Characterization of Fine Particles from Machining in Automotive Plants

Sampling of the full range of particle sizes was carried out on 16 processes in six different General Motors plants over a period of 2.5 years. This article deals with particle characterization from five of the processes that relate to machining, specifically, wet machining with water-based fluids from old and new technology processes, grinding with straight oils from old and new technology processes, and dry machining. The concentrations measured by different instruments were in reasonable agreement, although the light-scattering instrument generally produced higher values than filters. Of the processes studied, the old technology grinding using straight oils generated the highest particle concentrations. The new technology controls (enclosed, vented machines) were highly effective but more so for large particles than small particles. The particle size distribution was shifted to smaller particles with enclosed processes. Dry machining generated the largest particles of all processes studied.

Keywords:

• aerosols
• machining
• manufacturing
• particle emissions
• particle size
• particles

ACKNOWLEDGMENTS

Many people contributed to this project, including Jim Lewis and John Schweikert from GM Powertrain, and Ken Gunter from Michigan Technological University.

Special thanks to the UAW/GM Center for Health and Safety for funding the study, especially Mike White and Tom Weekley, Nancy Smith, Mary Morgan, Tom Kinman, and the UAW-GM Occupational Health Advisory Board representatives who consulted on the project; Carol Rice of the University of Cincinnati; and Kathie Hammond of the University of California, Berkeley.

Notes

^A RPA: Real-time particle analyzer.

^B Used for one process.

^C CI: Cascade impactor.

^D SS: Cyclone (model URG-2000-30EN; URG Corp., Chapel Hill, N.C.) on size-selective sampler for PM_2.5.

^E Traditional industrial hygiene sampler used as area sampler.

^A The APS was not used at this site for a background measurement due to the very cold conditions.

^A WB: Water-based metal removal fluid.