Coolant enhances worker health, safety

Conventional metalworking fluids are effective at providing cooling and lubrication during machining, but they have critics. One is Fusion Coolant Systems Inc., which offers products for supercritical CO₂ (scCO₂) as an alternative to those fluids.

“Traditional metalworking fluids have had a place in this market for a long time at the expense of health and safety that goes along with the workers,” said Craig Happel, vice president of sales for the Canton, Michigan-based company. “It’s almost been a necessary evil.”

The well-documented risks to worker health and safety include respiratory harm and skin damage, such as dermatitis, and workers must be shielded from overexposure to chemical compounds in metalworking fluids, such as biocides, defoamers, chelating agents and surfactants. “It is basically a cocktail of chemicals that workers have been exposed to for many years,” Happel said about traditional coolant.

The company offers two scCO₂ products: Pure-Cut and Pure-Cut+. The former is a dry lubricant without oil. Pure-Cut is marketed primarily to medical device manufacturers, which often strive to avoid introducing contaminants to machined surfaces, Happel noted. “It’s a solvent, so it cleans while it machines.”

On the other hand, Pure-Cut+ has oil, but only a minute quantity, about 0.5 ml (0.017 U.S. fl. oz.), is applied each minute to achieve the necessary level of lubrication, he said. The oil, however, completely dissolves inside the scCO₂ stream.

With Pure-Cut+, about 0.5 ml (0.017 U.S. fl. oz.) of oil is applied each minute to achieve the necessary level of lubrication. Image courtesy of Fusion Coolant Systems

“It’s almost like a coating or film being released, so we are able to get into microstructures,” Happel said. “Our particles are microsized, chilled ball bearings.”

The warm stream travels through the machine tool and then quickly becomes cold when released from pressure as it moves to the cutting zone, he added. The standard operating temperature is -31.7° C (-25° F), which can be independently controlled, along with the lubrication level.

Happel contrasted that temperature with two metalworking fluids that are applied in a cryogenic state. The temperature for liquid nitrogen is about -196.1° C (-321° F), and the temperature for traditional CO₂ is about -78.3° C (-109° F). The temperature of scCO₂ makes it relatively safe to touch.

“If you touch liquid nitrogen, that’s pretty much a guaranteed trip to the emergency room, and it’s not a fun day for you,” he said. “We are not cryogenic. That’s a very important point.”