In the previous blog, CO2 composite spray technology was introduced with a focus on basic components and operational characteristics of a spray system. This blog completes the introduction with a description of various performance aspects of a CO2 composite spray and includes initial laboratory test results for this new machining fluid technology.
Managing Heat
A CO2 composite spray manages machining heat through both physical (thermal transfer) and chemical (i.e., Rehbinder) effects. Frictional heat generated at the cutting edge is eliminated indirectly using chip-tool-workpiece temperature control and directly through juvenile surface reactions using a suitable lubricant chemistry, including carbon dioxide itself. Efficient heat removal is achieved through adjustable heat capacity, phase change phenomenon and reactive chemistry within the spray.
Penetration and Sticking Power
For CO2 composite sprays of the second kind, the combination of sublimating solid coolant and subcooled lubricants (mass) with near-sonic air flow (velocity) creates significant surface penetration power (Force = mass x velocity), which allows the coolant and lubricant particles to penetrate deeply into cracks and crevices and intimately contact machining surfaces. Particle velocities of between 50 m/s and 300 m/s are easily obtained with CO2 composite sprays. Upon entering the cutting zone, the cooling lubricant spray provides chip cooling and chip evacuation during sublimation or evaporation of the CO2. During expansion, electrostatically-charged CO2 gas and lubricant uniformly coat and penetrate cutting interfaces. Compared to conventional high pressure flooding techniques, CO2 composite sprays operating at 120 psi can exert particle-fluid impact stresses of over 8,000 psi.
Cutting Performance
In standardized cutting tests (see Table 1 below) performed by an independent testing laboratory (TechSolve, Inc., Cincinnati, Ohio), it was demonstrated that CO2 composite sprays using a bio-based oil additive outperformed conventional flood processes using standards: synthetic oil, soluble oil, and semi-synthetic fluids with extreme pressure agents, in terms of both uniform tool wear and cutting force (see CO2 Composite Spray data line 1 in the cutting force figure below).
Hard Machining Advantages
CO2 composite sprays offer several technical advantages and opportunities for challenging machining applications involving superhard tools and hard or abrasive substrates. These include:
• Supercharge existing cutting fluid chemistries in minimum and bulk amounts with increased coolant power and cutting zone penetration
• Increase machining efficiency for harder and more abrasive materials
• Improve surface finish
• Test new advanced coolant-lubricant additives in minimum quantities on-the-fly without having to change-out coolant sumps
• Optimize challenging machining processes with customized combinations of coolant, lubricant and advanced cutting tool coatings such as PCD, CBN and coated HSS
Another advantage provided by CO2 composite sprays is that they are a very clean and lean technology. Implementing CO2 composite spray technology can reduce or eliminate the use of flood coolants. This conserves fossil fuels, water and energy, and eliminates (or reduces) the generation of nonproductive outputs, hazardous wastes, air emissions, wastewater, or other pollutants.
Wrap-Up
CO2 composite spray technology improves machining productivity while reducing operating costs and environmental pollution. CO2 composite spray technology can be implemented along side many older and newer machining and metalworking processes, including machinery, materials, methods, processes, cutting tools and fluids, augmenting a successful conversion to a clean and lean metalworking operation.
Future blog articles will focus on specific commercial machining applications and challenges which have been addressed with CO2 composite technology.
David Jackson serves as the Chief Technology Officer for Cool Clean Technologies, Inc, based in Eagan, MN. He may be reached via e-mail at david.jackson@coolclean.com.
In the previous blog, CO2 composite spray technology was introduced with a focus on basic components and operational characteristics of a spray system. This blog completes the introduction with a description of various performance aspects of a CO2 composite spray and includes initial laboratory test results for this new machining fluid technology.
Managing Heat
A CO2 composite spray manages machining heat through both physical (thermal transfer) and chemical (i.e., Rehbinder) effects. Frictional heat generated at the cutting edge is eliminated indirectly using chip-tool-workpiece temperature control and directly through juvenile surface reactions using a suitable lubricant chemistry, including carbon dioxide itself. Efficient heat removal is achieved through adjustable heat capacity, phase change phenomenon and reactive chemistry within the spray.
Penetration and Sticking Power
For CO2 composite sprays of the second kind, the combination of sublimating solid coolant and subcooled lubricants (mass) with near-sonic air flow (velocity) creates significant surface penetration power (Force = mass x velocity), which allows the coolant and lubricant particles to penetrate deeply into cracks and crevices and intimately contact machining surfaces. Particle velocities of between 50 m/s and 300 m/s are easily obtained with CO2 composite sprays. Upon entering the cutting zone, the cooling lubricant spray provides chip cooling and chip evacuation during sublimation or evaporation of the CO2. During expansion, electrostatically-charged CO2 gas and lubricant uniformly coat and penetrate cutting interfaces. Compared to conventional high pressure flooding techniques, CO2 composite sprays operating at 120 psi can exert particle-fluid impact stresses of over 8,000 psi.
Cutting Performance
In standardized cutting tests (see Table 1 below) performed by an independent testing laboratory (TechSolve, Inc., Cincinnati, Ohio), it was demonstrated that CO2 composite sprays using a bio-based oil additive outperformed conventional flood processes using standards: synthetic oil, soluble oil, and semi-synthetic fluids with extreme pressure agents, in terms of both uniform tool wear and cutting force (see CO2 Composite Spray data line 1 in the cutting force figure below).
Hard Machining Advantages
CO2 composite sprays offer several technical advantages and opportunities for challenging machining applications involving superhard tools and hard or abrasive substrates. These include:
· Supercharge existing cutting fluid chemistries in minimum and bulk amounts with increased coolant power and cutting zone penetration
· Increase machining efficiency for harder and more abrasive materials
· Improve surface finish
· Test new advanced coolant-lubricant additives in minimum quantities on-the-fly without having to change-out coolant sumps
· Optimize challenging machining processes with customized combinations of coolant, lubricant and advanced cutting tool coatings such as PCD, CBN and coated HSS
Another advantage provided by CO2 composite sprays is that they are a very clean and lean technology. Implementing CO2 composite spray technology can reduce or eliminate the use of flood coolants. This conserves fossil fuels, water and energy, and eliminates (or reduces) the generation of nonproductive outputs, hazardous wastes, air emissions, wastewater, or other pollutants.
Wrap-Up
CO2 composite spray technology improves machining productivity while reducing operating costs and environmental pollution. CO2 composite spray technology can be implemented along side many older and newer machining and metalworking processes, including machinery, materials, methods, processes, cutting tools and fluids, augmenting a successful conversion to a clean and lean metalworking operation.
David Jackson serves as the Chief Technology Officer for Cool Clean Technologies, Inc, based in Eagan, MN. He may be reached via e-mail at david.jackson@coolclean.com.
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