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"Anyone ever use investment casting?" Topic


15 Posts

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624 hits since 15 Apr 2017
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forwardmarchstudios Supporting Member of TMP15 Apr 2017 4:01 p.m. PST

It's rather cheap, and I've put in a few quotes, still waiting to hear back.
Has anyone ever used it before? How was the final product?

Personal logo Bobgnar Supporting Member of TMP15 Apr 2017 8:27 p.m. PST

Got a website we can look at. I've never heard of this in 50,years playing war games.

goragrad15 Apr 2017 9:17 p.m. PST

I have cast silver jewelry (centrifugal) and thought of doing it for miniatures. But haven't actually done it.

Hadn't thought of having it done for me. I remember reading about casting quantities of small fittings for modeling using investment casting in the encyclopedia (geek alert) in grade school or junior high.

Not a new idea.

As to quality, that will depend on the quality of the wax models – if you are looking at multiples of a single model, you will be casting those in wax and any flaws there will have to be addressed prior to the investment. If individual sculpts, the castings should be every bit as good as the model presuming that the sprues are properly placed and in sufficient quantity.

I had trouble casting some leaves with an interesting lace like pattern of holes due to their thinness and the fact that having enough sprues would likely have left the casting looking looking like a porcupine prior to their removal. But it would have been technically possible.

forwardmarchstudios Supporting Member of TMP15 Apr 2017 11:39 p.m. PST

goragard- They can now make the wax model with a 3d printer, then fill the space with metal- it's very cheap. But I'm not sure of the resolution you can get on it. I'll let you know.

Bobgnar- investment casting is when you make a wax model, surround it with another material, then melt out the wax and fill it with metal (or something else). At least, that is my understanding of it. It's actually an ancient technology, but the 3d printing aspect makes it faster. I should hear back Monday. 3d printing is kind of a Wild West.

shaun from s and s models Supporting Member of TMP16 Apr 2017 3:45 a.m. PST

also called lost wax casting, like any casting it all depends on the original master, if that is good then the casts could be as good, what are you thinking of making?

Mick the Metalsmith16 Apr 2017 9:33 a.m. PST

I am a jeweler but I can't say I would use it for figs. White metal contamination of my gold or silver would be a seriously expensive disaster. I did contemplate using bronze but the biggest issue is that making the waxes and the spruing for jewelry flasks which are typically 4 inches diameter and 6 inches deep would be too labor intensive and only a few figs could made in a batch. Burnout limits how many flasks you can do a day because most kilns are too small for more than5-10 flasks. The mold to wax step is avoided in normal pewter spin casting and that is a major savings in time. Lost wax can't compete for multiples of the same figure.

You also have a rough finish to cleanup in the casting. I don't want to have to file and sand all that bronze.

Pythagoras16 Apr 2017 12:42 p.m. PST

The company I worked for in the past used a lost wax process to cast small detailed parts in brass. They melted the wax from the very fine plaster filled canisters in a time controlled oven slowly overnight. We then placed the canisters in a spin caster that had a built-in crucible to melt the metal. We cast mostly in brass but did occasionally cast in aluminum, zinc and manganese.

However, I don't see why you could not do this on a smaller scale. Would it be cheaper? It depends on materials, supplies and what you wanted to cast.

forwardmarchstudios Supporting Member of TMP16 Apr 2017 2:41 p.m. PST

It seems very cheap, at least through the company I'm looking at. ~$.60 a piece, which isn't bad. I'm working on some 2mm infantry strips. 20mm or 30mm wide, 60-75 figures per piece in three ranks. It s part of a larger project, basically, the test to see if it will be economically feasible/do-able.

The service I'm looking at, from what I gather, can make the wax dummies with 3D printers very quickly and cheaply, then casts the pieces in metal to complete them. At least, I think that's what they do. Honestly,the 3d printing business is a bit hard to navigate. They'll get back to me Monday, I hope, with some more answers about my project. I'll update here, of course : )

goragrad16 Apr 2017 2:59 p.m. PST

forwardmarchstudios – I saw the fact that they can make the models using 3D printers, and the finish quality on those would be a major consideration in determining the quality of the casting.

Mick – what I cast wasn't terribly intricate (aside from the failed leaves), but even in the crevices the cleanup wasn't bad. Although the sterling was a bit harder to clean than the fine. Tumbling would be an option if very fine parts were not projecting.

I would also presume that jeweler's flasks would not be the device for the casting being discussed here (although I would probably use them if I went with this method not having the facilities discussed by Pythagorus).

Personally I was also thinking brass – at the time I had a significant quantity of scrap to hand. Also some tin I could alloy my scrap copper with.

Mugwump17 Apr 2017 6:32 a.m. PST

I believe bronze age miniatures did this at one time. They have since gone to spin casting pewter.

Mick the Metalsmith17 Apr 2017 1:29 p.m. PST

A 3D printer can be used two ways, it can create a wax model directly for investing and burnout(it's not melted out although much of it can be removed by melting and steam but you have to turn the wax to carbon gas or you will get imperfections in your cast). The other method is to make a hardier plastic 3D model for making the equivalent of a green model (my jewelry tool suppliers can do either) that then must still have the flexible latex or silicone mold that wax is injected to to make the burned out models.

Investment casting is only required for metals with high melting points--higher than what a rubber mold can handle (which can easily handle white metals such as pewter alloys which are less than that of gold, silver and bronze/brass). Since burnout requires high temps flasks will be small, and the space for figures within strictly limited. The conventional spin caster for pewter is much more time efficient for the number of figures involved for anything but to create a single metal prototype from a conventionally carved wax model.

If you rely on a 3D printer to make your masters for investing you might as well go the rest of the way and just make the spin caster molds for duplicate figures. Pewter gains nothing from investment casting and loses a lot of its advantages. Investment leaves residues and slight textures on the pieces and cleaning the casting will be a lot of work, silicone and latex molds in spin casters don't. I bet you will have other problems from gases and temprature levels that spin casters don't and finally there is no investment sludge to clean off and get rid of. Not something many consider. It really is an economy of scale issue.

Mick the Metalsmith17 Apr 2017 1:43 p.m. PST

By the way when I refer to s spin caster I speak of pewter casting machines where the rubber mold is huge wheel that is cast directly into. I use a centrifugal caster for lost wax investment casting, but they are two radically different tools. Most investment casters now use vacuum and pressurized casting machines but some holdouts like my self with smal volumes who like centrifugal

forwardmarchstudios Supporting Member of TMP17 Apr 2017 5:34 p.m. PST

Mick_the_Metalsmith-

Lots of good info there! Very good info to know. It's sounding like what I had in mind might not actually be do-able… maybe there was a reason all the investment casting examples were things like faucets, door knobs and coat hangers, and not 20mm wide strips of 2mm infantry figures…

I've contacted a spin caster/jewelry maker near me about doing some work as well- they haven't got back to me yet. For that matter, neither has the investment caster company, so maybe they're trying to figure out what to make of my order. Then again, only one business day has gone by so far, so they might just be busy. I'm already spoiled by the ten-minute response time for a lot of the 3d printer services…

I'd be open to a spin caster if I could find someone on the west coast to do it for a decent start-up price.

goragrad17 Apr 2017 10:37 p.m. PST

FYI, not all investment/lost was casting uses flasks.

Now that you have stated what you are casting, spin would probably be the better option.

For amusement though, here is a link to a description of the normal investet casting process (note that the models are attached to a central sprue to form a 'tree') -

link

On a final note, in looking at a couple of the companies doing investment casting, their webpages emphasize their capacities for large castings, large runs, and steel alloys and more exotic metals.

Mick the Metalsmith18 Apr 2017 8:11 a.m. PST

The link is pretty informative in a general way but it does describe a gravity pour casting instead of centrifugal. For small castings such as a figure the gravity pour will not be very useful, premature cooling becomes more likely and backflow will require extra careful sprueing . That process works better for larger items. The flaskless slurry coating of investment is again something better suited for larger items as investment is easily damaged and trying to maneuver a very hot large investment shell is a another issue. Flasks can be pretty big 5x8 inches is large enough for jewelry, but to protect a large tree in motion will involve industrial tools beyond the reach of a small studio and overkill for figures. Again economy of scale.

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