Yup. Should have tipped the molds. And should have repaired my pyrometer although I didn't want to go too hot with the metal anyway because these get used as-cast and I wanted a decent surface finish. I've cast this pattern several times before successfully and now that I think about it I've always tipped the mold toward the far corner. For reference the pattern is 12×12 inches 3/8 thick. Pete
This thing has kicked my butt one too many times. I think I've got it worked out. I just wasnt getting the metal in fast enough to reach the far corner whilst overcoming the friction of the surface. If both sides of the pattern were smooth the issue could probably have been overcome simply by tipping, but I increased the sprue size to 5/8 and made 4 smaller ingates per runner (total of 8) instead of 2 larger gates per runner. No tipping this time. Metal is of mixed cast and extruded from my "bastard" pile. Pete
Ah, I was wondering if anyone would catch that. In the course of troubleshooting my fill issue I checked into several sources to get myself back to some baseline configuration. For example I knew my size ratios had been cast to the wind, gate cope or gate drag, faceup or facedown, etc. I referenced Ammen's book and found his diagram in the gates&risers chapter as a basic configuration for a flat back plaque casting. The main thrust of the example was about utilizing the runner to carry debris past the gates during initial filling of the runner. The canting of the gates apparently should delay the entry of contaminated metal into the cavity so the runner can do its job (another case of me driving with my brakes on, the runners aren't really long enough to be of maximum benefit), but the idea that the metal would be more forcefully guided into the mold on the rebound was appealing to me. I also made the gates furthest from the sprue larger that I ordinarily would, knowing that the furthest gates let in a majority of the metal -all things being equal- and since the furthest reaches of mold had been the problematic area, more metal going in there was okay with me. Pete
The bounce back will push the metal into the last two ingates immediately. The first couple of ingates are probably not doing anything. If you want an even fill make the first ingate the largest and the last the smallest. I would make one long thin...very thin...ingate per side....better surface..better cleaning..less sand wash and easier to degate.
When you say long, do you mean the entire length of the mold cavity? In this case that would be 12”. When you say thin, are you thinking 1/8”? Or less? The edge of the mold is 1/4” thick. What you’re describing is what I understand to be a knife gate. Should it’s end profile be rectangular or should it taper from the runner to the mold? For example, 3/16” at the runner, then tapered to 1/8” at the mold? The runners are currently set at 1/2” away from the pattern. Pete
Just based off of what I do know and not really knowing your whole setup I would recommend an ingate at .040" thick and the longer the better...minimum would be somewhere around seven inches...bear in mind I do not know the weight or height inside the mold and those are factors. So if you want to be sure you make it solid go with 10 to 12 inches of ingate and you can decrease a little at a time to get your very minimum to reduce clean up. I think you would be fine at seven on length. I would not taper the ingate. Make it flat all the way across and move the runner to about within 3/16" of the casting. The closer runner will keep more heat in the ingate and will lessen the inertia created by the length of the ingate which reduces jetting.
