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TIL my vent rod placement was making my cores weaker
I was pouring a set of small gear housings last Thursday, same way I've done for maybe two years. The scrap rate was always a bit high, like one in five would have a small void. My lead, Carl, watched me set up a box and just said, 'Your vent is pointing at the wall, not the air.' I moved it to aim straight up out of the sand, and the next five pours were all solid. Has anyone else had a simple fix like that for core blow?
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angela_knight37mo ago
Wendy131 is right about the straight shot, but you also have to watch the vent's path through the sand itself. If it goes through a damp spot or a patch with too much binder, it can seal itself shut from the inside with baked gunk. I had that happen once, the vent looked clear but the middle was plugged.
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wendy1317mo ago
Your vent is pointing at the wall" is the whole story right there. It's not just about having a vent, it's about giving the gas a clear, straight shot out. I've seen guys put a vent in but have it run parallel to the parting line for an inch before it turns up. That little pocket can trap enough gas to ruin a core. Always drill that sucker straight up and out, no turns until it's clear of the sand.
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matthew3947mo ago
What about the vent diameter though? I've found that even a straight vent can choke if it's too small for the core box size. A big core needs a fat vent, like at least 3/8 inch, or the gas just backs up.
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