July 2012 / Volume 64 / Issue 7|
Shine a light
By Alan Richter, Editor
Machining hard materials is hard. There are numerous issues when turning, grinding and lapping hard, brittle materials, such as silicon, ceramics and glass, using conventional single-crystal diamond tools. Those issues include the formation of cracks and fractures in the workpiece, high tool wear, inaccuracy of the machined form and long cycle times, according to Dr. John Patten, director of the Western Michigan University Manufacturing Research Center.
To commercialize an alternative hard-material turning process developed at WMU, Patten and Dr. Deepak Ravindra, a senior research associate and postdoctoral fellow at the university, founded Micro-Laser Assisted Machining Technologies LLC. The company’s µ-LAM process reduces processing times by about 50 percent compared to conventional methods, Patten noted. In addition, the process causes recrystallization to occur in-situ during machining and heals, or anneals, a workpiece that might otherwise be damaged.
Courtesy of Micro-Laser Assisted Machining Technologies
The µ-LAM process focuses an energy beam from a continuous-pulse fiber laser to generate a temperature higher than 1,000° C and a pressure in excess of 100 GPa from a single-crystal diamond tool to render a workpiece material more pliable and ductile and less brittle and less prone to fracture. Unlike other laser-assisted machining processes, which use other types of cutting tools and are less precise, Patten pointed out that the µ-LAM process passes the laser through the diamond tool without heating the diamond because heating it may cause the diamond to degrade or possibly decompose when exposed to air. “The diamond is transparent to the laser,” he said. “It’s really a hybrid, coupled configuration that’s pretty slick.”
Patten noted the process focuses the laser directly in front of the tool tip, where the chips are being formed by the diamond cutting tool. The chips, which carry about 90 percent of the heat generated in the cut, are typically cooled with air. Coolant can be applied to cool the chips and workpiece surface without reducing the temperature at the laser/workpiece interface, he added.
The company has machined materials up to 50µm thick, but hasn’t needed to cut thicker ones, Patten said. “If a turning machine was good enough and everything was set up right, you could do a millimeter,” he added. “I don’t know what the limit is.”
Although all turned parts will have feed marks, Patten indicated that the µ-LAM process imparts “nanoscopic” ones. “We can create a mirror surface,” he said. “If the application doesn’t require an angstrom-level surface finish, then it’s good to go.”
The company is working toward commercialization of a system that it would sell as an accessory to a diamond turning machine, and the National Science Foundation awarded Patten and Ravindra a $150,000 SBIR Phase I grant to help ready the technology for commercialization. Patten estimates that the technology could save a typical part manufacturer $150,000 to $500,000 a year. “We’re pricing it on the value to the customer,” he said.
To test the technology outside of the lab, the company set up the µ-LAM system on a Precitech 700 series diamond turning machine at a plant near Pittsburgh. “By all accounts, it exceeded our expectations,” Patten said.
For more information, contact Micro-Laser Assisted Machining Technologies LLC, Battle Creek, Mich., at (206) 600-7366 or www.micro-lam.com.
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