| zgeist27 | 10 Nov 2006 8:04 a.m. PST |
I want to make a two piece mold of something I have made out of plasticard and cardstock. It's a hollow piece that I'd like to cast into a nice solid piece. My usual technique is to push the piece into some clay, then pour the mold rubber over the top. Then flip it over, remove the clay and pour the mold rubber over the bottom. But if I have something that I can't push into clay how can I make a mold? I was thinking maybe there was some type of liquid I could pour in first that would set (instead of the clay) – but it needs to be soft enough to not flex my item and I have to remove it later to mold the other half. Any suggestions on how to cast something like this? |
| darkplatypus | 10 Nov 2006 9:13 a.m. PST |
You might try suspending your piece halfway up in your moldbox, using pins or something similar to hold it in place. Then just pour the rubber into the box (in the corner, away from the piece) and let it fill up to about the halfway point on the piece. Let it set. Then cut out a couple notches on the rubber for alignment purposes, apply some mold release so the two halves don't stick together, and pour more rubber over the top to complete the mold. I've never tried this, but I think it's the way I would proceed in this situation. |
| Double Ace | 10 Nov 2006 9:16 a.m. PST |
Depending upon the material, you could freeze it first. |
| Cpt Arexu | 10 Nov 2006 9:57 a.m. PST |
why not just gently pack the clay around it, if you plan to cast rubber over it? if its a smooth split you want, set the piece into a hollow in the clay and then fill in the hole around it with small bits, smooth the surface, and cast away. I'd also try to fill the void in the item with foam or squashed paper or something to keep the item from flexing under the weight/pressure of the casting rubber |
| T Meier | 10 Nov 2006 10:37 a.m. PST |
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| headzombie | 10 Nov 2006 10:45 a.m. PST |
The pin method mentioned above works fairly well. I had to do it this past weekend. |
| zgeist27 | 10 Nov 2006 12:40 p.m. PST |
T Meier -
Wax! An excellent idea – especially considering I happen to have some from another project that never got completed, so the wax is just sitting around useless. Hmm, but I'll have to warm it and it might be warm enough to warp the styrene object I'm trying to cast.. Cpt Arexu -
The only clay that might be soft enough to do as you suggest would be silly putty – which isn't a bad idea. I wonder if they still make that stuff? darkplatypus & headzombie -
This sound possible – I will need venting holes anyway, so the holes the pins make could double for that. Great ideas everyone. Thanks for your suggestions! zgeist |
| Big Miller Bro | 10 Nov 2006 2:12 p.m. PST |
just a warning- hollow objects retain air (if airtight)- the strength of the rising has been known to pull a master right out of the rubber for me- so that you come back and find all your masters bobbing at the top of your rtv- I fill all my hollow masters with sand now. |
| Zephyr1 | 12 Nov 2006 9:14 p.m. PST |
Cpt Arexu -
The only clay that might be soft enough to do as you suggest would be silly putty – which isn't a bad idea. I wonder if they still make that stuff? Try Van Aiken's plasticene. (Should be available at your local arts & crafts store. Nice, soft, plastic-friendly, cheap, and can also be used for claymation…. ;) |
| dakenskys | 12 Nov 2006 9:24 p.m. PST |
One method that I use, is to cut a piece of plastic to an approximate outline around the area that you want to be your parting line, and prop it up with some wood dowels to set it at the correct height of your part line. I then use some clay to fill in the rough opening between the plastic and my model. This way, I'm not applying too much pressure on the original part. You can then pour your first half of the mold, and then when set, just remove the clay and plastic separator to pour the second half. |
