Introduction
Machining and metal-processing operations can generate airborne liquid aerosols when coolants or cutting oils are atomized. The appropriate mist collector depends strongly on the fluid being used, the machining process, the machine enclosure and the characteristics of the aerosol.
Powertech’s current product positioning distinguishes between water-based coolant mist and mist generated from neat cutting oils: Mistkiller™ is designed primarily for water-based liquids using centrifugal separation, while Powertech recommends an electrostatic fume extractor such as Fumekiller® for oil-based liquids such as neat cutting oil.
Key Takeaways
- Do not treat all machining mist as the same contaminant.
- Water-based coolant mist and neat cutting-oil mist can require different collection approaches.
- Machine enclosure and source extraction strongly influence capture effectiveness.
- Airflow, ducting and pressure requirements should be calculated from the complete installation.
- Coolant recovery may be possible where the collector is designed for it and the recovered fluid remains suitable for reuse.
Coolant Mist vs Oil Mist
Water-Based Coolant Mist
Water-based coolant mist can be generated during CNC machining, drilling, grinding, cutting and other operations where water-based metalworking fluids are atomized.
Powertech’s Mistkiller™ is designed primarily for this application.
Oil Mist from Neat Cutting Oil
Straight or neat cutting oils can generate fine oil aerosols during machining.
Powertech’s current Mistkiller™ page recommends an electrostatic fume extractor for mist from oil-based liquids such as neat cutting oil, while its Fumekiller® product positioning includes oil-mist collection.
Why Source Capture and Enclosure Matter
OSHA’s metalworking-fluid guidance identifies local exhaust ventilation as a primary method for controlling airborne aerosols and notes that enclosing the machine as much as possible can improve capture. The extraction system should therefore be designed around the machine’s enclosure, exhaust opening and operating cycle.
Centrifugal Mist Collection: Mistkiller™
Mistkiller™ uses a high-speed rotating fan to create centrifugal force. Powertech describes the process as drawing mist into the unit, throwing droplets against the internal surfaces, condensing the liquid and allowing collected water-based coolant to drain back toward the generating equipment for reuse.
- Designed primarily for water-based liquids
- Centrifugal separation
- Machine-mounted or standalone installation
- Optional prefilter and postfilter stages
- Periodic washing/cleaning of the relevant media
- Potential coolant recovery and reuse when process conditions permit
Electrostatic Mist Collection: Fumekiller®
Fumekiller® uses electrostatic collection to charge fine particles and collect them on oppositely charged collection surfaces. Powertech positions this system for oil mist and other fine particulate applications.
- Electrostatic filtration
- Suitable for selected fine oil-mist applications
- Reusable collection modules/cells
- Optional post-filtration where application requirements call for it
- Application-specific configuration and airflow selection
Mistkiller™ vs Fumekiller® for Mist Applications
| Parameter | Mistkiller™ | Fumekiller® |
|---|---|---|
| Primary Powertech positioning | Water-based coolant / water-based liquids | Oil mist and fine particulate applications |
| Main technology | Centrifugal separation | Electrostatic filtration |
| Typical use | CNC and non-CNC water-based machining/coolant applications | Selected oil-mist applications such as neat cutting oil |
| Liquid recovery | Powertech describes coolant condensation and potential return to generating equipment | Recovery depends on application and system design |
| Maintenance | Periodic cleaning of pre/post media as applicable | Collection-cell cleaning/maintenance according to system configuration |
Technical Selection Parameters
| Parameter | What to Establish |
|---|---|
| Machining fluid | Water-based coolant, soluble coolant, neat cutting oil or another fluid |
| Machine type | Turning, milling, grinding, drilling or other process |
| Machine enclosure | Fully enclosed, partially enclosed or open process |
| Mist generation | Spindle speed, coolant delivery, pressure and process conditions |
| Airflow | Required exhaust airflow and available machine exhaust points |
| Ducting | Length, diameter, fittings and pressure losses |
| Collection technology | Centrifugal, electrostatic or another technology suited to the contaminant |
| Recovery | Whether recovered liquid is suitable and intended for reuse |
Sizing airflow for a CNC machine? Read our guide: Mist Collector Airflow and CFM Requirements for CNC Machines.
How to Choose a Mist Collector for CNC Machines
Identify the machining fluid
For water-based liquids, Powertech’s Mistkiller™ is the relevant product family. For neat cutting oil, Powertech directs users toward electrostatic fume extraction.
Understand the machine
Establish how the machine releases the aerosol and how effectively the enclosure can contain it.
Design the system
The final design must then establish airflow, pressure, ducting and collector configuration.
Applications
Frequently Asked Questions
What is the difference between oil mist and coolant mist?
They are generated from different machining fluids and can behave differently in the air. The collection technology should therefore be selected from the actual fluid and process conditions rather than the word ‘mist’ alone.
Which mist collector is used for CNC machines?
It depends on the machining fluid and machine arrangement. Powertech’s Mistkiller™ is designed primarily for water-based liquids, while Powertech recommends electrostatic fume extraction for neat cutting oils.
Can coolant collected by a mist collector be reused?
Powertech states that Mistkiller™ condenses water-based coolant mist and that the collected liquid may be drained into the generating equipment for reuse. Reuse should still be based on fluid condition and process requirements.
Is centrifugal or electrostatic collection better?
Neither is universally better. The appropriate technology depends on the contaminant. Powertech’s current positioning uses centrifugal separation primarily for water-based liquids and electrostatic extraction for neat cutting-oil mist.
Conclusion
Mist collection starts with identifying the machining fluid and understanding how the machine generates and contains the aerosol. For water-based coolant mist, Powertech’s Mistkiller™ provides centrifugal collection and coolant recovery. For neat cutting-oil mist, Powertech positions Fumekiller®’s electrostatic technology as the relevant approach. In both cases, source capture, enclosure, airflow and system design determine practical performance.
Related Powertech Products
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