Ask Chuck Chandler, plant manager at SEW Eurodrive USA in Lyman, South Carolina, about the range of applications for the spiral bevel gear units produced there, and his response is simple: the world. The ultra-modern 385,000-square-foot facility, winner of Plant Engineering Magazine’s Top Plant Award in 2007, is running three shifts a day, six days a week, and busting at the seams to keep pace with record demand from SEW Eurodrive Assembly Centers around the world. But if you think these production challenges keep Chandler up at night, guess again.
“We’ve never been more productive or efficient,” he said. “And we have some of the latest Gleason technologies helping us get there. It’s a good problem to have.”
Grinding for More Precision
Ten Gleason Phoenix bevel gear cutting machines, including four of Gleason’s latest generation of 280CX machines, produce all of the spiral bevel gear sets used in SEW Eurodrive’s popular K Series of right-angle gear units. The K Series is an industry workhorse, renowned for delivering 96 percent efficiency and very quiet, wear-free performance across a 200 Nm to 50,000 Nm torque range. These gears are heat-treated and then lapped and tested on Gleason HTL TurboLapper and HTT TurboTester machines. But with the introduction in 2004 of a new family of servo gear units, designed for very high precision applications where positioning tolerances are often measured in microns, Chandler and his team recognized that lapping these gears as a hard finishing process wasn’t going to be good enough.
“The spiral bevel gearsets in these servo gear units must be produced with very tight tolerances and operate backlash-free, so we opted to finish grind them,” Chandler said. “Plus, by grinding gears and pinions independent of each other rather than having to lap them as mated sets, we have the added flexibility of finishing gears or pinions in the optimum lot sizes and on demand.”
Early on, SEW Eurodrive relied on Gleason and its Phoenix 280G Bevel Gear Grinding Machines to grind the gearsets at Gleason.
“We didn’t initially have the volumes or, frankly, the grinding expertise, to justify a grinding machine purchase,” Chandler said. “Outsourcing to Gleason gave us a chance to learn about the process and see firsthand how well the 280G performed, so when the time came, we bought one right off the floor at IMTS 2014.”
Proven Phoenix Performance
Today, this 280G is helping meet the world’s growing appetite for SEW Eurodrive’s servo gear units and performing so well that Chandler and his team are looking at a second machine and more opportunities to apply grinding, whether for noise reduction or to squeeze more torque out of a smaller gearset. The machine’s exceptional reliability has come as no surprise to Chandler, since the 280G is built on the same platform as his tried-and-true Phoenix 280CX cutting machines. It also features an exceptionally well-designed work area for swarf containment and evacuation. This is critical for ensuring fast, accurate bevel gear grinding, as well as helping to minimize the time-consuming and expensive maintenance challenges of swarf accumulation and contamination.
Virtually all of the usual wires, piping, and even the door rails have been moved out of the work area and put behind guarding, so swarf is easily contained and falls free for collection by the coolant chute positioned directly below the work area. In addition, the 280G is equipped with an integrated dressing unit with a unique telescoping design that enables it to extend into the work area for dressing, and then fully retract flush with guarding during the grinding cycle.
But what Chandler also appreciates now is just how productive the 280G is.
“We’re producing 24 different gears and pinions in the servo gear family, and once you set it up for a part for the first time, replicating that same part setup downstream is very fast and easy,” Chandler said.
He attributes some of this setup speed to the color-coded sets of quick-change coolant headers that allow the operator to easily optimize the flow of coolant for each part, critically important in order to avoid surface defects and achieve the desired surface finish and flank form accuracy.
The machine is also equipped with a quick-change grinding wheel spindle design, as well as a work spindle that allows conventional arbors to be installed to, and removed from, the front of the machine. All of these setup tasks are performed by the operator without tools. Non-productive time is further reduced through use of an automatic stock divider, mounted in close proximity to the work spindle, that operates simultaneously with wheel dressing.
Easily Automated for More Efficiency
As one would expect, SEW Eurodrive makes extensive use of automation. Robotic load/unload is used on 90 percent of the gear cutting machines and was easy to integrate on the 280G.
“Our studies show that manual load/unload is, at best, about 72 percent efficient, which means a machine will be waiting a lot,” Chandler said. “On the 280G, we use the robot to not only load and unload the machine, but also to hold the part for cleaning and pick and place the part at laser etching and palletizing.”
Automating Cutter Build
Perhaps the only productivity stone left unturned at the Lyman plant, until recently, was in the tool room, where as many as 25 cutter systems are built every three-shift day to meet the needs of 12 bevel gear cutting machines. True, tool room operators make good use of two highly productive Gleason BPG Blade Grinding Machines and a GBX Blade Inspection System to quickly and efficiently sharpen and inspect all the carbide stick blades used in these Gleason Pentac or older Gleason Tri-Ac face hobbing cutter systems. But much of the operators’ time was spent building, truing, and inspecting the cutter heads, a process that, according to Chandler, took upwards of 90 minutes per head and could result in costly blade misalignments and blade chipping despite the expertise of the technicians. So, it’s not surprising that, 18 months ago, Chandler took advantage of the opportunity to make his tool room the first beta site for Gleason’s new 500CB Cutter Build Machine.
“It’s inevitable that building, truing and inspecting cutter heads manually will result in the occasional blade misalignment, but even one is too many,” Chandler said. “This can cause a chipped blade downstream, and drastically reducing tool life as a result. Now, with the Gleason 500CB, all of those manual steps are performed automatically and with greater precision and repeatability by the machine. A process that once took 1½ hours now can be done in 30 minutes or less, and we’re no longer worried about misalignments and chipping blades. Plus, we’ve freed up our tool room people so they can be productive while the 500CB is doing its thing.”
Less Work, Better Results
The new Gleason 500CB Cutter Build Inspection Machine is the first of its kind to fully automate most of the critical steps in the cutter build and truing process. Its predecessor, the Gleason CB machine has, for years, been a solid workhorse in tool rooms worldwide and succeeded in lifting some of the burden from the operator’s shoulders by automating a few of the critical steps in the build sequence. But the 500CB goes much further than the original CB.
Now, after cutter build data is input, all the operator does is load the cutter head, position the build carriage, and load the blades into their respective slots. Next step? Press GO and walk away, with 30 minutes or so of time now available for other tasks. Now, all the other steps that have taken so much time and been so dependent on the operator and his expertise are performed automatically by the 500CB. Blades are positioned in their slots, clamp screws precision-torqued, and blade axial and radial position measured. As this process unfolds, the 500CB actually learns from the measurement feedback it receives, and loosens, tightens, and measures blades again as needed — just as the technician would do — until blades are trued to their optimum radial and axial position down to ±2 microns if needed. It’s an adaptive process, too, with the 500CB learning from every build to optimize future builds. Once the operator has loaded the cutter head, positioned the build carriage, and loaded the blades, he’s free to perform other tasks while the 500CB completes the build, truing, and inspection operations.
If the operator chooses to, he can view a screen on the machine’s CRT charting every blade’s position and runout in real time. And, at any point in the process, start to finish, the operator can use the intuitive operator interface with software “wizards” to guide him through every step of setup and operation.
According to Chandler, the 500CB’s impressive functionality isn’t limited to just a few cutter systems types or sizes either. It can be easily applied to both newer Pentac cutter systems and the older Tri-Ac cutter heads still in use, as well as the wide range of cutter head diameters running on SEW Eurodrive’s cutting machines, from as small as 70 mm (2.75”) to as large as 533 mm (21”).