There’s lots of pictures and videos out there about casting using centrifugal spinning but I thought it would amuse my blog readers to take a break from announcements and updates for a peek under the hood of Dream Pod 9’s metal casting.
First off there is the rubber blank, I have cut the pre-punched center hole out, it will be replaced with a metal form to hold the space for pouring in the metal.
Here is a picture of Squishy, that’s the name we gave to the Vulcanizer. It’s job is to apply heat and pressure to the mold. In this case I’m going to fit the top and bottom plate to the cylinder and put the prepared rubber blank in Squishy for about ten minutes, this softens the rubber ready for parts.
The next step is to put the alignment acorn nuts in. This image is posted on the wall and is important to remind me not to forget them.
The nuts ensure that the two halves of the mold can be aligned accurately again. If I forget to do this the mold is worthless except as a door stop. The parts have to be all in the mold with the orientation correct so that metal will eventually flow into all the spaces.
After an hour and a bit the mold will be cured. I get the mold out of the form and cut any excess rubber that has squeezed out around the edge from the pressure. A small notch is added to make aligning the sides easy. Then you pry the two halves apart and check the results. This pic has the middle ring cut and the gates cut into the middle.
This picture shows the vents cut to let air out of the mold. The knife I use for this makes your average x-acto blade look kind of blunt. Each mold requires at least one blade and can take up to three. Cutting the mold can take from ten to twenty minutes.
Then we head over to the centrifugal casting machine, splash a bit of talc on the two mold halves and put them together in the machine and cover it with the locking plate. Here is casting machine #2, also known as Pod 2.
Then we get a ladle of liquid metal out of the melting pot and pour it into the spout of the centrifugal caster. The machine automatically engages the pressure plate to push the mold up against the cover plate to lock the two halves together. Another automatic switch also starts the plates and mold spinning. Newer molds need less pressure and speed. Older molds often require a higher pressure and temperature.
After about 45 seconds you can pull the mold out and open it to check that all the parts have filled in well. In this pic you can see that not all the parts have filled in.
This is the second spin, now the mold has heated up and the vents have opened up enough for all the air to get out and there are no problems with the mold.
Now if you have been paying attention to the Dragonfly/Varis announcements you’ll know that the Dragonfly and Varis weapons do not include a Mortar, and should include an auto cannon. This is a case of missing a part, but I threw a bunch in the Greyhound mold I did in the afternoon so there won’t be a lack of auto cannons. The Mortar is there to ensure i don't run out when packing Crusader IVs for Peace River.
So there you go, a quick walk through the process of casting metal molds. One thing this process emphasizes is that the reason why Heavy Gear miniatures have to be cast in so many parts is because of their complex 3D shapes and the amount of detail on them. When all parts have to be laid out in a flat plane between two sides of the mold there are only so many ways that liquid metal will flow into the shape to give a good cast. Otherwise the possible poses would be very limited and we'd lose the ability to pose our models. It also allows mixing and matching of parts for some very unique homebrew kitbashing projects (When parts from different models are put together for a unique look. Here's an example of that I put together last year from a Cobra and an Artimis AA tank:
I should paint that guy up. And no- it will not be getting rules, it's a pretty ridiculous model (though a nice homage to the classic Robotech destroid mecha)!
dave.mcleod [at] dp9.com
forum handle: dave
Currently painting: A Dragonfly!
Submitted by Dave McLeod on Thu, 05/08/2014 - 10:36am