The search for intelligent life on Mars took a big leap forward on February 18, 2021, when Perseverance, NASA’s latest Mars Rover, touched down on the surface of the Red Planet. Its mission? To seek signs of ancient life and collect rock and soil samples for possible return to Earth, as well as pave the way for future human exploration. It’s the most ambitious of NASA’s Mars missions, with a larger, more sophisticated Rover that builds on the lessons learned by previous Rovers dating back to 1997.
Fortunately for NASA, “intelligent life” can be found a lot closer to home at Forest City Gear. Gears produced by this well-known precision gear jobber in Roscoe, Illinois, have been used on every Rover, helping ensure these vehicles operate dependably, whether traversing the rugged Mars terrain or surviving in temperatures down to minus-130°F.
NASA puts its trust in Forest City Gear, and Forest City Gear in turn trusts Gleason — this time for North America’s first GP300ES Gear Shaping Machine with a 1,500-strokes-per-minute cutter spindle speed that’s significantly faster than anything in its 300-mm diameter size range. The GP300ES is the company’s seventh CNC shaping machine, making Forest City Gear one of the largest and most productive shaping resource available for contract gear production. And now, with the GP300ES, it’s one of the fastest.
“We are fortunate to be the first company in North America to put this new, faster GP300ES into production,” said Forest City Gear Director of Operations Jared Lyford. “It’s a versatile, highly-productive machine that’s added throughput for our customers seeking faster turn-around and higher quality, particularly for gears that require a unique approach to standard cutting strategies via higher feeds and speeds.”
Improving on the Legacy
According to Lyford, several important aerospace “legacy” projects already have benefited from the new Gleason shaping machine. Most notable is a family of aerospace internal and external spur and helical gears, fine and medium pitch, and involute splines — all made from 440C stainless steel.
440C stainless is a grade known for its superior strength and hardness, making it ideal for many aerospace applications. Lyford pointed out the material also can be a challenge to shape.
“We could overcome the machinability issues we’d been encountering when shaping these 440 parts by increasing the feeds and speeds to the very upper limits of our shapers (all of which are the latest models with guideless helical capability) — but then lead integrity would suffer as a result,” he said. “That’s the shaping conundrum in a nutshell: a process ideal for generating critical features against shoulders with limited clearance — but with inherent limits on how fast you can machine.”
With demand growing fast for not only aerospace parts of this type but other high precision work, Forest City Gear went shopping for a new shaping machine — one that ideally could add capacity and shape at much higher speeds than traditionally possible with machines in the 300-mm size range.
Serendipitously, Gleason had just improved on one of its “legacy” shaping machines: the popular GP300ES. The new version is designed to address the long-standing shaping conundrum and deliver cutter spindle stroke speeds as high as 1,500/minute.
This is 40 percent faster than the existing model and anything else in its size range. In short order, Forest City Gear purchased the first of these new-series GP300ES machines ever to be installed in North America. To accommodate Forest City Gear’s ambitious delivery requirements, Gleason even arranged to have the machine — typically built at its Ludwigsburg, Germany, facility — assembled at the Gleason headquarters in Rochester, New York, instead.
Built for Speed
When the earlier GP300ES and the new, faster model are compared side by side, there aren’t any obvious differences. But, while the enhancements made might be subtle, they are significant. Gleason began by developing a new balancing weight that minimizes unbalance for all cutter-spindle-stroke axis lengths and speed ranges. New control parameters for the stroke-and-tool-back-off axes were applied as well to achieve the higher stroke rates. The back-off axis also features a new-design back-off cam specially designed to operate more reliably at the higher stroke rates.
To accommodate the potential for more noise and vibration, Gleason also stiffened the housing sheet metal and added insulation. New leveling wedges with two-chamber air spring elements also were added for greater vibration damping.
Increased Speed, Problem Solved
Now, with the new GP300ES, Lyford reports the problems experienced with the 440 stainless parts have been eliminated.
“With the higher surface footages, we can slow the rotary feed enough to put less of a chip load on the cutter to get the required quality but without impacting cycle times,” he said. “In fact, we’ve about doubled surface feet per minute (SFM) for production of almost every part we produce on that machine, while at the same time reducing chip load. This results in improved quality and extending tool life. I believe this machine really marks the beginning of a new chapter in shaping, both for the industry and Forest City Gear.”