details DESIGN
Tractor Part Gains Strength Without Gaining Weight
JITEN SHAH, PRODUCT DEVELOPMENT & ANALYSIS, NAPERVILLE, ILLINOIS CASTING PROFILE
Cast Component: Engine bracket for John Deere 7R Series tractor.
Material: Gray iron. Weight: 29 lbs. Dimensions: 11 x 19 x 19 in.
Process: Vertically parted green sand. Application: Agriculture.
Corner radii and fillets provide smooth transitions for better aesthetics and lower stress concentration.
• In the casting process, all the appendages will have radii, as opposed to sharp edges, and all the junctions will have corner fillets for smoother transitions. Te overall effect is reduced stress concentration associated with sharp changes in the cross sections.
• Te automated vertically parted green sand mold process is suitable for coreless parts, where all the features have to be oriented such that the pattern can be drawn away from the tooling at the part- ing plane. Determining the parting plane is the first and most critical step at the beginning of the complex cast component design.
the potential for a high scrap rate, engineers at metalcasting supplier Waupaca Foundry Inc., Waupaca, Wis., proposed design changes to ensure efficient manufacturability. Te end result was a more robust, high quality casting that provides significant added value.
A
n engine bracket for John Deere features multiple attachments for better manufacturability, durability, lower scrap and overall reduced cost. Te original design for the John Deere 7R Series tractor had several characteristics that led to high scrap due to breakouts during casting shakeout and handling. To reduce
As-cast ribs provide strength and better structural stiffness.
• Ribs have to be oriented perpendicular to the parting plane wherever possible and given draft, especially with the green sand process, or else a core will be needed.
• Carefully designed ribs and appendages make structural casting components stron- ger and stiffer at lower component weight.
16 | METAL CASTING DESIGN & PURCHASING | Mar/Apr 2014
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