What Do Cooling / Cutting Fluids Do? Their Functions

The topic of this article will be the role that cutting fluids/lubricants play in separating and shaping materials. Cutting fluids have 5 basic functions.

The Functions of Cooling (Cutting) Fluids

Reducing friction through lubrication
Carrying away heat through cooling
Removing foreign materials through flushing, thereby increasing the service life of tools.
Improving the surface finish of workpieces. (Cleaning)
Chip Removal (Disposal): Increasing the chip-removal volume per unit time.
Alongside these main functions, cutting fluids also keep the work area clean and protect it from corrosion.

Lubrication

Machining operations occur within the mixed-friction zone. By lubricating this zone, cutting fluids reduce friction at the cutting point, thereby reducing tool wear, workpiece heating, and also the energy requirement.

For high and extremely high demands, cutting fluids include specially active substances that react with the material being machined at high pressures and temperatures. This prevents the peaks of the surface roughness on the workpiece and tool from welding together.

These types of additives are EP (extreme pressure) additives. To be effective, cutting fluids need to withstand the lowest temperatures and pressures.

In addition, AW-active (anti-wear additives) are added to the cutting fluid, which forms a retaining film layer on the surfaces of the tool and workpiece, preventing direct contact between sliding surfaces.

Cooling

The cutting fluid needs to be removed from the heated zone as quickly as possible, so that the tool and workpiece are cooled. This increases machining precision and prevents changes to the metallurgical structure within the surface layer.

The cooling effect of cutting fluids depends on flow rate, the shape and direction of the coolant jet, viscosity, and the type and temperature of the cutting fluid.

The larger the flow volume (flow rate) of the cutting fluid, and the higher its specific heat capacity, the faster it cools. In water-mixed cutting fluids, the evaporation of the water also aids cooling.

Flushing and Transport

The cutting fluid must also flush away and carry off shed chips and other solid materials from the machining area.

The ability to flush away chips and other solid materials depends, above all, on the viscosity, flow volume (flow rate), and pressure of the cutting fluid. The cutting fluid’s carrying capacity and its tendency to leave deposits depend on the type and size of the swarf.

Cleaning

All cutting fluids must be used clean, and cleaned if contaminated. This is because, during use, friction dust, chips, and foreign oils (such as machine oil, hydraulic oil, or anti-corrosion oils) can reach the workpieces through the cutting fluid circuit.

Clean cutting fluid provides a better surface finish on workpieces while also reducing the amount of scrap parts. Cleaning is achieved through a filter, a sediment tank, and a magnetic separator system.

Any cutting fluid residue remaining on workpieces must often be removed from the surface before beginning machining, and especially before a final surface treatment step, such as galvanizing or painting.

Removal (Disposal)

During the maintenance of cutting fluids, chips, filter sediment, oil sludge, and the oil-water mixture are removed. When these materials are prepared at the facility, they must be separated from oils or water. Before sending waste to an incineration facility or a storage site, its composition (what it contains) must be disclosed and approval must be obtained from the relevant authority.