Cryogenic cooling in machining is an advanced process in metalworking and other fields where low temperatures, usually below freezing, are used to cool the tool and workpiece during the machining process. This method offers several advantages over conventional cooling methods using cooling lubricants. Cryogenic cooling involves the use of liquid nitrogen or other refrigerants to greatly reduce the temperature during the machining process. Temperatures can be reduced to -196 degrees Celsius or even lower.
Advantages
Cryogenic cooling offers various advantages, including a significant reduction in friction and heat generation during machining. This extends tool life, improves the surface quality of the workpieces and facilitates the formation of chips. Compared to conventional cooling lubricants, which often contain environmentally harmful chemicals, cryogenic cooling is more environmentally friendly as it does not release any harmful chemicals. Cryogenic cooling is mainly used in the machining of difficult-to-cut materials such as titanium alloys, hardened steel and ceramics. They are used in various industries, including aerospace, automotive and medical technology.
Challenges
The implementation of cryogenic cooling requires specialized equipment and the availability of liquid nitrogen or other refrigerants. In addition, handling extremely low temperatures may require strict safety precautions. Machining of alloys widely used in orthopaedics due to their unique properties can be complicated by a significant reduction in tool life, productivity of the cutting process and deterioration of surface quality. Against the background of the above-mentioned complexities, cryogenic cooling method was developed. It implies the use of liquid nitrogen as a refrigerant at a temperature of 197︒С to increase heat dissipation and reduce the chemical reaction between the cutting tool and the workpiece material. In their study, Shokrani et al. showed the effects of the machining medium when milling CopraBond K (466 HV) material with a cutter diameter of 12 mm, at a cutting speed of 200 m/min and a feed rate of 636.6 mm/min. A significant improvement in the roughness parameter Ra was observed during cryogenic milling compared to low-lubricant and lubricant-free milling by 35 % and 42 % respectively (Figure 2).
Significant reduction of cutting edge wear by 91 % as well as effective control of the degree of wear by minimizing crater wear must also not go unnoticed [1].
Overall, cryogenic cooling during machining enables more efficient and precise cutting, especially with demanding materials. It offers solutions to manufacturing challenges that are difficult to overcome with conventional coolants and helps to improve the quality of the manufactured workpieces.
Reference:
[1] Alborz Shokrania, Vimal Dhokia, Stephen T, Newman “Cryogenic high speed machining of cobalt chromium alloy” University of Bath, Bath, United Kingdom