Mold Release Technique

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Alexander
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Mold Release Technique

Postby Alexander » Thu Feb 11, 2016 3:07 pm

Howdy all,

I recently built a curing oven and so far I've had it go up to temperatures to 165F. I use the oven to making composite tubing. I will recently be getting ahold of some prepregs that cure at low temperatures. I have my methods for the tubes not sticking to the mandrel, but its just a complete hasle.

I was wondering if using a mold release such as frekote 700 would work, but I am a little worried that if 165F is not enough for the mandrel to expand enough for it to release the tubing as it cools down. I use aluminum mandrels to make the tubing.

What do you guys think? Will it work or not?
Alexander Solis

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patelldp
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Location: New York

Re: Mold release question

Postby patelldp » Wed Feb 24, 2016 9:52 am

Alexander,

My guess is that you can do some simple calculations to figure out how much the mandrel will expand/contract. If you cure your tube at 165F and then reduce the temp well below room temp, you're going to get a significant amount of contraction. Cap one end of your mandrel (assuming it's hollow), and pour salted ice water down into the tube to get maximum contraction.
Dan Patell
TRA 10904 L3

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Barkley
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Re: Mold release question

Postby Barkley » Wed Feb 24, 2016 10:57 pm

HI Alexander
I use Frekote 770NC and the thinnest mylar film I can find. Treat the mandrel with a couple of coats, give it one tight wrap of the mylar, then another shot of Frekote on the film. Very very easy, and using this method I've yet to have a subpar tube.
If you're applying the glass straight to the mandrel without the film, you still should be good with the Frekote if your oven is going up to 165F and your mandrel is thin walled. (I don't use an oven, but I've run a heat gun down the inside of the tube during layup and cure for a ghetto version of one.) If it's still sticky then stand the piece upright in a cooler and pack both the cooler and the interior of the mandrel with ice. If that still doesn't work, drill a hole through the mandrel aft of where the work stops, slide a good sized bolt through it, chill it, then use a come along on the bolt (while everything's still chilled) to break the bond.
That's the sum total of my stuck tube knowledge. Hope any of the above helps.
Chris

Alexander
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Re: Mold release question

Postby Alexander » Mon Feb 29, 2016 9:39 pm

Hey guys thank you for the responses. I have actually moved on to another method. So far I have pulled out two small tubes with success and no hassle. Best of all I don't have to wait 24 hours for the de-mold and there is not much time wasted on prepping the mandrel. I'll share the technique later on when I feel confident in that it will always work.
Alexander Solis

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tfish
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Re: Mold release question

Postby tfish » Mon Feb 29, 2016 10:14 pm

cool....

Tony

dixontj
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Re: Mold release question

Postby dixontj » Tue Mar 01, 2016 6:59 am

Alexander wrote:Hey guys thank you for the responses. I have actually moved on to another method. So far I have pulled out two small tubes with success and no hassle. Best of all I don't have to wait 24 hours for the de-mold and there is not much time wasted on prepping the mandrel. I'll share the technique later on when I feel confident in that it will always work.


Yes, please share.

Alexander
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Re: Mold Release

Postby Alexander » Wed Mar 09, 2016 8:57 pm

Alright guys three tubes pulled out and hoping on a fourth today, I had one get stuck, but I'm certain that was my fault. I'll be explaining the do's and dont's and you should be happy with no more mylar or wrapping of anything else and it will save you lots of time and frustration.

I posted the link to the material in another post. The material is non-porous teflon fabric with an adhesive backing on one side. Basically you wrap it around the mandrel, avoiding wrinkles. Now in the photo below you will notice that the wrap is not overlaping and you can see some of the metal underneathe. You want to avoid the overlap and if you get an overlap you cut that part off. If you wrap a tube with an overlap, it will get stuck and you will have to chop that awesome tube you just made.

image.jpeg


Finally the last two things you will need is wax paste and baby oil.

image.jpeg
image.jpeg
Last edited by Alexander on Sun Mar 13, 2016 5:12 am, edited 1 time in total.
Alexander Solis

Alexander
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Joined: Tue Nov 24, 2015 9:45 am

Re: Mold Release

Postby Alexander » Wed Mar 09, 2016 9:03 pm

With the wax paste you apply it to the areas where the metal is exposed on the seam. This creates a barrier so the epoxy does not stick to the metal.

image.jpeg


After you have done this, apply baby oil to the teflon using a paper towel or anything of your choice. Here is something you should not do, after applying the wax do not avoid the dried up areas of the wax, otherwise the tube will grip and get stuck. With the baby oil try to wipe it over the wax and it should be all smooth again. The baby oil helps in the tube to slide off.

image.jpeg


Be sure to apply it close to the seam and also all around the mandrel. Now you are ready to lay up your tube. Here is something that will help, because due to the baby oil, the fabric will slide off the mandrel. Using a (glass,kevlar, or carbon) sleeve will help as a base layer for the fabric to grip on to.

Hopefully this helps and I'll keep you updated on the test tube and let you know if it pops out.
Alexander Solis

Alexander
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Re: Mold Release Technique

Postby Alexander » Wed Mar 09, 2016 9:47 pm

Here is the carbon tube, for some reason I had to wack it in order for it to release. I assume this is because I have very minor overlap. Be sure you avoid overlaps as this makes it difficult to remove the tube. Again dont worry if there is exposed areas of the metal mandrel as covering it with wax paste will help not get it stuck.

image.jpeg


So far this has been 4 tubes and one stuck and I feel confident in this set up. Hopefully this will help you guys in your next composite layup.
Alexander Solis

Alexander
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Joined: Tue Nov 24, 2015 9:45 am

Re: Mold Release Technique

Postby Alexander » Wed Mar 09, 2016 10:56 pm

I found the material, this should be it. It is pricey, but think about all the money you'll save on not buying mylar or parchment paper all the time.

http://compositeenvisions.com/non-porou ... -1803.html
Alexander Solis


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