. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . CAsting innOVAtiOns
terrain and vegetable debris make abrasion-resistant material important. Unfortunately, the fabricated drive wheel assemblies on the company’s 30,000-lb. drive train equipment were wearing out too quickly, so the company sought out a metalcaster to improve the part life and reduce cost. Craft Pattern & Mold, Maple Plain,
V
Minn., had worked with Valley Fab- rication before on other agricultural equipment parts. The pattern and prototyping shop suggested replac- ing the mild steel used in the original fabrication with austempered ductile iron (ADI), which is a more abrasion- resistant material. “I didn’t have much experience
with ADI,” said Peter Degroot, Valley Fabrication’s engineer on the project. “But there has been a consider- able difference in the wear of the wheels—a factor of two or maybe more in length of service.” At first, Craft Pattern cast the outer portion of the wheel, where
45-Piece Conversion to Single Casting Doubles Service Life
alley Fabrication, Salinas, Calif., builds a variety of agricultural harvesters that operate in conditions where muddy soil, rough
Valley Fabrication uses cast drive wheels on harvesting equipment for spinach, leafy romaine lettuce and celery.
the wear-resistance was needed, and bolted that onto a welded center sprocket. After the new design was in production for a year, Valley Fab- rication returned to Craft Pattern to produce the entire wheel as a casting in order to reduce the cost. With the directive to drive down the
price, the metalcaster worked to stream- line its nobake sand casting process. “Normally, we would gate on the
outside,” said Tony Cremers, president of Craft Pattern. “For this part we gated on the center hub and fed through a thinner section. This reduced the amount of sand we needed on the outside, making the cost of the casting more affordable.” Originally, the outside diameter
of the wheel was machined, but Craft Pattern was able to achieve tight enough tolerances via casting to eliminate that step. Finishing processes were reserved for machin- ing the center hub and drilling in bolt holes. “With each design step, we were
able to eliminate some type of cost,” Cremers said. The final single-piece casting design
for the drive wheel—converted from a 45-piece weldment—yielded a net savings of 30%. “To our end-user, there’s a double
savings,” Degroot pointed out. “For a slight savings in price, he gets twice the life.”
The 280-lb. cast drive wheels serve as the main drive component for a track-driven pro- duce harvesting machine.
July/August 2010
Visit
www.craftpattern.com for more information.
MetAl CAsting Design & PurChAsing 47
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