Flask advice

Bad and potentially dangerous. When starting out, people use 5 gal plastic buckets all the time. You can get by but inevitably everyone spills a little during a pour, it immediately melts the bucket, and sand and molten metal run out the side and onto the ground. Also, you'll have approaching 700lbs of sand in a 55gal barrel. That's expecting a lot of palstic container and the larger casting will make that sand very hot, hotter than the plastic can take, and then besides a fail, you'll have a very lerge molten metal spill in the vicinity of you and your feet. Even so, you are correct, you must be able to vibrate it and that's no small task. A flimsy flask makes it even worse. Have you seen my molding rig and A60 pouring aparatus? If a plastic trash can would do, I never would have expended the effort to build those.

The price of admission goes up dramatically in all aspects of the game as the size of your castings increase.

Now, you might be able to build a conforming wood/particle board flask to help reduce sand volume and weight.......but you still need to be able to vibrate it, which you can do as it fills to keep the weight down. Remember, it's not just large enough to fit the casting, you'll need additional sprue and cup height. Then you need to be able to handle the crucible from a relatively high pouring height. A full A20 of aluminum is about all I care to do without lifting equipment. Have a look here. I don't recommend the metal sprue, but you will need a generous pouring cup.

Automotive Intake Manifold Lid | The Home Foundry

It's still very heavy and difficult to manage. Shortly after this I said screw it and built my molding rig.

Best,
Kelly

 

Probably not from a volume perspective, but if you use something like dense castable refractory, and it's thermally massive, that could take a lot of heat out of your melt. Some handle thermal shock and molten metal contact better than others. That's one of the reasons I use the moldable ceramic fiber and fiber board construction, and since it is unwetted by molten aluminum.

http://forums.thehomefoundry.org/in...le-offset-pouring-basin.688/page-3#post-38781

Best,
Kelly

 

The mold does not need to be "hard" in lost foam casting, just compacted. In fact, that is one of the fundamental features of lost foam casting. It uses dry unbound mold media that is compacted by vibration, not binder. Though ramming a foam pattern can still produce viable castings, ramming a foam pattern in green sand is counter to the purpose of the lost foam process and as you appropriately state, can damage or distort the foam pattern. With care and proper attention, when you fill a lost foam mold with dry unbound sand while vibrating to compact the mold media, the pattern will retain it's shape. The LF process differs in many ways compared to conventional open cavity green/or other bound sand casting.

Welocme to THF Foundry Rat

Best,
Kelly

 

From the the looks of your Avatar, looks like you stay busy. Glad to have another avid caster on the forum.

I have friends that were/are life long foundrymen and pattern makers. When I started lost foam casting about 8 years ago, I invited them over to my home foundry to watch a pour. When I showed them a foam pattern with a bunch of cavities, cores, back draft, and what would have been very complex parting lines in conventioanl sand casting, and told them I was was just going to vibrate the foam pattern in a dry sand flask (actually a 5-gallon bucket!), and then pour molten metal on it, and the metal would the replace the foam, they laughed at me and said "I thought we taught ya better".

Then when I pulled the fully formed casting out of the sand fifteen minutes later, they just sat there silent scratching their.....head.

Besty,
Kelly

 

I'd be interested in hearing (in a new thread so we don't hijack Kent's thread) how you "vented" this and other lost foam castings and how you think the venting works. Maybe you could start one in the lost foam casting subforum?

Best,
Kelly