PDA

View Full Version : Lost styrofoam casting!



Mcostello
06-12-2005, 07:08 PM
I would like to try some lost styrofoam casting and am wondering if any has any advice. What tyrofoam to use, glue needed, etc.

Spin Doctor
06-12-2005, 08:06 PM
Seeing as how you have to build the mlod for the foam casting to start with I can't see this as a really practical approach for the HSM uless you are going to carve the master out of foam to start with JMO

thetinkerer
06-12-2005, 09:16 PM
When doing foam casting there are two main types of foams - the polystryrene that we see in packaging which has bubles in it and there is another type available from plastic/foam suppliers which has very fine bubbles. The latter will give you a better finish.

what are the steps in foam casting

1. carve the object out of foam

2. attach a sprue

3. coat with a wallboard ceramic coating to improve surface finish and allow to dry (this step is optional)

4.put the pattern in a bucket of fine, clean dry sand with the sprue sticking out of the top

5. Pour metal in as quick as you can!


best of luck with it

The tinkerer
http://home.people.net.au/~thetinkerer/

Carl
06-12-2005, 09:21 PM
Step 6 above should be: make sure you dont breath the fumes coming from the burning styrofoam.

[This message has been edited by Carl (edited 06-12-2005).]

kap pullen
06-12-2005, 09:33 PM
Mcostello,

Lost foam casting seems to be a quick and effective way to make mlods.

Search hot wire foam cutter and you will find much info on making a cutter for your foam as well as casting techniques.

http://img.photobucket.com/albums/v206/kappullen/P1010056.jpg

Here is a pic of my hot wire cutter as well as a metal template and a couple of castings for trial.

I have gotten to the point of making sheet metal cutting templates bent to cut two sides of a part in the wire cutter in one setup.

Use your imagination and don't feel as negative as spindoctor in your thoughts.

My hot wire rig consists of 4' of nicrome wire (.024"), a battery charger, and a harbor freight router controller.

lots of luck

kap

Norman Atkinson
06-13-2005, 02:09 AM
Just a note for the safety concious.

The gas- or when I wanted to do it- was phosgene.

Lest we forget, there are a lot of tidy white graves from many nations in France as a result.

Norman

gkman11
06-13-2005, 06:57 AM
For a hot wire cutter, I just grabbed a piece of stainless tie wire that I had on hand. Worked good. Fed a 6A battery charger with a variable transformer set at about 40%.

If you are not on top of metalurgy, just use broken up castings for your melt. Heavy pieces can be "roasted" over your fire until they get crumbly and broken up to fit your pot.

Wait 'til your melt is a little pink before you pour.

It takes a hot fire and a L-0-0-0-NG time to melt. I finally made an melt oven out of Kaowool (from McMaster Carr) to stop loosing heat and speed things up. Just a round wire mesh cage with 2" Kaowool wire-tied to the inside. Fired with propane.

One time I forgot to watch it, the aluminum appeared to be on fire then the 1/4" steel pipe pot burned through. Luck I still have feet. Plan on anything going wrong.

Swarf&Sparks
06-13-2005, 09:02 AM
some good info here
http://www.backyardmetalcasting.com/links.html

Rgds, Lin

Radmachine
06-13-2005, 09:08 AM
An excellent reference web site on this process:
http://www.buildyouridea.com/cnc/hblb/hblb.html

Radmachine
06-13-2005, 09:10 AM
Another one:
http://www.dansworkshop.com/Hot%20wire%20foam%20cutting.shtml

BillH
06-13-2005, 11:43 AM
Kap, those castings for an oddball 0-4-0 frame? http://bbs.homeshopmachinist.net//smile.gif As for the hotwire, stainless steel fishing leader works very well too and ofcourse, is easy to find.

[This message has been edited by BillH (edited 06-13-2005).]

andypullen
06-13-2005, 01:39 PM
Look like truck frame castings to me....

Andy Pullen

Mcgyver
06-13-2005, 02:47 PM
<font face="Verdana, Arial" size="2"> stainless steel fishing leader works very well too and ofcourse, is easy to find.
][/B]</font>

so to for a guitar string, high e - also has lots of nickel in it.

QSIMDO
06-13-2005, 05:47 PM
Ford (and probably a bunch others by now) uses lost foam casting for engines.

They are able to get 3 whiskers from net shape and extremely complicated designs.

I interviewed one of their engineers some years ago..."P.Poor Memory says the plant was in NY state?

Mcostello
06-13-2005, 10:02 PM
Thanks all, now to get busy and cut some foam!

BillH
06-13-2005, 10:43 PM
Yeh Andy, I think your right

JPR
06-14-2005, 01:49 PM
Kap,
From the picture I assume that you are using the battery charger as a power supply? How are you varying the voltage?

Thanks, John

Spin Doctor
06-14-2005, 01:56 PM
I really wasn't being negative as the first thing I thought about was the lost foam industrial process. I guess I had a brain fart and forgot about the making a part out of foam for a one time master

kap pullen
06-15-2005, 09:36 PM
jpr,

The router control controls the output of the battery charger.

May not be kosher, but it works.

Here are a couple of castings and pattern fresh from the foundry today.

The patterns have maybe 10 minutes in them once the templates are made.

One part is partly cleaned up.

http://img.photobucket.com/albums/v206/kappullen/foam1.jpg

My foundryman, American Alloy Foundry in Baltimore says that foam produces poor finish castings. Looks true to me.

He burns thru the foam with a hot wire, and peels it out of the mold before casting.

That saves all that poison gas.

He uses a hard setting sand for the mold.

He's been at it 37 years and says he learns something every day, just like me in the machine shop after 35 years.

I fooled with melting bronze in the back yard years ago. I now will leave it to the pros. I don't need a mold blowing up in my face at this point in life.

He is also casting a hitching post, and two bronze cannon barrels that will go with these axles.

kap

wierdscience
06-15-2005, 10:05 PM
Niffty!I like the idea,certain alloy engine blocks are produced that way so it has to work,seems like Saturn's have a lost foam block.
The hot wire,nichrome is best,but a lb spool of stainless mig wire mounted under the table makes it easy.When it burns out,reel off another piece just like toilet paper.

Kap,ever try cutting wax with your hotwire rig?I have been wanting to try it,but it's way down on the list of roundtoits.Seems a fellow could do lost wax much the same way as foam.

john hobdeclipe
06-16-2005, 05:16 PM
I've been thinking of trying the lost foam process mainly for one-off artsy type creations. Is there any reason I would not be able to use an electric kiln, like a ceramic firing kiln? Has anyone tried it? How did it work? Thanks.

kap pullen
06-16-2005, 10:47 PM
wierd,

No I haven't tried wax.
That is an interesting idea.

I should have said above, "the router control, controls the 120 volt input to the battery charger" but didn't.

This process gives me too many ideas to afford, or ever finish up.

kap