Finally got a clean pull on a tricky core box pattern

I've been fighting with this one core box for a small gear housing for about a week. The draft was right, but the sand kept tearing on the back edge every single time, leaving a ragged finish. I tried ramming it softer, ramming it harder, even spraying the pattern with a light oil. Nothing worked. Yesterday, I remembered something my old foreman in Toledo said about 'letting the sand talk'. Instead of ramming the whole thing evenly, I packed the problem corner super light and just tapped it with my fingers. Then I rammed the rest normally. When I pulled the box, that corner came out perfect. It was like the sand just needed a little room to move. Has anyone else had a spot that needs a totally different packing method than the rest of the mold?

2 comments

2 Comments

adam_thomas3d ago

My old foreman in Milwaukee swore by uniform ramming, but your Toledo trick just proved him wrong.

miles_campbell393d ago

My first year in the foundry, I was so sure you had to ram everything like you were mad at it. I ruined a perfect pattern for a simple flange three times before the shop lead came over, sighed, and just wiggled his fingers into the sand around the edges. Pulled clean as a whistle. Felt like a total clown. Sometimes the obvious trick is the one you fight the hardest.