Spent 3 hours chasing a sand inclusion that was there the whole time

I pulled a casting yesterday that looked perfect on the outside, but after we cut the riser off there was this big sand inclusion right up against the core print. Simple fix would have been to check the core wash coverage before closing the mold, but I was in a rush to get it knocked out before lunch. Three hours of grinding and welding later it finally passed. Has anyone else had a defect hiding right in plain sight like that?

3 comments

3 Comments

pat_harris3d ago

the core wash coverage before closing the mold" - yeah that's always where it gets ya. I read somewhere that most sand inclusions happen right at the core print because the wash gets thin there when you're in a hurry. Same thing bit me last month on a big ductile iron valve body. Had to grind out a spot the size of a quarter that was hiding right where the core met the mold face. Now I always give that area an extra squirt of wash before closing, even if it means my lunch gets cold.

taylor.brooke3d agoMost Upvoted

See I gotta push back on that a little. Extra wash can actually trap gas if you lay it on too thick at the core prints, especially with ductile iron where the rapid carbon burnoff needs room to vent. Had a guy at my old shop go overboard on wash coverage and ended up with pinholes right where the gas couldn't escape, took us forever to figure out why. Maybe the real trick is hitting that spot with a controlled spray instead of piling it on, keeps the coverage even without blocking the vents.

jesse_smith103d ago

Ha, gotta love foundry problems where you can't win no matter what you do. You put on too little wash and get inclusions, you put on too much and get pinholes (classic rock and a hard place situation). Sounds like the only safe move is to quit cold turkey and take up knitting, but I hear those needles can cause blowholes too. Honestly though, I've had better luck just accepting that lunch is always gonna be cold anyway, so I just pack soup in a thermos and call it a day. At least then I can give that core print all the wash it wants without worrying about my sandwich getting stale.