Metal Melter

[Onoff]

This suggests you lacquer the PVA model but then do actually burn it out:

What about lost PVA (watersoluble)?

I haven't found any resources online, which is a little odd. After all it's readily available in filament form and not too expensive. Hopefully this...

forums.thehomefoundry.org

 

[Kram]

13 hour burnout on that plaster mix

What size is the print? Try to get the mold under 120mm diameter so it will fit easily in furnace. I can do the runner/pouring basin in green sand if you make the plaster open on the back.

I like the idea of ceramic shell casting - you paint/dip the mold with layers of plaster so that you use a lot less of it, easier baking and the pack the dry mold in sand. Sand will allow any gasses and steam out easier.

Cured sodium sillicate sand may be water resistant enough for pva.

 

[Onoff]

What size is the print? Try to get the mold under 120mm diameter

I'm lost, what's a "13 hour burnout"? In an oven, with a gas torch?

It's this big:

Really lost btw!

I thought I'd just pour plaster over it, burn / pick it out the give it to you!

 

[Kram]

Yeah that will fit no problem.

From the pdf

I assume its thickness dependant, but for jewelery the plaster is usually a solid 3 or 4 inch dia lump.

 

[Onoff]

Yeah that will fit no problem.

From the pdf
View attachment 341541
I assume its thickness dependant, but for jewelery the plaster is usually a solid 3 or 4 inch dia lump.

So I need a furnace to burn the PVA out?

That brings proceedings to a halt somewhat!

 

[Kram]

It will fit in mine, just needs to be baked dry before posting.

 

[Onoff]

It will fit in mine, just needs to be baked dry before posting.

I can't achieve 730degC with anything here that's for sure.

 

[JMS1972]

So I need a furnace to burn the PVA out?

That brings proceedings to a halt somewhat!

Yes that's what is holding me up. I have the parts but need a round tuit.

Veg Oil Guy covers the process in his videos

Just allow the plaster to set and send it to @Kram ?

 

[Onoff]

Yes that's what is holding me up. I have the parts but need a round tuit.

Veg Oil Guy covers the process in his videos

Just allow the plaster to set and send it to @Kram ?

You mean something like this?

Should I print a 120mm dia, mould? How high?

When you say "set", then for how long? Do I accelerate the drying process in the oven here? If I did it upside down then potentially that could melt out the PVA/PLA or at least soften it to dig it out.

I will sit and watch that clip.

Has @Kram then got to go through a 13 hour burn out process? Still struggling with the term, is it to harden the mould and drive out moisture, burn out the model or both?

Are programmable furnaces a thing? X degrees for so many hours then turn the heat up for another set time etc.

When he's perfected his furnace we can copy it!

 

[Onoff]

Watching the VOG video where he turns his furnace into a burn out oven and other than baulking at the price of the CAL 9500P PID, I couldn't help but think I'm sure they didn't do this in the old days when making horse brasses!

That sort of cost makes it unviable tbh to really take any further. Even to disperse moisture from the plaster I need to get to 400degC.

What are the alternatives to plaster, sand?

 

[Onoff]

Jesus now he's vaccuming the plaster to get the air out and spouting "only a few hundred Pounds" for this, that and the other. Then "you'll need a second furnace" and that you'll need to keep the plaster at temperature right until you pour the molten metal. Game over I think.

Off to search for a cold cast brass effect resin.

 

[JMS1972]

Jesus now he's vaccuming the plaster to get the air out and spouting "only a few hundred Pounds" for this, that and the other. Then "you'll need a second furnace" and that you'll need to keep the plaster at temperature right until you pour the molten metal. Game over I think.

Off to search for a cold cast brass effect resin.

There's a reason it is used for jewelry! but seriously you need the vacuum to get really sharp detail. I would think most horse brasses are sand cast in an open mold (mould?) Similar to what you show. The problem with that is you need a design with draft.

If you go the resin route make a silicone mold and you can cast loads. .

It's a hobby in itself I'm slowly picking up the bits to do investment casting fairly cheaply. He does have videos for lots of homemade gear.

 

[Seadog]

Mould, and jewellery

 

[JMS1972]

Mould, and jewellery

I thought looked worng blooming auto erect....

 

[Onoff]

There's a reason it is used for jewelry! but seriously you need the vacuum to get really sharp detail. I would think most horse brasses are sand cast in an open mold (mould?) Similar to what you show. The problem with that is you need a design with draft.

If you go the resin route make a silicone mold and you can cast loads. .

It's a hobby in itself I'm slowly picking up the bits to do investment casting fairly cheaply. He does have videos for lots of homemade gear.

What's "with draft"?

The horns on this for instance "curve". If I pulled the model out of sand I reckon I'd destroy the impression?

 

[Onoff]

Presumably it's called investment casting as you've to invest so much time & money!

 

[Onoff]

Bear with me on this:

1) Print in PVA, the negative image of the cow i.e. a hollow print that the cow shape would fit into
2) Fill with casting wax
3) Immerse in water - PVA dissolves, wax stays in place
4) Pack wax in sand?
5) Melt out wax?
6) Pour in brass

???

 

[Kram]

Cant sand cast with overhanging features without complex split molds. The ears are not going to work like that, and negative text that small would be difficult.

PVA wont handle wax temperatures? Same with PLA? 65-80c.

The burn out is no problem, I will do it, but it may not be the full 13 hours, not in one day. When Ive done plaster before it was left to dry out a day, then I torched it for 10 minutes to a uniform 300c , poured and got a mini steam explosion.

Casting wax is extremely expensive. Theres nothing wrong with standard candle wax - it is harder and brittle but will take a mold and burn out the same.

Can sillicone be printed? High temp sollicone may be useful for other stuff.

 

[Onoff]

Cant sand cast with overhanging features without complex split molds. The ears are not going to work like that, and negative text that small would be difficult.

PVA wont handle wax temperatures? Same with PLA? 65-80c.

The burn out is no problem, I will do it, but it may not be the full 13 hours, not in one day. When Ive done plaster before it was left to dry out a day, then I torched it for 10 minutes to a uniform 300c , poured and got a mini steam explosion.

Casting wax is extremely expensive. Theres nothing wrong with standard candle wax - it is harder and brittle but will take a mold and burn out the same.

Can sillicone be printed? High temp sollicone may be useful for other stuff.

Learning all the time here!

Silicone can be printed but not with the printer here or many "home" printers I don't think. Happy to be proved wrong.

When you did plaster did you vacuum it?

Is it worth then us trying a negative in PVA here then filling with candle wax and dissolving the PVA thereafter? Got to have a try surely?

This ceramic shell casting, literally like dipping a strawberry in chocolate is it?

 

[Kram]

Can the pva stand molten wax at 70c? I would guess it will deform?

Im not sure what hes using as slurry, likely not plaster as it sets and thats a massive bucket. He does 9 coats of slurry then sand.

Skip to 5 minutes.. and speed it up, lo g video but useful stuff. I guess lost foam is pretty similar to lost pla/wax in a shell.