mold for white metal mini ?

[Revliss]

any know how the mold is made for casting white metal ? went i wose digging a round. i see some say sculpey is not good as a master for molding for white metal, but there is the mini company " RACKHAM" that seem to use sculpey alot for they master for white metal but they mold is a bit more expansive. how is that made ?

 

[Jeff]

Yes I know how they are made. You lay out the figures on a more or less yaw piece of rubber or silicone. You press the master in to the rubber you might have to make a cavity for some thick parts and then you push the rubber up against the piece. Once this is done you add mold release so the two parts do not stick together you put a second pice on top of the first and put them in to a metal frame and put that in to a vulcanizer which is a heated press you heat the whole thing up while putting pressure on the mold the pressure pushes the rubber tightly around the figure and the heat makes the rubber solid.

Our little company uses a low temp silicone that only needs to get up to about 200 degrees.
This means we can use masters that are made out of materials that would melt under the heat and pressure that other mold materials need to be put under. It is better to have a master made out of a more resilient material then sculpey. It can be very brittle after it is baked.

" RACKHAM" may do what we do and that is to make an intermediate mold of the original master. Before making up the production mold

 

[Revliss]

as in they made a resin cast before making a the white metal mold ? ? is that one of the way it done ?

 

[carl reid]

Jeff is correct with his description of white metal mould making. What you need to take into account is the vulcanizing process is a very harsh environment for a master. Not only is there heat but there is a lot of pressure. It is better to make the master from a more robust medium, if it is to be vulcanized. However the silicone is one solution to this problem, but you still have the pressure. The other way is to cast the masters in resin, again there is a but some PU resins give off a gas that reacts with the vulcanized rubber. So it needs to be cast in a resin that can withstand the process. I suggest epoxy resin. But these are not easy to cast! I use a Sika epoxy resin called XD4500, for such purposes. But it needs to be cast by an experienced caster. It is very viscous, it's kind of like pouring toffee. But it works because I have done it. This can be vulcanized. But again it is a very expensive way to recreate your work. The best solution is make the master in Magic-sculpt, Milliput, A+B etc.... This is the safe option!

I hope this helps a little

carl

 

[Ray]

Most of my customers convert the original figure by use of the lost wax process. Two New Zealand customers use the actual lost wax method/process with wax, while one of my American customers uses a kind of resin I know nothing about that can be burnt out just like the wax without leaving a residue like most resins do. These are nice simple, though I'm afraid, not inexpensive methods for obtaining durable masters. The resin method is especially nice from my point of view as the mold used to obtain the resin copy can be used to make a normal resin figure as well and is normally less expensive than that used for a wax casting. In addition, many jewelers are willing to make the conversion for you.

I've sold to a guy that uses resin castings in the vulcanization process. I don't know the specifics of the rubber he uses though I suspect it is a low temp silicone like Jeff mentioned. This method is especially appealing to me as I can make the 'mother' mold and resin castings for the customer, (and sometimes keep the original for my portfolio too) thus protecting and preserving the original myself. It often happens that the caster will, especially when making molds for a wax casting, damage the original in the process. I suppose it doesn't matter if the original is damaged so long as the caster doesn't ruin his mold at the same time, which has happened. Of course as the pattern maker repairing damage to a figure that still needs to have a usable mold made from it only means more work for me, but I have a real strong aversion to doing things twice which is what repairing something I've already made feels like to me. So far, none of my originals has ever been damaged beyond repair in any of the processes mentioned. We did come close one time though when a customers cat took a shine to a couple of 1/48 scale lumberjacks.

I don't think I would ever recommend putting one of my figure originals straight into the vulcanization process because of my armatures being made up in part from resin castings. The resin, which is encapsulated in putty, gives off gas when heated which is sure to expand and cause a de-lamination of putty from its surface. Those who use putty throughout may be able to get away with putting their originals into the process. None of the polymer clays, Super Sculpy, Fimo etc, are suitable for use in a high temp vulcanization process. However, they are imminently suitable for making RTV molds from.

Were I to find myself in need of converting from polymer clay to metal I am sure I would make an RTV mold first and either have the resin used in a lost wax process or have the resin copy used to make the mold for the wax. Extra steps I know but then making a mold and resin castings, as much as I dislike the process, is much less stressful than the loss of an original sculpt.


Ray

 

[Jeff]

We do use resin castings in our production molds. So our production molds are made from first generation resin castings. If you are using the black natural rubber you really need a metal master in the production mold. It is vulcanized at higher temps and higher pressure.

 

[Ray]

Jeff,
Do you use resin castings for things that are less rigid than a figure? I'm thinking of things like rifles, with thin cross sections and very little rigidity, and wondering if you experience any distortion or bending of the resin during mold making. Just curios, I don't have an application in mind at the moment.

Ray

 

[Jeff]

I think it might be possible. it really depends on how fragile the master is. the rubber is pretty soft and if the pressure is even it might just work. What scale gun? What type of gun? it is hard to say to much I have done some pretty thin parts but it just depends how it goes. if it all goes wrong you have lost the castings and about $40.00 dollars in rubber.

 

[Revliss]

been digging around more and it seem there a lot of artist that use sculpey firm for they master ... the guys at ENIGMA Miniatures use it too.