The milling operation is essentially an interrupted machining process. This causes the temperature at the cutting edge to fluctuate constantly between high temperatures (approximately 1000 °C) and low temperatures.
1. The influence of cutting fluid
Temperature changes are exacerbated as the cutting edge cuts in and out. As a result, the cutting edge is subjected to thermal shocks and cyclic stresses, which lead to possible cracks and, in the worst case, premature end of tool useful life.
The hotter the cutting area, the less suitable it is to use cutting fluid.
In finishing operations, the use of cutting fluids does not reduce tool life as much as in roughing operations because less heat is generated.
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Thermal cracks appear on the cutting edge
2. Dry milling
Dry milling increases the life of the cutting edge. Temperatures do vary, but remain within the design range of the carbide grade.
Rough milling operations should always be performed without the use of cutting fluids.
3. Wet milling with cutting fluid
There are some exceptions where cutting fluid should be used:
1) Finishing of stainless steel and aluminum alloys - used to prevent metal particles from adhering to the surface structure
2) Milling superalloys at low cutting speeds - used to lubricate and cool parts
3) Cast iron milling for wetting and flushing away dust to protect the environment and health and ensure part accuracy
4) Milling of thin-walled parts to prevent geometric deformation
5) When processing deep cavities, a minimum quantity lubrication system (that is, compressed air containing a small amount of special oil) can be used to assist chip removal
Use compressed air and oil mist
In MQL systems, the "oil mist" volume is only a few milliliters of oil per hour and is exhausted through an ordinary filtered ventilation system.
Use high flow internal coolant and external coolant
If wet milling must be performed, adequate cutting fluid should be used.
