Metaldyne machines knuckles for Ford's Panther platform on a new highly computerized line at its Edon, Ohio, plant. To reduce the possibility of positioning errors, each part is chucked only once and then sent through all necessary machining operations.
Perhaps it's a sign of the growing interconnectedness of the auto industry that Metaldyne (Plymouth, MI), which makes chassis, engine and transmission parts, holds interior supplier Lear Corp. (Southfield, MI) up as a business model to emulate. Lear has had great success in transforming itself from a component supplier to a one-stop-shop for the design, engineering and manufacturing of interior modules. Metaldyne would like to follow suit when it comes to front and rear corner modules. "We want to design and manufacture as much of the corner as possible, " says Pete Ravenna, product engineering supervisor at Metaldyne's chassis group.
Currently, most of Metaldyne's chassis business, which accounted for about $165 million in sales in 2001, is in components, but its module business is growing. And the company has been awarded new programs that will bring in at least $124 million more in chassis sales through 2006. Metaldyne officials think that the tenor of the times is particularly advantageous for their strategy, since automakers are increasingly more willing to outsource large chunks of a given vehicle and the engineering that goes with it. However, in addition to proving its engineering chops, Metaldyne must continue to hone its manufacturing prowess to expand its module business. And that's where its plant in Edon, Ohio, comes in.
At 100,000ft2, Edon is not a massive facility, but it packs quite a productive punch. The plant floor is chockablock with vertical and horizontal machining centers, CNC lathes, and multi-spindle chuckers that process knuckles, wheel hubs and driveline yokes and flanges. Annually, it churns out about 2.4 million yokes and 1.2 million knuckle and hub assemblies, also known as "mini-corners." Of those assemblies, 550,000 are destined for the Ford Escape; 450,000 go to Ford's Panther platform, which includes the Town Car, Crown Victoria and Marauder; and the remainder end up on Dodge Ram trucks.
Surfaces are regularly machined to tolerances measured in tens of microns at Edon, but some products require even greater precision. Providing that precision without breaking the bank is something that the people at Edon think puts them ahead of the competition. Case in point: their approach to finish-turning the hub flanges on the Escape module.
Variations in the surface of the hub flange of just a few microns can lead to brake noise, vibration, steering wheel judder and uneven stopping. Turning the flanges prior to assembly–a common industry practice–doesn't always solve the problem because of the stack tolerances that accumulate during assembly. So Metaldyne came up with a patented way of turning the flange after the unit is fully assembled. The process precisely measures the surfaces to be finished with a probe, and then applies a load to the assembly similar to what it will experience on the road. The turning process itself removes so little metal that according to engineering manager Dave Hinske, "Very few chips are created. Most of the metal just burns off." By utilizing this process, the company says it has reduced surface variation from 50 to 20 microns–well below the rest of the industry–while achieving lower parts costs and reducing warranty claims.
For machining Panther platform knuckles Edon has taken a decidedly high-tech approach. Early in 2002, it began part production on a state-of-the-art six-machine line co-developed with Italian machine tool maker MCM S.p.a.(Vilgolzone, Italy). Each of the six machines are capable of performing all of the necessary machining processes on each knuckle including milling, drilling, reaming and cutting all ball joint angles and tapers. The highly automated line monitors each tool via re-programmable chips embedded in the toolholder, which record tool type and size and measure tool life. The chips prohibit the wrong tool from being installed, and ensure that an operation will not be performed if a tool is out of balance (resulting in a scrap rate of only 0.05%). Further, the use of highly precise shrink-fit tools has eliminated some secondary processes and increased tool life by 30% to 40%. The line is also equipped with a video inspection station that uses 10 cameras to take snapshots of pre-determined areas of each knuckle and compare the machined surfaces with a perfect image stored in memory. Additionally, two parts per fixture per shift are automatically routed out of the main line flow for manual measurement and inspection.
Cory Ryner, a manufacturing engineer at Edon who helped launch the new line, says that the line has not only exceeded expectations for precision, but has proven to be remarkably robust, earning a 99% rating in Ford's stringent "overall equipment effectiveness" measurements. And those are just the kind of numbers Metaldyne will need to impress automakers and fulfill its chassis strategy of becoming masters of the corner.