Preset it and forget it

END USER: OKAY Industries Inc., (860) 225-8707, www.okayind.com.
CHALLENGE: Minimize tool runout, extend tool life, reduce scrap and prevent fixture damage.
SOLUTION: An offline cutting tool presetter.
SOLUTION PROVIDER: Koma Precision Inc., (800) 249-5662, www.komaprecision.com.

Every parts manufacturer faces a test of its ability to innovate at some point. OKAY Industries Inc.’s challenge was to design a better process for measuring and inspecting its cutting tools. The Berlin, Conn., company frequently machines 303, 304 and 17-4 stainless steel, as well as H-900 17-4, which is hardened to about 45 HRC, for medical, defense, arms and automotive applications.

The company handles production runs that total up to tens of thousands of parts per week. The cutting tools, however, are not large, mainly consisting of endmills from 3mm (0.118″) to 0.0763mm (0.0030″) in diameter and smaller, noted Joshua Palotti, lead CNC specialist at OKAY Industries.

Joshua Palotti, lead CNC specialist at OKAY Industries, checks a tool on the Hathor Six offline tool presetter from Koma Precision. Image courtesy Koma Precision.

When applying microscale tools, runout of as little as 0.0002″ (5.1µm) —which is imperceptible to the human eye as they rotate—can cause problems, Palotti explained. “The first part would be way over size, the tool would instantly snap or tool life would be very inconsistent,” he said. “If we were expecting to run 300 cycles with a 1mm endmill, we might run from 100 to 300 cycles, depending on the runout.”

In addition, when finish milling one stamped part, there was only 0.0005″ (0.0127mm) of clearance between the workpiece and clamp, so excessive runout caused the tool to hit the clamp, Palotti noted. The clamp gripped a 0.020″ (0.508mm) land and the clamping force would be reduced if the tool hit the clamp, causing the part to move. This, in turn, required OKAY to rebuild the clamp, a 2- to 3-hour process that involved disassembling the entire fixture and creating a new one.

He added that some inexperienced operators applied worn tools, exacerbating the problem.