Workholding: Building chucks to hold wheels

Unless you’re stuck on the side of the road with a flat, you probably don’t give much thought to the tires on your car or the wheels on which they’re mounted. Yet automotive wheels are complex components. They require specially designed tooling and equipment, as well as extensive technical knowledge, to manufacture.

One requirement of precision wheel manufacturing is secure, accurate workholding. But Jay Duerr, president of LMC Workholding Inc., Logansport, Ind., said it goes much further than that. “The biggest requirement in this industry is good customer support.”

Duerr’s customers range from a small manufacturing facility that produces a couple of million wheels per year to a large-volume customer that rolls around 12 million wheels annually out of a single plant. “If they call because they just broke a chuck,” said Duerr of the latter, “you’d better have a new one ready for them in a few hours. You simply can’t shut down a production line running volumes like this.”

The first operation of wheel turning is one the most critical, and requires a delicate but firm grip. Image courtesy of LMC Workholding.

Another industry requirement is rigidity. That might seem easy to achieve in a wheel chuck measuring several feet across by simply adding more mass. However, Duerr pointed out that wheel manufacturers are increasingly sensitive to energy costs. They don’t want big, bulky chucks on their CNC lathes. “You can’t sacrifice rigidity, but power consumption is a huge portion of the manufacturing cost in this industry. That’s why wheel chucks must be strong but also relatively light.”

LMC’s lightweight-series chuck is an example. The largest grips wheels up to 24″ across (610mm) but weighs only 236 lbs. (107kg). Duerr said this chuck—like most wheel chucks—incorporates axial (Z-axis) clamping and radial centering technology and must be delicate enough to not distort thin-walled wheels.

“When you’re running a large chuck like this at 2,500 to 2,800 rpm, it creates some interesting harmonics and deflections that must be mitigated,” Duerr said. “This becomes even more challenging with everything being automated these days—[not to mention] the ever-changing OEM requirements. It’s an intensive process that must be tightly controlled.”

Flexibility is also important. If you walk through a new car dealership or aftermarket parts store, you’ll see that wheels are growing larger and more complex. Wheel manufacturers do not want to invest in new chucks with each passing model year. Therefore, they demand chucks that accommodate an array of wheel sizes and designs, but are still accurate, repeatable and—because wheel lot sizes are often in the 500- to 1,000-piece range—easy to change.