The Role and Types of Cutting Fluid

During CNC machining, I have seen that when cutting, the nozzle next to it will spray out a liquid like oil. In fact, this liquid is cutting fluid. Machining oil is one of them.

Cutting fluid is a lubricant used on CNC machine tools. It has the functions of lubrication, cooling, cleaning, etc., so cutting fluid plays a very important role in the automated processing of CNC machine tools.

1.The role of cutting fluid

1) Lubrication

The cutting fluid can form an oil film on the surface of the workpiece and the tool, and can penetrate into the smallest metal gaps and irregular places to reduce the friction between the metals. The following effects can be achieved:

Reduce tool wear and extend tool life.

Reduce cutting resistance and consume less processing power.

Prevent burrs on the edge and improve the accuracy of the machined surface.

2) Cooling

The cutting fluid can reduce the heat generated during cutting. Its temperature can be as high as 600-1000℃. Especially for workpieces with low thermal conductivity such as stainless steel, the heat is difficult to dissipate and the workpiece will become hot. Using cutting fluid to reduce the temperature can bring the following effects:

Reduce tool thermal deformation and extend tool life.

Prevent thermal deformation of workpieces and tools, and stabilize machining accuracy.

Achieve high-speed machining.

3) Cleaning

Jet cutting fluid can wash away the chips generated during the cutting process and clean the workpiece, which can bring the following effects:

Prevent chips from adhering and scratching the workpiece.

Prevent machining defects caused by chip blockage and accumulation.

Prevent chip entanglement and tool breakage.

2.Classification of cutting fluid

Cutting fluid can be roughly divided into two categories: non-soluble cutting fluid and water-soluble cutting fluid. Non-soluble cutting fluid can be used directly, mainly for lubrication (a few are mainly for cooling), and water-soluble cutting fluid is generally diluted with water for cooling.

1) Insoluble cutting fluids

Insoluble cutting fluids are cutting oils with oil as the main component. They have good “lubrication” effects and can effectively prevent CNC machine tools and workpieces from rusting. They are mainly used for cutting operations that require high precision.

Insoluble cutting fluids are divided into inert type and active type. The inert type is used for light cutting of soft metals and can effectively improve tool life; the active type is used for difficult-to-process materials and low-speed processing, such as gear processing, which can effectively improve processing accuracy.

2) Water-soluble cutting fluid

Water-soluble cutting fluid is a cutting oil mixed with water and oil. It has good cooling effect and is widely used in high-speed processing of machining centers. Commonly used water-soluble cutting fluids are washing liquid, solution and soluble solution.

① Washing liquid

It is a water-soluble cutting fluid mixed with water, oil and surfactant. It has a milky white liquid appearance, large oil particles, strong versatility, and is widely used in machining centers.

② Solution

Water-soluble cutting oil made of water, oil, surfactant and soluble substance is a translucent liquid with fine oil particles. It has excellent cooling and permeability.

③ Soluble fluid

Water-soluble cutting oil mixed with water and soluble substances. The oil particles are extremely fine, the liquid is usually green, and it has excellent cooling and durability.