Cutting fluid
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Cutting fluid or coolant is a liquid added to reduce the friction coefficient between the grain and workpiece by way of cooling and lubricating the cutting site of machine tools by flooding or spraying during broaching, boring, grinding, milling, sawing, shaping or tapping. The coolant containing EP additives is added to the sump of equipment with lathes, milling machines, shapers, bandsaws. Liquid (water or petroleum oil) cooled water tables are used with the plasma arc cutting (PAC) process.
Metal cutting operations involve generation of heat due to friction between the tool and the pieces and due to energy lost deforming the material. This heat needs to be carried away otherwise it creates "white spots".
There are generally 3 types of liquids: mineral, semi-synthetic and synthetic.
Mineral coolants, which are (petroleum based) began in the late 1800s. Semi-synthetic coolants are an emulsion or microemulsion of water with mineral oil beginning in the 1930s. Synthetic coolants originated in the late 1950s and are usually water-based.
A hand-held refractometer is used to determine the mix ratio (also called strength) of water soluble coolants to verify effectiveness. Numerous other test equipment are used to determine such things as acidity, and amount of conductivity.
Cutting fluids have been associated with skin rashes, dermatitis, lung disease and cancer. Safer environmental formulations for workers and the environment provide a natural resistance to tramp oils allowing improved filtration separation without removing the base additive package.
Bacterial growth is predominant in semi-syntheic and synthetic fluids. Tramp oil along with human hair, skin oil are some of the debris during cutting which accumulates and forms a layer on the top of the liquid, anaerobic bacterials proliferate due to a number of factors. Early signs of replacement usually is noticed by the "Monday Morning" smell (due to lack of usage from Friday to Monday) and is a sensory sign of the breakdown of the coolant.
The properties that are sought after in a good cutting fluid are the ability to:
- keep the workpiece at a stable temperature (critical when working to close tolerances).
- maximize the life of the cutting tip by lubricating the working edge and reducing tip welding.
- prevent the growth of bacteria or fungi.
- filterability to remove contaminates.
- safer for the individual metalworker and the environment during disposal following replacement.
Cutting fluid may also take the form of a paste when used for some applications, in particular hand operations such as drilling and tapping.
In many areas, disposal of cutting fluid is subject to environmental regulations intended to prevent pollution. Modern cutting fluid disposal may involve techniques such as ultrafiltration using polymeric or ceramic membranes which concentrates the suspended and emulsified oil phase.
Water is a great conductor of heat but is not stable at high temperatures, so stability is often achieved by chemistry modifications.
[edit] Other lubricants
- Dielectric fluid is the cutting fluid used in Electrical Discharge Machines (EDM). It is usually deionized water or a high flash point kerosene. Intense heat is generated by the cutting action of the electrode (or wire) and the fluid is used to stabilise the temperature of the workpiece, along with flushing any eroded particles from the immediate work area.
- Kerosene has been used when working on aluminium.
- Lard for press tool work
- Mineral oil
- WD-40
- ws-32 for suitable condition of cuts
[edit] See also
[edit] References
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de:Kühlschmiermittel
