Precision Shapes Inc. routinely takes on the tough stuff. Thanks to expert help and great cutting tools, the tough stuff just got a lot easier.
Few machinists like to cut Inconel. With a machinability rating in the low teens, it’s among the most challenging of all heat-resistant superalloys. It’s hard on cutting tools, the chips are darned near impossible to break, and the feeds and speeds relatively glacial. Adding insult to injury, Inconel’s expensive—at roughly ten times the cost of aluminum or stainless steel, scrapping a workpiece is something most machinists (and their bosses) would rather avoid.
Why, then, would any machine shop not only accept orders for Inconel parts, but actively pursue them? Ask Shawn Shepherd, process engineer at Precision Shapes Inc. (PSI) in Titusville, Fla., a shop that specializes in machining Inconel and other difficult nickel-based alloys. “Seven years ago, we were like any other shop—afraid of Inconel,” he said. “But ever since our Sandvik Coromant sales representative Matt O’Neill started helping us with some of our machining processes, we’ve been looking for more. Today, probably 70 percent of our work is with Inconel; the rest is all titanium and other nasty materials.”
In 1940, PSI founder Paul Fasnacht emigrated from Germany to New York City. He brought his machine shop with him. At that time, his company specialized in continuous, long-length milling of parts for the rail and air industries, a process that Fasnacht patented and which PSI still offers today. Upon Fasnacht’s death in 1972, long-time employees Ronald Lockyer and Joseph Metzger purchased the company from his widow, eventually moving it to Titusville.
Fast forward to today. The two business partners have since passed away, and Metzger’s two daughters—Susan Palma and Cheryl Cleveland—now own PSI. Over the past ten years they’ve continued and improved upon the company’s legacy, delivering a variety of precision-machined parts to what is literally a who’s who list of aerospace and defense customers, including Goodrich Aerostructures, GE Aviation, Northrop Grumman, and many others, earning strategic supplier awards and an AS9100 certification along the way.
The 30,000-ft2 (2787.1-m2), 60-employee CNC machine shop, a woman-owned small business (WOSB), produces everything from seat brackets and actuator levers to wing clips and heat sinks, many of which leverage the long-length milling process to machine part profiles en masse before sawing them to length and finish machining the balance of the workpiece.
This wasn’t the case with a recent job, however. The 5½” diameter by 2″ (139.7 by 50.8 mm) long Inconel 625 rings started out looking like “monstrous hockey pucks,” requiring roughly ¾” (19.05 mm) of material to be removed from each side down to a diameter of 2½” (63.5 mm) with a 1¾” (44.45 mm) hole punched through the center. Tool life was so poor that roughing, semi-roughing, semi-finishing, and finishing tools were needed to complete each face and the outer profile, for a cycle time of nearly four hours per part. Worse, the CNMG rougher had to be indexed four times per cycle, adding considerable expense to a part that was slated to run for the next year—1,100 pieces in all.
PSI quickly grew concerned about its ability to deliver, and actually ordered another Mazak Quick Turn 250 CNC lathe in order to meet its obligations. At the same time, Shepherd called Sandvik Coromant’s O’Neill to see what could be done to increase tool life and hopefully reduce cycle time, an effort that seemed doubtful considering that the turret was already filled with his Coromant cutting tools.
As it turned out, O’Neill had a new trick up his sleeve, one that would not only meet both of his customer’s objectives quite handily, but do so to such an extent that the second lathe proved unnecessary. The solution? CoroTurn Prime.
“I love long-running parts like this because they’re an opportunity to save the customer a tremendous amount of money,” said O’Neill. “I knew that CoroTurn Prime was a good candidate for this application because of how much faster it could feed, but to be honest, I had no idea how much better it would perform compared to their existing tools.”
When O’Neill arrived, the roughing operation alone was taking just shy of three hours to complete. He and Sandvik Coromant Machining Specialist Dave Edwards reprogrammed the job “the PrimeTurning way,” rolling into the cut, pushing the tool hard on the straightaways, slowing around the corners, all the while taking full advantage of Prime’s chip-thinning geometry to remove as much of the difficult material as they could in the shortest time possible. They also kicked up the cutting speed, going from 80 to 170 sfm, and more than tripled the feed rate to 0.020 ipr.
The results were impressive. Said O’Neill, “I was hoping for a 50 percent cycle time reduction—we got 80 percent, and more than doubled tool life at the same time, saving them an additional $250,000 per year above and beyond the productivity improvements. We were all pretty awestruck.”
Shepherd agreed. He said that he and the PSI team have continued to fine-tune the turning process since O’Neill left. By dropping the cutting speed slightly, they’ve been able to eliminate the semi-roughing and semi-finishing tools, further reducing tool costs and the downtime needed to change them. And as it turns out, the second Mazak lathe was needed after all, because the customer has nearly doubled its order quantities, something that he and the others at PSI no longer dread.
He’s also begun looking for other ways to use PrimeTurning, starting with an Inconel shaft job. “It was a great success story for us,” he said. “We’re always looking for continuous improvement opportunities here, and this was one of the more successful ones. Because of the support we’ve received from Sandvik Coromant, we’re confident that we always have the right inserts, the right feeds and speeds, and we’ve become known to our customers as an ‘Inconel House.’ That might not sit well with some shops, but for us it’s exactly where we want to be.”