Transcript Environmentally Conscious Design & Manufacturing ME592E-1

Environmentally Conscious
Design & Manufacturing
Class 7: Cutting Fluids
Prof. S. M. Pandit
Environmentally Conscious Design & Manufacturing (ME592)
Date: March 20, 2000
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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
Environmentally Conscious Design & Manufacturing (ME592)
Date: March 20, 2000
Slide:2
Background and Motivation
Cutting Fluids
Oil Based
Chemical
Straight Oils
Emulsions
Synthetics
Semi-synthetic
+ Additives
+ Additives
+ Additives
+ Additives
Additives:
Organic (Aromatic hydrocarbons)
Inorganic (Chlorine, Sulphur, Phosphorus)
Biocides, Odorants
Environmentally Conscious Design & Manufacturing (ME592)
Date: March 20, 2000
Slide:3
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
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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
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Dimension Error - 1
•
How we define
surface error in
the boring
experiments:-
Out of
roundness
Surface error
Angular position
Environmentally Conscious Design & Manufacturing (ME592)
Date: March 20, 2000
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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
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Role of Fluids on Heat Transfer
Boring experiments:
Sources of dimensional
error:
• Thrust force
• Heating effects
Environmentally Conscious Design & Manufacturing (ME592)
Date: March 20, 2000
Slide:8
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.
Environmentally Conscious Design & Manufacturing (ME592)
Date: March 20, 2000
Slide:9
Temperature History
Environmentally Conscious Design & Manufacturing (ME592)
Date: March 20, 2000
Slide:10
Surface Error
Environmentally Conscious Design & Manufacturing (ME592)
Date: March 20, 2000
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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:12
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:13
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)
Environmentally Conscious Design & Manufacturing (ME592)
Date: March 20, 2000
Slide:14
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:15
Mist in Machining
• Experiments
with mist
formation
during turning
Environmentally Conscious Design & Manufacturing (ME592)
Date: March 20, 2000
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Liquid Film Disintegration
Boundary Layer Theory
Thickness varies inversely
with distance and
Reynold’s number
Flowing Fluid Film Thickness
Mean droplet diameter of the same
order of magnitude as film thickness
Environmentally Conscious Design & Manufacturing (ME592)
Date: March 20, 2000
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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:18
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:19
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:20
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
Environmentally Conscious Design & Manufacturing (ME592)
Date: March 20, 2000
Slide:21
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:22
Summary
What have we discussed?
• Effect of using Cutting Fluid on surface
error in boring operations
• Understanding the mechanism of mist
formation
Environmentally Conscious Design & Manufacturing (ME592)
Date: March 20, 2000
Slide:23