The essentials of manufacturing microtools

Cutting tiny parts and part features with an endmill smaller than a human hair ranks high on any shop’s “let’s avoid that” list. The feed rates are glacial, and the available spindle speed is usually far from adequate. Often the only way to know the tool has broken is with a microscope.

Now imagine making the cutting tool itself. Manufacturing microscale endmills and drills requires ultraprecise machinery and specialty grinding wheels—never mind extreme skill, the right carbide grade and abundant patience. Thankfully, a number of toolmakers have become proficient at this microscopic task, leaving shops to worry about just one thing: making parts.

Kyocera Precision Tools Inc. is a Costa Mesa, Calif., toolmaker that produces endmills down to 0.004″ (0.1mm), reamers to 0.008″ (0.2mm) and drills to 0.0015″ (0.04mm), with geometries virtually indistinguishable from their larger counterparts. Micro industrial product and sales manager Joe Negron said many of these tools are applied in the medical and semiconductor industries. One of the keys to success in this micro realm is reducing runout—when the tool is manufactured and afterwards during use.

Microscale tool grinding requires extreme patience, attention to detail and a high level of skill. Image courtesy of Mikron Corp. Monroe.

“This is where you separate the men from the boys in terms of manufacturing technology,” Negron said. “If you are unable to tightly control runout during machining, the tool will fail right out of the box. And without proper blank preparation when grinding—which means starting with a perfectly round, straight piece of carbide—manufacturing yields fall dramatically, which, in turn, drives up costs and makes tool longevity questionable. Compared to larger tools, where 0.0005″ runout isn’t going to hurt, you have to control it within millionths for microtools.”

The communications coordinator at Rollomatic Inc., Mundelein, Ill., Bjorn Schwarzenbach, agreed that minimizing runout and blank preparation are critical to microtool grinding. He added that controlling deflection is also important.

“When you consider that you’re usually starting with a 3mm-dia., or 1⁄8″, blank, a relatively large amount of material is removed compared to the finished tool diameter. Therefore, deflection of the wheel and the tool can be pretty severe if left unmanaged,” Schwarzenbach said. “In Rollomatic’s case, we manage wheel stability with our PerfectArbor system, which compresses the arbor as a means of centering it on the wheel and provides a very rigid connection. For the tool, there’s the Nanoset steady rest and U-block workholding system, which work together with the wheel arbor to minimize deflection.”

Dress for Success

Schwarzenbach also said accurate wheel dressing via the CNC is necessary to achieve the extreme precision required on microscale tools, where diametral tolerances of 0.000039″ (0.001mm) are common.