Ive always just dumped my metal down into the mold. but now im seeing the bottom to top method. Pros? cons? Idk. ive got a bunch of stuff on my IG @Ferrisbeu
You can control fill rate and velocity and reduce turbulence through bottom filling. Go to any gating school and it will be what they teach you. That being said I will still pour some castings from the top. Depends on how clean I want them and how structurally sound they need to be. Bottom gives best results for both cases but sometimes is unnecessary and reduces yield. If you are getting good castings why change?
I get decent results. sometimes a bit rough finish near the pour point but nothing huge. Im not a technical caster. its mostly just stuff I give away.
You will get roughness at metal entry point of bottom fed as well if sand conditions are not right or you have too much head pressure with your gating design or your temp is too high. When we installed new machines with much taller molds we experienced quite a bit of pressure related defects and had to change the type of gating systems we were running and had to change some of the sand properties to accommodate the higher pressure that comes with taller molds. That being said it is easier to dump it into the top but depending on casting design you can get hideous results from doing so. Thin wall castings almost always have to be poured from the bottom or you will get a myriad of defects resulting from turbulence inside the casting.
