Changing the cutting fluid

Changing the cutting fluid is an essential part of a machine shop’s fluid system maintenance and process reliability. When done correctly, changing the fluid extends both the life of the fluid and the tools, ensuring that machining quality remains high and consistent.

If the system already contains cutting fluid that is still in good condition, the change can be done by gradually adding new cutting fluid to the old one, so the original fluid is slowly diluted. This method is often recommended when the fluid properties are still suitable and there are no signs of contamination, odor issues, or bacterial growth in the system. This way, you can switch to the new product in a controlled manner without unnecessary production downtime.

Ensuring Compatibility

Before adding new cutting fluid, it’s important to make sure that the new and old fluids are compatible with each other. For this, a compatibility test is conducted to see whether combining the fluids causes foaming, separation, or other problems that could affect the stability of the emulsion.

The compatibility test is done using three different ratios:

• 10/90 – 10% new and 90% old fluid
• 50/50 – equal parts of both
• 90/10 – 90% new and 10% old fluid

These ratios simulate the different stages of the fluid change: beginning, middle, and end. If all samples remain consistent without separation or cloudiness, the products are compatible and the change can be carried out safely.

Changing All Fluid in the System

If you want to empty the system completely, it is recommended to use a system cleaner before adding the new fluid. The cleaner removes accumulated impurities, oil residues, metal shavings, and microbial growth from the system, which could shorten the life of the new fluid and cause corrosion or odor problems.

Once cleaning is complete and the system has been thoroughly rinsed, the new cutting fluid can be mixed and filled into the system at the concentration recommended by the manufacturer. This ensures that the emulsion is balanced from the very start and works optimally.

Summary

A carefully performed cutting fluid change ensures that the system stays clean, the emulsion remains stable, and the machining quality stays consistent long into the future. This also prevents microbial growth, foaming issues, and premature fluid change needs—keeping the entire production process controlled and cost-effective.