I'm having shrinkage problems pouring aluminum bronze, using 89 Cu - 11 AL mix. Is this a normal thing with it ? Any suggestions appreciated. Thanks, John ,,,,
???? yes aluminum Bronze has a higher shrinkage then Brass or bronze, so you will have to compensate, and/or design for the increased shrinkage... or change alloys , if you post a picture with an example of your issue perhaps we can help V/r HT1
I used the off set basin to sprue pour method and elevated the opposite end slightly. This the second try, first one was better but had a slight shrink where this had at about the same place at the ricasso.
That is the area to last freeze in your casting. Had to get metal somewhere and so it collapsed from the area of least outward pressure---the top of the casting. It is not as easy to explain the second small shrink on the lower surface. Looks like you will need a riser at the ricasso. (Learned a new term today, "Ricasso." Thanks you.) I would think the same is almost certain to hapen with 356 AL or cast iron. Denis
Hard to predict, but, a single riser at the top of the ricasso seems like it should be sufficient. Maybe placed right at the juncture of the handle and ricasso so that the base of the riser is easier to blend once the riser is cut off. How big? Maybe 2/3 the diameter of the ricasso and as high as wide with a flat or even concave top to promote collapse. (Note that both areas of collapse were in molded concave spots. Concavities definitely are the easiest areas to collapse. Metalostatic pressure is least on top surfaces. So, collapse occurs in concavities, if present, on top surfaces at the point of latest freeze.) Denis
I almost didn't post this but I thought like me there probably others here new to casting. So in the interest of safety, I decided it's better to learn from others mistakes rather than your own. I was working late in the shop and getting pretty tired, but I didn't want to call it a day yet. So I decided to ram up another mold for the dagger as mentioned in the previous posts. When mulling the sand I got it a bit wet but thought it should dry after about a day in the mold. Now the local adobe/sand I use will ram almost solid as a brick, not very porous at all and should have been allowed to dry longer, in fact I can re-use the drag pattern again. Anyway when I poured I got a steam flash, no problems, I was lucky. So, to the newbies like me probably not a good idea to do casting work when you're tired and keep your sand as dry as possible and still work satisfactorily. But I ain't gonna let it beat me,,,, pour # 5 next. To be continued ,,,,, And by the way Denis, it looks like your suggestion of the riser on the handle would have worked great,,,, Thanks,,
Thanks for posting the safety reminder about wet sand, such lessons are important for newbies like me. My kids would love your patterns, into that old school medieval thing. How is the BBQ molding bench working?
Thanks for the reply Tops. Good on your kids, it's an interesting period in history. The bench is working out great, no having to bend over at all, my old back is happy.
