Help with casting weapons

[manglord]

Anyone have any hints/tips on mold making/casting weapons? I've tried to press a blaster into a clay bed, and it's really difficult to build the clay up to the parting line. Usually after I've tried to press the blaster into the clay, i end up with a low spot around the middle of the blaster. Do some of the clays vary in hardness?
If any of you have had successful results with casting in 2 pieces, could you share please. Thanks in advance!

[Jesse James]

First, www.FFURG.com has casting tutorials readily available for you manglord...  Check 'em out first for any inquiries and see if that helps.

Next up though, personally I would avoid casting with clays...  RTV Silicone is the route to go.  You get much cleaner/easier to manage molds out of RTV, and a lot less headache.  Making a 2-part silicone mold is easy, the cost is what's usually prohibitive to most people about casting.  Clay just is a waste of time/resources to me...   

[patreektherodian]

After making a mold,  I use a pressure cooker pot rigged with an air pump (no heat!!!)  If you can get it to cast in an environment of 30 - 40 psi, you will get a nice casting with no bubbles.

[Jesse James]

Agreed with that...  It's more complex, but if you have the urge to build a pressure-caster, you're far better off with casting.  You'll waste less material, you'll make the most of your work...  Patreek's steering you the right direction if you really want to delve into casting.

[manglord]

Patreek, What kind of pump do you use, is it an industrial type unit? Do you think i could pick one up for under a Bill? Sounds interesting, as i have experienced air bubbles messing up my molds.

[patreektherodian]

Lately I've been using a sports foot pump. but I  used an electric car tire pump at one point.  The whole set up cost me less than 60$  Smoothon actually recomends psi of 70 but I think that is to much. I will post a diagram. I could show pics but I don't think it would explain as well.

[patreektherodian]

A=is a valve that goes up and down when psi rises

B= a valve that had a removable piece. I sealed it from the inside with smooth-on  rubber mold.

C = There was a rubber release valve that I replaced with a piece that I got from an auto parts store. It fit perfectly and does not leak. It's the type of stem you would see on a car tire. I don't know how else to explain it

[patreektherodian]

If the pic does not show up try this link

http://s93.photobucket.com/albums/l63/patreektherodian/?action=view&current=savemon.jpg

[patreektherodian]

[manglord]

Wow! would you believe i have two packs of valve stems, both rubber and the metal ones as well. Talk about luck...Thanks for the diagram, now i have to check the garage, i thought i saw a pressure cooker pot  around too long ago.

[Jesse James]

Make srue your pot's seal is good.  If it's dry rotted, air will leak out, and you may not get the PSI you need to crush the airbubbles via pressure casting.  If it's old and beat up/bad, they're only like $40 or less at Target/Wal-Mart too, so replacing them is a cinch.  I got a bigger pot for a bigger price for the express purpose of casting larger pieces.  The depth/volume of room helps for that.

You can go all out too with compressors and pressure pots and whatnot.  I have a set-up for that in my garage...  I can do large volume casting with it, and also cast fairly large (small starship-ish) sized pieces.  I also can blow my hand off if I'm not careful.

[BrentS]

I remember reading a thread (over at rebelscum I believe) about the dangers of pressure pots.  It was enough to scare me   You are still dealing with pressurized air inside a metal pot.  Just make sure you are aware of what you are getting into.

[manglord]

Maybe before i get started, i should mold both my right and left hands...just in-case .
But seriously, it shouldn't be a problem. I've got a huge compressor that runs a 4 bay garage with hoists and all. The compressor tank is like 4 feet tall and 7 foot long and my boss just told me i could use his pressurized paint pot, it's kinda like a pressure cooker...it's got a gauge and the seal is still good. Thanks everyone!

[patreektherodian]

Sounds like you are all set up. Just don't blow your roof off. Experiment with differrent psi but 30 to 45 should be enough. Don't go overboard. I like to use plastic that cast slow (20 minutes)

[Jesse James]

Sounds like you've got a set-up similar to mine in the garage manglord.  That's exactly what I use, but modified some for use specifically for pressure casting.  Same deal though (paint pot with large professional compressor for auto repair, nail guns...  you name it).

It's basically more efficient, and I can do increidbly large castings by comparison to my little pressure cooker set-up in the house.  I use that in the winter a lot though, as casting supplies don't do well to fluctuating temperatures in the garage, and sometimes I just don't like the cold.  And since more often than not my castings are smaller (for figures, weapons, etc.), I can usually put off any large part castings till the Spring and Summer anyway.

Good luck...  And I wouldn't worry too much.  I have safety valves on my equipment and likely you do too...  But do be careful.  I do know someone who blue his hand (whole hand) off with a blown paint pot.