Rubber molds

Looking for a A product for making some gun parts out of lost wax. Will be ising old oraganil parts. And It would be nice if it doesn't cost me a are and leg.

Freeman's is the go to source for pattern materials& supplies. I use several of their products to make and duplicate foundry patterns. More to the point, I noticed a couple weeks ago when researching an order that they have the rubber mould products too. Didn't spend much time looking at those, but they have online videos on how to use them, like they do for many of the products I use. You might check it out. They are easy to buy from, & , IMO reasonable for what their products can do or save you in time and confidence when making patterns. Once again, though, I don't have personal experience with the rubber/flexible type productsl.

smt

The most common product line I'm familiar with is from Smooth On-

http://www.smooth-on.com/

Rubber molds to produce waxes are usually associated with bigger production runs, you might want to consider Green Sand or something similar. Important to keep in mind as well, is that you will see about 4% shrink for a quick and dirty constant. When I was in the foundry we used to coat sample parts with a layer of wax to build them up if that was the only pattern available. The idea that you can use an existing part to get an exact and functional copy is a common misconception. If you use a wax molded from your existing part, you will have two shrinks, one from the wax and one when poured.

the silicone i use shrinks less than 0.1% during cure. and while i don't know the actual % value, the wax i use doesn't shrink enough for it really be measured. got it from a foundry that used to cast all the trigger mechanism parts for the various galil rifles.

and in my experience, smooth-on products generally suck.

100% silicone in a tube

try this idea. I use it for wax castings often. Make a pour spout out of oil based clay or wax and attach it to the part you want to make.

Coat your material in a non silicone based release agent like vaseline. You need to do this quite well. Lithium grease works well too.

Take a tube of 100% silicone, do not use "type II" only type one! Usually around $4.00 a tube. Type 2 never works.

Coat your hands in a 1:1 solution of Dawn concentrated dish soap and water. I just use a small bucket filled with this solution and dip my hands into it.

Pump as much silicone as you need to make your molds into a second bucket of clean water.

Reach into the silicone bucket with SOAPY (the silicone will not stick to you as long as you keep your hands moist with this solution) hands and pick up the silicone in a blob and build a cookie of silicone around the part. It will dry in an hour or so because the water acts like a catalyst to the silicone.

Cut your part our of the silicone by leaving it partially attached. Cut in a zig zag so the two halves cant mismatch.

Pour in your wax and let cool. If your part is too thin it may require more cuts, or a softer rubber from smoothon.

forgot to add

Yoj must also soap whatever surface you plan to set your mold on while it dries.

If you are going to be making alot of the same parts, a vulcanized silicone mold and a centirfical casting machine would give you good detail. The vulcanizing under pressure around your original parts pretty much eliminates a shrink factor in the mold. You only have the final cast metal shrink to consider then.
Lots of info about this here... http://www.tekcast.com/

Trythis.

When you say type I is it acetic cure or Neutral cure?

Vladimir

RTV (room temperature vulcanizing) materials are the latest in no shrink mold making. What metal are you casting?
Payson.

Try here; http://www.riogrande.com/

They would have anything you would need to do lost wax casting.

Todd

Yellow brass is the main one and German silver
Mainly. I get RioGrande catalogs and know how pricey they can be. It is bad enough the priceing on a lot of this material with out there mark up .
David

Wow! This is a very interesting thread!

You guys have been there and done that!

Best regards,

Stan-

PM sent.
Payson

Lost wax molds

David/toledo,
I started a small lost wax foundry (5 employees) and ran it for 8 years before selling it.
It is not a pastime for sane individuals. If you are not sane please pm me with questions or I will be happy to share what little I know with you or anyone else on line.
To elaborate a bit on the mold making, you have recieved some good advice already.
First, you must determine how you are going to get the wax into the mold. Bear in mind that there as many kinds of wax 'alloys' as there are steel alloys. The Kindt Collins company, in Ohio, knows wax inside and out and always treated us well. I am sure some waxes can be static poured into a mold of a part with little detail, but your best results will come with the use of a wax injector. A wax injector is sort of a pressure cooker type of concern. It has a heating element, a spring loaded nozzle, and a pressure gage and regulator. The cheaper ones come with a hand pump, others use reduced line pressure. We would inject the wax at 1 to 15 psi. This forced it into tiny details and, when left under pressure until the wax cooled, "held up" the part and pervented sinks and voids.
We almost exclusively used silicone rubber molds. High production shops use metal molds and higher injection pressures. Silicone caulks will work, but are, of course, not engineered to be an ideal mold material. We bought our material by the gallon from Dow Corning or Silicones Inc. out of Georgia. There are a slew of different silicone formulations,
a good friendly formulation is GI-1000 from Silicones Inc. Dow has a very good pamphlet on mold making. You might even be able to con them out of some samples.
Vulcanized tooling works well, too, but the pattern must be more rugged and the equipment is expensive. The silicones can be done "on the cheap"
Since you are going to fill the mold with wax under pressure, it must be confined in a plastic (acrylic works fine) or a metal enclosure, or the rubber will do strange things and you will end up with a shoe full of hot wax.
I could babble on but hopefully this will at least get you started in the right direction.
Jim