Precision machining refers to a process that achieves dimensional accuracy in the range of 0.1 to 1 μm and surface roughness as low as Ra 0.02 to 0.1 μm. This technology is a fundamental aspect of mechanical manufacturing and serves as an indicator of a country's overall manufacturing capability. However, traditional precision machining often requires lower cutting speeds compared to conventional methods, which can result in reduced efficiency, higher costs, and longer production cycles. For instance, when machining aluminum alloys, the typical cutting speed for precision machining is around 100 m/min, significantly lower than the 200–300 m/min used in normal operations. To address these challenges, high-speed precision cutting has become a critical research area, aiming to improve both accuracy and productivity.
In this study, we conducted high-speed precision cutting tests using diamond tools on a CNC lathe. By optimizing cutting parameters such as depth of cut, feed rate, and cutting speed, we achieved a high-quality surface finish with Ra values below 0.1 μm. The impact of various factors—including tool material, cutting edge geometry, and whether dry or wet cutting was used—on surface roughness was analyzed. The workpiece used was LY12 high-strength aluminum alloy, with dimensions of Ø140 × 150 mm. Two types of diamond tools were tested: polycrystalline diamond (PCD) and natural single-crystal diamond (ND). Both were ground to achieve very fine surface finishes (Ra < 0.02 μm), but with different edge geometries—linear wiper and circular tip.
The results showed that natural diamond tools produced better surface roughness, especially in terms of Ry (maximum height of the profile). At a cutting speed of 800 m/min, the Ra value for natural diamond tools was 0.0778 μm, while PCD tools had an Ra of 0.1068 μm. This difference highlights the importance of tool sharpness in high-speed cutting. Additionally, the grinding quality of the tool edges played a significant role in determining surface finish. When using PCD tools with different levels of grinding quality, the Ra values varied from 0.109 to 0.235 μm, depending on the cutting speed.
Wet cutting, using an emulsified cutting fluid, significantly improved surface roughness compared to dry cutting, particularly at high speeds. Dry cutting led to chip accumulation and built-up edges, which increased surface roughness. In contrast, wet cutting reduced these issues and allowed for smoother surfaces similar to those achieved at lower speeds.
Cutting parameters such as feed rate and depth of cut also influenced surface roughness. While increasing the cutting speed initially raised roughness, it eventually stabilized, especially for natural diamond tools, which showed less sensitivity to speed changes. Feed rates above 0.02 mm/r caused rapid increases in roughness, indicating that smaller feeds are more suitable for ultra-precision machining. Similarly, the back knife (depth of cut) affected surface quality, with optimal performance observed at ap = 0.03 mm.
In conclusion, both natural diamond and polycrystalline diamond tools can produce high-quality surfaces under high-speed cutting conditions. Natural diamond tools offer superior surface finish, while PCD tools provide cost advantages. The choice of cutting parameters should consider machine vibration, tool geometry, and economic factors. Overall, high-speed precision cutting represents a promising approach to improving efficiency and surface quality in modern manufacturing.
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