'Wheel Service' Relies on Imaging Technology

John Lewis, Cognex Corp.

Image-based bar-code reader helps NASCAR race teams feel more secure on their wheels.

NASCAR teams go through a lot of wheels. A single team typically owns about 260 wheels, consisting of both single- and double-stem versions of the 15-in. steel wheels NASCAR requires, according to Champion Tire and Wheel of Charlotte, N.C. Keeping track of them – storing them, transporting them and making sure the right ones get to the right races – is so involved that the teams contract “wheel service” work out to companies such as Champion.

“Carrying wheels is a major source of wear and tear on the teams’ race haulers,” said Todd Carpenter, the company’s general manager, who explained that teams use about 60 wheels per car per race. “Also, if the teams handle their own wheels, they need space to store them when they aren’t racing, and they have to handle the tire mounting and dismounting. It’s clearly advantageous to have someone else take care of these things so they can focus on racing.”

Besides transporting bare wheels to the racetracks, where the tires are mounted by Goodyear, Champion hauls the mounted assemblies back to Charlotte, where the used tires are dismounted and sent to recycling. Then the wheels are cleaned, restocked, reindexed and reshipped to the next racetrack.

No two wheels have bar codes or labels in exactly the same place. Images courtesy of Champion Tire and Wheel.

Champion has painted each team’s ID on its wheels, and the company tracks them in a computer system, into which the teams can log to see the status of their wheels as well as which are going to which races. Approximately 20,000 wheels reside in Champion’s climate-controlled, secure facility. A fleet of more than 30 semitrailer rigs travels 60,000 miles per truck per year to haul wheels to and from the tracks.

Image-based automation

Every day, some 1000 race car wheels move through the automated facility from a truck trailer back into storage after a race. Each bar-coded wheel moves along a conveyor line through a variety of inspection stations before it reaches its storage spot. Champion previously used a laser scanner to read bar codes, but with that system, an average of 200 wheels a day would be kicked out to a manual inspection line because their bar codes could not be read. The operators typically would try to run those wheels through the line a number of times to see if they could get the scanner to read; when that didn’t work, someone had to use a scan gun to manually read those codes. This took an extra 20 to 30 minutes per day, and the scan gun data didn’t get entered into the computer system. Also, those wheels missed the lug hole check.

Wheels move along the conveyor line for inspection at Champion Tire and Wheel in North Carolina. Moving the wheels on a conveyor system also reduces the risk of damage.

With the old system, the laser scanner was positioned on the conveyor line after the tires were dismounted and the wheels were washed, just before they reached the lug-hole check station. The scanner’s 80 percent read rate was in large part due to the heat and a duty cycle that caused the bar codes to wear out and become harder to read.

The image-based bar-code reader Champion used to replace the laser scanner was the Cognex DataMan 302L, which can handle bar-code quality degradation for a read rate at Champion of 97 percent, 17 percentage points higher than that of the laser scanner. The reader is a fixed-mount device with a high-resolution (1280 × 1024) sensor for reading very small codes in a large field of view as well as codes placed on small components.

A Cognex DataMan 302L reads the bar code on a wheel. The system has 97 percent accuracy, compared with Champion’s former laser-scanning system, which offered 80 percent.

The system has eliminated time spent manually capturing bar codes, and allows all wheels to go through all inspection stations and get tracked by the company’s computer system. “It helps us ensure that every wheel we send to a race delivers the performance the teams expect,” Carpenter said.

In addition, the image-based system offers maximum depth-of-field flexibility because it uses a liquid-lens module employing two iso-density liquids: Oil is an insulator, and water is a conductor. Varying the voltage across the liquid-liquid interface leads to a change of curvature, which in turn changes the focal length of the installed optical lens. For Champion, this means that the code stays in focus even when the distance from the camera to the code is changing – because the bar codes can be located anywhere on a given wheel. The liquid lens also is rugged (no moving parts) and compact, and it has fast response times, good optical quality and low power consumption.

The end result? Only 30 wheels need special handling each day, compared with the 200 that were kicked out to manual inspection under the laser-scanner system. The 3 percent of bar codes that are unreadable now are caused by extreme damage. “We replace the labels now if they can’t be read by the DataMan,” Carpenter said. Operators no longer need to try over and over to get kicked-out wheels through the scanner. “There’s less frustration for the operators now,” Carpenter said.

Every wheel Champion handles is bar-coded and scanned every time it moves in and out of its facility, creating a complete history of that wheel.

Engineering success

Champion built its business on understanding what race teams need, and uses its key players’ background in engineering to handle wheels in a way that optimizes performance.

“We try and look at what we do from a crew chief’s perspective, and ask ourselves how we would want our wheels and tires handled if we were them,” Carpenter said. “Because we’re engineers, we have automated our approach, with the main objective being consistent and predictable wheel performance.”

Handling does significantly affect performance. So, for example, rather than bouncing the wheels or stacking them, Champion uses a conveyor system because that is less likely to cause damage. Also, every wheel is bar-coded and scanned every time it moves in or out of its facility, which creates a complete travel history of that wheel. And as each wheel comes back from a race, it undergoes a thorough inspection process to check the roundness of the wheels and the lug holes as well as lateral and radial runout.

Wheels move along the conveyor line for inspection.

This inspection process helps ensure that damaged wheels are not returned to stock. “If something should happen to cause a wheel to go out of spec,” Carpenter said, “our bar-code systems won’t allow for that wheel to ever be checked out of our facility.”

Meet the author

John Lewis is market development manager at Cognex Corp. in Natick, Mass.; email: pr@cognex.com.