Coolant dragout, evaporation, and wastage are common challenges faced by many metalworking shops. If you’ve been wondering why your CNC coolant seems to disappear faster than expected or why you keep having to top it up, you’re not alone. These issues not only increase your coolant consumption costs but can also impact tool life, machining quality, and overall productivity.
In this blog, we’ll explain what coolant dragout is, why evaporation matters, and how you can reduce wastage to get the most out of your metalworking fluids.
What is Coolant Dragout?
Coolant dragout happens when metal working fluid leaves the sump because it clings to the workpiece, tooling, or swarf as they exit the machining zone.
This results in increased coolant consumption as the fluid leaves the sump. As the lubricant is continuously 'dragged out' with each workpiece, you’ll need to top up your coolant more frequently, increasing your operational expenses. Not sure how long your coolant should last? Read more.
Recognising High Levels of Dragout and Wastage
Common signs that your workshop is experiencing high levels of coolant dragout and wastage include:
- Excessive residual coolant on workpieces and tools
- Frequent need to top up coolant levels
How Evaporation Contributes to Coolant Wastage
While dragout removes the oil and water, evaporation only affects the water content of your coolant.
- Evaporation removes water only, not oil, which causes your coolant concentration to increase
- In hot climates like Australia, evaporation can significantly raise the concentration level, making your coolant more viscous and potentially more prone to corrosion (synthetic fluid) or foaming
- In mineral coolant evaporation can cause instability and increase the risk of bacteria infestation
Sometimes it can be tricky to work out what is happening when your tank gets low - is it dragout or evaporation? Often, it's a combination of both. This is why we stress (at minimum) weekly concentration checks to ensure you coolant is balanced and healthy.
How to Minimise Coolant Dragout and Wastage
Minimising coolant dragout and wastage can significantly enhance your operational efficiency. Here are some effective strategies:
1. Switch to Neo-Synthetic Coolant
Traditional soluble mineral oils inherently have higher dragout due to their sticky nature. Neo-synthetic coolants, on the other hand, use advanced polymer technology that drastically reduces dragout and wastage:
- Low Dragout Properties: Neo-synthetic coolants are solutions, not emulsions. This prevents tramp oil absorption, ensuring the coolant remains effective and does not cling excessively.
- Enhanced Lubrication: These polymer-based coolants activate at higher temperatures, providing exceptional lubrication precisely when needed. And if you're worried about less lubrication in a synthetic fluid - don't be. That might have been true 15 years ago, but the technology has advanced to the point that the lubrication is on par with (or better than) the naturally occurring lubricating properties of mineral oil.
- Longevity and Maintenance: Although more expensive upfront, neo-synthetic coolants like Excision's XDP3800 can last significantly longer, often exceeding three years in the sump (when taken care of), delivering a superior value proposition.
Note: For low-intensity operations, synthetic coolants may not offer enough lubrication since their polymers activate under heat. Also, watch out for corrosion issues in hard water areas.
| Feature | Mineral-based Coolants | Neo-Synthetic Coolants |
|---|---|---|
| Dragout Levels | High (sticky, adheres strongly) | Low (slippery, minimal adherence) |
| Tramp Oil Absorption | High (frequent thickening issues) | Very Low (resistant to tramp oils) |
| Lubrication Efficiency | High | High (polymer technology) |
| Sump Life | Shorter (often <1 year) | Longer (can exceed 3 years) |
| Maintenance Requirements | High | Low |
2. Optimise Coolant Concentration
Maintaining optimal coolant concentration is critical for reducing coolant waste and dragout. Proper concentration ensures that the coolant retains an effective balance between lubrication and water content.
- Use a refractometer regularly to ensure your coolant concentration remains within the recommended range (typically 5-12%).
- Avoid overly diluted solutions, which exacerbate lubrication issues, bacterial growth, and tool degradation.
Read our blog to learn more about coolant concentration and using a refractometer.
You can also use our coolant concentration calculator to help you with top-up.
3. Implement Proper Drainage and Recirculation Systems
Effective coolant management systems are essential. If switching to a synthetic coolant is an option for you, making sure
- Drip Trays and Recirculation: Ensure your CNC machines have effective drip trays and recirculation systems to capture and reuse coolant efficiently.
- Air Blow-off Systems: Using compressed air to remove excess coolant from workpieces after machining can significantly reduce dragout and wastage. This could be as simple as quickly blowing off a finished part with an air gun to help any excess coolant onto the drip tray. For high-volume or repetitive operations, automation could be worth the investment.
4. Regular Coolant Maintenance
Maintain your coolant regularly, especially during extended downtimes or seasonal shutdowns:
- Check and maintain the correct coolant concentration
- Recirculate coolant periodically to prevent stagnation
- Remove tramp oil promptly to prevent thickening and additional dragout
- Consider maintenance biocides to prevent bacterial growth during periods of inactivity
For help with coolant maintenance, read our blog on summer maintenance.
5. A Note on Evaporation
Evaporation is a fundamentally environmental factor, which means you can't really control it. That being said, you need to be aware of it, especially when topping up your tank, as you do not want to make an over-concentrated tank more concentrated.
The main way you can stop wastage with you coolant is controlling the dragout.
How to Monitor and Manage Coolant Loss
One practical way to gauge how dragout and evaporation affect your coolant is to track your coolant consumption over time. If you notice your coolant disappearing faster than usual, or if parts remain wet with coolant residue, you might be facing excessive dragout or evaporation.
Final Thoughts
Managing coolant dragout and evaporation not only saves money but also improves machining performance. Long sump life means less downtime for coolant changes, healthier coolant means safer working conditions, and optimal lubrication extends tool life, improving productivity and part quality.
For tailored advice or to explore coolant solutions suited specifically to your machining needs, reach out to our technical experts at Excision. Let’s work together to maximise the efficiency of your machining operations.
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