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Our shift switched to a new sand mix six weeks ago and I'm seeing way more core wash
Honestly, the binder ratio changed from 1.5% to 2% to 'improve green strength' according to the supplier sheet. After three full runs, the drags are coming out with way more surface defects, especially on the complex gear housings. Has anyone else had this happen after a formula tweak from corporate?
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rowanhernandez5mo ago
Yeah, we had to fight that exact change last year. Ended up adding more venting to the core boxes and backing the binder down to like 1.8% as a compromise. The green strength spec was too high for the geometry.
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umar493mo ago
@cole549 nailed it, higher binder always messes with the venting on tight geometry.
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cole5495mo ago
Tbh, that binder increase is probably the whole problem. More binder can make the sand less breathable during the pour. I've seen that exact change turn a good mix into a core wash nightmare, especially on complex parts. You might need to push back on that spec or tweak the venting.
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