Dry Milling or Wet Milling: What's the Best Decision to CNC Machining?

The milling process is essentially an intermittent machining process. This causes the temperature at the cutting edge to continuously fluctuate between high temperature (about 1000 ℃) and low temperature. Dry milling or wet milling: what's the best decision to CNC machining? Generally, we will choose dry milling for roughing processing and wet milling for finish milling.

First of all, we should know its biggest factor, cutting fluid.

Influence of cutting fluid

As the cutting edge cuts in and cuts out, the temperature change will increase. As a result, the cutting edge is subjected to thermal shock and periodic stress, which can lead to cracks, and in the worst case, the CNC cutting tool‘s useful life may end prematurely.

The higher the temperature of the cutting area, the less suitable the use of cutting fluid.

In the finishing process, since the heat generated is reduced, the use of cutting fluid will not shorten the tool life as much as in rough machining.

Our's Solution:

• Cutting without coolant/ Sufficient coolant
• Select a tougher and more thermal shock resistant grade

Dry milling

Dry milling can extend the life of the cutting edge for milling tools. The temperature will indeed change, but it will remain within the design range of the cemented carbide material. The rough milling process should always be performed without the use of cutting fluid.

Wet milling with cutting fluid

There are some exceptions where cutting fluid should be used:

• Finishing of stainless steel and aluminum alloy-used to prevent metal particles from adhering to the surface structure
• Milling of superalloys at low cutting speeds-used to lubricate and cool parts
• Cast iron milling, used for wetting and flushing away dust, to protect the environment and health and ensure the accuracy of parts
• Milling of thin-walled parts to prevent geometric deformation
• When processing deep cavities, a micro-lubrication system can be used to assist chip removal

In the micro-lubrication system, the amount of “oil mist” is only a few milliliters of oil per hour, and it is discharged through a common filter ventilation system.

If wet milling must be performed, sufficient cutting fluid should be used.

Various similarities and differences between dry machining and wet machining are given below in table format.

Similarities between dry milling and wet milling

• In most cases, the processing of materials can be carried out under dry or wet conditions. However, their effects will be different. Some exceptions include wood cutting (only dry milling), cutting of HSTR alloy (only wet milling), etc.
• Regardless of the dry cutting environment or the wet cutting environment, cutting tools are used to remove material, and the material is removed in the form of chips.
• In both cases, the cutting force remains more or less the same (because the cutting force mainly depends on the material of the workpiece, the process parameters and the relevant characteristics of the tool).
• The same cutting tool can be used in both cases. However, the cutter can be modified to efficiently deliver fluid and enhance its effect.

Differences Between Dry Milling and Wet Milling