"Two Part Silicone Rubber Molds in a Spin Caster" Topic

It seems that most of the materials I wish to use to make the masters of the figures I'd like to produce simply can't take the heat and pressure of the vulcanization process.

I'd like to know if anyone thinks, would it be possible to make master molds out of liquid silicone rubber and use them to make the production masters out of pewter for the production molds?

As they're master molds they probably don't need to survive long periods of regular use, rather as long as I can get a half a dozen good quality shots out of it I'd probably set.

???
the material you are sculpting with cant take the vulcanization temps?
they make silicon molds for lower temp vulcanisation.
I dont know about using liquid silicon though.
good luck.

I'm afraid they would warp, as they are spun.

@RavenscraftCybernetics

I'd probably be using this: link

It has problems at temperatures over 80c

I did it some years back with Dow-Corning 3120 RTV. I haven't checked for other or newer products in more than 10 years, so there may be better options out there.

This stuff sets up pretty firm and didn't warp during the spin process, but does not allow for deep undercuts.

Here are links to the 3120:

link

link

link

Considering I'd be casting in 15mm I doubt any of the undercuts would be TOO deep.

I'm still open to other suggestions but thanks, it's something to look into.

right you need to add a step to make your master master, by using "investment casting" or your going to be spending big bucks replacing production molds made from softer stuff more.

Ouzel, I believe there's a miscommunication.

I'm not going to be using production molds made from softer stuff. I'm thinking soft master molds that last just long enough to do what I need them to do: Produce enough pewter masters to fill in a production mold which I can make using the standard methods. Like I said, I probably don't need more than a half-dozen good runs from the from the soft master. I intend to put the figures I used to make production molds into storage.

I'd use investment casting but it's beyond my tooling capability and the materials I'd be using, I'm not sure if they're suited to it or not.

Aren't you describing what the Centricast system does?

link

Ian

Psyckosama, you need more than a handful from the master mould. You need to be able to back to it in 2 years and run it again as well (production moulds wear out, masters get lost etc.)

What material have you sculpted in that is causing the issue?

Second to FreddBloggs, what are you using for your masters?

Dave
Stone Mountain Miniatures

UV cured Acrylic plastic with a low temperature tolerance (80c). They're the kind used in highly detailed 3d prints. I have reason to doubt they'd survive vulcanization or even leave a usable mold for that matter.

i reckon it could be moulded in a low temp silicone mould.
i have vulcanised some things at about 80 deg

I'd be very thankful if you could link me to a site that sells such molds…

It would be worth a try.

The Centricast system would be a good option for masters, but I found the moulds to be too soft to stand up to continued use.

What kind of silicone do they use? I'm quite interested in their material but am not going to be buying their molding machine.

link

Thanks. I'm still interested in the low temp vulcanizing rubber as well as it would probably be cheaper.

I also need to hit up the local jewelry shops down town to see if I could pay anyone to do simple investment casting for me.

I have to say, thanks everyone. You guys are great.

Talk to Mike at historifigs. He vulcanizes 3d prints all the time.

The Centricast system would be a good option for masters, but I found the moulds to be too soft to stand up to continued use.

Tony Barton (AB Figures) uses a Centricast system and the red cold-cure silicone for masters: he sculpts in Fimo. Production moulds are traditional black rubber made either at Eureka Miniatures (15mm) or AB Figures UK (20mm).

While the machine itself may not be right for Psyckosama, the two-part mould making system sounds right for making discs that could be spun in a conventional casting machine, yet not subject originals to high pressure and temperature.

I use low-temperature silicone myself, but haven't tried it below 100 deg C. It's OK for Plastikard. The pressures can still go high if you don't keep an eye on the gauge…

Ian

That's the other half of the issue. I wouldn't be using a true vulcanization machine but a can in an oven, like Zombiesmith's method.

I'm trying to get started On the Cheap. It's not easy.

I have a centricast machine and it does just what you are looking for. However it sounds as if you are combining two issues, the machine and the silicone rubber.

Dow 3120 is excellent, albeit you cannot have undercuts, and would work well with the centricast machine or equivalent.

I personally use smooth-on rubbers – link

but the 3120 is undoubtably more rigid.

What's the difference between a centricast machine and a standard machine? Could I dial down a standard machine to match centricast speeds?

The Centricast machine is in essence a safer version of Zombiesmith's lash-up. :-) Pressure is applied by tightening the mould-clamping screws, and so it's not a high-volume set-up.

Standard casting machines come in different flavours, about the most expensive of which is a variable speed, air compressor machine (which gives the added control of variable mould sealing pressure).

A number of figure casters use comparatively simple bob-weight machines without variable speed. A bob-weight machine uses weights on arms to apply pressure (the size of the weight and its distance up the arm affect the pressure applied to the mould). Of the ones I know of, some are home built (Pendraken, Baccus); others are relics of British industrial glory (mine, Black Hat). We cut moulds to suit the machines, and tend not to change anything once it all works.

As a guide to cost I was this year quoted over GBP 4,000 for a bob-weight machine and nearer GBP 6,000 for a compressor machine. Ex tax… And that's why some miniatures businesses with engineering expertise make their own.

Psyckosama:
Are you planning to use your castings strictly for your own hobby/gaming, or do you ultimately plan to go into production in order to make money with your creations?
The answer to that question is key. If the later reason you must be prepared to spend some funds somewhere along the way or you simply won't get there from here.
In answer to your initial question you can use silicon molds in order to copy your initial master. But then you would have to compensate for several levels of shrinkage; shrinkage of the silicon mold itself, shrinkage due to the silicon warping under centrifigal stresses, and lastly shrinkage of the metal used to cast your metal masters/production models. (If the material used in making your main initial master reacts poorly with RTV silicone then that's another problem altogether.)
The overall problem you are referring to above is prototyping your initial master in order to make what is termed 'production models' in the trade – and specifically production models that will hold up long enough to form a cavity in the heat and pressure of the vulcanizing process. Production models are used to make the first production molds (molds used to cast saleable items) and if they survive the initial vulcanizing process they can be used again to make addition production molds when the first ones burn out.
Contact me off this message board if you want to discuss this some more.
Toby Barrett Thoroughbred Figures

My plan is pretty much a Zombiesmith special :p

I intend to make a vulcanizing can like his as well, but I don't think 3d printed originals would survive long enough to make a lasting impression.

I know of a couple of other companies experimenting with 3D printed master models, which they will be putting into a low-temp vulcanised mould. As long as the model survived the first moulding, you'd have a master mould to take a full set of castings from, ready for the production mould.

what does a zombiesmith operation look like or have ?