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davidh
12-23-2008, 02:45 PM
last year i found lots of info about lost foam here and decided i wanted to try it. i already had a small furnace that needed trying so i started reading.

i cannot remember who he was but one guy did extensive expermenting for making lineal bearing mounts for his cnc router table. excellent documentation on progress as he tried things.

the best solution for coating the foam was a fairly thin water mix of the powder used when doing sprayed ceilings in your house. cost was under $10 at home depot.

i mixed half gallon of it and painted or dipped or both all over the foam except where you are going to pour the aluminum (or brass) allowing a day or so to dry.

this slurry will ult. be the outside finnish of your aluminum, and it just washes off your aluminum with a hose.

my first attempt was the "D" of foam that i cut & hot glued to some packing peanuts, using a 25c paint / chip brush i coated with the ceiling goop, dried it, sunk it into a pail of strained lake superior sand and poured away.

http://i260.photobucket.com/albums/ii12/tooldoc/23.jpg

http://i260.photobucket.com/albums/ii12/tooldoc/47.jpg

neonman
12-23-2008, 03:03 PM
Now, that is one of the most clever uses of an old lawn mower I have yet seen.

Neonman

dewat
12-23-2008, 05:25 PM
here's the link to the site you are probably talking about

http://www.buildyouridea.com/


I haven't yet done any green sand/ petrobond casting so all thats left is lost foam

http://i81.photobucket.com/albums/j218/dewat/Mobius010.jpg

tiptop
12-23-2008, 11:35 PM
Doc,
Is the orange hose the supply line for gas to fire your furnace? Do you run it on propane or natural gas? I am just curious because a friend just gave me a furnace that looks just like yours, blower and all. I had one that I built and used for about ten years but it was of the gingery style.

Jay

davidh
12-24-2008, 09:23 AM
the orange hose is quick coupled to a shut off and regulator that goes to a 20 lb propane tank. i also have my home/shop 600 gallon tank plumbed with shutoff and quick coupler as an option as its a lot cheaper fuel than the 20 pounder.

its just a cheap air hose and i use a good parker hannifin quick disconnect on it .

i would not be quite as carefree if this was used in a poorly ventalated area but its very much out in the open.

i need the propane tank to be easily changed from one purpose to another with regualtors , etc, and from one shop to another.

the lawn mower not only holds the furnace but also all the tools and tongs needed to do the pour safely.

the furnace works great so far, and i do this outside in the summer or in the open garage in the winter. i did need to make a new cover for the furnace last year and i;ve built a few crucibles using 4" well casing to increase my ability but i still have the ceramic crucibles for smaller pours.

its very interesting to see how this process works and how many creative things can be done with just foam and a hot knife or wire. like evans, i just butcherd up some stuff and stretched some .030 stainless welding wire between some terminals. nichorme did not work for my stuff and may not really be the right product as evan has pointed out its difficult to maintain an even temp for straight cutting.

i used a fancy power supply i have for chrome plating to run it but only because it was easiest at the time.

i think anyone that plays with metal (guys on this forum) should try this or at least particapate with someone doing it at least once. it will open up a completely new area of your creative mechanical brains.

alanganes
12-24-2008, 10:03 AM
Nice work. I too, like the lawn mower deck setup, very clever recycling there. When you say that you coated the foam with ceiling coating stuff from HD, are you talking about the "popcorn" texture stuff?

Thanks for posting this stuff...

malbenbut
12-24-2008, 10:10 AM
Like the mobius strip Dewat, what are you going to use it on?
MBB

davidh
12-24-2008, 12:12 PM
Nice work. I too, like the lawn mower deck setup, very clever recycling there.

i just hated bending over and lifting the heavy thing. im old !



When you say that you coated the foam with ceiling coating stuff from HD, are you talking about the "popcorn" texture stuff?

the name onthe bag is :
USG Non aggregated wall & ceiling spray texture

there is no stuff in it but powder that looks like powdered sheet rock mix


Thanks for posting this stuff...

this site is all about sharing knowledge, thats what makes it so dang great.

alanganes
12-24-2008, 02:10 PM
this site is all about sharing knowledge, thats what makes it so dang great.

Yes indeed. Thanks again. Looks like I'll have a ('nother...) project to try out, come springtime...


-Al

dewat
12-24-2008, 06:52 PM
Like the mobius strip Dewat, what are you going to use it on?
MBB


A couple of years ago someone on this site

http://www.backyardmetalcasting.com/forums/index.php

asked how for ideas about casting one and that's what I came up with, I used some blue foam and steamed it until I could bend it and glue together. I think he wanted something thinner and wider. I haven't done anything with it since. :D

hwingo
12-25-2008, 06:29 PM
I know this is an old topic but I too have had an interest in this for sometime and would like to obtain more information.

When I was in Dental School, we “waxed” crowns and partial denture frame-works, invested these in metal rings, placed in a burn-out oven, and used a spring loaded centrifuge to "sling" molten metal into the investment ring. Naturally, these were small parts and nothing on the scale of what people do at their home foundry.

Dental impression materials (Poly Sulfide) were expensive and today's new dental material (Vinyl Polysiloxane) cost far more than then. The down side to accurate impression material is, this material is not reversible, i.e., it cannot be reused for a different impression. However, if the mold is properly care for, dimensional stability of this impression material is quite good and the mold will last a long time without loss of accuracy.

A very accurate reversible material, i.e., one that can be used over is Reversible Hydrocolloid. However, dimensional stability is time sensitive as the impression has ZERO shelf life when compared to Vinyl Polysiloxane. I doubt this could be used with hot wax which brings me to my point:

1. What impression material is currently used with foam or wax?

2. What foam is being used? I’ve heard that can foam does not burn out well.

3. What wax is being used and where is it obtained? Is it expensive?

That about does it for now but have more questions regarding foam and wax.

Harold

davidh
12-25-2008, 10:23 PM
1. What impression material is currently used with foam or wax?

i have not used foam with any impressions, the model itself is burned or carved from the foam. i have also not tried lost wax as its a different process all to gether i think.

2. What foam is being used? I’ve heard that can foam does not burn out well.

canned foam is not very good for lost foam work, you are correct. the foam i used is closed cell insulation as uned in home construction. the blue or yellow stuff you put under your new concrete slab or glued on to your basement walls on the outside. it does burn out quite well if given a little help with vents of it coming out of the sand or even little things like drinking straws that you can hot glue onto your carved or wire burned original..

3. What wax is being used and where is it obtained? Is it expensive?

i have seen the wax advertised at different jewelery supply web sites but have not checked it out.

That about does it for now but have more questions regarding foam and wax.

i would be happy to share all i know about the subject however im but a bare novice that has really enjoyed tinkering with it. if you want to pm me i have no problem with that. . . davidh