SteveH

I titled this generically so it could evolve and be added to, but I thought folks might get a kick out of seeing the process involved with making replacement parts.

I am casting a replacement part for Cathy (Mizkaki) for her Boye Needle Round display. Her's is missing the arrow in the center that is the handle to turn it with. Mine came with one in perfect shape. so, RTV it is.

RTV = Room Temperature Vulcanization. (Cures at room temp, no heating required)

It is a two part rubber compound that can not only cure at room temp but once cured can handle the temperatures involved with molten pewter (around 200 F) I have used this method to cast brass/bronze/copper but it fries the mold in a cast or two. For those metals I usually use sand casting.

Here is the Original Part in the plastic case we use to pour the mold into. We first put down a layer of soft Sculpey clay to simulate the second half of the mold. At the top right you can see the baked Sculpey that acts as the form for the pour cone. (once we add the rubber and it dries, that part will be hollow)
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Here is Heather mixing the goo...
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the goo (No matter how yummy this looks DO NOT TASTE IT)
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poured into the mold cavity
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and this morning after getting most of the bubbles out last night and letting it set up.
(it is cold and damp out so it will take a little longer to fully set)
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When Heather takes the 1st half of the mold out later today, I will post more pictures showing the prep and pouring of the 2nd half.

Tartan

Very cool! Must be great to be able to make missing parts. I love watching what the new 3D printers can do too.

SteveH

yeah, when they can effectively print metal parts, I'm all over it....

Candace

Love this thread:> I've always been curious about mold making. I have a nylon gear that needs a 3D printer as they're no longer made:<

J Miller

I've made a few small parts using hand tools, but nothing like that. I'll be watching so I can see the finished part.

Joe

SteveH

Ok, so here it is now.

Heather has removed the RTV first 1/2 of the mold,
Then placed it upside down in the same plastic holder
The used Sculpey is in front... ewww (Vaseline is the source of the slimy look)
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The next step is to make sure the Vaseline in still providing a thin cover (acts as a mold release so the RTV does not stick to the 1st half)

Then mix and pour the second 1/2 of the mold.

GEMRM

More, more, we want more !!!
This is great to see, please continue as you progress through the stages.

foufymaus

Oh yes! I wonder if it could be used to make cams... cant wait to see how this turns out.

SteveH

The mold is complete.
Still needs cleanup of "flash" (mold over flow)
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With a little cleanup
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The business end...
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SteveH

I need to let it air cure for the day. I will try casting a test piece this evening.

I still need to make the bracing boards.
I will use hardboard (1/4") and cut two pieces just larger than the big flat sides.

Then talc dust the molds
Then sandwich them together and put rubber bands around to hold them together

Then melt, pour, wait, and pray....