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experiments with household goods casting

 Post subject: Re: experiments with household goods casting
PostPosted: Fri Jan 13, 2012 6:34 am 
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I've had some results with a new material - It's an epoxy plastic glue (one part epoxy).

For reasonably thin items it sets quite hard within the day (as the solvent evaporates off)
Thicker parts take longer. Highly viscous and does not take fine detail well.

Intresting potential for sculpting flesh, as the epoxy 'skins' over in a few minutes letting you push the 'flesh' underneath around with semi-natural skin curves on top.

EDIT Note how warped the cog on their stomachs are though. I removed them from the mould a little early, and even when set this stuff is not very rigid. It softens to rubber like consistency in hot water, which I needed to get the plasticine off.


Image

Image

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 Post subject: Re: experiments with household goods casting
PostPosted: Fri Jan 13, 2012 4:48 pm 
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U R a Madd0c !!!!!!!!!!!!!!!!!! :o

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 Post subject: Re: experiments with household goods casting
PostPosted: Sun Mar 25, 2012 10:56 pm 
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This page seemed like it might offer some ideas for you. :)

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 Post subject: Re: experiments with household goods casting
PostPosted: Thu Mar 29, 2012 6:05 pm 
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more careful measurements made

one vit c tablet will produce about 100ml of gas at room pressure

therefore acheiving high pressure would be more easily done with a bike pump. i happen to have one of these. i have also found a shop on my street where you can get stuff cast up in steel. its between a lingere shop and a noodle stall -
my street is awesome

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 Post subject: Re: experiments with household goods casting
PostPosted: Thu Mar 29, 2012 6:09 pm 
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Makes me wish the idea of a main street was still 'cool' in the US.

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 Post subject: Re: experiments with household goods casting
PostPosted: Thu Mar 29, 2012 6:10 pm 
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Simulated Knave wrote:
This page seemed like it might offer some ideas for you. :)


awesome. the polymerisation of styrofoam. looks. hopeful

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 Post subject: Re: experiments with household goods casting
PostPosted: Wed Apr 18, 2012 12:48 pm 
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madd0ct0r wrote:
i have also found a shop on my street where you can get stuff cast up in steel. its between a lingere shop and a noodle stall -
my street is awesome



LOL, that IS awesome!


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 Post subject: Re: experiments with household goods casting
PostPosted: Sat Apr 28, 2012 12:02 pm 
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Needing a lot of robo-insect legs, i ran another experiment:

findings:
1 - one piece molds do not work when the sprue has large areas in the center you can't get a knife to.
2. No matter how much of a hurry you are in - Mold release IS required
3. Today the plastic misbehaved and turned into a giant foaming pile of ash, that clear silicone simply burns to easily.

time to try again. the experiment requires it.

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 Post subject: Re: experiments with household goods casting
PostPosted: Sun Apr 29, 2012 7:17 am 
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hmmm. further findings:

the slicone appears to have reacted with the actual metal of the origional.

I know that one part silicone uses a tin catalyst, and that tin is a major part of casting alloys, so maybe there's an extra effect here I was unaware of?

ether way. repeat, but this time with release agent.

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 Post subject: Re: experiments with household goods casting
PostPosted: Sun Apr 29, 2012 9:07 am 
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Interesting, how did it react with the original?

I've poured plenty of DBT catalysed rubber over tin-rich masters without any ill effects befor, so would be interesting to see.

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 Post subject: Re: experiments with household goods casting
PostPosted: Sun Apr 29, 2012 10:59 am 
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mostly just a dulled patina on raised edges. very low friction.

current theory is that these edges were the ones that got rubbed and banged about more setting up, so metal lost its oxide layer there. meets the silicone and bang! very fast curing compared to rest of mold leaving a 0.1mm thin layer of high strength silicone bonded to imperfections in the metal.

but i'm making that up as i go along, we'll see. testing will continue

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 Post subject: Re: experiments with household goods casting
PostPosted: Sat May 05, 2012 7:38 am 
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Ok: I seem to have a reasonable method set up now for open top moulds. It's slightly different from pouring silicone so I'll detail it here:

1. Build lego box (if lego isn't a household good, it should be)

2. line box with clingfilm. I normally only bother with the bottom, but doing the sides too would save me a lot of grief.

3. Squirt large amount of silcone caulk into box. It's best to leave the nozzle off the gun to get a nice thick dollop.

4. place clingfilm over box and squash silicone flat with your fingers. Doing it from the center out will eliminate most airbubbles, and all of the ones in the top 5mm that we care about.

5. wipe origional with suitable mold release. KY jelly works fine. Peel back cling film and gently press the piece in. The silicone is thick enough to hold it up without support. (NB this means a non-horizontal mold line is near impossible to do)

6. Leave it in a very well ventilated area (preferably outside) to cure. The gas given off is basically evaporated vinegar. It's not dangerous unless you have a wife or girlfriend or a valuable marble statue nearby. Typically after a few hours I take the base off the mold to double the curing area.
I'm working in a hot and humid tropical country, so curing might take longer for you. The silicone shrinks very slightly as it cures, so if you leave it to set for a good while you'll get sharper edges then if you remove the original early.

7. Optional 2 part mold development.
- after step 5, wipe top and surface of silicone with ky jelly (best to be generous here), build a second layer of box with lego and squeeze in more slicone, cover in clingfilm and press down, remove clingfilm to aid curing. This experiment is still running, I think i may have separated the halves and removed the original too soon (curing time logically s a function of mold thickness) but we'll see.

Image

1-part 'robo claw' mold. looking at the left 2 parts of the pink cast, I removed the originals from the mold 18hrs earlier: you can see how they're more rounded then the right hand parts.

Pink is the one part petro resin glue. As said previously, it's a bit soft and hard to get a decent edge in, but is easy and cheap for one part molds.

white is pure superglue. IF you want to try casting anything in superglue, don't.
1) you will glue the mold to the table, your fngers to the table, some sprue to your fingers, the bottle to the table ect.
2) It shrinks a lot. maybe 50% volume lost.
3) It's really difficult to get out of molds, even silicone ones. You will damage the mold each time
4) it's brittle. of three claws cast, only one came out whole.

I think i once experimented with superglue and tissue to try and make it more stable and less brittle, resin glue is easier.
I was worried it'd be too soft to support the weight of the demon engine, but as you can see, no problem.

next i think i'll try some real resin. Maybe make a batch and then pour every mould i still have to see results.

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 Post subject: Re: experiments with household goods casting
PostPosted: Tue Jun 05, 2012 10:03 am 
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I never showed photos of the resin did i?

hmmm.

well. It's a two part local brand resin. Both parts have the consistency of very sticky blutack - we're not talking a a pouring resin here. From the smell and taste (don't ask) I'd guess it's very smilar to milliput, in that it's a two part epoxy liquid with clay mixed in to thicken it.

It's dries hard and brittle, and gives a beautifully sharp edge compared to to the pnk glue or the hot glue (yes, I tried casting that too)

all three of these experiments were done in a 2 part mold to make a swirling firery blade thing for a chaos war engine.

The hot glue component had the advantage of being very rubbery, and so actually shrugging off being dropped, bent ect. It might also allow me to fulfill my childhood dream of a 28mm army of 'monsters in my pocket'. (indestructible terrain also sounds good)

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 Post subject: Re: experiments with household goods casting
PostPosted: Mon Aug 13, 2012 9:55 am 
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greetings comrades!

I am no longer in vietnam, and as such:

1) I can buy modeling materials easily now
2) all in progress experiments were left behind as too heavy for baggage
3) plastic bags are 5p in all stores, so I am slightly less keen on using them for feedstock.

On the other hand, I have a few friends here who could be easily persuaded to try metal casting with me...

I think my next project will be making a chinese chess set, since I have bugger all space for modelling / gaming right now.

Experiments will continue and fun will be had, comrade.

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 Post subject: Re: experiments with household goods casting
PostPosted: Tue Aug 14, 2012 10:48 pm 
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While I can sense the relief at being back within access of modeling kit and tools, I must say I will miss your more extreme experimentation, and especially the fascinating commentaries on the boards.


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