Lost Plastic casting questions

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Windshadow
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Lost Plastic casting questions

Post by Windshadow »

hackney wrote:.... Any tricky new designs I print to work out the details before machining....
[img]http://www.blackiron.us/graphics/steam-hammer-fig3.gif[/img]
I have been designing(not a precise copy of a real monster) a working model of a 19th century steam hammer that will have the base frame at about 18" tall (when it is done I think the whole thing will be about 30" tall ) and I designed some patterns for things that would have been cast iron in the real thing in OnShape this is a project to help me learn OnShape since I can no longer afford the Shark software that is the 3D solid modeler I once knew.

I have to think about the metal I want to cast these parts from... Aluminum or "hard" lead alloy I can do out behind my barn but anything else the patterns will need to go to a foundry if I want bronze or cast iron.... a commercial founder will I guess accept plastic patterns for a one off job but I have been thinking about lost plastic casting.... I once made a casting of a housing part for an antique 1923 fire engine pump out of Styrofoam for a lost foam casting in bronze which is what gave me the idea. What FDM plastic would be best for what I want to do?

This is the info on the sort of thing i am considering... my model will be large enough to do actual work so I am tending to Cast Iron if I can find a place to cast the parts without chilled hard spots. one advantage to doing it this way is that I can use the neg space of the models to print fixtures to hold the parts for machining on my Bridgeport and engine lathe and my shaper.

Steam hammers are industrial grade power hammers and would have been found in commercial manufacturing. According to Douglas Freund (Pounding Out the Profits, p 4.), “Steam hammers had begun to assume a prominent place in English and French forges during the 1840’s.”

Below is some steam hammer information from Marvels of Science and Industry from the International Exhibition (Centennial Exhibition) 1876 Philadelphia. Book by Joseph M. Wilson, 1880, printed New York, pp. 129-134.

MESSRS. B. & S. MASSEY, of MANCHESTER, ENGLAND, make a fine exhibit of STEAM HAMMERS, which present some peculiarities of design different from the usual steam hammer, and appear to operate with great efficiency. They are double-acting and work without jar or shock, giving blows dead or elastic, and of any degree of intensity, rapidity of action or length of stroke desired, the larger hammers being controlled generally by hand, and the smaller ones arranged so as to work both self-acting and by hand. The action is therefore completely under control, and can be varied according to the kind of work to be done. - Generally with self-acting hammers there is great difficulty in obtaining the heavy “dead” blow so often required; but in these, by means of a hand-lever connected directly with the valve, the hammer may be changed instantly from self-acting to hand-working, and perfectly “dead” blows delivered at any time without the least delay. Their small hammers are particularly intended for smiths’ work, being applicable to the lightest kinds of forgings, such as usually done by hand, and their use is rapidly replacing that of handwork, resulting in great economy of labor, fuel and material even in the smallest smith-shops.

The hammer shown illustrates one of the large size hammers running up to 10 ton or more in weight.
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Captain Starfish
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Re: Lost Plastic casting questions

Post by Captain Starfish »

PLA.

Cheap, easy to print, stiff, its downfalls of low melt and crappy inter-layer adhesion don't affect you in this application and it flashes to smoke as soon as hot metal touches it.

Was it davidw on here who did a whole bunch of casting posts? Worth a dig around.
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jram
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Re: Lost Plastic casting questions

Post by jram »

Hi windshadow, I've had really nice results with PLA using the ceramic slurry process and casting bronze.Sometimes I will sand the model to hide the layer lines.
Machines- Rostock Max v2 with E3D v6, Corsair 750 power supply, PEI bed,injection molded carriages and new arms. Aluminum mount. X carve with x controller. Stratasys Uprint SE
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Windshadow
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Re: Lost Plastic casting questions

Post by Windshadow »

Thanks for the info and the search pointer guys.
There is a lot to think about including surface finish requirements once i get past a working digital model in OnShape.
It looks like it will have to be bronze at an artist centric foundry as iron casters that will take small one off jobs seem to provide chilled spot white iron castings (think areas of the castings harder than the hinges of hell and very brittle they cast things like door stops and wood stove parts that will not be machined)
I may need to rethink the end game for this project and the working parts to be machined instead from Durabar. Perhaps the base castings could be done in the white iron as they will require little machining and what they will require could be done abrasively ... lots to think about yet
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dmo
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Re: Lost Plastic casting questions

Post by dmo »

I've had great results with PLA. You may want to experiment with some metal core filament. I've used copper that has had some interesting effects with aluminum. Amazon has a 60% bronze one that I haven't tried yet. I'm still experimenting with different non-metal colors as well. Depending on how thick your piece is you may want to consider hollowing out some of the support. On larger pieces it cause a lot of air pockets that cause the metal to burp out more. They also make a lost wax filament that will burn clean but it is pricey and from what I've read harder to work with.
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Captain Starfish
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Re: Lost Plastic casting questions

Post by Captain Starfish »

Windshadow, on the prep side sanding PLA is pretty easy if you can get in to all the nooks and crannies. The toughest part of the job is not accidentally gouging it during finishing because these plastics are so soft.

Sounds to me like you need to lift your home foundry game so you can cast iron yourself. Perfect excuse to go finding refactory cement etc :D
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