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TIL a trick for getting cleaner cores with less scrap
We kept having issues with core blowouts on our medium sized gray iron castings, maybe one in ten would come out with a bad spot. Tried adjusting the sand mix, the binder, nothing really fixed it. Then our old foreman, who retired last year, stopped by and said to try pre-heating the core boxes just a bit before you shoot them. Not a lot, just enough that you can't hold your hand on it for more than a few seconds. We hooked up a simple heat gun to warm the aluminum boxes for about 90 seconds before each cycle. Scrap rate on that job line dropped to maybe one in fifty almost right away. The heat seems to help the sand skin set faster against the metal. Anyone else tried something like this on their core shooters?
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rileygarcia2mo ago
We had a similar problem with thin wall ductile iron parts. The pre-heat trick is solid, but we found the timing really matters. If the box got too hot, like over 160F, the binder would start to cook right in the shooter head and cause a whole different kind of jam. It took a week of messing with the heat gun timer to find that sweet spot around 140.
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shane_hayes1mo ago
One of the old-timers I worked with years ago mentioned something similar about heat soaking into the box over time. He said if you run a bunch of shots back to back the box can heat up way more than you expect from the gun alone. We never tested it ourselves but his trick was to shoot a few parts then let the box sit for a couple minutes to let the heat even out. Sounds like your 140 sweet spot makes sense if the binder is that sensitive. Might be worth checking if your box temp creeps up after the first few cycles too.
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bennett.harper2mo ago
Yeah I always thought more heat was better for flow. Your point about the binder cooking at 160F makes total sense now. We had a shooter head jam last month and I bet that was the cause. Gonna check our box temp tomorrow because we just crank the gun and hope for the best. You might have just saved me a huge headache.
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