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JUL/AUG 2013  

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News/Features: About Tooling

Ever set up a Swiss-style machine and run out of tooling stations? With many Swiss machines today boasting upwards of 20 or even 30 tooling stations, it’s hard to believe you might run short. But on older or smaller machines, as well as when running complex jobs involving multiple operations, this is sometimes the case.

If you have a few million tiny holes to drill, you could order up a tractor-trailer’s worth of circuit board drills and get to work. You might be done by Christmas. Or you could find one of a handful of shops that owns an electron beam driller and get those holes drilled before lunchtime.

Back in the mid-1980s, tired of fighting with the guys in my tooling department over the shop’s meager supply of boring heads, I decided to buy my own. The head came from China, and the salesman assured me it was every bit as good as his U.S. brand, at half the price.

In the rapidly growing medical device industry, bigger is not necessarily better. In fact, when it comes to machining medical parts, the trend of “going small” is getting bigger.

Difficult-to-machine workpieces usually represent “an inconvenient truth.” As material developers improve a metal’s strength and resistance to heat and wear, while often reducing its weight, its machinability declines. Enhancements to alloys such as austenitic stainless steel, titanium and high-temperature superalloys generate an ever-increasing laundry list of machining problems, including built-up edge, chatter, workhardening and excessive tool wear. They make it difficult to impart acceptable surface finishes when micro-endmilling.

As parts and part features shrink, so do the tools required to machine them. Process factors that are not critical when using macroscale tools literally become make-or-break considerations at the micro-scale. An inappropriate cutting parameter or toolpath can snap a tiny tool instantly.

That’s certainly the case with endmills, one of the most commonly applied micro-tools. Micro-endmills 0.005" in diameter and smaller operate under their own set of “unbreakable” rules.

Three critical factors must be controlled when holding cutting tools in the spindle for micromachining: runout, runout and runout.

“For very small tools, the amount of runout dramatically affects tool life,” said Alan Miller, engineering manager for BIG Kaiser Precision Tooling Inc. “As tools get smaller, the acceptable amount of runout goes down with them.”

Single-crystal-diamond tools are routinely used to cut optical-quality components on special turning machines. But they also can run on conventional machine tools—often to great advantage.

While they are specialty tools, dovetail-style cutters have a broad range of applications. Dovetails are typically used to cut O-ring grooves in fluid and pressure devices, industrial slides and detailed undercutting work. Dovetail cutters have a trapezoidal shape—like the shape of a dove’s tail. General purpose dovetails are used to undercut or deburr features in a workpiece. O-ring dovetail cutters are held to specific standards to cut a groove that is wider at the bottom than the top. This trapezoidal groove shape is designed to hold the O-ring and keep it from being displaced.

Many part manufacturers don’t think indexable tools and micromanufacturing are a good match. In reality, indexable tools are often used in conjunction with Swiss-style CNC machines to produce parts down to 0.005" in diameter.

On a daily basis, indexable tools are used on Swiss machines to produce dental implant screws, watch parts and circuit board components, all of which fall into the micromanufacturing realm. Proper application of indexable tools can provide machine shops with a competitive advantage in serving these markets.