From stringy to sandy: Medical Manufacturing

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END USER: Acumed LLC, (888) 627-9957, www.acumed.net. CHALLENGE: Accurately direct high-pressure coolant on Swiss-style machines to control chips when turning. SOLUTION: A Swiss-style insert holder with high-pressure, through-coolant capability. SOLUTION PROVIDER: Streamliner & Associates Inc., (814) 440-1548, www.streamlinertools.com

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Imparting a fine surface finish is usually paramount when machining medical parts. For example, at Acumed LLC, which makes orthopedic tools and implants, surface finish requirements range from about 32 to 8 rms, noted Randy Singer, machinist level 4 for the Hillsboro, Ore., manufacturer.

That’s especially challenging to achieve when chips become stringy and scratch the workpiece. That was the kind of chip control problems Acumed was experiencing when Swiss-style turning, the primary machining operation the company performs. The parts manufacturer machines various materials, including cobalt chrome, titanium and 17-4 PH, 316, 440 and 455 stainless steels. “And every once in a while I get to turn a piece of aluminum,” Singer added, but noted that 316 generates the stringiest chips.

Courtesy of Acumed

Several Streamliner Swiss-style insert holders Acumed uses to turn and thread parts for the medical industry, such as the ones shown.

Because stringy, wraparound chips can cause unacceptable surface finishes, Acumed had to perform secondary finishing operations or put stops in the part program to allow manual chip removal, increasing cycle time.

High-pressure coolant helps break chips but needs to be precisely directed at the tool/workpiece interface. The shop’s Swiss-style machines typically used an external, tubular brake line to deliver high-pressure coolant, but Singer found it challenging to effectively and consistently aim the line. “If you’re off a couple of degrees,” he said, “it takes time to monkey around to get it to where it’s hitting perfectly.”