I am casting aluminum using foam as the original. I am burning out the foam in a kiln. What temp does the foam burn out at? The foam is a Dow high density like that used in building sheet insulation. Can you advise me on venting the investment mold?
I work with metal casting but I am not an expert on the lost foam method.
here is what I know about it:
- Typically the lost foam method does not require you to burn the foam in a kiln.
- All you need is the part shape in foam
- You can glue a foam rod to the "foam part" at a location that is not critical ( this will be your pouring site)
- you then need to glue a couple of small foam pieces ( small rods, 1/4 in diameter or so) at the other end of your part in respect to your large foam tube. This will be your venting site.
- Your part should be the lowest point in this system, all rods need to point upward.
- take the assembly and cover it with "green sand" ( pack it as you go) in a box .
- no need to burn the foam out, just pour the aluminum right in and the foam will disappear.
I am thinking you might be talking about lost wax method in which you need to burn out the wax and get the mold to a high temperature.
As a warning, Burning out or just burning construction grade foam (or any foam) is highly toxic and dangerous. If you are going to do this then be sure to do it in a safe area with no one around while wearing the proper safety equipment (I.E. Respirator, Goggles and Face shield if needed).
I've played a bit with aluminium casting but have not tried the lost wax/foam method. How have you got on with this.
I have only used split moulds where you pack your former in, split the moulded sand, remove the former then replace the mould and pour. This is OK but a lost wax proccess would take the tricky bit out of the equation. The splitting of the mould.
I would love to hear how you have faired and pick up a tip or two
Just had a thought as I was typing. If its building foam your using, would it be "fire proof". ie: Would it not burn/melt or need a very high temp to combust ?
I did some lost foam casting almost 30 years ago using approximately 1.5l of melted aluminum. The foam original was made using insulating foam (pink) and the green sand was home-made. The results were very good although not as detailed as is possible using the sand casting techniques used with cast Iron.
i have done some lost foam casting, it's probably the simplest form of metal casting available. no need to really worry about temperatures, if your alu is liquid it's hot enough! just leave a bit of the foam object sticking out of the sand and pour onto that. or stick a new piece of foam on that sticks out the top of the sand. try not to get too close, and do outside and wear chemical mask. apparently you can get better detail by painting the object lightly with watered down acrylic paint.
I am interested in casting also. This is what has brought me to reprap. It looks
like a good machine to make molds/plugs out of. You should be able to scale the
part to allow for shrinkage. I have 17 years as a machinest and feel that casting is
way under used. Check out youtube and the users myfordboy or and I am not sure of the spelling
tubalacain? They seem to be the best at it. Has anyone tried making the plugs on the reprap?
I know there would be work on the finish, but I think that overall it would save a lot
of time. Sorry if this isn't written very well I am doing this from my phone.
Much the same here BosenMike99, although looking at copper and nickel alloys rather than aluminum. I have found over the years that casting is underrepresented same as you have. But with 3D printing, I see a huge opportunity here.
I have had some success at aluminum.casting but.more from the sand casting approach. Instead we f working like a machinist woodworker and creating a pattern for making the sand mold....I 3d print the pattern using my files scadd to the proper size. There are many different casting alloys out there and would not advise dumping too much time into anything read on a forum. Meet the foundry. Ask the shrink rate. Make a pattern. Leave the foam for another project.