Hi,
I'm new to casting and this site. I am wanting to cast small aluminum parts. I discovered a couple places that talk about lost foam casting. Does anyone here do this and can you give me any suggestions, hints, tips, etc. I am building a electric furnace to melt with. Any help is appreciated. Thanks Ron

I've done a little casting, so here's some tips.

1. Wear safety equipment. Molten aluminum is hot (duh.)

2. Pour quickly. Pour as quickly as you can without making a mess.

3. Use risers to fight shrinkage.

Which ever method you chose, lost foam or traditional green sand, you will need a pattern. In lost foam, the pattern is made of foam and left in the mold. The molten metal vaporizes the foam. It creates a lot of gas so your sand needs to be permeable.
Green sand patterns are removed from the mold and need draft (taper) to draw smoothly. They can be reused many times.
Most people don't realize that molten aluminum is more dangerous than molten iron. Aluminum is poured around 1600 degs while iron is poured in the 2600 deg ranges. at those temperatures, iron will bounce of skin like water drops in a hot frying pan but molten aluminum sticks to the skin.
Always spend the money to buy protective clothing and facewear.

I would like to add to the earlier post, riser size, contact size and placement can be critical. Do it wrong and your results will be negative.

Ive been doing permanent mold process for 3 years now and have very little knowledge of what i'm doing.I use an electric resistence furnace and most molds pouring A356.1 aluminum ispoured around 1300.Gates and risers are your most important requirement but chillers and cooling placement is just as important.

Foamcutter, You mite want to check out this Guy,
http://www.buildyouridea.com/

Woodie1,
Thanks for the link. Ron

Yes this is casting metals, but my question is on lost foam casting.
I hope the knowledge/experience base may be here.

I've seen (but lost the location of) Lost Foam Casting with resin and fiberglass.

Process I guess is:
1. Build a mold (plug) Thats the foam part - cnc comes in here
2. 'glass it - this becomes the female mold
3. Cut/split (part lines) whatever
4. get the foam out - what here/how? Carve it melt it?
Won't be pouring in hot molten metals - so thats out.

Ideas? or do I start a new thread?

Thanks & :cheers: , Jim

Jim,

I think that the term "lost foam casting" is what threw us. Usually that refers to making a foam part and either putting plaster around or making a sand mold. Then when you pour your metal in it burns the foam away.
What you are talking about is to make a foam part then glass it and loosing the foam inside to form a new mold. It might work. Once you loose the foam the inside surface is somewhat rough and hard to put parting agent onto.
A better way is to make the foam part and put resin on to firm up the surface and make it non-porus. Sand it really smooth. Apply parting agent and wax. Then make a new mold from that. Your inside surface of the mold will be as smooth as the part you started with.
Try this link: Here (https://www.cstsales.com/How_to_Articles/index.htm)

Good Luck,
Chris

Edit: OK, so I couldn't explain it nearly as this website. This is where I learned my lessons.
http://web.umr.edu/~foundry/first.htm

Ok Folks,
I first posted on this site back in June looking for information on lost foam casting. You all helped Thanks so much. Back then I knew little about casting and had no equipment. I have since built a small furnace that will melt a little over a quart of aluminum. Yesterday I did my first melt using a foam part coated with plaster. I have learned a lot since June thanks to people here and sites they sent me to and etc.. The parts I cast did not turn out real good but I made some really cool aluminum muffins (stole wifes muffin tin) since I didn't know how much to melt and I melted way way too much. Even though the parts I wanted did not do well I learned a few things and the next melt should go much better. Anyway the reason I am posting now is to say thanks to all that helped and if anyone is interested in seeing what I did so they can try it I will be glad to post more as I go along and get better. I will even try to get some photos posted, I am a professional photographer by day. Ron

Hi Ron,
Last year I built my own first furnace, (propane). I've cast several succesful pieces. One of the things I did learn, was to attach in such a way, a larger spru opening of sorts that was not foam. I.E.
I would bury my created piece in loose sand and as my sand reached the top of my piece impose an alum can with the top and bottom cut off. to sort of act as a super spru. What I believe this did was to force the gas from the foam out thru the sand and not back up the spru, thus causing my piece to be flawed by haveing the molten metal be forced back up the spru by the gas so to speak. I've have many more failures than successes, but this method also exacerbated the desire to build my first CNC carver/engraver. To remake all the pieces I'm trashing. Right now I look at this way, as long as I can get the surface I need milled,lathed or otherwise to the place I need it. It does really matter what the rest of it looks like. Sorry for the rant.
If I can be of any help in this method of casting please feel free to drop me a line.

Peace
In GOD
Neil

MERRY CHRISTMAS.

thuffner3,
Thanks for the reply Neil. I too have experienced the gas blowback from the melting foam. I am trying to cast a muffler and header for a small gas engine with the aluminum. I am using a foam mold of the muffler that is filled inside with sand so it will be hollow. My biggest challenge with it so far has been to get enough aluminum poured in fast enough for it all to cast. The walls are only about 3mm thick on part of it and the rest is about 6mm thick. Plus I am inserting two steel exhaust stacks in the foam mold to be cast in the aluminum. So I keep adding more risers in different places around the muffler to try and carry aluminum directly to that area and not depend on the muffler wall to carry enough aluminum to that spot. I was coating the foam in plaster to start with but that didn't seem to let the gas out so now I am just lightly ramming up the foam in green sand. The green sand I am using is just play sand with a small amount of oil added to make it stick together. I like the oil better than using water for the green sand since the oil does not create any steam, it just smokes a little from the oil burning out of the sand. I don't know if this makes sense to you. Anyway it's a great learning experience, I too now know several ways it won't work to cast. Have you tried different types of foam? I am looking to try and build a CNC carver also, how is yours built. Have a great Christmas and a Fun New Year. Ron

Hi Ron,
I was just reading this afternoon, (wish I would have kept the link.) That anything under 6mm would be to thin. The foam cools it down to quickly. The only foam I'm using right now is the blue and pink two inch stuff. I work in construction, so it's plentifull for me. Have you checked out Backyardmetalcasting.com yet. All one word. With lots of links to guys who are doing nothing but this type of thing. As for my CNC machine, here's a link to it below.

Peace.
Neil

http://f1.pg.photos.yahoo.com/ph/thuffner3/album?.dir=/CNC+stonewood+carver.&.src=ph&store=&prodid=&.done=http%3a//f1.pg.photos.yahoo.com/ph/thuffner3/my_photos

Would it not work better to ram the sand in good, and then dissolve the foam out with a solvent? Its likely dangerous/explosive as hell, but the noxious fumes from melting/burning foam are not so good either.

Surely, a real foundry could give you some tips?

The fumes are not bad at all.
The other problem with ramming green sand around foam is you tend to distort the piece. I.E. twisting, indentations,misalignment,etc.
The molten metal is so hot that foam really doesn't have a chance to burn. it purely vaporizes. The funk for me is during shake-out. Man that is a real stinker. Worse than a green egg and ham fart after 12 beers, included the steak and onions too.

Peace
Neil

"Man that is a real stinker. Worse than a green egg and ham fart after 12 beers, included the steak and onions too."


Hu, did you two go to the same school of quotes?

Man something smells around here :D

Thanks for the laugh.

Ken

I was just reading the "make your idea" site and there he uses acetone to disolve the foam after coating it with the texture plaster. He 's had excellent results.
www.buildyouridea.com

Yes on smaller solid projects melting the foam out would work well, but with my current project which is a small engine muffler, melting out the foam before hand would let the sand inside the foam just fall out. It needs the foam there to hold it in place until the Aluminum melts the foam and fills the space. This way I get a hollow molded piece. I hope to try again this weekend, I think this last foam mold has enough risers to make it work. was going to try it this last weekend but it was way to windy and cold to be outside trying to cast, plus it started to rain about the time I would have been pourig, not a good thing.

thuffner3- I agree the big stink is the shake out. It seems the sand just holds all the stink until you start to dig the part out and then it's like a big nasty fart from a big dog that's been fed way too much chili. Anyway I will let you know how this pour goes after. By the way Nice CNC Router on your site. Thanks for the input. Ron

Have you tried cores with anything foam yet? I've not developed a decent core recipe but have seen quite a few, something to do with mollasses and wheat paste?

Neil,
Nice looking engraving on the stone.
What is the material your CNC is made out of? It's black with lots of bolts, can't figure it out.

Thanks
Hager

A home owner had a nice looking aluminum fence taken down because their dog could fit through the wicketts. I originally had planned on melting it all down. Then I saw a CNC machine, And.
Well you saw the rest of the story.

Merry Christmas All.

And for all the politically correct,

I STILL SAY -w- VIGOR

MERRY CHRISTMAS

Like your axis bearing mounts, did you mold them yourself?
Was there much machining involved to get them cleaned up.
Thanks
Hager

thuffner3,
Yes the muffler I am trying to cast I am using blue foam as the muffler and filling it with sand as a core to make it cast hollow. that is why the challenge with the many risers bcause the walls of the muffler are only about 3mm thick at the thinnest point and 6mm at the thickest. I will try to get a photo of it before I try to cast this time so you can see easier what I'm talking about. How much Z travel do you have on your router? What software are you using? Thanks Ron

Morning Ron, Hagar,
Z travel = 2.5 " right now. Soon to change.
The material came from a fence that was removed form a job I did last year. Seems the lady didn't bother to check the demension of the wicketts and her dog kept getting out. I was going to melt it all down untill I ran across my first CNC machine. Now I'm hooked.

Peace
Merry Christmas
Neil

Innovation, and sharing, that's whats this forum is all about. Seeing something that was trash to one person, taking it and turning it into something useful then sharing it with others. Others see what can be done and how to do it, and off they go, designing, building, redesiging, rebuilding. Driven by that spark of creativity.

Merry Cristmas to you all and a Happy New Year.
Hager

I have been looking at the links posted here and I am interested in the design of the furnaces (i.e. the R2 design). I know it is propane powered but what is the grey wall material? It looks like cement, but I am more inclined to belive it is something else. Also the burner design apperars to be a tube with air or gas holes.

I am familiar with the process of invesment casting and such, but I was wondering how one would get into home froundary work as a hobby and what good sources there are for people to learn how to do this safely at home?

Any information will help.

Type home foundry into google and then read until your hearts content! Ron Reil has a good and simple burner design, its the one that I am using. The grey stuff is refractory cement. A high temp cement mix. Check out www.backyardmetalcasting.com, Lionel has some good stuff on there. There is a forum on there as well that is a lot like this (knowledgable, and non-kn... people who share ideas for free!). My whole furnace setup including propane tank and burner, and molding sand cost about $50.
Oh...there really isn't any way to be absolutely safe about metalcasting, just be cautious and use common sense. Check out that forum. They'll take care of you!