Environmentally Conscious Design & Manufacturing (ME592) Date: March 20, 2000 Slide:1 Environmentally Conscious Design & Manufacturing Class 7: Cutting Fluids Prof. S. M. Pandit

Environmentally Conscious Design & Manufacturing (ME592) Date: March 20, 2000 Slide:2 100 million gallons of cutting fluid is consumed annually in the United States Environmental degradation, Health Hazard Need to reduce cutting fluid use Background and Motivation

Environmentally Conscious Design & Manufacturing (ME592) Date: March 20, 2000 Slide:3 Additives: Organic (Aromatic hydrocarbons) Inorganic (Chlorine, Sulphur, Phosphorus) Biocides, Odorants Background and Motivation

Environmentally Conscious Design & Manufacturing (ME592) Date: March 20, 2000 Slide:4 Introduction Functions of Cutting Fluids Heat transfer - Tool wear & life - Dimensional accuracy Lubrication Chip flushing, corrosion prevention, cleaning

Environmentally Conscious Design & Manufacturing (ME592) Date: March 20, 2000 Slide:5 Introduction Questions addressed Why use fluid? Dimensional error due to heat transfer How (health hazard)? Exposure to mist

Environmentally Conscious Design & Manufacturing (ME592) Date: March 20, 2000 Slide:6 Dimension Error - 1 Surface error How we define surface error in the boring experiments:- Angular position Out of roundness

Environmentally Conscious Design & Manufacturing (ME592) Date: March 20, 2000 Slide:7 Dimension Error - 2 Single tool boring of aluminum cylinders Radial, tangential and axial forces cause deformation

Environmentally Conscious Design & Manufacturing (ME592) Date: March 20, 2000 Slide:8 Boring experiments: Sources of dimensional error: Thrust force Heating effects Role of Fluids on Heat Transfer

Environmentally Conscious Design & Manufacturing (ME592) Date: March 20, 2000 Slide:9 Heat Transfer Model w d 2  dz 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.

Environmentally Conscious Design & Manufacturing (ME592) Date: March 20, 2000 Slide:10 Temperature History

Environmentally Conscious Design & Manufacturing (ME592) Date: March 20, 2000 Slide:11 Surface Error

Environmentally Conscious Design & Manufacturing (ME592) Date: March 20, 2000 Slide: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.

Environmentally Conscious Design & Manufacturing (ME592) Date: March 20, 2000 Slide: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]

Environmentally Conscious Design & Manufacturing (ME592) Date: March 20, 2000 Slide:14 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) Health & Env. Effects - 2

Environmentally Conscious Design & Manufacturing (ME592) Date: March 20, 2000 Slide:15 Mist in Machining Modes of mist formation (1) Liquid film disintegration - Low velocity - High velocity of fluid impact on workpiece (2) Evaporation / Condensation

Environmentally Conscious Design & Manufacturing (ME592) Date: March 20, 2000 Slide:16 Mist in Machining Experiments with mist formation during turning

Environmentally Conscious Design & Manufacturing (ME592) Date: March 20, 2000 Slide:17 Liquid Film Disintegration Boundary Layer Theory Flowing Fluid Film Thickness Mean droplet diameter of the same order of magnitude as film thickness Thickness varies inversely with distance and Reynold’s number

Environmentally Conscious Design & Manufacturing (ME592) Date: March 20, 2000 Slide: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)

Environmentally Conscious Design & Manufacturing (ME592) Date: March 20, 2000 Slide:19 Drop Mode Drop diameter (maximum) can be predicted with good experimental correlation by considering equilibrium of surface tension and centrifugal forces.

Environmentally Conscious Design & Manufacturing (ME592) Date: March 20, 2000 Slide:20 Ligament Mode At high flow rates, empirical relations predict ligament diameter, which is related to the drop diameter Ligament diameter Drop diameter

Environmentally Conscious Design & Manufacturing (ME592) Date: March 20, 2000 Slide:21 Evaporation / Condensation Supersaturated vapor (P 0 /Ps>1) will recondense The rate of droplet growth is proportional to supersaturation and drop size and inversely proportional to temperature

Environmentally Conscious Design & Manufacturing (ME592) Date: March 20, 2000 Slide: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

Environmentally Conscious Design & Manufacturing (ME592) Date: March 20, 2000 Slide:23 Summary What have we discussed? Effect of using Cutting Fluid on surface error in boring operations Understanding the mechanism of mist formation