Online since 2002. Over 3300 puzzles, 2600 worldwide members, and 270,000 messages.

TwistyPuzzles.com Forum

It is currently Thu Jul 24, 2014 1:21 pm

All times are UTC - 5 hours



Post new topic Reply to topic  [ 7 posts ] 
Author Message
 Post subject: Mold question
PostPosted: Tue Feb 04, 2003 9:53 am 
Offline
User avatar

Joined: Mon Sep 09, 2002 2:19 pm
Location: Yaroslavl, Russia and Maryland, USA
Generally the mold is made with silicone rubber, for it takes great detail from the original, and also gives a "non-stick" (or, rather poor stick) surface to a cast plastic. At the same time a mold from silicone rubber is not very durable, and gives you only a couple dozen or so castings.

However, most puzzle parts are pretty straight, and don't really have that intricate detail that needs to be reproduced precisely, like hair lines, etc. Can a mold be made from different material? What would that be? How long would it hold?

For example, can a mold be made from the same polyuretane resin that we use for casting? Would a mold release solution work so that a casting does not stick to the mold? Or can a cheaper resin be used for a mold?

I'd like to understand this deeper, so please forgive me if I am completely dumb on this. :-) Thanks!


Top
 Profile  
 
 Post subject: Re: Mold question
PostPosted: Tue Feb 04, 2003 10:15 am 
Offline
User avatar

Joined: Wed Nov 24, 1999 12:18 pm
Location: Palerang Shire, NSW, Australia
There is also the possiblility of using polyurethane rubbers, however, you're usually casting polyurethane plastic pieces and you will need plenty of silicone spray to stop them from sticking. A missed spot will mean your mold and piece are basiccally ruined. I find that I get plenty of castings out of a mold. And the only reason it get's ruined it because I forgot to spray it first. Also when sites mention that silicone is sometimes not durable that is because of somtimes using large molds, with plenty of possibility of damage. You generally try to avoid small nicks in the rubber as that starts a tear.

I've found so far that silicone rubber / polyurethane plastic is the best thing for what we do.


Top
 Profile  
 
 Post subject: Re: Mold question
PostPosted: Tue Feb 04, 2003 1:21 pm 
Wayne, you talk about using two part moulds in your article, I have a couple of questions.

You don't seem to use pourers and vents like in the posted article. Do you use simple two part moulds, fill the two halves and bring them together? If so, how do you stop the resin pouring out as you close them? Don't you get a lot of resin leak between the two halves of the mould? Isn't there an issue with bubbles along the join line? How is the finish effected on the final piece? Do you need to sand them or just trim with a scalpel?

I understand it isn't practical to use vents etc on smaller pieces, I just wanted to pick your brain for tips. I have just got a bunch of parts from my stereolithography guy and I am going to have to make two part moulds.

Max


Top
  
 
 Post subject: Re: Mold question
PostPosted: Tue Feb 04, 2003 1:28 pm 
Offline
User avatar

Joined: Wed Nov 24, 1999 12:18 pm
Location: Palerang Shire, NSW, Australia
Yep, what I do is make a two part mold, no vents or anything like that.

I have both halves of the mold face up and fill them with resin. Actually you slightly overfill them. Depending on your working time, spend time removing any bubbles lock in sharp places out with a sharp steel or plastic tool (don't pierce the mold).

Use the tool to prod the liquid surface. When it becomes thick like a gel, it's time to get it together. Then it's all in the wrist. Quickly but carefully close on half on the other while trying not to capture air, and trying not to spill too much out.

Once the two halves are together, press from one end to the other sqeezing out more resin and bubbles along with it.

Do large pieces first because the cure quicker. Then move to smaller pieces.

It's a technique that you need to master after a few goes. Doing the closure right before gel time, helps a lot.


Top
 Profile  
 
 Post subject: Re: Mold question
PostPosted: Wed Feb 05, 2003 8:56 am 
Offline
User avatar

Joined: Mon Sep 09, 2002 2:19 pm
Location: Yaroslavl, Russia and Maryland, USA
Wayne, I don't see this as a method for making hollow parts (i.e. caps). For example, a hollow polyhedra that has walls only. How do you do that, then?


Top
 Profile  
 
 Post subject: Re: Mold question
PostPosted: Thu Feb 06, 2003 8:56 am 
Offline
User avatar

Joined: Wed Nov 24, 1999 12:18 pm
Location: Palerang Shire, NSW, Australia
I would still use the same method. Check the article I write on making the 2x2x2 rhombic dodec (http://www.twistymegasite.com/2x2x2dodec.asp. I made the pyramids out of card, and a two part mold to cast the card.

Maybe send me a drawing of the kind of part you're wanting to cast.


Top
 Profile  
 
 Post subject: Re: Mold question
PostPosted: Thu Feb 06, 2003 12:35 pm 
Offline
User avatar

Joined: Sat Nov 24, 2001 8:31 am
Location: New York
Anyone need some pigment?
I've got 2 cans of pigment (pint each i think)
one black, one blue. I also have a can of Synlube if anyone wants it. All i ask is that you pay the shipping. They are all sealed (execpt the lube). Cost me about $30


Top
 Profile  
 
Display posts from previous:  Sort by  
Post new topic Reply to topic  [ 7 posts ] 

All times are UTC - 5 hours


Who is online

Users browsing this forum: No registered users and 8 guests


You cannot post new topics in this forum
You cannot reply to topics in this forum
You cannot edit your posts in this forum
You cannot delete your posts in this forum
You cannot post attachments in this forum

Search for:
Jump to:  

Forum powered by phpBB © 2000, 2002, 2005, 2007 phpBB Group