Clay molds for aluminum casting?

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dorin
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Clay molds for aluminum casting?

Postby dorin » Sun Feb 26, 2017 2:01 pm

Suppose you made a mold from clay and fired it in a kiln...would you be able to successfully pour aluminum into it, or would the kiln firing deform the mold?
(Or are there other problems I am not even thinking of?)
Thank you,
MIke

OddDuck
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Re: Clay molds for aluminum casting?

Postby OddDuck » Sun Feb 26, 2017 4:21 pm

Shrinkage would be a major concern. This is done, by the way, with lost wax, aka investment casting. These are one-shot deals, too. The mold is destroyed to remove the casting. If you are talking about a permanent or semi permanent mold thermal shock would be the biggest problem. When you poured the metal in, unless the mold was heated to near pour temp it could potentially crack.
"If you took the bones out they wouldn't be crunchy!" -Monty Python's Flying Circus

jscarmozza
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Re: Clay molds for aluminum casting?

Postby jscarmozza » Mon Feb 27, 2017 6:11 pm

Have you thought about molding your pattern in core material rather than green sand? I've had some success doing that, but you'll get the sand cast, not the smooth invest cast finish.

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steamin10
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Re: Clay molds for aluminum casting?

Postby steamin10 » Mon Feb 27, 2017 10:16 pm

Not so! Using a hardening core mold can, and then giving it a wash of clay (slip) or even sugar and starch as a wash, will refine the surface. It will also make the sand tighter, which may effect the gas off during a pour, but change the finish.
Big Dave, former Millwright, Electrician, Environmental conditioning, and back yard Fixxit guy. Now retired, persuing boats, trains, and broken relics.
We have enough youth, how about a fountain of Smart. My computer beat me at chess, but not kickboxing
It is not getting caught in the rain, its learning to dance in it. People saying good morning, should have to prove it.

dorin
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Re: Clay molds for aluminum casting?

Postby dorin » Tue Feb 28, 2017 7:29 am

I have not thought of core material.
The only success I have had is with kinetic sand, but it gets a little pricey.
It does leave a pattern..but not too bad.

Could not find an image of the original casting, but here it is cleaned up a bit.

Starting to think of spring and trying again. Our last poor was too late in the year...a cold day with a cold wind.
The aluminum solidified in the crucible...or at least starting too...giving us ugly results.

-MIke
Attachments
001.jpg

jscarmozza
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Re: Clay molds for aluminum casting?

Postby jscarmozza » Tue Feb 28, 2017 9:07 am

Right again Big Dave, I forgot how well the finish was on the sprues and runners when I applied the core wash when pouring the cab roof. They had a better finish than the casting! Dorin, check out the advice Big Dave and OddDuck give on making cores in the pouring thin sections post. John

GLBowers
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Re: Sand mixture for molds for brass casting?

Postby GLBowers » Sat Sep 02, 2017 9:39 pm

I'm trying to mix sand, clay, oil, and alcohol to be able to cast brass. The formula I'm using is from Kent State (100 lb. sand, 6 lb. clay, 3 lb. oil, .2 lb. alcohol). The sand I'm using is Sakrete Play Sand. The clay is Natural Clay cat litter. The oil is Supertech full synthetic 2-Cycle Engine oil. The alcohol is 91% Isopropyl Rubbing Alcohol from Walmart. I mixed 16oz. Sand, .96oz. Clay, .48oz. Oil, and .032oz. Alcohol - which leads me to my problem, it isn't sticking together like it should - the mixture is too dry, I think. Can anyone give me some guidance - do I add more oil until I get the proper packing properties? Your help will be appreciated. Thanks, Garman

OddDuck
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Re: Clay molds for aluminum casting?

Postby OddDuck » Sat Sep 02, 2017 10:33 pm

Wrong clay, I can almost guarantee you. The clay you need for k-bond or petrobond is different than naturally occurring clay. It is chemically treated to make it organophyllic instead of hydrophyllic (pardon if I have the spelling wrong...). It absorbs oil instead of water. Google bentone, or petrobond. To the best of my knowlege there is no off the shelf, local equivalent for it, and no, Oildry is not bentone. Hate to say it, but your sand may well be unfixable if you used regular old bentonite instead of the right version of bentone.
"If you took the bones out they wouldn't be crunchy!" -Monty Python's Flying Circus

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steamin10
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Re: Clay molds for aluminum casting?

Postby steamin10 » Sun Sep 03, 2017 1:38 am

Odd and Dorin et all.. Kitty litter is used in cat boxes and to pick up other garage mess on the floor. It is next to worthless for casting. The Kent state formulae is right on, and basically what I use. I use white filter sand for pool filters, as it is clean and washed and about 100 mesh, very fine. In my area we have sand dunes around Lake Michigan, but organics and sifting just is not worth the time. Sand is the cheapest part of the ingredient, and several hundred pounds is less than a twenty. Isopropal is the wrong alchahol, but still works on the 2 cycle oil, which is the only component that must be renewed as it eventually leaves the sand. A small amount of alky and a remulling will usually bring back the finer qualities. (Stepping on and squishing the sand and flipping it with a flat shovel works best, as the sand needs to slip past itself for good distribution. Chopping with a square shovel is a poor second, but works eventually. This is foundry practice for many years to keep sand so it balls when squeezed in your fist.. If it wont form, you will never get a good pull from your pattern.) When Petro is right, it is a wonder to cast with. When it is out of condition, it is as maddening as anything else that dont work. While really good for brass, remember that iron contaminated aluminum wont flow or give you detail. Trust me. Use cast aluminum of the best you can find, heat fast and pour quickly to get the best. Holding aluminum, slow heating, iron rivets and steel trash is a road to poor performance and wasted time.
Big Dave, former Millwright, Electrician, Environmental conditioning, and back yard Fixxit guy. Now retired, persuing boats, trains, and broken relics.
We have enough youth, how about a fountain of Smart. My computer beat me at chess, but not kickboxing
It is not getting caught in the rain, its learning to dance in it. People saying good morning, should have to prove it.

GLBowers
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Re: Clay molds for aluminum casting? Brass Casting

Postby GLBowers » Sun Sep 03, 2017 1:33 pm

Odd Duck and Steamin 10,

Thanks so much for your reply's. The items I chose for mixing were not just me making uneducated guesses, but info (I thought) researched out. Clearly I'm not as good as I thought in my research. I was trying to get ingredients that I could obtain easily in my area (Hagerstown MD) from Hardware stores, etc.. Would youall be able to list for me what you would recommend I use and where it can be purchased by me (examples: Lowes, Walmart, etc.) if you can. I am new to this "Casting Brass" thing - I'm a total novice! I have woodworking skills and am a retired Band Director. I combined the two and enjoy restoring 19th Century Rope tension Drums (this is where the need for Casting Brass has become an interest) and playing in professional Civil War Brass Bands. Check out my Links if you have time (I think you may enjoy):
https://www.facebook.com/pg/GBManufactu ... e_internal
https://www.facebook.com/federalcitybrassband
https://www.facebook.com/26thNCBAND

Your guidance and help will be greatly appreciated.
Thanks,
Garman

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steamin10
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Re: Clay molds for aluminum casting?

Postby steamin10 » Mon Sep 04, 2017 9:55 pm

I can tell you to search for a small cast shop, and offer to buy some of their used sand, as most shops renew and update often. They may take into account that any quantity of used (up) sand they give or sell you will go toward maintaining their stock at lower cost. Second, talk nice to them, and they may volunteer to make a trial cast with some excess if you can provide an appriate mold. Crafters and art people are good at helping lost souls, IF IT ISNT a lot of trouble. Third, no better way to get perfect castings, than to become a customer with samples, with well defined needs.

Now having said that( let the pros do it) it is really not beyond the garage guys abilities, if yuo do your homework, and follow all the steps. They were casting bronze in China, over 2000 years ago. It is not rocket science, so dont get lost trying to re-invent the wheel. If need be, pay the freight and UPS/mail order a small quantity of mulled sand 50lbs or so, and care for it. Store it in a galvanized trah can, or cut down food barrel with a tight lid, and keep the cats kids, and sawdust out of it.It will last a good long time.

To answer the supply question, Isoprpol and methanol are commonly availaable at most big box stores, as is fine filter sand. Do not get play sand, s that is rounded and pebbly, not sharp grained and uniform. I live near Chicago, so there are supply houses for the 50 or so cast shops that inhabit the midwest. In other areas of the country, you wont be so lucky. However the dry powder I used came from a supply houe in a red color (iron oxide added that prevents scabbing with brass and bronze) and had the petro bond brad name . Mice ate the bag for me with the resulting spillage, but point is it is available by the bag, just add the cheap sand and chemicals to get what you want. I have a mini mull that only mixed about a good shovl ful at a time, and a 1/5 yard barrel mixer, that gets a coupla shot -put balls added to beat the mix. You can use a shovel and squish and flip, but use plastic sheet or some similar barrier so as not to lose the oil and wet ingredients. A mar-light shower panel is good and cheap and will last a good long time. If you go it alone, pay attention to the formula, as too much oil or alky will have varied effects on the mix, and it tends to get stronger and tighter for several days after being created.

As for quantity, small aounts of sand will change quicker than a larger pile. I have several hundred pounds, enough to fill a 30 gallon grease barrel. But say ten lbs and wooden boxes of 6 x 6 or 8 x 8 can do the smaller jobs with less materials, and if you burn a box up, so what, make another that works for you. Just because the commercial guys have steel forms all the same, and a silo of sand doesnt mean you have to. Jewlers use soup can sized molds and equipment to make gorgeous castings, and so can you. Keep in mind the scale of the things you want to do, and act accordingly.

I would like to see your first attempts, as there is always a learning curve.
Big Dave, former Millwright, Electrician, Environmental conditioning, and back yard Fixxit guy. Now retired, persuing boats, trains, and broken relics.
We have enough youth, how about a fountain of Smart. My computer beat me at chess, but not kickboxing
It is not getting caught in the rain, its learning to dance in it. People saying good morning, should have to prove it.

GLBowers
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Joined: Sat Sep 02, 2017 5:16 pm

Brass Casting with sand mixture

Postby GLBowers » Mon Sep 04, 2017 11:00 pm

Steamin 10,

I really appreciate all you shared with me. I totally understand you can't beat the professionals at their trade, however, I have the drive and perfectionism to accomplish a high level of quality on a moderate level of brass casting (you have seen that drive and perfectionism in my work if you've viewed my Facebook business page). I am attaching photos below of what I need to cast and I will be sure to share with you my progress with this project - it's the least I can do in an on going endeavor to thank and show appreciation for your guidance and help.
Thanks,
Garman


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