Lost Foam Casting

[Biggermens]

Hello there

I am doing some lost foam casting and i think i am doing good
I have 2 question

One
Is there some kind of formula to Figure out the proper size of the gate ???

Two
What would be a good coating for my foam pattern ?? I have been using Durabond 90
CGC - CGC DURABOND®90

Anyone have any better suggestions ???


Thanks in advance
Biggs

[acourtjester]

HI Biggs

I have been using wall texture mix by Litex I bought it a Low’s.
I had tried to use Duro-bond but found it did not dry as good and I had bad castings with it.
Too violent of a pour full on bubbles.

Have fun
Tom

[Biggermens]

Hello Tom

Your casting look pretty nice, How many good part did you get for bad parts?
I also find durabond to be very violent.
Do you spray the wall texture on and paint it on ??

I hope i can find this stuff in canada

Thanks
Biggs

[awerby]

But the formula for gates and risers is pretty simple: you need to provide either a gate or riser with more cubic volume than the thickest part you're casting. That way, there will be liquid metal for the solidifying metal to draw from. If the part is the thickest thing in the mold, then the gates and risers will come out fine, but the part itself will show shrinkage porosity, soft edges, and other shrinkage defects.

Andrew Werby
United Artworks- Sculpture, Jewelry, Furniture,and other Art Objects, plus Art Resources, Techniques of Sculpture, Jewelry and Lapidary, an Online Bookstore, and a Custom Art Referral Network

[acourtjester]

Hi Biggs

Most of the parts came out good I am still learning on the lost foam procedure.
I did the normal green sand many years ago and did well with that. As you know lost foam is quicker and easier to do. I dipped or poured the wall texture over the foam and it works well. I did find that small spaces can be a challenge as the texture does not fill in completely without extra help. I use a stiff wire to break bubbles and stir the mixture over the part to get good coverage. I have a part I want to cast that had a 1” cylinder like hole trough it and it had a problem drying inside the hole. I put it in the oven over night with a light bulb and the oven light on to help and it seems to have worked. I will see when I pour in the aluminum. I did find that I use a hot stiff wire to melt some of the foam in the mold before I pour it helps. I have read that a guy used a solvent to dissolve the foam before he pours. I did not want to do that as he is the only one talking about doing that and I don’t was it to blow up.
Also if you use a big reservoir above the part so there is plenty of aluminum to fill up the part you can see it in the pictures I sent. I did not find the uses of risers has been needed. Another thing is I make up the texture stuff and let is sit for a day or two to remove lumps in the mix made it like pancake mix or slightly looser.
Here is a torch holder I cast and machined.



Have fun
Tom

[Biggermens]

I must say that is a nice looking part

[tony978]

Hi acourtjester,
what is the exact product your using ? The lowes around me does not carry any wall texture by Litex .

Thank you
Tony

[acourtjester]

HI Tony
Litex is the brand I used and I got it from Home Depot.
The guy I got the info on this lost foam stuff used
Hamiltons White Line Drywall Texture mix
his site is LFMC
His look to have a slight yellow tint to it mine is off white.
His may be better but I could not find it here so the Litex is what I used and it worked very well.
Durobond looks great but casts bad I don't know why Biggs and I both had the same problem with it.
Have fun
Tom

[Biggermens]

I wonder were we can get commercial lost foam coating ??

Thanks
Biggs

[diyengineer]

Wow this has really helped me A LOT. Tomorrow im going to try and knock out a few parts. I will load up my results when i get a chance.

[diyengineer]

HI Tony
Litex is the brand I used and I got it from Home Depot.
The guy I got the info on this lost foam stuff used
Hamiltons White Line Drywall Texture mix
his site is LFMC
His look to have a slight yellow tint to it mine is off white.
His may be better but I could not find it here so the Litex is what I used and it worked very well.
Durobond looks great but casts bad I don't know why Biggs and I both had the same problem with it.
Have fun
Tom

Couldn't find that brand at lowes or home depot any more. I just got the generic 18 pound bag of drywall mud, the 20 minute cure (non premixed powder, must add water)

I mixed it 1:1 and it was pretty watery, i tried 3/8 cup drywall powder to 1/4 cup water and it had a very good consistency almost like pancake mix on the wet side. I tried 2 cup powder to 1 cup water, and it becomes toothpaste.

Seems like the 3/8 cup to 1/4 cup water was the best for dip coating. Going to let it dry overnight, and tomorrow ill pack them and pour them up.