Dana Corporation
Manufactures drive shaft components for the big three auto makers. At Northfield, we’re proud of the part we play in helping them solve their production challenges.
Challenge – Getting a grip on the situation
Dana needed a chuck to be mounted on a balancing machine holding a drive shaft on one end, gripping the component called a slip yoke. These drive shafts, for the Daimler Chrysler Corporation, were complicated by several factors.
- The shape of the part – long and thin –
- The grip force required to hold a 5ft. long drive shaft
- The accuracy 1/10,000 T.I.R.
- The speed – as high as 8,000 rpm – during the balancing process.
Normally, balancing operations are performed at only 900 rpm, but Dana needs to balance this part at simulated road conditions. Since the shaft will deflect (bend) at high speeds, this is the state they want it balanced at. For production cars, drive shafts typically rotate up to 3,000 to 5,500 rpm. This component, used in Daimler Chrysler’s high-performance stock racing cars hit 200 mph with their drive shafts rotating at 8,000 rpm.
Solution – Sometimes, two chucks are better than one.
To solve the problem, Northfield engineers decided to use a diaphragm chuck, rather than a sliding jaw chuck. Before making the final decision we conducted several tests using solid models on our CAD systems. This ensured that our diaphragm chuck wouldn’t lose grip force at these high rpms.
Our solution consists of two separate diaphragm chucks, with two separate sets of jaws, mounted one in front of the other. This accommodates the long, thin shape of the part. With one set of jaws gripping near the front of the piece and the other gripping near the rear.
Results
The result is accuracy of a 1/10,000 T.I.R. and repeatability to 50 millionths of an inch and extreme rigidity.
The chuck also uses a male spline driver mounted in the center of the chuck. This helps drive the shaft on start up and stop, and guide the shaft into the jaws during loading. These drivers are .002in. undersize of the internal spline and must not influence the centering of jaws. The spline driver is a gauge quality piece of tooling supplied by Michigan Spline Gauge Co.. Providing a concentricity of less than 50 millionths with the chuck.
In Dana’s production car area, the chuck runs the same component. In the stock car application it is used to run a several different components. Parts and tooling can be switched and still maintain an accuracy of less than a 1/10,000 T.I.R.
Finally…
This chuck was designed to be air opened with a self-contained clamping system to meet Dana’s safety standards. It uses the spring pressure of the diaphragms for clamping that will hold the part in place if air pressure and power are lost during the balancing operation.