CASTING INNOVATIONS
CADI Knife Outperforms Steel Fabrication Yetter Farm Equipment, Colches-
ter, Illinois, was having issues with its fertilizer knife on its Magnum Coulter for applying fertilizer at high speeds. T e multiple-piece steel part was time-consuming to fabricate and prone to dimensional issues and premature wear. Several other com- ponents were welded to the knife that also wore prematurely and made for multiple part numbers. T e complete knife assembly was expensive to re- place and resulted in user downtime. To solve the problems, Yetter
worked with Lethbridge Iron Works Co., Lethbridge, Alberta, Canada, to convert the component to a casting. T e initial design stage included prototyp- ing three diff erent cast materials, 27% high chome iron, austempered ductile iron (ADI) grade 5 and fi nally carbidic austempered ductile iron (CADI). Ultimately, CADI was chosen for its
superior abrasion and impact resistance. CADI increased the impact resistance over the chrome iron and had better wearability than the ADI. T e new 7.5-lb. knife design also incorporated better protection for the anhydrous am- monia tubes and beavertail, which were subcomponents prone to wear. T e fertilizer knife is attached to the coulter disc to ensure it keeps the coulter blade free of residue and the fertilizer delivery tubes from wear. T e unit creates a 4-in. trench in the soil to apply the fertilizer and then shatters the trench cavity’s hard side walls to close the trench quickly. To create the single component,
Lethbridge Iron Works used two cores. A shell core was used for the mounting ears and holes to keep the ears parallel to each other for assembly and superior dimensional stability. T e second core created the cavity for the
tube delivery, which also incorporates a mounting hole for the beavertail. T e square mounting hole for the tube as- sembly was incorporated in the green sand mold to eliminate any machin- ing requirements. Parting lines were robotically ground with a diamond coated wheel to achieve the desired surface fi nish and dimensional control. T e conversion to a casting design
resulted in a 60% cost savings for Yetter, along with better dimensional control and cosmetics. In addition, inventory logistics were simplifi ed because the Magnum coulter units will have the same knife. Order ac- curacy has increased due to all units having the same part number, and assembly time is more effi cient. The end customer has greater flexibility to change forms of fertilizer, and the time and cost to replace a broken part has been reduced.
The cast carbidic austempered ductile iron fertilizer knife (show as right and left hand versions) represents a 60% cost savings for the customer.
August 2016 MODERN CASTING | 47
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