3. Surface quality of the machined parts
Figure 6 shows the comparison of the surface roughness values ​​of the parts to be machined under several different cooling methods. The surface roughness of the sub-dry cutting parts is smaller than that of air cooling, and the air cooling is smaller than the natural cooling. The same is the sub-dry cutting. If the cooling method I from the rake face is changed to the way of cooling the jet in both directions of the front and the back flank, the Ra value is smaller. This shows the difference in the cooling method and method. The quality is also different: from the mechanism to discuss this phenomenon, it can be considered: reduce the friction between the chip, the tool and the surface being machined; reduce the deformation of the material in the cutting zone, the bond between the chip and the rake face; The chip can improve the durability of the tool, reduce the Ra value of the workpiece surface, and improve the surface quality of the part.
4. Cold air cooling performance
Figure 7 shows the comparison of cutting performance between cold air cooling and sub-dry cutting under different cold air temperatures under the same process conditions. It can be seen from the figure that as the cold air temperature of the cooling medium decreases, the cutting force is reduced, but the sub-dry type is reduced more. This leads to two revelations:
a. This phenomenon is consistent with the basic theory of heat transfer. The heat transfer and heat transfer processes can be enhanced by three ways, namely increasing the heat transfer coefficient, increasing the heat transfer area and temperature difference. In this test, as the cooling temperature decreases and the temperature difference increases, the cooling effect becomes more pronounced.
b. The cutting force curve of the sub-dry cutting is more rapid, indicating that the sub-type cutting is beneficial in inducing the low-temperature brittleness of the material, reducing the friction, and maintaining the cutting ability of the tool, and thus the comprehensive effect of many factors is simpler than that of the single-type cutting. The effect of the factors is good. However, comprehensive optimization should be carried out in terms of cost and effect.
Fourth, the conclusion
Sub-dry cutting and cold-air cooling cutting are a better cooling cutting method. With the increase of cutting heat and cutting force, the cooling effect is more remarkable, and the sub-dry cutting is more obvious.
Sub-dry cutting can protect the dimensional stability of the machined parts, significantly improve tool life and reduce the roughness of the machined surface, which is conducive to the realization of precision machining and automated machining.
Generally, the lower the cold air temperature, the better the cooling effect will be; however, due to the combined effects of many factors, the cold air temperature and the cooling effect are not completely linear, and comprehensive optimization is needed from various aspects such as production cost and cooling effect. further research.
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