CNC Knowledge: Dry milling and wet milling, how to choose?

The milling operation is essentially an intermittent machining process. This causes the temperature at the cutting edge to continually fluctuate between high temperatures (around 1000°C) and low temperatures.

1

Effect of cutting fluid

Temperature changes intensify as the cutting edge moves in and out. As a result, the cutting edge is subjected to thermal shock and cyclical stress, which leads to a risk of cracking and, in the worst case, a premature end to the tool life.

The higher the temperature in the cutting zone, the less appropriate it is to use cutting fluid.

During the finishing operation, less heat is generated, so using cutting fluid does not reduce tool life as much as when roughing.

2

dry grinding

Dry milling extends cutting edge life. The temperature changes, but remains within the design range of the carbide material.

Rough milling operations should always be carried out without using cutting fluid.

3

Wet milling with cutting fluids

There are a few exceptions when cutting fluid must be used:

(1) Finishing of stainless steel and aluminum alloys to prevent metal particles from bonding to the surface structure.

(2) Milling of high temperature alloys at low cutting speeds for lubrication and cooling of parts.

(3) Cast iron milling, used to humidify and remove dust to protect the environment and health and ensure the precision of parts.

(4) Milling of thin-walled parts to avoid geometric deformation.

(5) When processing deep cavities, a minimum quantity lubrication system (i.e. compressed air containing a small amount of special oil) can be used to facilitate chip removal.

Use compressed air and oil mist

In a minimum quantity lubrication system, the amount of “oil mist” is only a few milliliters of oil per hour and is exhausted through an ordinary filtered ventilation system.

Use high flow internal and external coolant

If wet milling must be carried out, a sufficient quantity of cutting fluid must be used.