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-   -   How to make Acrylic mold for clear lens? (http://www.sculpture.net/community/showthread.php?t=4582)

289cobra 01-28-2007 12:29 PM

How to make Acrylic mold for clear lens?
 
I am looking for information on how to replicate a couple of acylic headlight lens for a 50's childs electric car. The clear lens are about 3 3/4 inch diameter. They are faceted on the inside so a mold would be required. I have not worked with acylic or mold making in the past so if there is someone out there that can direct me to someone that can create these for me, great.


Thank you in advance for any help.

charper 01-29-2007 03:17 PM

Re: How to make Acrylic mold for clear lens?
 
Do you have access to a vacuum former? If you do, you could make your mold out of wood and then just thermoform the soft acrllic around it. You could even make the mold out of sculpey clay if it was just a one or two time mold...the sculpey won't withstand much more heat from the vacuum former after that.

charper 01-29-2007 03:33 PM

Re: How to make Acrylic mold for clear lens?
 
also check out this internal thread re thermoforming

http://www.sculpture.net/community/s...vacuum+forming

289cobra 01-29-2007 08:51 PM

Re: How to make Acrylic mold for clear lens?
 
Charper,
No, I do not have access to a vacuum former.
The former post you mentioned describes heating and forming acrylic over an original clear lens.
In my case I need to duplicate a pattern in the original lens.
Any other help is appreciated.

Daniel 02-01-2007 03:36 AM

Re: How to make Acrylic mold for clear lens?
 
You could make a silicone mold of the original lens, then cast it in a clear urethane resin. This will give you an exact copy of the original. The problem with this type of resin, though, is that there will probably be many tiny bubbles in the casting that were introduced during mixing. To get an optically clear, bubble-free piece you have to pressurize the mold to 60psi after pouring the resin. You should also have access to a vacuum chamber to pull the air bubbles out of the silicone before you pour your mold. Make sure that the silicone you use is platinum-cure RTV, not tin-cure. The tin-cure kind can inhibit the curing of the clear urethane and you will end up with a tacky surface.

smooth-on carries all these materials and has a how-to section on their website www.smooth-on.com. "Crystal Clear" is their clear urethane. Make sure you get the right formula for the thickness of your lens. There are different ones for various part thicknesses.

289cobra 02-01-2007 12:08 PM

Re: How to make Acrylic mold for clear lens?
 
Daniel,
Thank you very much for the information. It has convinced me that this is not a project I can complete myself.
Is there someone that you know that would like to take on this project for me?
Jim


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