The Benefits Of Laser-Assisted Micro Machining

Sept. 18, 2007
With laser heating of cutting tool paths, researchers score a micro machining breakthrough on hard materials.

Need to shape miniature, hard-to-machine parts with three-dimensional micro and meso scale features? Test results at Georgia Institute of Technology show that mechanical micro machining can still be the best way -- if a laser is used to soften the tool path.

In addition to achieving a reduction in cutting force, the researchers expect the laser assist will also benefit cutting speeds and part accuracy as well.

For example, in micro machining of H13 mold steel (42 HRC), researchers have been able to reduce cutting force by as much as 56%.

Researchers say predictive models for temperature and machining force have been validated against experimental data, and work is proceeding to transfer the results to micro milling applications.

The goal, explains Shreyes Melkote, professor of mechanical engineering, is to take advantage of the metal removal potential of mechanical micro machining while minimizing tool deflection and catastrophic tool failure risks. Despite the potential advantages, today's mechanical micro machining technology is limited by the workpiece materials that can be processed and the relatively low stiffness and bending/shear strength of the micro tools, adds John Morehouse, research engineer at Georgia Tech's Manufacturing Research Center (MARC).

Doctoral candidate Ramesh Singh shows an example of a complex three-dimensional micro-scale feature created in hardened steel using the laser-assisted mechanical micro grooving setup. Given the tight tolerances specified on such small features, even small tool deflections can negatively impact part feature accuracy, Morehouse says. In order to overcome such limitations, researchers in the Precision Machining Research Consortium at MARC tried localized laser heating with a micro grooving process. They found that softening the cutting zone did more than reduce the cutting force. Melkote says it reduced tool deflection and stress. Part feature accuracy and process efficiency became the benefactors, says Melkote.

The laser is beamed directly in front of the cutting tool and is used to soften only the volume of material to be removed by the tool, explains Morehouse. The objective, says Morehouse, is to have no heat-affected zone in the workpiece after machining.

Today's conventional practice with hard micro part materials demonstrates the alternative -- low feed rates that lead to what the researchers call an unacceptably slow and inefficient micro machining process with much greater accuracy and quality risks.

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