Two Parts Every 35 Seconds — for Four Years Running

Being a Tier 3 supplier to automotive and appliance OEMs is high-volume, extremely competitive work, where success depends in large part on fast, accurate, and above all dependable equipment. Fortunately for Bill Overbay, manufacturing supervisor at Miyama USA Inc. in Louisville, Ky., his latest round of machine tool purchases hit each one of those objective. “We now have five Kent USA machining centers in all, and most have been running nonstop for the past four years,” Overbay said. “We’ve had no problems whatsoever.”

Miyama USA is a wholly owned subsidiary of Miyama Kogyo Co. Ltd. in Japan. Since 1980, the Kentucky shop has supplied a variety of automotive and appliance customers in the U.S., with capabilities that include stamping, machining, robotic welding, assembly, and other value-added services. The company and its 50 employees take pride in 100% on-time delivery and unerring quality, both necessary attributes in an environment where business is determined by margins of pennies per part.

And the winner is … — After winning the bid nearly five years ago on a long-term contract for an automotive seat gear, Overbay and his team were faced with tooling up for the big job, beginning with the purchase of three, new CNC vertical machining centers. At first, it seemed the parts were small enough that a drill-tap machine might be a sensible choice, but because each gear required semi-finish and finish-boring operations, Overbay knew that a 40-taper machine would be needed to accommodate the adjustable boring heads, each of which weighs close to four pounds.

Still, he didn’t want to sacrifice speed and accuracy. “When you’re a Tier 3 supplier, price-per-part is everything,” he said. “This presents a strong argument for finding the least expensive machine available, but we also needed one that was fast enough to meet our cycle time objectives — and able to consistently hold tolerances down to 20 microns (0.0007 in.) on a pair of holes.” 

Overbay evaluated several well-known machine-tool brands, and then contacted an old acquaintance, Glen Goins, president of Amerigo Machinery Co.

“Glen’s been in this business longer than anyone and I trust him to stand behind his equipment; he’ll do whatever’s needed to treat his customers right,” Overbay recalled. “He showed us a couple different options, but it was the KVR-2418 vertical machining center from Kent USA that we kept coming back to. Where everyone else makes you pay for a 12,000-rpm chilled spindle upgrade, a better control, and other needed machine options, Kent USA includes those features as standard, and has a lower price.”

Running hard — Notwithstanding the cost, the KVRs have proven to be extremely reliable for Miyama USA. Each of the machines produces two seat gears every 35-seconds, and does so 16-hours a day, five days a week. With three tool changes per cycle, that comes out to nearly 1.5 million tool changes annually.

“Aside from the routine maintenance to replace the tool pods every year or so—something that’s quite reasonable, considering the high number of tool changes—we’ve had no appreciable downtime, and the only failures are when the operator accidentally stops the machine in the middle of a tool change,” Overbay reported. “And, after four years of moving to the exact same four points, we have almost no visible wear on the ball screws.”

Tool life has been exceptional, too. The seat gears are made of 400-series stainless steel that’s been heat-treated to 62 Rc, hard enough that relatively expensive PCBN (polycrystalline cubic boron nitride) cutting tools are necessary.

Due to their brittle nature, however, these tools require rigid, stable machining conditions if they’re to last as long as possible. Again, the Kent USA KVR machining center does not disappoint, producing up to 3,000 parts per tool, a figure that Overbay said the shop is quite proud to achieve.

Looking forward — Because of this long-standing (and ongoing) success, Miyama USA now has invested two additional KVRs, bringing the total to four machines dedicated to seat gear production and one for general shop work.

Overbay estimated the shop has made more than four million of the automotive components so far, with all of the machines still going strong.

“To be honest, I initially thought we were buying an inexpensive machine that, hopefully, would last long enough to get us through the project. But, over the past four years, I’ve been pleasantly surprised by the quality,” he said.

“A lot of people think I’m joking when I tell them how many tool changes we’re doing each year. My response is that the machines are fantastic. The price was significantly lower than competing brands, they’re fast and accurate, and even though we push them very hard each day they just keep on making parts.”