Making Molds for Non-Bullet Items

[Daekar]

Hey Folks,
I've been thinking that it would be great to combine my 3D printer and a bit of bullet casting, so I'm looking for a way to make a mold, even a single-use mold, from a 3D printed original piece. Does anybody know of a product which would allow me to do that? I was imagining some kind of clay which hardened into a mold or a super high-temp papier-mâché or something. Even if it ended up only being able to tolerate the melting point of pewter, that would be enough... I'm sure I can get my hands on pewter to melt if necessary.

[Rcmaveric]

Depending on what your casting. You make a two part object then make a sand or plaster mold. Surface finnish wouldn't be the nicest. Plaster might give you a better finnish surface than sand.

Might look into silicone molds. I am not sure how high of a temp the can stand.

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[Blanket]

cast able silicone rubber

[Daekar]

cast able silicone rubber

I did a bit of searching yesterday, but I didn't see any silicone rubber mold compound which said it would stand up to 750°F. Do you have a specific product in mind? If so, I'd love to hear about it, that sounds ideal.

[Daekar]

Depending on what your casting. You make a two part object then make a sand or plaster mold. Surface finnish wouldn't be the nicest. Plaster might give you a better finnish surface than sand.

Might look into silicone molds. I am not sure how high of a temp the can stand.

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Plaster looks like it can take the heat no problem... never thought I would get into lost-wax! Do you know if it's practical to create plaster molds without the wax step?

[pastera]

Plaster looks like it can take the heat no problem... never thought I would get into lost-wax! Do you know if it's practical to create plaster molds without the wax step?

If you use a 2-part mold then you don't need the 'lost' part of the process. You would pretty much create a 3d printed mold for each half of the plaster mold.

[Blanket]

we used it at work to spin cast zinc, can't remember the brand

[bedbugbilly]

I know nothing about 3D printing . . . but I'll pass this along as it might apply - I have made molds out of plaster before. One I did when I was a kid - I made a plaster mold - a two piece mold - and used a Civil War Enlisted Men's U.S. belt plate (buckle_ to create the bottom of the mold - the upper half of the mold formed the flat back of the belt plate. In the upper half of the mold, I used paper cylinders to form the sprue and riser hole for the pour. I poured the belt plate out of zinc and it turned out very well - front of the buckle was smooth and nice because I poured the mold out of "runny" plaster and IIRC, the mold form I fadeout of 1/2" plywood and after the bottom half was poured with plaster, used a vibrating sander wo vibrate the mold box to get rid of any air bubbles in the plaster. The plaster held up fine at whatever temperature zinc melts at. It was a "one time" mold.

I have had experience in sand casting as well - used to teach foundry in my shop classes and we would pour aluminum - been years though. I would imagine that depending on what you wanted to pour, a 3D printer, from what little I know about them, could be used to create the pattern. As in any sand casting though, your pattern would have to have the proper "draft" to withdraw the pattern without damaging the sand mold after it is rammed and like any sand casting, you would have to use the correct measurements (we used what was called a "shrink rule" - a ruler with the dimensions on it taking into consideration the shrinkage of the material being poured when it cooled).

In college, we were also instructed on the lost wax process using a centrifugal casting machine. Perhaps 3D printing could be used to create the patterns. This process is used in creating such things as poured jewelry, etc. and you might read up on the lost wax process to see if it is something that would work for what you want to do. Usually, the patterns for the mold are made out of wax, the mold made with the wax pattern inside and then after the mold "sets" (hardens), the mold is heated to melt and drain the wax from the mold leaving the cavity ready to be poured. I had a friend who worked his way through college - a fantastic artist who was studying electrical engineering - he should have just done his art. He would us such things as dead bees and stalks of wheat, etc. as the patterns for his castings. He would then basically burn the pattern up by heating the mold since bees, wheat, etc. don't melt like wax. He would then pour the castings using the centrifugal casting machine and even such fine details as the hairs on the bees would come out perfect - he would then make a mold and pour a wheat stalk with the head on the stalk - use a nice walnut base and when done, the bee was shown as if it landed on the stalk. He used both gold and silver for his pours and I know he sold quite a few to the professors.

I hope you'll post some photos of your 3D work as you experiment - interesting stuff!

[country gent]

For the castable polyurethanes ad silicones look at Alumilites web site. They have a pretty extensive selection.

You can always cast in the lost wax process. Max the image from wax with fills and vents. coat it ia ceramic slurry and let cure then fire it on the pot when melting the metal and to melt the wax out. Fill and let harden.To a point the thinner the clay slurry the better the detail but the more coats it will take to get the build up needed.

If your 3d printer can use a wax then you could print the parts very accurately.

[waksupi]

Something I came across for sand casting, is to use florist foam to make your pattern. Pack it into the mold with a casting gate attached to the mold. Pour in the metal, and the foam goes away. I've used it to make butt plates, side plates, and trigger guards.

[Handloader109]

There are a lot of folks that use the 3d printed item as lost wax type item. Plaster molds for the most part. Youtube is maybe your first stop../

[bangerjim]

Carved cuttlefish (like birds chew on) make semi-good molds. The ancients did that for a long time. They will eventually burn out, but works for several drops! Carve what you need in them and pour away.

[fcvan]

I watched a program recently where where a car part was cast at a foundry, the mold was 3D printed using a mixture of sand and glue. Mold was a one time use deal, kind of like plaster of Paris. I knew several hobbyist jewelers who did lost wax, neat setup.

I have been saving up old brass which I hope to make into a belt buckle with my Wife's name in her handwriting. I know she will love it!

[r6487]

there is a guy over in africa who is casting shotgun slugs using a socket for the mold. there are posts with some pics over on the casting for shotguns board.