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Can we talk about why everyone thinks shell molding is better than green sand for small runs?
After running 200 castings last month in Ohio I had to stop and rework 30 of them from the shell mold because the finish was too brittle, but my green sand setup on the same parts gave me zero scrap and I will never waste time on shell for short orders again, has anyone else dealt with that kind of failure rate?
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ellis.mia5mo ago
Tbh 30 out of 200 scrap is brutal. I'd call that a shell molding speedrun record for wasting time and money. Green sand might not look as pretty coming out but at least it doesn't fall apart in your hands like a bad biscuit.
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wesley_martin5mo ago
Idk man, you bring up a good point about shell mold thickness. I've seen guys push for a super thin shell to save on the resin and it always ends the same way, with parts cracking or the finish flaking off like old paint. Maybe it's just me but I'd rather have a green sand casting that needs a little grinding than a shell mold part that falls apart on the bench. And the whole "shell gives you better surface finish" thing doesn't mean much if you have to scrap every fifth part.
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gavinlopez5mo ago
Man, 15 percent scrap is rough. That's not a process issue, that's a full blown disaster (and not the fun kind). I gotta wonder if the shell mold was just too thin for those parts, or maybe the sand mix was off. Green sand might look like it came out of a mud puddle, but at least it holds together when you need it to. Honestly, sounds like shell molding got a little too big for its britches on that job.
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