Why Does Cutting Fluid Foam? 5 Common Causes

Based on years of experience and on-site observation, we have identified five main causes of foaming:

1. Limited Coolant Tank Space

Insufficient tank space leads to poor liquid circulation, which allows foam to form on the surface and persist—especially under high-pressure conditions.

2. Accumulation of Chips and Debris

If metal chips are not cleaned regularly, they can block drain holes, disrupt coolant flow, and accelerate foaming, making operations unstable.

3. Excessive Water Pressure or Improper Return Flow Angle

When cutting fluid is injected with high pressure into the tank, large amounts of air get mixed in, resulting in persistent and stable foam.

4. Prolonged Machining Time

Extended use can alter the chemical properties of cutting fluids, reducing their defoaming capacity and making foam control difficult.

5. High Concentration or Low Fluid Level

Excessively high concentration, improper oil-water ratio, or low tank levels can destabilize emulsification, causing foaming.

How to Effectively Reduce Foaming in Cutting Fluid

Here are the most practical and effective methods for resolving foaming issues:

A. Check Coolant Tank Structure and Fluid Level

Ensure the tank is filled to the proper level and avoid using small or poorly designed tanks. The fluid return should not directly impact the surface; install a buffer return pipe or anti-cyclone device.

B. Clean the Tank and Drain Regularly

Chips and debris are breeding grounds for foam. Clean the tank weekly and keep the drain holes and filters clear.

C. Temperature Control

Monitor coolant temperature. High temperatures, especially in synthetic fluids, can increase foaming due to changes in viscosity and foam stability.

D. Test Water Quality

Soft water with low mineral content can lead to increased foam—particularly when new fluids are introduced. Adjusting water hardness can help minimize foaming.

E. Evaluate the Defoaming Performance of Cutting Fluid

Shake the cutting fluid for 10 seconds and observe whether the foam dissipates quickly: If the foam remains stable and does not dissipate, it indicates insufficient defoaming performance. If the foam dissipates quickly, it suggests that the formulation of the fluid is stable, and the issue may be related to the tank design or water quality.

Case Study: Two-Year Foaming Issue Finally Resolved!

The foaming issue with cutting oil disrupted the workflow of a motorcycle customization client, causing inconvenience and frustration during CNC milling processes. The two-year foaming problem, especially prevalent when machining aluminum and iron parts, led to coolant overflow, necessitating frequent cleaning and maintenance. This not only wasted time but also increased costs.

FAQ