cryogenic cooling during machining - snsce.ac.in · pdf filecutting fluids cutting fluid is a...
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CRYOGENIC COOLING
DURING MACHINING By
Dr.K.Senthil Kumar Associate Professor / Mechanical
TOPICS TO BE DISCUSSED
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Machining Process Need for Cooling Cryogenic Cooling Applications during machining
Production Process
Conversion of raw material into a finished product through sequence of operations
A product can be made from
Metal Forming processes Ex: Casting
Metal Joining processes Ex: Welding
Metal Removal processes Ex: Drilling
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Machining Process
Metal Removal process
Removal of material from a work piece to obtain required shape and size
Machining, as well as all Manufacturing operations is a system consisting of the work piece, the tool and the machine
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Categories of Machining
Process
Cutting: Make use of single-point or multipoint cutting tools for metal removal, Ex : Turning, Drilling etc
Abrasive processes, such as Grinding.
Nontraditional Machining (NTM) or(UCM) : Processes which utilize Electrical, Chemical, and Optimal sources of energy Ex: EDM, ECM, AJM etc
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Heat generation during
Machining
Heat has critical influences on Machining.
It increase tool wear and thereby reduces tool life
Leads to Thermal deformation, Environmental problems, etc.
The properties of materials vary with the temperature – the mechanical process and the thermal dynamic process are inter-related
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Cutting fluids
Cutting fluid is a type of coolant and lubricant designed specifically for metalworking processes, like machining.
There are various kinds of cutting fluids, which include oils, oil-water emulsions, pastes, gels, aerosols (mists), and air or other gases.
Depending on the type of application, it may be referred to as cutting fluid, cutting oil, cutting compound, coolant, or lubricant.
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Properties of a
Cutting fluids
Maintain the work piece at a stable temperature (critical when working to close tolerances). Very warm is acceptable.
Maximize the life of the cutting tool by lubricating the working edge and reducing tool wear.
Ensure safety for the people handling it (toxicity, bacteria, fungi) and for the environment upon disposal.
Prevent rust on machine parts and cutters.
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Cryogenic Cooling
Cryogenics is the study of the production and behaviour of materials at very low temperatures.
Scientists assume a gas to be cryogenic if it can be liquefied at or below −150 °C (123.15 K; −238.00 °F).
Common cryogenics are helium, hydrogen, neon, nitrogen, oxygen, argon, krypton, xenon, methane, ethane, and propane.
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History of Cryogenic
During World War II, scientists found that metals frozen to low temperatures showed more resistance to wear
Ed Busch founded a cryogenic processing company in Detroit called CryoTech in 1966
He experimented the possibility of increasing the metal tools life to anywhere between 200%-400% using cryogenic tempering instead of heat treating
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Common Applications
of Cryogenic
Certain rare blood groups are stored at low temperatures, such as −165 °C.
To cool super conductors in underground power transmission
Special cryogenic chemical reactors are used to remove reaction heat and provide a low temperature environment.
Cryogenic food freezing is helpful for large scale food processing industries.
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Common Applications
of Cryogenic
The freezing of foods and biotechnology products, like vaccines, statin drugs requires nitrogen freezing systems
Certain soft or elastic materials become hard and brittle at very low temperatures, which makes cryogenic milling (cryomilling)
Tupolev developed Tu-154, with a cryogenic fuel system which uses liquefied natural gas or LNG as fuel, and made its first flight in 1989.
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Liquid Nitrogen
• Nitrogen is a safe, non-combustible, and non-corrosive gas which accounts to 78% of air we breathe
• The normal melting and boiling point for nitrogen (at 100 Pa) are -210 and -196 °C
• Liquid nitrogen causes freezing cold environment, where delivered.
• It is colourless, odourless, tasteless, and inert fluid, and presents a potential liquefied gas that can be used during machining process.
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Liquid Nitrogen Production
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Applications during
Machining
• Used for cooling the cutting tool and/or part during the machining process.
• Applied at the cutting zone which is exposed to the highest temperature during the machining process.
• When delivered at the cutting zone, it immediately evaporates and returns back to the atmosphere.
• It leave no residue to contaminate the part, chips, machine tool, or operator and eliminates disposal costs related to Coolant Lubricant Fluid usage. 10/11/2017
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Cryogenic Machining Setup
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Potential benefits of
Cryogenic Machining Sustainable machining methods (cleaner, safer,
environment friendly, more health acceptable, etc.) to eliminate numerous costs associated with conventional cutting fluids and clean-up operations
Increase of material removal rate & cutting speeds without increases in worn tool and tool change over costs – increase of productivity
Increasing of tool life due to lower abrasion and chemical wear
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Potential benefits of
Cryogenic Machining
Machining of hard parts and hard to machine alloys
Improvement of surface roughness of machined work piece
Quality improvement of produced parts by preventing mechanical and chemical degradation of machined surface
Improvement of manufacturing flexibility due to reduced production times and high output, etc.
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Cryogenic Machining Vs Coolant
Lubricant Fluid (CLF) Lower cutting temperatures in cutting zone
Improvement of chip breakability
Decreased BUE formation probability
Decreased of burr appearance probability
Inert environment assurance
No oil-based emulsion used
No additional processes needed
Safer Environment, Easy disposal.
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