Excerpt from the October 2020 Modern Casting Article by Travis Hepfner.
An AFS Green Sand Division revealed foundries are handling new sand additions differently from what has historically been standard. Here, one foundry shows why and how it eliminated new sand additions altogether.A recent survey by the AFS Green Sand Division asking foundries about their new sand addition practices revealed what was once considered a common practice was not so definitive for every plant. While 300 lbs. of new sand per 1 ton of iron poured has been an industry baseline, discussions with many sand foundries showed that for some, the practice of adding new sand had been eschewed for using their core sand as “new” molding sand.
In the survey of 47 sand foundries, 10 were not adding new sand, other than the core sand input. One of those foundries was AFS Corporate Member Cadillac Casting. While presenting at the virtual 2020 Sand Casting and Additive Manufacturing Conference last month, Travis Hepfner, quality engineer at Cadillac Casting, shared the foundry’s path to eliminating new sand additions.
Cadillac Casting (Cadillac, Michigan) is a ductile iron foundry that runs high production volumes on its 32x32 horizontal molding line, consuming about 127 tons of sand per day. It uses two 100B batch mullers to feed sand to the cope and drag machines. A premixer feeds the majority of the bond to the sand before it enters the storage bin leading to the mullers.
Like most sand foundries, Cadillac Casting was adding new sand regularly to its system, but a key change to the product mix led the company to reconsider its process.
From the middle of 2018 into 2019, the iron foundry transitioned from high-volume, no-core knuckles (in quantities of millions per year) to high volumes of carrier castings, which required heavy cores weighing 30-40 lbs. each. This change in product mix meant a significant increase in core sand additions to the sand system. Cadillac Casting went from returning all the sand it could to maintain its levels while also adding new sand, to ending each day with a surplus of 10-20 gons of sand.
Rather than continue to throw out an abundance of sand each day, Cadillac Casting stopped adding new sand, relying solely on the core sand additions to maintain the appropriate level of sand in the system.
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