"lost wax" and application to mold production.

[Anvils Hammer]

So Ive been thinking about how to make molds a lot recently..

I need to go from having a split mold of a single part, to having a split mold which can create 15-30 copies of that part in one go, for production casting.

My process, which I think is the best way forward, is to make a split mold, get 5 casts, make a split mold, get a number of sprues, each each with 5 parts, and put all the sprues in a single "mold block".

I can use a different number of "master sprues" depending on how high I expect demand to be for a given component.

The one problem, which I discovered to day, is that cutting the "split" around complicated shapes like axes and guns, is a massive pain in the ass. It took me at least 15 minutes to get 5 rifles out of the master mold, and im more likely to cause damage to the mold.

Making a producton mold with 15 copies of the rifle would take forever to cut the splits and they would probably not be that clean.

So I had an idea.. lost wax casting.. its not a new idea.. it was around long before silicone and polyurethane.

I think if I pour the master molds using molten wax instead of resin, I should still be able to get the parts out fine, and the detail level will be the same (pressure cast the wax as normal...)

When the silicone mold has cured around the wax masters,I can dump the whole thing in hot water for 5 minutes, then cut the split lines neatly and instantly.. as the masters are in liquid state again..

For production of the molds with 5 parts, Ill keep using resin, but for the production molds, I think filling the master molds with wax might work really nicely!

Worth experimenting with anyway..

Has anyone else tried/considered this? am I totally mad?

AH

[mangozac]

You must have been a mad scientist in a past life

I like the idea, although I would have thought the mould would have to get pretty hot to melt the wax well enough. I'm not sure that the additional steps (including mucking around casting the wax) would work out any more economical though.

[Anvils Hammer]

Ive just done a test.

melting candle wax on the stove was no problem.. had to ask my sister for a how to.. she makes candles!

Pouring the liquid wax was no trouble, exactly the same as resin.

It stayed liquid fine, it was starting to go a bit clowdy as I put it in the pressure pot.

It takes a while to cure so im going to leave it over night.

I know for a fact that that parts will probably be perfect, but will be incredibly brittle, no way I will get them out the mold in one peice.

Im going to get some "proper" casting wax designed for this process, need to phone aroudn tommorow..

melting the wax is a hassel, but the rest of the prosess, assuming it works as well as resin, should take the same ammount of time.

The advantage will be that it will be really really easy to cut the split lines fast and exactly where I want them to go, which is essential for more complicated parts!

AH

[mangozac]

Did you ever try making a resin mould plate for the split mould like you discussed in the past?

[Xeones]

Years ago I did some work with bronze casting using the lost wax method, but I was working at a much different scale than what you are interested in trying (not to mention using molten metal), so I doubt my experience or advice would translate well to the sort of endeavor you are trying here. Actually, I'm not really clear how you plan to go about this.

When I did lost wax, I created my sculpture out of sculptor's wax (including channels and vents) and then cast the mold around it. Once the mold was cured, molten bronze was poured into the mold, the wax was vaporized, and the bronze filled the voids left by the wax. While this process can give you very intricate detail, the molds I used were then destroyed once the bronze cooled (usually several days later depending on the size of the piece) so that I could remove the finished bronze piece. I assume you are trying to somehow save the mold so you can reuse it? How do you plan to remove the wax to clear your mold for the resin? simply heat it up and let the wax run out? The wax I used was easier to sculpt with than candle wax, but then, it had a much higher melting point too --perhaps too high for a silicone mold to handle, I'm not sure.

I'm intrigued anyway. Let us know what you end up finding out.

[Anvils Hammer]

I tried with candle wax,

The parts filled ok and the detail was good, but a little fuzzy in places, the parts also broke up, as I knew they would.

I might at some point purchase some "proper" casting wax and have another go.

Yes, Id heat it up and let the wax run out in boiling water.

The idea is that I can make a production mold from wax sprues, and thus get a much more accurate, cleaner split.

@Mango, I never tried it.

I may at some point, but I strongly suspect it couldnt be done without creating flashing on all the duplicates..

I may experiment though, with putting cling film in the split then pouring the resin.

For the time being, it looks like Ill just have to lump it with my razors and cut the split a fresh each time, im getting pretty damn quick at it though so not the end of the world!

AH

[Anvils Hammer]

I contacted the "Proto-wax" company mentioned in another thread.

They are sending me a sample print of my shotgun .STl file in wax, excited! will let you guys know how it compared to the other sample print I got in a "normal" material.

I also think Ive found a UK company which has the same machine Ive had shapeways parts printed on, so hopefully if its not to much more expensive I can drastically reduce my lead times on printed parts!

AH

[Fleafa]

Which UK company is that?
Any idea what the protowax costs are like yet?

[wormwood]

Printed wax originals could be used to create lost wax metal masters, which could in turn be used for making flexible molds for casting resins. Bronze would be really good for this. Sure you'd have to contract it out, but it'd have excellent detail and be nigh indestructible.

[mangozac]

Or you should be able to make resin masters from the wax prints (as I expect is the plan?).

[Fleafa]

I spoke to the ProtoWax guy today and he says the file I sent him, which wuld cost £50 or so to print in plastic, would cost several hundreds with their current wax. That said, they are in the process of testing a replacement wax which would bring that cost down to well under £100.
The wax is very fragile, but I have a sample on the way too which I intend to cast from. I'll let you all know how it goes.

[wormwood]

The reason I was suggesting using a bronze intermediary, was that wax con be invested in plaster without being damaged or deformed by the process, but there's some question as to whether this holds true for sillicone molds being made directly from wax prints.

[Fleafa]

Hence testing with a sample

[mangozac]

Fair point Wormwood, but I reckon it's definitely worth the experiments AH and Fleafa are going to do. I'm surprised that the wax rapid prototyping is so much more expensive though...

[Fleafa]

Its the cost of the wax itself, apparently.