An easy cell

Three companies take the hassle out of wheel production.

Three companies take the hassle out of wheel production.

Wheel manufacturers can purchase, from a single source, an integrated wheel cell that combines two Okuma lathes, a Chiron drilling center, and a robot from Fanuc Robotics.

Chiron's WM 05 CNC drilling machine finishes the front and rear sides of a wheel in one chucking. Its indexing table, which swivels 360°, turns at 27 rpm.

To minimize chuck clamping, the Okuma LAW-V24's automated handling unit retracts immediately after loading a workpiece on the chuck.

The LAW-V24 vertical lathe has two V6 turrets, each holding six tools.


Sure wheel manufacturers can build their own cells by buying separate lathes, drilling machines, and robots. But why should they if an integrated package is faster and more productive, say Okuma America, Chiron America, and Fanuc Robotics. The three companies have pooled resources, developing a cell that turns out an aluminum wheel in as little as 53 sec. The cell combines two lathes from the Charlotte-based Okuma America Corp., a drilling center made by Chiron America Inc., also of Charlotte, and a robot from Fanuc Robotics North America Inc., Rochester Hills, Mich. As the lead company, Okuma oversees cell integration and coordinates sales, service, and support.

Integrating these systems, says Peter Hazle-hurst, vice president/general manager for Okuma's West Coast Technology Center in Torrance, Calif., gives end users 98% uptime, in an industry where 95% is considered pretty good. And using standard machines keeps the cost of the package down.

End users get other benefits as well. "Our customers send their wheels to our facility, and we program the cell," comments Hazlehurst. "We'll do all the work up front, run the wheels through, and, for the most part, increase productivity, depending on wheel style, by 25% to 60%."

Productivity and quality are keys to any manufacturing operation, but especially in competitive wheel production. Shops are making bigger and brighter wheels faster and cleaner than ever before. But difficulties arise when dealing with numerous wheel styles produced in ever-smaller batches and large wheels that require extensive material removal. In addition, machining must compensate for casting variances when the amount of excess material, as well as where it is located on the casting, varies from wheel to wheel.

The wheel cell handles all these challenges, says David E. Potter, Fanuc Robotics' general manager, North American distribution, through careful coordination between the machine tools, the robot, and the control system. "We maximize cell productivity, uptime, and effectiveness by synchronizing machining operations." This ensures that no machine sits idle, explains Robert J. Pernsteiner, Chiron's senior vice president and general manager.

All three companies worked hand-in-hand to shave cycle times. For example, his company changed its machine doors to facilitate load/unload. Then the lathe became the longest operation. So Okuma made revisions, changing from single to double doors and speeding chuck actuation. Fanuc altered processing within the control to optimize operations.

At work in the cell
A wheel casting enters the production cell on an inbound conveyor, of which there are two types: manual or automated. With the manual system, an operator places the casting on the conveyor in a specific orientation. The automated system, on the other hand, uses vision and measurement systems to check both wheel style and positioning.

After gaging is complete, the robot moves the wheel from the inbound conveyor to the first-operation lathe in a preset position. For a basic cell, an S430-iF robot sports a special gripper that holds 15 to 20-in. wheels in a stable and accurate position. Besides picking and placing wheels, the robot coordinates communications within the cell through its control system.

The first-op lathe, an Okuma LAW-2S, turns the inboard side of the wheel. The 4-axis system, which is customized for wheel production, features an airblow system that blows off chips and a Mayfran ConCep 2000 chip-conveyor coolant system that removes metal fines.

"Chip control is the single largest issue in the industry," says Hazlehurst. "When chips get in the coolant, they damage ballscrews and spindle bearings and shorten tool life. And chip buildup in the machine wears turrets and way covers and degrades surface finishes."

Once machining the inboard side of the wheel is complete, the robot removes the workpiece, transferring it to the Chiron CNC machine, which drills lug and valve-stem holes.

Wheel cells are configured with either a Chiron WM 05, which drills up to 20-in. wheels, or a WM 08 for larger wheels. Both the WM 05 and the WM 08 produce a 20-in. wheel, notes Hazlehurst. "Which one to use depends on the amount of work you're doing. And that's where we help the end user decide."

According to Chiron, its machines have the fastest chip-to-chip time in the industry, as low as 1.5 sec, and toolchange times as fast as 0.5 sec. Fixturing rotates 360°, letting users finish front and rear sides of a wheel in one chucking. The machines also have Renishaw probes that measure wheel centerline and pilot bore size and software that compensates for lug-hole radial and linear position.

Upon completion of the drilling operations, the robot retrieves the wheel and passes it to the second-operation lathe, either an LAW-2S or LAW-F machine, which turns the street side of the wheel. While many wheel styles only need a 2-axis machine for the second operation, end users often prefer the flexibility of a 4-axis machine.

Finally, the robot removes the finished wheel, placing it onto the outbound conveyor. It then tends to other wheels in the cell.

A bigger and brighter future
In just the last two years, the average diameter of an aftermarket wheel has ballooned from 17 to 20 in., driving the development of beefier machine tools. Superfinishing has also made inroads, offering an alternative to the costly, and environmentally hazardous, chroming process. To accommodate these trends, Okuma is offering an LAW-V24 vertical lathe that handles 15 to 24 1 /2-in.-diameter wheels and a superfinishing machine that provides mirror finishes.

The LAW-V24 has a box-type base and column for rigidity and thermally balanced base structure and pre-tensioned ballscrews that en-sure accurate positioning and movement. The machine's vertical structure exploits gravity — for instance, firmly fixing a workpiece to the chuck by its own weight. The machine is available as part of the wheel cell or as a standalone.

While the superfinishing machine is currently sold only as a standalone, Okuma has quoted it as part of its wheel cell. "Superfinishing would be used on the second operation only," says Hazle-hurst. "But two superfinishing machines may be needed to balance the cell."

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