The Problem with Foam Generation in Cutting Fluids
Cutting fluids are used to improve the cutting performance of many machine tools. They also reduce wear and extend tool life. Their effects on productivity and profitability are often clear, as they reduce overall costs compared to a dry cutting process. However, one of the greatest challenges in cutting fluid applications is the generation of foam.
Foam is an unwanted by-product of cutting fluids caused by mechanical action due to the machines high-velocity movements, and turbulence or splashing of the fluid caused by the cutting process. The foam affects the lubricity and cooling of the cutting process. If the foam overruns its container, it can cause problems with the operator, an obstruction to the process, and potential damage to the environment.
The most common consequences of foam are poor finished surface quality and reduced machining performance. More specifically, foam will reduce lubrication, heat transfer, and cooling efficiency, resulting in poor surface finish, increased cutting forces and torque, and higher power consumption.
To reduce foam generation caused by the mechanical action of a machine tool, cutting speeds should be adjusted to avoid turbulence or splashing. In some cases, a smaller droplet size is necessary for a smaller bubble surface area, creating a solution concentration that is less prone to foam. In addition, anti-foaming agents, drag-out systems, and other techniques can be employed.
Most cutting fluids contain a surfactant or wetting agent that helps to reduce foam. This agent lowers the surface tension of the fluid and reduces bubbles. Depending on the application, special additives can also be added, such as silicone-based or mineral-based surfactants, to further reduce foam.
In addition, many cutting fluids contain a foam-suppression additive, which works by breaking down the foam surfaces and keeping the bubbles small. This helps to minimize the total amount of foam generated, and it can also keep the fluid cooler and increase its lubrication properties.
Finally, using an air knife or a chopper can reduce foam in cutting fluids by breaking down large bubbles. The air knife is placed diagonally from the cutting surface in order to thin out the foam and prevent it from overflowing and causing further problems. The chopper also breaks down bubbles, except it does so with a machine-mounted revolving cutter.
Overall, foam generation caused by cutting fluids can be minimized and controlled with the use of the right cutting fluid, additives, and other techniques. Taking into account the potential problems associated with foam and following the best practices outlined above will help ensure machining performance and quality while maximizing productivity.
