Mag Industrial Automation Systems has developed what it describes as a “breakthrough in cryogenic machining” with a multipatent-pending technology. The result is significantly faster cutting speeds for increased metal removal rates and longer tool life.
The liquid-nitrogen (-321°F) cooling system can also be combined with MQL (minimum quantity lubrication) to reduce tool friction and adhesion, enabling even higher metal removal rates or longer tool life. Ideal applications involve aggressive metal removal in the hardest workpiece materials, such as titanium, nickel-based alloys, and nodular or compacted-graphite iron (CGI).
“We are still in development but have achieved 60% speed increases in milling CGI with carbide and up to four times using PCD [polycrystalline diamond] tooling. With the addition of MQL, we tripled speeds with carbide but showed no further benefit to the fourfold increase with PCD," said MagG Vice President of Engineering Doug Watts.
"These tests focused on metal-removal increases, while keeping tool life equal to what would be achieved with conventional coolants. Early results indicate this technology could dramatically improve the life-cycle cost model for machining in a 'hard-metal' environment by reducing the required number of machines and associated plant infrastructure, or possibly increasing tool life beyond anything thought possible today. Cost-wise, cryogenic machining becomes even more competitive when you consider it's a non-issue environmentally. There is no mist collection, filtration, wet chips, contaminated workpieces or disposal cost, and certainly less energy consumption without all the pumps, fans, and drives that go into handling coolant."
According to Watts, the key to the new system's efficiency is its ability to concentrate the cooling effect in the body of the cutting insert.
"Cryogenic machining has never been done this efficiently before, with liquid nitrogen passed through the spindle and into the insert," he explained. "Through-tool cooling provides the most efficient heat transfer model and consumes the least amount of liquid nitrogen. Our development work to date has focused on milling and boring, where consumption has been about 0.04 L per minute per cutting edge. We believe drilling and tapping should be even less."
Watts added that tests by MAG have shown the range of capabilities for diamond tooling can be expanded significantly with cryogenic cooling—for example, extending the heat limit in CGI by 3 to 4 times. Carbide tooling, which is more affected by abrasive wear, responds best when MQL is combined with cryo cooling.
The through-spindle cryogenic cooling system is suitable for motorized, belt-driven, or geared spindles. At the recent IMTS show, a through-spindle cryogenic delivery system was demonstrated on a Mag vertical machining center.
"We are actively seeking partners to participate in further development and hope to commercialize the technology next year," Watts said.