Scientific selection and application of defoamers for metalworking fluids

In the field of modern mechanical processing, metalworking fluids play key roles in cooling, lubrication, rust prevention, and cleaning. However, in the actual use process, the foam problem has become a common problem that puzzles production efficiency. Excess foam will not only reduce the cooling effect of the processing fluid, but also lead to a series of problems such as the decline of processing accuracy, equipment corrosion and so on.

In the process of high-speed cutting, grinding and other machining, the formation of foam is mainly due to three factors: surfactant effect, violent agitation at machine speed and temperature change. A large amount of foam will reduce the cooling efficiency, cause the machine workpiece to overheat, affect the lubricating performance of the processing fluid, and aggravate the tool wear. Moreover, a large amount of foam overflow will pollute the equipment environment and increase the cleaning cost. Defoamer molecules can partially reduce the surface tension of the liquid film, break the liquid film, accelerate the drainage of foam liquid film, and shorten the life of foam.    

The common types of defoamers for metalworking fluids can be divided into organosilicon defoamers, polyether defoamers, mineral oil-based defoamers, and composite defoamers. Organic silicone defoamers are highly efficient and heat-resistant, suitable for high concentration emulsions. However, excessive use may cause the processing fluid to become cloudy or residual. Polyether defoamers have good compatibility and are suitable for water-based cutting fluids. They have long-lasting foam suppression and are suitable for aluminum alloy processing and precision grinding. Mineral oil-based defoamers have low cost and are suitable for oil-based processing fluids with low foam tendency, but may affect the biological stability of environmentally friendly liquids. Composite defoamers combine the advantages of organic silicon and polyether, balancing rapid defoaming and long-term foam suppression.     

Choosing the appropriate defoamer is a key step in optimizing the performance of metalworking fluids, so the scientific selection of defoamers requires comprehensive consideration of processing technology, defoamer characteristics, and cost factors. It is suggested that enterprises establish a complete management system including foam index monitoring, defoamer consumption records, and processing quality tracking. In the future, with the improvement of environmental protection requirements and the advancement of processing technology, multifunctional, intelligent, and environmentally friendly defoamers will become a development trend.