Page 401 - AWSAR 2.0

uneasy working environment for workers. Direct or indirect contact of workers with cutting oil and its residue may result in health problems such as skin and lung diseases. Hence, it is the need of the hour to switch over to greener, cleaner, and sustainable machining techniques from conventional, unhealthy, and less efficient practices of machining. Hence, to address above-stated issues, cryogenic machining comes into the picture. In cryogenic machining, cryogenic fluids such as liquid nitrogen are employed in place of oil-based cutting and lubrication fluids. Liquid nitrogen is environment-friendly. It is not a greenhouse gas and creates a nitrogen environment when in use, to eliminate oxidization during the process. Therefore, it can produce contamination-free components for special machining requirements, for instance instrument and components used for medical purposes. It also eliminates the cost of disposal management and infrastructure
associated with flood coolants.
It eliminates toxicity, bacteria,
oily work environment, and
investment in pits and filtration
associated with the use of oil-
based cutting and lubrication
during machining. Before going
onto the outcome of this
research, let us understand the
basic mechanics of machining
in brief. The process of cutting
produces heat; the faster the
cutting speed, and the higher
will be the heat. Each tool
material has a critical
temperature where it
deteriorates to fail quickly.
Different work materials bring
tools to a critical temperature at
different cutting speeds. Alloys such as Inconel 718 have a very short tool life of 3–5 min. Hence, it is necessary to reduce the
Mr. Chetan Agrawal || 377
temperature of the cutting zone using various techniques. Conventional techniques for disposing of heat are less sustainable. Economic, environmental, and social aspects of any process are the main pillars to evaluate the sustainability of the process. The adoption of cryogenic machining can help in reducing waste and environmental pollution, improving productivity, and ensuring a healthy and safe environment for workers. During this research, we studied the machining of various materials under cryogenic environments, and the results were compared with those of dry and wet machining techniques. For example, cryogenic drilling experiments performed on Inconel 718 (difficult-to-machine nickel-based alloys used in hot sections of the turbine of aero engines) revealed an improved hole quality (measured in terms of cylindricity, circularity, and surface roughness) and a 95% improvement in the tool life of the drill bit. Similar was the observation
when titanium alloy (which is also increasingly used in the aerospace industry) was machined under cryogenic conditions. Reduced power consumption at a higher level of cutting parameters, better chip formation, and improved surface quality were some of the key observations of this study. The third experiment was to investigate the machinability characteristic of CFRP composites under cryogenic conditions. One of the key problems encountered when drilling composites was delamination, which was found to be reduced under cryogenic conditions. Hole quality and
surface finish were also found to be improved when CFRP composites were drilled under cryogenic conditions. One of our collaborators,
Simple operations such as drilling, grinding, turning, and milling are common in manufacturing industries and fall into the machining category. In the case of hard metals and alloys, a lot of heat is produced during machining due to the relative motion between the hard workpiece and the harder cutting tool.