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/diy/ - Do It Yourself


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File: 20190702_182033.jpg (837 KB, 2560x1440)
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I have been for a minute working on a aluminum filter to test my methods of casting metal items. I'm using sodium silicate plus fineish sand to create a block mold I inject with CO2 to solidify it. Then I flip it over on my foundary and heat using propane for about 6 to 8 hrs to melt and evaporate the pla to create a hollow cavety I fill with liquid metal meanwhile its reasonably hot.

So far the photo that you see is an incomplete test of a burnout we're not all the pla probably melted out. I'm working on the method and timing it takes.

Now that the intros out of the way I'm looking to create a better surface quality without investing in super expensive ceramic coatings. I doubt any spray paint would survive. I'm looking for ideas. Becuase of the nature of this baby powder isn't gonna work.

I figure I can dip the item in sodium silicate itself and then take plaster of Paris in sprinkle the powder on to the coating In let dry. I have a bag of fine silica powder but I cant find it right now.

Any other ideas are welcome
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>>1640715
Just dunk your PLA sacrificial in a bucket of plaster of Paris, leave the sprue ends sticking out, and let it cure. You'll never get amazing detail with sand.
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>>1641298
You can pick up print lines by using petrobond to cast with. Sodium silicate generally is better for making a more durable mold, but if OP wants DETAIL he's going to have to spend a bit more money on a good lost wax/PLA setup, or learn the nuances of casting in something like petrobond.
Petrobond is pretty cheap, too, and the learning curve isn't so bad. YouTube has a lot of great videos on amateurs pulling fantastic results. I reccomend looking up swdweeb or Paul's Garage. They both are very informative, Paul's Garage is a little bit less-so and more watching him throw shit at the wall and see what sticks. Swdweeb has a lot more success than failure, and I feel like he's learned about all he can in regards to mold making, and should start experimenting with new alloys.
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>>1641329
Paul's Garage: https://youtu.be/8fi_ebY696U
This guy has hardly any time to fuck around with trial and error, and apparently no time to watch swdweeb (who I found through Paul's channel) far surpass him. He makes mistakes swdweeb solved months ago, and still pulls fantastic results with a fairly decent success margin. The linked video being an example of one of those successes.
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>>1641333
swdweeb: https://youtu.be/SzSvWZij2q8
This is the short version of swdweeb's video where he makes a aluminum bell, which I feel is VERY similar to the design in OP's image (funnel?). He gets a very decent result with just the petrobond.
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>>1640715
Dude.
http://www.ceb.ac.in/knowledge-center/E-BOOKS/The%20Complete%20Handbook%20of%20Sand%20Casting%20-%20C.W.%20Ammen.pdf
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>>1641353
Not OP but thanks anon. Fukken saved.
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>>1640715
Op here

So the last thing that I molded I dipped the part in sodium silicate as a binder and then I sprinkled and pressed plaster of Paris (silica powder) into three or four layers and then I encased it in sodium silicate sand that I cured with CO2.

The detail was amazing absolutely perfect. I just printed out a riser tube about 10 mm in diameter. I think what I'm going to do now is make multiple layers like I have just done about 15 to 20 and then I will put it in my Foundry furnace tub melt and cure the shell of the object without any sodium silicate sand around it.

This is because the sand is such a good insulator it takes hours to burn out so I figure if I'm just using multiple layers in a shell the pla will melt and evaporate much quicker with less energy.

Then I will in case it in loose sand allowing for aluminum to pour and solidify in the shell before pulling it out and breaking it off.

>>1641298
The reason why I'm not using plaster of Paris like that is because you need two times the amount of plaster for the same volume of water. In considering that plaster of Paris is $25 per bag and you need about 2 inches around the whole funnel the volume gets pretty expensive
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>>1641329

I'm not using petrobond or any sand clay casting because I need to create a hollow funnel like feature. And the sand it's not going to withhold the burnout temperatures while I place it over a furnace to melt the pla out. One good shake and the whole mold collapse. That's why a concave object like such needs to be encased in a shell. For my purposes.
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>>1640715
I upscale my pla parts by 10% made a silicon mold and put wax in it, then used the wax to make the plaster mold and melt it out
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>>1641925
Silicon mold, or silicone mold? There is a difference.
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>>1641925
Why do you upscale Your Parts 10%
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>>1641950
To accommodate for the parts shrinking as a result of being cast twice
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>>1641833
My third post has a video demonstrating a funnel shape being cast using petrobond, but if you want to waste a shit ton of money trying to perfect the meme of "lost PLA casting," go for it. I gave you the tools to succeed, but it's on you not to be an idiot.
But good luck wasting prints and failing to get a good cast due to partial burnouts and other retarded gimmicks. If you want detail and functionality on the cheap, you're going to want to get some oil bonded sand.
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>>1642223
You are held back by your lack of creativity. There is never 1 way to do things. Petrobond is not the best.
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>>1642580
Dude is shooting down ideas because they're too expensive or don't provide good surface results. He seems unequipped to do a proper burn out with his current setup.
There's pros and cons of all methods, and OP specified he's not willing to bankroll what he'd need to get good lost PLA results. He's bitching about the cost of a bag of plaster of paris. It's rare for there to be an answer when some idiot pops on /diy/ requesting a solution with very specific requirements and then tacks on "it needs to be cheap."
This is one of those rare occasions there's a solution, with video proof of the concepts in action doing EXACTLY what he wants. But he's got his heart set on figuring out a way to burn out a material that was never designed to be burnt out.
Seems to me OP's the one with the issue of lacking creativity by anchoring himself to a gimmick.
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>>1640715
Skip all that. Make some ceramic slurry. Dip it a bunch. Pour into heated mold and maybe sand around gently in case of cracks or extreme temps. Maybe gently keep forge lit and taper down temps.

You went full factory out the gate like me. I gave it up. Goodluck man.
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>>1644819
That doesn't make any sense.
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>>1644819
How does one make a ceramic slurry anon? Genuinely asking.
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>>1647095
Depends on the ceramic, but typically some quantity of water with some quantity of mineral powder.
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>>1644819
>>1647095
>>1647115
Also, protip, make a wax positive, dip it in plaster slurry, get it with a water torch (hydrogen gas). Voila, plaster negative.
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>>1644819
>>1647115
Could you give some tip to were to look for information about something like that ,ceramic coating for casting ?Thinking about buying a SLA 3d printer that prints in castable wax /jewellery wax and i am deeply interested in making my own gym equipament. So doing casting would be great .
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>>1642223
Can confirm. Oil sand is tons better. The bentonite gel and sand shit sucks. Moisture is different every fucking time.
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>>1647116
>pressuring hydrogen.

Pls no



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