface obtained.
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