Top Tool

Posted by Dave Kari, Director of EDM

The amazingly delicate medical component prototype is only 1.3 mm wide. So it's equally amazing that it requires 142 separate hits by the tool – all of them performed within a few square millimeters – to precision micro stamp the coining, forms, features, bends and bevels included in each stainless steel part.

As recently as five years ago this complex key micro component in a coming medical miniaturization milestone could exist in the designer’s mind, but not in a surgeon’s hands.

The difference-maker today at Top Tool is one of the very few .00078in. wire electronic discharge machining (EDM) systems online in U.S. manufacturing. Not only does it possess the .00078in. capability, it also features a dual spool capability to cut using different size wires.

Using EDM with a small wire is the only approach to succeed at a .021in. x .013in. punch used to pierce a micro-sized opening in the prototype component. This component is possible only because the wire is small enough to cut a virtually undetectable .002in. radius.

At these millimeter and micron levels, the cutting process is always on the edge between controlled and uncontrolled. Or stable versus unstable. The “razor’s edge” metaphor isn’t remotely close to representing the small window – a narrow range of acceptable conditions – where “the small wire” does its work. You would have to get inside small-wire EDM to really see what happens during this non-conventional ma-chining process. It’s about a different level of material removal.

So think small as you submerge into the die electric water tank. You make your way into the collection tube. That’s where micro flecks of degraded wire and burnt (cut away) material debris – “swarf” in machin-ing terms – are washed along like river bottom gravel in a stream of takeaway water. But not all of the micro debris is as harmless as gravel. The biggest pieces might as well be very large boulders.

On an EDM with a larger, more typical wire diameter, the system is not precise enough to detect or be disrupted by the boulder problem. By the time a larger wire senses the boulder, it would be too late. But the .00078in. wire, with its sophisticated sensors, is so algorithmically powerful it can sense being nudged off the programmed path. In the worst case scenario – without maintenance to remove the debris – the boulder-size flecks are even large enough to break the wire.

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