Mist generation at a machining center

Area of Science:

• Industrial Hygiene
• Aerosol Science
• Mechanical Engineering

Background:

• Controlling occupational exposure to metalworking fluid mist is crucial for workplace safety.
• Effective control strategies rely on understanding mist particle size and generation rates.
• Existing methods often involve enclosing machinery and using air cleaners to return filtered air.

Purpose of the Study:

• To quantify metalworking fluid mist particle size and concentration.
• To investigate the influence of machining parameters on mist generation.
• To provide data for selecting appropriate air cleaning systems for enclosed machining centers.

Main Methods:

• A vertical machining center was fully enclosed, with exhaust air ducted for analysis.
• Mist concentration and size distribution were measured using a time-of-flight aerosol spectrometer and cascade impactor.
• Experiments involved face milling aluminum, varying coolant flow rate, tool RPM, and metal removal conditions.

Main Results:

• Mist concentration increased with higher tool speed and fluid application velocity.
• Metal removal itself did not significantly affect mist generation; fluid and tool motion were key factors.
• Mist concentrations showed proportional relationships with tool speed (2nd power for face mill, 3.5th power for end mill).
• The shape of the mist particle size distribution remained largely consistent across tested variables.

Conclusions:

• Metalworking fluid mist generation is primarily a function of fluid dynamics and tool motion, not the cutting process itself.
• Understanding these relationships is essential for optimizing air filtration and controlling worker exposure.
• The findings support the development of more effective engineering controls for machining operations.