Casting Call

CASTING CALL

YAMAHA UNVEILED A NEW casting technology earlier this year, Controlled Fill Aluminum Die-Casting.

Big deal, right? Consider this: Yamaha claims the new process can result in a 30 percent weight reduction in cast components, and up to a 80 percent reduction in parts count by allowing what are now assemblies to be produced as a single component. Let’s see, 30 percent off of a YZF-R1 is about 120 pounds. Does a 300-pound R1 get your attention?

In conventional die-casting, aluminum is injected under high pressure into a metal die. Unfortunately, air comes in with the aluminum, weakening cast parts by creating porositythat is, little air bubbles, resulting in areas that say, “please tear on the dotted line.” Also, the aluminum cools rapidly as it enters the mold, and a balance has to be struck between injection speed, air entrainment and wall thickness on the part. Inject too slowly, and very thin walls are likely to harden too quickly, thus not allowing the aluminum to completely fill the mold.

Accordingly, improvements in die-casting have been going on for years. To minimize porosity, several things have been tried, including filling the die with oxygen-which reacts with the incoming metal, leaving a light dispersal of aluminum oxides rather than bubbles-and pulling a partial vacuum inside the mold. Yamaha’s process takes this one step farther, with better sealing on te mold and a six-fold improvement in the vacuum level In addition, engineers use a ter perature-controlled die, and inject the aluminum at five times the normal rate.

The result, according to Yamaha, is the ability to make castings as big as 3 or 4 feet long with a minimum wall thickness of 1.5mm, or 0.06-inch. That means for engine cases or a frame structure, for instance, material can be placed only where it’s needed for strength, instead of being added simply to make a casting possible.

Is CF die-casting a revolution? Not quite, and a 30 percent weight reduction isn’t going to be universal. That’s almost certainly an extreme case. But it is another step down a road that’s going to lead to ever-lighter and betterperforming motorcycles.

-Steve Anderson