The correct way to mix water-soluble cutting oil is to always slowly add the oil to the water, never the other way around. This ensures proper emulsification and prevents issues with the cutting fluid's performance.
Here's a more detailed explanation:
Why Add Oil to Water?
The reason for this specific mixing order lies in the properties of the emulsifiers contained within the cutting oil concentrate. These emulsifiers are designed to help the oil disperse evenly throughout the water, creating a stable emulsion.
- Emulsifier Reaction: When you add oil to water, the emulsifiers readily surround the oil droplets and allow them to disperse effectively.
- Preventing Inversion: Adding water to oil can cause an inverted emulsion. This means the water becomes the continuous phase and the oil is dispersed within it. Inverted emulsions are less effective coolants and lubricants, and can lead to premature tool wear, poor surface finish, and microbial growth.
- Maintaining Stability: Adding oil to water contributes to a more stable and consistent emulsion over time.
Mixing Procedure: A Step-by-Step Guide
- Determine the Correct Ratio: Consult the cutting oil manufacturer's recommendations for the appropriate oil-to-water ratio. This is crucial for achieving optimal performance. Ratios are typically provided as a percentage (e.g., 5% cutting oil to 95% water).
- Use Clean Water: Start with clean, preferably soft or deionized water. Hard water can interfere with the emulsification process.
- Add Water to the Tank: Fill your mixing tank or container with the required amount of water.
- Slowly Add the Cutting Oil: Gradually pour the cutting oil concentrate into the water while continuously stirring.
- Stir Thoroughly: Continue stirring the mixture until the cutting oil is completely dispersed and the solution appears milky and uniform. A mechanical mixer is ideal for larger volumes.
- Check the Concentration: Use a refractometer to verify that the cutting oil concentration is within the recommended range. Adjust as needed by adding more oil or water, always maintaining the correct mixing order.
Common Problems and Solutions
- Separation: If the emulsion separates, it may indicate an improper mixing ratio, contaminated water, or incompatible materials.
- Foaming: Excessive foaming can be caused by high water hardness, contamination, or an inappropriate cutting oil for the application.
- Rancidity: Microbial growth can lead to rancidity and unpleasant odors. Proper maintenance, including regular sump cleaning and the use of biocides, can prevent this.
Example
Let's say you need to mix 20 gallons of cutting fluid at a 5% concentration.
- You'll need 20 gallons * 0.05 = 1 gallon of cutting oil concentrate.
- You'll need 20 gallons - 1 gallon = 19 gallons of water.
- Add 19 gallons of water to the mixing tank.
- Slowly add 1 gallon of cutting oil concentrate while stirring continuously.
- Verify the concentration with a refractometer.
