Casting Bronze Box Shape in Green Sand

Mike, The cavity wall will need to have generally 1deg or better draft and be smooth, also sometimes if you ram it up too hard it actually grips the wall too much. It really is better to make a proper core. The other problem you may have is filling the thin wall. If you heat the metal up too much (in order to fill it) you may get hot tearing, not enough will cause misruns. Gating will be critical. I do this sort of thing every day. Good Luck Alan Black

This would be a good project for lost foam casting. This was my first:

What generally happens when raming up a mold with a large "greensand" type core such as a box would have is that once this cavity is filled and ramed, any further raming is often suffiicient to break the bond of the sand thats contained in the cavity to the sand that would be flush with the edge of the box, or as your raming the cavity it seperates..Its from trying to make the surounding greensand packed in the recess and from vibrations. All the pattern has to do is shift one little bit during the entire ramming process and it will make problems when you go to seperate the cope and drag. I would ram this up just like a bell.

I had the same problems with bells. I now take the pattern, and liberally dust the inside with parting dust, and ram the sand fiirmly inside the large cavity with a mallet or raming tool, and strike it off at the opening. I then ram up a drag, very firmly and strike it off. I take the ramed up bell (box) and place it with the struck off sand on the drag thats been ramed and struck off. I use a mallet to firmly embed this ramed piece at least 1/8 to 1/4 inch below the already struck off surface. Cope down to the bottom of the edge and slick the surounnding area well. Apply parting dust, place the cope on the drag and ram up the cope, firm but not as firm as the drag was. Apply greensand in the cope and ram it evenly and lightly all around, untio you get it buiot up to the cope top. Its best to ram a bit oon one end, then the other, then the side and then the other side, working from the pattern outwards evenly all around the pattern. Don't even try raming the sand along the edges of the cope very firmly. Thats where pressure is generated and this is also a cause of shifting the pattern off its already bedded in seat. Fo it sufficient to pack sand but not overly firm. I would open the mold with the drag pn the bottom, , draw the pattern, and clean up any areas, cut my gates runners and sprue, close mold.

I have at times bumped the pattern, and allowed the greensand core to become loose inside or that I could actually see it was getting loose, and then just pressed it back into the pattern before placing on the drag. That way I was sure it would remove from the pattern, but was sufficiently rammed and would not crumble on me.

I am assuming your pattern is smooth and has the proper draft inside and out. 1 deg is very small amount of draft especially for an item that deep into a mold, so you may want to increase it a bit, as it will take some skill to remove a pattern that deep with that amount of draft. Visit my website:

Roy's "ram-up core" approach sounds like it would work too with a thin walled pattern like this. I assume you were using parting dust. Looses cores like this can float in many situations. 1 degree is plenty if it has a smooth surface. Alan

Although not a replacement for plenty of draft, and a lot of parting compound, another technique is to use gaggers. A gagger is a piece of metal stuck into the sand (far enough from the cavity wall so it won't interfere with the pour) to support the sand at the junction of your green sand core and the rest of the mold.

It can be as simple as a nail stuck into the top of the core at an angle. Although I think I would weld a couple of washers on the ends of a piece of wire (washers perpendicular to the wire) and ram a couple of these in.

Paul K. Dickman

Took the tour of your shop. Thank you! I'm impressed and envious.

Wayne

I've done this before with aluminum:

What I did is ram the inside of the pattern full of sand as Roy mentions, then gouge out a groove in it to locate it on the drag. Slick it down, ram the cope, turn over, apply parting dust and ram drag, seperate. Core should be stuck in the pattern, which should be stuck in the cope. Mine always ends up tight so I pull out the pattern+core with needle nose pliers as gently as I can. After that, plenty of rapping will loose the core from the pattern, and it can then be placed on the drag. Shift it around a little to get it centered exactly over the groove. Cut sprue in cope, slick down and toss it on the drag.

Tim

jk