Losone, Switzerland – To demonstrate just how far the
capabilities of small wire EDM (electrical discharge machining) have come in
the past decade, researchers at Swiss-based GF
AgieCharmilles produced this micro-size mountain bike. First introduced
some 30 years ago, EDM uses electrical discharges that form an arc between an
electrode and work piece to achieve a desired shape.
The tiny cycle was
machined out of 1-mm-thick Inox stainless steel using a 0.020-mm wire. The
smallest internal radius measures a mere 0.013 mm, with a tolerance of +/- 1 μm.
One of the biggest
obstacles to overcome in achieving these ultra-small features, says Head of
R&D Micro Machining Dr. Ivano Beltrami is controlling the micro gap. "That
means first being able to electronically measure a distance between electrode
and work piece at the level of only a few (two to ten) micrometers and second
being able to keep the gap width relatively constant."
It's particularly
difficult, he says, because of the particle contamination in the dielectric
and the stochastic nature of the spark formation.
Asked if the wheels
on the bike actually spin, Beltrami says "No, it's challenging enough to
actually have the wheels at all."
While there is no
practical application for a flea-sized micro bike, GF AgieCharmilles is seeing
a slew of commercial products that are getting downsized – including 3-D mold
inserts for electronic devices, punching tools for micro gears and lead frames and micro diaphragms for optical applications.
So can things get
smaller? "The biggest limitation to further advancements in the technology is
the current market size, which is still relatively small and in turn limits the
investments," says Beltrami. "But from a technical point of view, even smaller
structures are feasible."
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