Forming Wheels - By Spinning
At Kawasaki, ATV wheels are produced in house - and even for other companies. While other companies may roll formtheir wheels, they've found spinning to be advantageous to meet the requirements of their production system.
They’re awfully busy at Kawasaki Motors Manufacturing Corp. USA (Lincoln, NE). Not only do they produce all-terrain vehicles (ATVs) at their plant, but they also produce jet skis, motorcycles, utility vehicles, robots, and light rail cars. And in its manufacturing of the ATVs, of which they’ll be making some 140,000 this year, they produce their own wheels. Not only do they produce wheels for their own products, but they produce them for other manufacturers, as well. Which puts their wheel production on the order of 1.6-million. It’s worth noting that they once outsourced the wheel production. But in order to reduce costs and to control their just-in-time production, they decided it was better to do the job themselves.
Given the variety of products produced at the plant, flexibility is a must, because mixed-model production is a way of life there. “A lot of manufacturers do batch production, where they’ll run a large batch of a single ATV model, and then change over and run a batch of another model,” according to Kent Grothe, engineering supervisor at Kawasaki. “We find that to be inefficient. But by running different models down the same assembly line in small quantities, we can level our schedule throughout the year and stabilize our manpower requirements so we aren’t caught in the cycle of hiring and laying people off.” Another thing that they do that some other companies don’t is to spin form the wheels. Grothe said that while auto companies often roll form wheels, spin forming “allows us to stay true to KPS principles”—that’s “Kawasaki Production System.” “If necessary, we can run as few as 500 wheels on a single setup, which is unheard of for a roll-forming line. They have to setup for several thousand to be efficient.” The spinning machines are custom-built for Kawasaki.
To produce the wheel blanks, Kawasaki installed a stamping press line that employs a hydraulic press from AP&T (Monroe, NC) and coil handling equipment from Coe Press Equipment (Sterling Heights, MI). “Before the AP&T/Coe line,” Grothe said, “we were buying all of our blanks outside. Every rectangular blank used to make the wheel tube was handled by three vendors: a steel mill to make the master coil, a service center to slit the master into smaller coils, and a processing center to cut the slit coils to length. With the new line we have replaced one of these vendors with an in-house process—and as you take any of the middlemen out of the process, you cut the material costs significantly.” In addition to which, Grothe calculates that they’ll get payback on the equipment in two-years.
The lot sizes are generally in the 2,000- to 3,000-piece range. Five hundred pieces is the lower limit because otherwise the changeover would be excessive. Wheel blanks vary in width from 7.5 in. to 12 in. and in length from 26 in. to 40 in. For steel wheels, the outside rim material is made from 13-, 14- or 16-gage material and the center discs are made from 6- to 12-gage material.
After blanking, the blank is rolled into a circle, and the two ends are flash butt-welded. The rim is spun in a CNC-controlled flow-forming operation to create the basic shape. Then, a second spinning operation forms the rim’s bead hump, bead seat, and outer curl. An automated MIG-welding system attaches the stamped center disk to the rim. There’s a leak test, visual inspection, then painting and shipping.