Questions for one time use mold

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Tactonyx

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Greetings. Not exactly sure where to post this, so mods, be gentle with me if it's in the wrong place.
I have a question concerning cheap, disposable molds that have a one or two time use. I've browsed through the stickies and I have failed to find anything that could help.
I have a very unique peice that I had to lathe, it is a smooth tear dropped shape peice that's about 13" (325mm) long and 2.5" (64mm) thick. The peice needs to be hollow and the walls about 2 to 3mm thick. I would use rubber to make the mold, but I only need one or two peices, and I don't want to invest significant resources on mold just to cast one peice.
I'm curious, could I make a paper mache mold, seal the inside and bondo the outside, and be able to cast this part? Or am I gonna have to bite the bullet and buy some more rubber to cast this particular peice?
Any thoughts? Suggestions or input is welcomed. Thanks.
 
alginate... use alginate.. it works well for that purpose. relatively inexpensive. problem is does not flex well and works better if you use a release agent on the original. i use Vaseline (cheap and easy to find). there are several videos on you tube and there are several suppliers readily available on line. i order the by the pound in a bag. cost range from $6-$120 depending on how much you need. probably about 1 to 2 lbs would be more than you need so possibly about $15.. there are different types of alginate as far as set time and strength.. also dental alginate is fine to use and i generally will use it due to it's fast set time (impatient). dental alginate will set in 2 min and a slower one is 6 min. life casting alginate is good as well and set time is slower but it is the same.
 
The problem with alginate is that it falls apart in short period. I would not use it for this plus resin is killer on it. It will tear it apart. A very simple method that does actually work is the clear caulking for Lowes, Home Depot or Walmart. Get enough tubes so you can do it all in one batch. It is very cheap so you can make multiple molds if needed but they are short tem. If you need a mother mold use Plaster of Paris because it will be strong enough yet cheap.

Ithica
 
Dang showed up by Ithica.. lol.. he is right though i hadn't thought about the clear caulking. though i have never had problems with the alginate and resin and i like it due to set time. but for local quicky Ithica is right. I guess because i have alginate on hand at the house it was what i would have instinctively gone for. that is one thing i like about the forum. many minds and there will be a solution.
 
Dang showed up by Ithica.. lol.. he is right though i hadn't thought about the clear caulking. though i have never had problems with the alginate and resin and i like it due to set time. but for local quicky Ithica is right. I guess because i have alginate on hand at the house it was what i would have instinctively gone for. that is one thing i like about the forum. many minds and there will be a solution.
]

My apologies, that was not my intent. You are correct because you used what you already had. There is more than one solution and both will work. Once again I am sorry for the misunderstanding.

Ithica
 
God no Ithica I did not intend to imply anything was making a joke... Yours is the better solution and like I said that is what I like about the forums... 1 helping each other out and 2 with the amount of minds and experience here a good solution can and most likely be found... Respect
 
Hey, thanks guy's for the timely response. Both sound like a good idea, and I think I'll give the caulk a shot since that stuff is more accessible. I'll be sure to post results, stand by...
 
I was going to suggest the clear silicone as Ithica did, which is a great method, or hot glue actually. I was going to suggest the glue method for two reasons: very inexpensive, and can be re-melted for another use. Obvoiusly couldn't be re-used in a glue gun, but possibly melted down in a pan for another one time mold.

-Matt
 
Thanks Matt, that is a really good idea. I can't believe I'd totally forgotten about that. I got a ton of glue sticks hanging around the house. Time to put them to good use...
 
The problem with alginate is that it falls apart in short period. I would not use it for this plus resin is killer on it. It will tear it apart. A very simple method that does actually work is the clear caulking for Lowes, Home Depot or Walmart. Get enough tubes so you can do it all in one batch. It is very cheap so you can make multiple molds if needed but they are short tem. If you need a mother mold use Plaster of Paris because it will be strong enough yet cheap.

Ithica

I agree with Ithica.
But i will also add that the caulking does not dry evenly or quickly (Days if not weeks), so the addition of a small amount of corn flour will allow it to dry internally. I have been looking into the use of caulking for differernt types of moulds. Apparently you can also add Xylene (Toxic! Wear a mask) to thin it out and make it into a pourable silicone substitute. I do not know if its possible to add both and have a fast drying, pourable substitute, but i will try it.

Links:
http://www.instructables.com/id/How-To-Make-Your-Own-Sugru-Substitute/
http://forums.reprap.org/read.php?1,64640,65107,quote=1
http://www.myheap.com/book/chapter-07/siliconecaulkmolds.php


Cheers.
 
Just throwing another option on the table, not likely the best option, but something else to think about.
Latex molds are fairly inexpensive but dont last as long, and take time to make. (2 hours between thin painted on layers). But you can get >10 puls out of them depending on how thick you make them.
 
Thanks for all of the suggestions, guy's. I would like to avoid plaster if at all possible, as bad things happen with me and plaster. If my hot glue mold fails, then I'll probably give the latex rubber a shot. But I probably won't be doing that here until near the end of next week, once I knock this other project out of the way.
 
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