Snow brings green machining to laboratory

University of California scientists working at Los Alamos National Laboratory have developed a novel machining technique that uses a jet of solid carbon dioxide (CO2) to cool/lubricate the surface of metal parts and remove the cut material during machining. Called Snow-Machining, the process could someday eliminate the use of oil-based or synthetic chemical fluids for metal cutting and metal parts cleaning in industry.

The Snow-Machining technology creates a high velocity stream of small, micron-size dry ice particles through the process of adiabatic expansion of liquid carbon dioxide as it passes through a 0.012 inch diameter nozzle. The resulting particulate CO2 acts as a mechanical force to blast away the waste metal material while at the same time cooling and lubricating the surface of the machined part.

Experts in the Department of Mechanical Engineering-Engineering Mechanics at Michigan Technological University estimate that American industry uses more than 100 million gallons of metalworking oil each year and that the amount of cutting fluids used is at least several times that of metalworking oil.

The use of “snow” means that the machining process can be made to produce virtually zero hazardous waste, since carbon dioxide is environmentally benign. Other advantages over traditional cleaning and cooling fluids come with the fact that carbon dioxide also is inexpensive, nonflammable, recyclable and plentiful. The Los Alamos process was developed to improve “dry” machining techniques for the nuclear weapons programs. Although the Laboratory has moved toward using “dry” machining technologies in many of its manufacturing techniques, the technology is limited to depth of cuts of less than 1/1000th of an inch and feed rates of 2/10,000ths of an inch per revolution.

The Snow-Machining system has already demonstrated improved performance and cost savings over traditional dry machining in terms of enhancing the surface finish and by increasing the life of the cutting tool.

The result of a collaboration between the Chemistry Division’s Supercritical Fluids Team and the Small Scale Experiments group of the Nuclear Material Technology Division, the technology has been expanded into traditional machining applications by the Laboratory’s Pollution Prevention program, where the process will help reduce/eliminate the amount of radioactive hazardous liquid wastes produced by the machining and the cleaning of uranium at the Laboratory.

The invention follows on the heels of an earlier Laboratory success where scientists developed the use of liquid carbon dioxide to replace cleaning fluids in the dry cleaning industry. The Los Alamos invented process is now widely used in the commercial dry cleaning industry.