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Cutting

Fluids

image: wikipedia.org

By Glenn McKechnie - Photograph taken by Glenn McKechnie, CC BY-SA 2.0, https://commons.wikimedia.org/w/index.php?curid=294427

Lecture Video

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Functions

Cool workpiece and tool

Temperature is an important factor in tool life
Influences surface integrity

Lubrication

Reduces power requirements
Increases production rates

Chip removal

Also should provide corrosion protection

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Oil vs. Water

Main Advantages

Oil - Lubricity

Water - Cooling Capacity

Water is capable of dissipating heat 2.5 times faster than oil.

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Wetting

Surface reaction can be:

Hydrophobic
Hydrophilic

Contact Angle

wikipedia.org

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Should a cutting fluid's contact be:

Hydrophobic

Hydrophilic ?

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Types of Cutting Fluids

Inactive Cutting Oils

Mineral Oils

Straight (or Neat) Mineral Oils
Used with low-speed applications
Compounded Cutting Oils

Blended with additives such as animal and vegetable oils. Increases wetting ability. Allows fluid to penetrate tool/chip interface.

Fatty Mineral Oils

Improve surface finish in machining steel, brass, copper, and aluminum

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Types of Cutting Fluids

Active Cutting Oils (EP Lubricants)

Cause a film to develop on tool surface and provide anti-weld properties.
Contain

Sulfur
Chlorine
Phosphorous

Amtecol.com

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Types of Cutting Fluids

Emulsified Oils (soluble oils)

Oil droplets suspended in water by blending the oil with emulsifying agent.
Advantages:

Greater heat reduction, higher cutting speeds
Potentially cleaner working conditions
More economical (diluted with water)
Better operator acceptance (cleaner, cooler parts)
Improved health and safety benefits

Not a fire hazard
Misting and fogging are reduced

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Types of Cutting Fluids

Chemical/Synthetic Fluids

Contain no petroleum oil

True-solution Chemical fluids contain no wetting agents, usually clear

Surface-active chemical fluids have wetting agents.

Semichemical/semisynthetic Fluids

Contain mineral oils

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Types of Cutting Fluids

Advantages of Chemical and Semichemical Fluids

Rapid heat dissipation
High degree of cleanliness
Light residual films are easy to remove
Ease of mixing, little agitation needed

Disadvantages

Lack of lubricity
High detergency, irritates hands
Tend to foam
Disposal problems

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Types of Cutting Fluids

Gaseous Fluids

Air
Compressed Air

Vortex tube

Argon, helium, nitrogen have been used, but are expensive.

Image:

http://en.wikipedia.org/wiki/File:Tube_de_Ranque-Hilsch.png

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Types of Cutting Fluids

Pastes and Gels

Waxes, soap-like lubricants, graphite compounds
Used where lubrication is much more important than heat removal.

Tapping
Drilling

Used when working against gravity

http://www.lpslabs.com

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Factors in Cutting Fluid Selection

Machining time per part

Number of rejects from unacceptable surface finish

Machine downtime due to tool changes and maintenance

Cutting fluid consumption per part (carryout & evaporation)

Cutting fluid batch life

Cutting fluid disposal or recycling costs

Compatibility (workpiece and tool)

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Application of Cutting Fluids

Manual

Flood

Mist

High pressure - through tool

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Flood Application (Video)

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Mist Application Video

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High Pressure Through Spindle

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High Pressure Through Tool

Through Lathe Tooling

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High Pressure Through Spindle

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Filtration

Clarification/Separation Methods

Tramp oil skimmers
Settling (Weirs)
Centrifuges
Magnetic Separators

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Coolant Consumption

Water evaporation

Makes coolant more concentrated

Evaporation from tank

Evaporation from heat & atomization of cut

Carryout

Tends to make coolant less concentrated

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Maintenance Considerations

Storage of Concentrate

Water Quality

Hardness/Softness

Rancidity Control

Bacteria found in fluids

Aerobic
Anaerobic

Fungus

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Maintenance Considerations

Physical Tests

Concentration (refractometer)
Viscosity
Flash Point
Stability
Emulsion Stability
Residue
Foaming

https://commons.wikimedia.org/wiki/File:Refractometer.jpg Fernando G.

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Maintenance

Considerations

Chemical Tests

pH
Corrosion

Microbiological Tests

Image: Wikipedia.org

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Health and Safety

Since cutting fluids are generally alkaline, machinists whose hands and forearms undergo prolonged exposure to them, frequently develop dermatitis. While impermeable gloves might prevent this, they may interfere with dexterity and pose a safety hazard around moving machinery.

http://www.cdc.gov/niosh/topics/skin/occderm-slides/ocderm9.html

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Health and Safety

Types of Risk

Oral Toxicity
Inhalation Toxicity
Dermal Toxicity
Skin Irritation
Eye Irritation

Rule of thumb: Inform (SDS) & Minimize contact with workers!

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Mix Ratios

Convert mix ratio to % concentration:

Known: A:B

100 * 1/(A + B)

Example: If mix ratio is 8:1, percent concentration is 1/9 or 11.1%

Convert % concentration to ratio:

Known: C% concentration

(100-C):C

Example: If the mix percentage is 10%, the ratio is (100-10):10 = 90:10 or 9:1

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Topping up fluid mix

Find the capacity of the reservoir.
Measure current coolant concentration. Compare this to the target concentration.
Multiply the reservoir capacity by the current % concentration. This is how much concentrate is present now.
In a separate container, add the amount of concentrate that would make the target concentration in a full tank.
Subtract this from the volume that needs to be replaced. This is how much water you need.
Now add the concentrate to the volume calculated in step 5. Stir thoroughly and top up tank.

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Example

A 100 gallon tank has 60 gallons of coolant at 11% concentration.

Top it up to have a 100 gallons at 7% concentration.

How much coolant do you need to add?

How much water do you need to add?

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Example

You will also need to remember how to find the volume of common shapes.

Top up the 100 gallon tank to have a 7% concentrated solution. It currently has 60 gallons at 11% concentration.

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Globally Harmonized System

Of classification and labeling of chemicals