Miniature Tools Created for Micromachining

Tiny polycrystalline diamond cutting tools fabricated by scientists at the University of Kentucky in Lexington, George Washington University in Washington and Pennsylvania State University in University Park are suitable for the machining of hard and brittle materials such as glass.

Described in the December issue of Journal of Micromechanics and Microengineering, the drills and end mills may find a place in the production of micromolds or in the direct inscribing of patterns in glass/quartz substrates for lab-on-a-chip devices and biomedical arrays.

To create the tools, the researchers employed wire electro discharge machining to cut 1 × 12-mm cylindrical blanks from tungsten carbide wafers coated with a 1-mm-thick layer of polycrystalline diamond. Further processing by wire electro discharge grinding and microelectro discharge machining yielded the desired 50-µm-diameter shapes.

In tests of the tools, they produced 50-µm-deep, 2-mm-long grooves in soda lime glass and 5-µm-deep, 500-µm-long pockets in ultralow-expansion glass. The feed rates were 1 µm/s for the cutting of grooves and 1 to 10 µm/s for the cutting of pockets. After machining, no fracturing was apparent around the rims of the grooves, and the pockets displayed an average surface roughness of 0.3 nm.