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Hello all! Im working on some custom Nightwatch chapter space marine shoulder pads. Ive done plenty of molding of more complex shapes, but shoulder pads has so far eluded me. What is the easier way in your opinion to mold shoulder pads? With a two piece top and bottom mold, or with the one piece, shoulder pad flat on the table type mold and why do you think so? Thanks!

first, make a small, waterproof "box" of lego. next, glue it to a thick piece of paper. now, put a tiny dab of weak glue ( gw super glue is the weakest I know of) and glue the shoulder pad (by the side edge, not the grill one). fill with liquid mould, whichever you use. BAM. one piece shoulder moulds. hope I helped.

Awesome thats how i was thinking of doing it, although when you say grill edge and side edge what do you mean exactly?

Basimpo wrote:
Awesome thats how i was thinking of doing it, although when you say grill edge and side edge what do you mean exactly?

the bottom edge of the shoulder pad has a weird circley grill thingy on it.

I still dont know what you mean. The bottom edge when its on a model, or when its laying down flat on the table?

I've successfully cast quite a few custom shoulder pads for marines.

I put two 1/4" wood dowels on the bottom corners with super glue and stand it in a piece of modelling clay. That's bottom corners when the shoulder pad is "standing up". So on the smaller of the two radii.
You want the volume of the clay to be about 1.5x the volume of the shoulder pads and dowel sprues so you can fill the reservoir area and then just put it in the vacuum/pressure pot.
The bottom of the shoulder pad should be about 1/4" above the clay.

Mix and pour silicone.
Let cure.

Remove clay (dowels stay in place).
Snap off and remove dowels (shoulder pad stays in place).
Make a small cut along the bottom edge of the shoulder pad and remove the master.

I've tried both vacuum casting (-29 in/Hg) and pressure casting (50psi) with these moulds and they come out just fine either way.

Is there such a thing as a vacuum/pressure pot for amateurs without incredibly thick wads of cash? I've been considering doing some resin casting for my class projects but am a bit lost on how to go about it right. It seems a lot different than the processes taught to me in my art metals and metal casting courses.

LUTNUT, you wouldn't mind sending a picture would you? Id greatly appreciate it!

Zuul! pressure casting and vacuum degassing are two separate things that can be done with one container, but needs two different machines. Check out harbor freights paint tank. That works as a pressure chamber and a vacuum chamber. For pressure casting (What you do when you pour resin into a mold) youll need an air compressor. I used a cheapo depot pancake 2.5 gallon compressor that filled the paint tank and itself in about 5 minutes, almost too long to really effectively cast but it does the job!

Vacuum degassing is what you do to mold rubber. Yes, both the resin and the mold rubber have bubbles, but the 2 times I tried degassing resin it like exploded and formed one nice solid piece of nasty plastic.
Vacuum degassing certain rubbers can be done away with if you are careful and patient. I didn't degass my first 30-40 molds and they still came out great. Oomoo 30 is known for this quality of being a low viscosity so that air bubbles don't really rise up.

Also, don't get it twisted: Molding and casting is expensive. You got to either have a goal or absolutely love doing it (Like me. I find molding and casting more fun than any other aspect of 40k...weird right?)
Send me a PM if you need more help.

On model

 Zuul wrote:
Is there such a thing as a vacuum/pressure pot for amateurs without incredibly thick wads of cash? I've been considering doing some resin casting for my class projects but am a bit lost on how to go about it right. It seems a lot different than the processes taught to me in my art metals and metal casting courses.

Metal casting is quite different. I do lead casting as well and there is no pressure or vacuum involved. The usual method for casting pewter minis is spin casting where the centrifugal force pushes the molten metal into the cavities which are on the outside of a spinning wheel. My lead casting isn't gaming related (it's hunting/shooting related) so I just use gravity pour aluminum moulds.

Compared to 40k it isn't too expensive to get into casting. I bought most of my stuff used from a local commission sculpting and painting studio. I paid $200 for a pressure tank, vacuum pump, and air compressor. If I bought retail the pressure tank is about $150 (it's a pressure paint pot for spraying houses/decks with regular hardware store paint), the vacuum pump is about $100, and a cheap compressor can be had for $100 or so. The air fittings to add dual valves to use the pot for vacuum or pressure was another $25. That is Canadian prices. Since you have access to Harbour Freight as you are in the USA I've read online that all those prices can be cut by at least 25% if not 50% off what I list here.

Tin cure silicone rubber (requires vacuum degassing) is about $100/gallon. Platinum cure silicone rubber (can be vacuum degassed but isn't necessarily required) is about $200/gallon.
Polyurethane resin (standard white/grey resin used in mini casting including from FW) is about $100/gallon.
There are next to no gases or fumes given off and I do it in my kitchen. If you get into clear polyester resin you need a respirator and a ventilated work area.

Basimpo wrote:
LUTNUT, you wouldn't mind sending a picture would you? Id greatly appreciate it!

First pic is my replumbed pressure tank. Left side is positive pressure, right side is vacuum.
Second pic is a shoulder pad. I erased the image from the centre as it was an original sculpt from a client and haven't asked if it's okay for me to use it online. The gates (dowels) on the bottom edge are way too tall. It doesn't effect the cast but just wastes resin.
First time using the attachment system. Let's see if it works...

Up front public service announcement - I use all this for the duplication of custom parts and one of a kind projects or other special stuff - if anyone out there is considering this for a "cheap" way to get any existing available gw part (melta's, grav weapons) it is MUCH cheaper and easier just to buy them (or get the bits on ebay) - casting is time consuming and getting good at working with complex parts or molds (the shape of the master can dramatically affect the complexity of how the mold must be made) is an art. Again, not accusing anyone of anything, or implying - just sharing information - especially if someone else is reading this thread and thinking this is a way to get cheap or free parts.

 Zuul wrote:
Is there such a thing as a vacuum/pressure pot for amateurs without incredibly thick wads of cash? I've been considering doing some resin casting for my class projects but am a bit lost on how to go about it right. It seems a lot different than the processes taught to me in my art metals and metal casting courses.

This was mostly answered already, but I can throw in my thoughts as well, as I do a lot of fabrication and casting (not just for gaming, but I have a lot of friends who do work with a friend on special affects/props and fabrication).

As suggested above, my pressure pot is just a painting pressure pot from harborfrieght, I think with one of their "super deal" coupons, it was about $70.

I got a vacuum chamber (for degassing silione - again, as mentioned above...) off ebay, for less than $100 and its very good quality and has lasted me for years.

I got an affordable vacuum pump at harbor freight for about $100.

Mostly I make terrain (I LOVE making custom bases, its a very fun project) or vehicle parts or odd sculpts (I had to make a bunch of hutt's for a star wars project once) but I have not tried shoulder pads (I need some custom pads for my custom chapter) - as my sculpting skills are not very precise, I am considering 3d printing my master, and casting those up (I need about 60 of them).

There are a lot of other posts on here on casting, but to be honest check out some of the other dedicated casting resources out on the net - resin addict is a really good one.

best of luck and have fun!