Machsupport Forum
General CNC Chat => Show"N"Tell ( What you have made with your CNC machine.) => Topic started by: Jammerm on September 09, 2012, 07:53:17 PM
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This is adapted from a post I saw on a hotrod site. He had used a router to route out hisname by hand and poured Pewter in it and busted it out. I routed my son's name in reverse using F-engrave and used the rails on the back half to hold the letters together. Just for this test, I cast the letters with hard type lead. Next time I'll route the letters a little deeper and cast it with Pewter. I have to be a little careful with that, the pewter is $16 to $20 per pound. The Lead is less that $1/pound, I don't have near that much in it. I've several hundred pounds of old letterpress type. The name pattern is still fine and can be used again. The back piece with the rails broke when I tried to get the piece out.
The black on the pattern is graphite to keep it from sticking.
(http://i183.photobucket.com/albums/x310/Jammer_55/Misc%20Items/IMG_0003.jpg)
(http://i183.photobucket.com/albums/x310/Jammer_55/Misc%20Items/IMG_0004.jpg)
(http://i183.photobucket.com/albums/x310/Jammer_55/Misc%20Items/IMG_0006.jpg)
(http://i183.photobucket.com/albums/x310/Jammer_55/Misc%20Items/IMG_0009.jpg)
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Very, very cool! Hope you make lot's of money!
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Hi Jammer,
Another brilliant idea. ;)
I do admire your casting work.
Tweakie.
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Hi Jammer,
Another brilliant idea. ;)
I do admire your casting work.
Tweakie.
Ditto! Great job- :)
Dave
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Thanks, by the way my son has a '56 Buick Century. He doesn't have his license yet, but he' got a car.
I'm going to try one more like a plaque and cast it in Aluminum or Zamak a Zinc/Aluminum alloy. Then on to Bronze. :)
I won't be able to use the MDF with Bronze, too hot. May try plaster or make a wood positive and cast it in sand.
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I won't be able to use the MDF with Bronze, too hot. May try plaster or make a wood positive and cast it in sand.
All of my aluminum casting attempts have been done in sand. Although, the very first time I tried pouring some molten- I had a couple of pieces of plywood that were left over scraps from cutting some wooden gears out on the CNC Router table. I will never forget that experience! I knew that the molten would probably burn the plywood, but I THOUGHT that it would at least solidify before too much burning occurred. WRONG! That plywood did not even slow the molten's descent down, on it's way to the ground! (It literally VAPORIZED the plywood on contact!).
Since learning from that experience, I have been making sand molds. And being retired, (and unable to afford Petrobond casting sand), I learned how to make my own foundry sand. After trying many different recipes, the one that finally worked with good results was: 80% sand, mixed with 15% Bentonite clay (CLUMPING type Kitty Litter), and 5% Charcoal ashes. I had to construct a special machine to use for grinding the kitty litter into powder, which consisted of a steel turn-table, with two grind stones (like those on a bench grinder) which ROLL against the surface of the steel turn-table. A variable-speed DC motor was used to drive the turn-table, at the slowest possible speed, while friction drives the grind stones.
The slow speed is needed to prevent centrifugal force from simply slinging the kitty litter to the outer rim of the turn-table, (and thereby OUT of the path of the grind stones). Only small amounts can be ground at a time, as it is after all, Bentonite clay, and will begin to clump onto the grind stones. A knife-edge was later added to the stones, to keep the clay scraped off during the grinding process. It is also helpful, to first DRY the kitty litter, by placing it in a pot, and into the foundry furnace, stirring constantly until it is completely dry. Once the kitty litter clay has been ground into the finest possible powder consistency, then pour it into the sand, add the charcoal ashes, and begin mixing by hand, until all three elements are evenly mixed.
I use one of those plastic tubs, with a snap-on lid to store the foundry sand in, to prevent (at least as much as possible) the sand mix from becoming too dry, or too wet. When using the sand to make the sand molds, I use a spray bottle of water, and lightly moisten the sand, stirring constantly by hand, until it becomes wet enough to form cakes when squeezed in my hand. At that point, it is ready to pour into the flasks to make the sand mold. The sand mix is re-usable, however (because of the kitty litter) has to be re-ground to break up the clumps back into powder form. I have learned, that this step is only necessary for a small amount. (The sand that actually contacts against the pattern being molded). The rest of the sand acts as just a "filler" of the flask. And when rammed up (packed into the flask) properly, it will ALL become very similar to concrete. Especially after a pour, and must again be broken up, and ground. A five gallon plastic bucket, with a few rocks thrown in, and turned tumbler-style (again, S-L-O-W-L-Y) will speed up the process.
Sorry to ramble, but I know that others are reading this with interest, and I just wanted to warn folks that metal casting is VERY DANGEROUS. I am actually amazed at the results you were able to achieve with the MDF, that it did not Vaporize on contact with the molten metal! I would hate to hear that someone tried this, and lost a foot or something, as the molten metal poured right through the MDF or other non-fire proof mold material. Metal Casting is very dangerous, and must be done with respect, paying attention at all times to what you are doing. Serious injury can occur!
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Hi Adprinter,
Excellent information indeed - thanks for sharing your knowledge and experience.
Tweakie.
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My greensand is made with Kitty Litter also, I ground mine in an old blender. I heard of guys just soaking the litter in water until it breaks down to mud, then dry it out some and add sand. I haven't tried that yet. I think my mix is about 10% clay to 90% fine sand. I've been going to add coal dust because it gives a better finish.
Everything stopped last year when I was downsized at work and then went on disability due to some health issues. Then we moved twice and I've ended up in Southern Tennessee. I didn't have a garage or any storage space so I put all my toys in a storage locker.
Well now my garage is finished and I just got out of the hospital...Again! Now, as soon as I'm allowed by the warden (aka wife) :), I'll get my CNC and all my casting stuff out of limbo and start doing something again.
I've cast Lead, Aluminum, Brass, and some Cast Iron. Hope to smelt some Iron this year, from ore I've collected. Casting is my primary hobby, I built the CNC to make some patterns for casting signs and gears and such. Can't wait to get back at it.
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Jammerm,
Neat idea and hopefully you'll get back to norm and enjoy what you like doing.
Long time ago we used pewter for forearm end caps on kentucky rifles we made.
At that time we just went to the flea market and bought all the pewter spoons we could find!
Just used paper wrapped around the forearm as a big spru and filed it to finished shape.
Have fun,
RICH
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Rich, that sounds like a good approach to a casting like that. I really like Pewter and have collected a few pounds of it at auctions and flea markets. Problem is, I don't always know what I have. I'm pretty sure it all Lead free from looking up manufacturers online and sticking with newer castings. I also bout a bar of pewter from a metal supplier. I got some Nickel too, I hope to make some Monel sometime but would have to build a tougher furnace.
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Adprinter, I forgot about the comment on the MDF. Yes, I was surprised how well it stood up to the heat. It was a Lead Alloy that melts at about 550F, I take it to about 600F to pour. It barely scorched the MDF, I think I could have cast a few more without trouble. If it had failed, I was going to try to cast it with Bismuth. It still has to be about 550F to cast. I wish I could afford some Woods Metal. I just don't have any Cadmium. Woods Metal melts at about 160F, that would be pretty neat to try.
I have had a few failures, metal shooting out between the flask, melted through what I thought was a thin steel plate, turned out to be Tin. That was fun, molten Aluminum everywhere. I want some petrobond for brass, it likes to spit and pop out of greensand. Glad I have good PPE.
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Adprinter, I forgot about the comment on the MDF. Yes, I was surprised how well it stood up to the heat. It was a Lead Alloy that melts at about 550F, I take it to about 600F to pour. It barely scorched the MDF, I think I could have cast a few more without trouble. If it had failed, I was going to try to cast it with Bismuth. It still has to be about 550F to cast. I wish I could afford some Woods Metal. I just don't have any Cadmium. Woods Metal melts at about 160F, that would be pretty neat to try.
I have had a few failures, metal shooting out between the flask, melted through what I thought was a thin steel plate, turned out to be Tin. That was fun, molten Aluminum everywhere. I want some petrobond for brass, it likes to spit and pop out of greensand. Glad I have good PPE.
Jammerm, what device do you use to measure temperature of the molten? I have a laser thermometer, but it will only measure up to about 500 degrees F. My foundery oven is a charcoal-fired design, using an old heat gun (aka glorified blow dryer) to air blast the charcoal. I have since learned that my scrap pieces of left-over oak (from my CNC carvings) yields a hotter burn (20 minutes from lighting, to molten vs 30-40 minutes using charcoal). Yes, it burns up faster than the charcoal. But it does the job (and since I already have it, the price is much cheaper than buying charcoal). My biggest problem, is coming up with a trivet to hold the crucible pot which will withstand more than a couple of firings. I have tried many designs. Including a disc brake rotor, with threaded rods casted in the same mortar mix used to line the furnace with, as the legs of the trivet. But the ends of the rods were exposed to the heat, and the threaded rods melted, and ran out of the mortar castings, which then crumbled and broke off. You mentioned the greensand spits and pops. I have learned, that the more vent holes you put in the sand mold, the better. Just be sure that you don't plunge your wire any closer to the pattern than about 1 inch. Also, before assembling the cope to the drag, go over each with a blow torch (I use a Mapp gas torch for this). It will improve the spit and pop problem. And it will save time (with failed castings) in testing whether or not your mold is durable enough to hold up for the casting. I.E.- if the torch causes it to crumble, you have just learned that the mold wasn't actually ready to use for a casting, because it would have been a failure anyway. Much easier to just re-mix the sand, and re-ram the pattern in the sand, without the need to also re-melt the useless blob of aluminum that would have otherwise resulted!
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This is a little kiln pyrometer I got from ebay, I think it was $75. I use it for Aluminum and for small brass melts. I submerge it in Aluminum but not brass. Mostly I just read the furnace temp.
(http://i183.photobucket.com/albums/x310/Jammer_55/Electric%20Furnace/20120609011.jpg)
This is a little electric furnace I built, it worked great. That's Brass in the crucible, I think it's 85-5-5-5. I got it too hot and the Zinc started burning when air got to it during the pour. I don't remember what I was casting. This was too hot for the elements, when I tried a second brass pour they broke and I'll have to replace them.
(http://i183.photobucket.com/albums/x310/Jammer_55/Electric%20Furnace/21120716029.jpg)
I was able to get a lot of fire bricks from an old foundry. I cut one of the 1" ones into triangles and use them for a plinth blocks. They have held up very well. I've also made some with refractory that has worked well.
I've got a mix of graphite and alcohol that I spray on the greensand and then light it. The alcohol burns off and heats the sand and the graphite makes a smooth surface. That's a good idea with the torch, I need to get a rosebud tip for mine.
This is my small gas furnace, it runs on propane with a blower attached. It uses a high pressure regulator and puts out a lot of heat at 5 to 10 pounds pressure. This is lined with commercial refractory rated for up to 3200 F. I don't have anything that can read that high of temp, but I think I've been close to 2600 F a couple times, especially when I used a waste oil burner. This little guy didn't survive the move from Ohio to Tennessee.
(http://i183.photobucket.com/albums/x310/Jammer_55/IMG_2022.jpg)
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This is a little kiln pyrometer I got from ebay, I think it was $75. I use it for Aluminum and for small brass melts. I submerge it in Aluminum but not brass. Mostly I just read the furnace temp.
What material is the sensor on the Pyrometer made of? I can't image submerging anything into molten metal, without it resulting in the sensor itself becoming a part of the molten metal. Thanks for responding! I could not recall the word used to describe the mortar material I used to cast legs for the trivet- "Refractory". Your little oven looks very similar to mine, except that mine was constructed from an old hot water heater tank, instead of a freon tank. It stands about three feet tall, and will accommodate up to an 8" diameter crucible pot. I have actually used the freon tanks, sawed in half-as crucibles placed inside my oven. Yes, the steel crucibles do burn holes thru them after only a couple of firings, such is life for the financially challenged! I have not yet tried melting brass, but I have a cast iron dutch oven I have been saving for this purpose. Do you have any experience with crucibles other than the carbide graphite variety? I have used stainless steel (of the dollar store salad bowl variety), plain steel (of the freon tank, or LP tank variety), also stainless steel pressure cooker pots, as well as cast iron cookware. Experience has taught, that the steel pots can be used as crucibles, but great CARE must be excercised, when stirring the molten, and spooning the dross. (So as to not poke a hole thru the bottom of the pot, which is usually in a near-molten state itself!). What experience have you had, with cruciibles? What material were they made of? Where did you find them?
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show us a brief video..unable to believe MDF can be a mold for melted metal pouring..
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Well, I didn't have a video and everything is still in storage. Again it was a lead alloy and was less than 600 F at the pour. If it would have been a heaver casting with thick areas that would hold heat, I imagine it would have burned the MDF. This is thin and cooled very fast. I was surprised how well it worked.
I haven't made any money, my son isn't much of a salesman. He took it home and hung it in his bedroom. I'll have to get with the local cruise ins here, there's one about every month.
The thermocouple is the usual bi-metal wire with the end welded with Nickel, I believe. The it has ceramic insulator on the outside. I have used just thermocouple wire twisted together, or clamped with a steel connector. Too much of a chance to get false readings with a set-up like that. I've also got a couple of these old temp controllers, they look like something from a Steampunk set-up. they work but don't do well over 1000 F. The one I have used is 1800 F max, this one in the picture I picked up at a flea market for $18, it's not working but they are pretty simple, I think I can fix it.
(http://i183.photobucket.com/albums/x310/Jammer_55/electric001.jpg)
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show us a brief video..unable to believe MDF can be a mold for melted metal pouring..
Do a search for evaporation foam casting. You would be surprised if you have never seen it I think.
Thanks,
Brett
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I like doing lost foam casting, it just stinks.
Drain Cover in blue foam
(http://i183.photobucket.com/albums/x310/Jammer_55/IMG_0087.jpg)
In Aluminum
(http://i183.photobucket.com/albums/x310/Jammer_55/IMG_0100.jpg)