Cutting fluid maintenance

Cutting fluid should meet the four objectives of cooling, lubrication, cleaning, and rust prevention, so we should start from these four aspects.
1. Cooling
The water content of high water-based cutting fluid is over 95% in conventional use, and over 97% in grinding;
2. Lubrication
Water soluble lubricants (polyvinyl alcohol, glycerol).
3. Cleaning
The combination of non-ionic surfactants (such as Pingjia and Taikoo oil) and anionic surfactants (sodium alkylbenzenesulfonate and sodium dodecyl sulfate) in cutting fluid can significantly reduce the surface tension of the cutting fluid and achieve the purpose of cleaning.
4. Rust prevention
There are many types of water-soluble rust inhibitors, which are usually divided into organic rust inhibitors and inorganic rust inhibitors. Generally, sodium molybdate (0.05%) is used instead of sodium nitrite to reduce pollution; Combined with organic rust inhibitor (boroamide), it achieves good rust prevention effect.
The maintenance work of cutting fluid mainly includes the following items:
1. Ensure unobstructed liquid circulation routes
Prevent impurities such as oil and debris, especially food or fabric, from entering the liquid supply system. Timely remove metal shavings, metal powders, mold mucus, decomposition products of cutting fluid itself, and grinding wheel debris from the circulation route to avoid blockage.
2. Antibacterial activity
It is well known that cutting fluid (especially lotion) plays an important role in inhibiting the growth of bacteria. Regular use of fungicides and ultra-fine filtration can be used to inhibit bacterial growth.
3. Purification of cutting fluid
The substances that pollute the cutting fluid mainly include metal powder and fine gravel powder, floating oil and free water, microorganisms and reproductive products, especially fungi of the order Mucor. Floating oil is a breeding ground for anaerobic bacteria, and if not removed in time, the cutting fluid will quickly become odorous.
4. Adjust concentration
Check the concentration of cutting fluid with a refractometer every day and adjust it in a timely manner. The correct concentration can ensure the stability of the cutting fluid.
The solid powder contained in the cutting fluid comes from the machined parts and cutting tools. This type of solid not only easily blocks pipelines but also poses the following hazards:
Floating oil refers to the oil used in the transmission and hydraulic systems of machine tools that leaks into the cutting fluid system due to poor sealing of the machine tool. The harm of floating oil is that it causes certain materials in the cutting fluid system to expand and deform, interferes with the emulsification balance of the emulsion, and causes the emulsion to lose stability. Moreover, floating oil often floats on the surface of lotion oil, blocking the contact between emulsion and air, resulting in anoxia of emulsion, rapid propagation of anaerobic bacteria, and accelerated deterioration of emulsion.
After the cutting fluid is contaminated by the three types of substances mentioned above, if the pollution is removed separately, the procedures are very cumbersome. We have developed an ultra-fine filtration method that can remove solid, liquid, and most bacterial pollutants. However, the ultra-fine filtered cutting fluid is only limited to the microemulsion or synthetic fluid with little oil, and its components will not form micelles or other agglomerates at low concentrations.