Changing cutting fluid

Changing the cutting fluid is an essential part of maintaining a machine shop’s fluid system and ensuring process reliability. When carried out correctly, the change extends the service life of both the fluid and the tools while ensuring consistent, high-quality machining.

If the system already contains cutting fluid and it is in good condition, the change can be carried out by adding the new cutting fluid to the existing fluid, gradually diluting the old fluid. This method is often recommended when the fluid’s properties are still suitable for use and there are no signs of contamination, unpleasant odors, or bacterial growth in the system. This allows the transition to the new product to be managed without unnecessary production downtime.

Verifying Compatibility

Before adding the new cutting fluid, it is important to verify that the new and old fluids are compatible with each other. This is done with a miscibility test, which shows whether combining the fluids causes foaming, separation, or other problems that could affect emulsion stability.

The miscibility test is performed using three different ratios:

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

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

Replacing the Fluid in the Entire System

If the system is to be completely drained, it is recommended to use a system-cleaning product before adding the new fluid. The cleaning product removes contaminants, oil residues, metal chips, and microbial growth that have accumulated in the system and could shorten the service life of the new fluid or cause corrosion and unpleasant odors.

Once cleaning has been completed and the system has been thoroughly rinsed, the new cutting fluid can be prepared and added to the system at the concentration recommended by the manufacturer. This ensures that the emulsion is balanced from the outset and performs optimally.

Summary

A carefully performed cutting-fluid change ensures that the system remains clean, the emulsion stays stable, and machining quality remains consistent over the long term. It also helps prevent microbial growth, foaming problems, and premature fluid changes, keeping the entire production process under control and cost-effective.