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Environmentally Conscious Design & Manufacturing

Environmentally Conscious Design & Manufacturing. Class 7: Cutting Fluids. Prof. S. M. Pandit. Background and Motivation. 100 million gallons of cutting fluid is consumed annually in the United States Environmental degradation, Health Hazard Need to reduce cutting fluid use.

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Environmentally Conscious Design & Manufacturing

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  1. Environmentally Conscious Design & Manufacturing Class7: Cutting Fluids Prof. S. M. Pandit

  2. Background and Motivation • 100 million gallons of cutting fluid is consumed annually in the United States • Environmental degradation, Health Hazard • Need to reduce cutting fluid use

  3. Background and Motivation Additives: Organic (Aromatic hydrocarbons) Inorganic (Chlorine, Sulphur, Phosphorus) Biocides, Odorants

  4. Introduction • Functions of Cutting Fluids • Heat transfer • - Tool wear & life • - Dimensional accuracy • Lubrication • Chip flushing, corrosion prevention, cleaning

  5. Introduction Questions addressed Why use fluid? Dimensional error due to heat transfer How (health hazard)? Exposure to mist

  6. Dimension Error - 1 • How we define surface error in the boring experiments:- Out of roundness Surface error Angular position

  7. Dimension Error - 2 • Single tool boring of aluminum cylinders • Radial, tangential and axial forces cause deformation

  8. Role of Fluids on Heat Transfer • Boring experiments: • Sources of dimensional error: • Thrust force • Heating effects

  9. Heat Transfer Model w d2dz2 - 2 H + g(z,t)/k = wq/t g(z,t):heat source strength, k: Thermal conductivity, H: Ratio of convection coefficient and thermal conductivity.

  10. Temperature History

  11. Surface Error

  12. Cutting Fluid Mist Mist: formed by condensation or atomization -- size range from submicron to 20 microns. Such aerosols are generated during machining operations such as drilling, milling, boring, drilling and turning.

  13. Health & Env. Effects - 1 • NIOSH:-1.2 million are exposed to cutting fluids [Hands et al., 1996] • Bacteria / fungi in cutting fluid produce toxins [Thorne et al., 1996] • Mist collectors are sometimes ineffective [Leith, 1996]

  14. Health & Env. Effects - 2 • Airborne particulate from 5 mg/cu. m to 0.5 and 0.1 mg/cu. m (UAW and OSHA) • Aerosols from PM10 to PM2.5 and PM1.0 (EPA)

  15. Mist in Machining Modes of mist formation (1) Liquid film disintegration - Low velocity - High velocity of fluid impact on workpiece (2) Evaporation / Condensation

  16. Mist in Machining • Experiments with mist formation during turning

  17. Liquid Film Disintegration Thickness varies inversely with distance and Reynold’s number Boundary Layer Theory Flowing Fluid Film Thickness Mean droplet diameter of the same order of magnitude as film thickness

  18. Turbulent Splatter • Empirical correlations • Splatter occurs when the dimensionless group • proportional to the Weber number and inversely proportional to the nozzle diameter exceeds 2120 • The fraction splattered can also be predicted • (2.5% for high values of the dimensionless parameter)

  19. Drop Mode Drop diameter (maximum) can be predicted with good experimental correlation by considering equilibrium of surface tension and centrifugal forces.

  20. Ligament Mode At high flow rates, empirical relations predict ligament diameter, which is related to the drop diameter Ligament diameter Drop diameter

  21. Evaporation / Condensation • Supersaturated vapor (P0/Ps>1) will recondense • The rate of droplet growth is proportional to supersaturation and drop size and inversely proportional to temperature

  22. Mist Droplet Motion • For very low flow rates (Re < .001), small particles (diameter < 0.1 micron) experience Brownian motion • At higher flow rates and larger particle sizes, the spatial and temporal aerosol distribution is a function of gravity and drag

  23. Summary • What have we discussed? • Effect of using Cutting Fluid on surface error in boring operations • Understanding the mechanism of mist formation

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