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Old 01-28-2013, 04:17 PM   #21
Extreme

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Im a noob to composites and wondering if the special gelcoat cup gun I see advertised is a good investment as I plan to make many parts?
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Old 01-30-2013, 12:58 AM   #22
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in your opionion, it makes sense IMC if the mold isn't high gloss? With resin infusion and also RTML I have little pinholes in the piece...it makes sense to do a IMC, then infusion/rtml and then an other finishing coat?
2K paint is lighter than gel coat, and his cure cycle is shorter
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Old 01-30-2013, 04:33 AM   #23
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I use IMC since 1 year with infusion. For me it's a good solution when you can't apply a top coat in good conditions.
I apply my IMC with a spray gun, if your mould has a good finish surface, your final part will have a beautifull surface.
If you have some dust when you apply your IMC or during the cure, those imperfections doesn't really appear after infusion.

On the specifications of my IMC, you can wait 72h before infuse. Generally I put my IMC at the end of the day and infuse the next day. I prefer to wait because if you put to much IMC, you can some issues because the IMC doesn't catalyse correctly.
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Old 01-30-2013, 09:46 PM   #24
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Quote:
Originally Posted by GAB981 View Post
in your opionion, it makes sense IMC if the mold isn't high gloss? With resin infusion and also RTML I have little pinholes in the piece...it makes sense to do a IMC, then infusion/rtml and then an other finishing coat?
2K paint is lighter than gel coat, and his cure cycle is shorter
In my opinion IMC's do not make sense if:

1) The mold cannot produce a high gloss orange-peel-free surface. The IMC can be polished if it's slightly hazy. Semi-permanent releases will sometimes get hazy after many molding cycles. This haze can be easily removed on the part by using a Swirl Remover and few minutes of hand work.
2) The layup contains voids. Voids cosmetically will not look good even if the IMC is spanning them. The IMC is also prone to breaking if it's spanning a void.
3) The resin and curing technique do not eliminate fabric print-thru.
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Old 01-31-2013, 01:33 PM   #25
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i tried an IMC for the first time a couple of days ago... i used a 2pk epoxy high build primer paint and built up a reasonable thickness, waited 4hours then laminated over with epoxy matrix e-glass multi-axials. So far everything looks fine and no noticeable pirnt, however it has not been exposed to sunlight yet and i suspect it might show up then... i also have some 2pk Extreme hard wearing epoxy finish coat to try (used on oil rig pylons), i cant see it being much different as i beleive the chemistries are similar so it should work ok and provide a super tough exterior coating... i think the trick would be to simply infuse over this type of coating within the "recoat window" of the paint so its still chemically active.

Thanks for the tip...
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Old 02-01-2013, 04:04 AM   #26
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Quote:
Originally Posted by wyowindworks View Post
In my opinion IMC's do not make sense if:

1) The mold cannot produce a high gloss orange-peel-free surface. The IMC can be polished if it's slightly hazy. Semi-permanent releases will sometimes get hazy after many molding cycles. This haze can be easily removed on the part by using a Swirl Remover and few minutes of hand work.
2) The layup contains voids. Voids cosmetically will not look good even if the IMC is spanning them. The IMC is also prone to breaking if it's spanning a void.
3) The resin and curing technique do not eliminate fabric print-thru.
ok thanks wyowindworks. This morning I have do an infusion in a half IMC mold, this afternoon I demold and then I will see how it is. I have fabric print-thru also with a test with rtml, 1 layer 200 gr carbon + 1 650 carbon, with much resin, but there is always a little print-thru.
I post a picture this afternoon
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Old 02-01-2013, 05:55 AM   #27
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Quote:
Originally Posted by wyowindworks View Post
In my opinion IMC's do not make sense if:

1) The mold cannot produce a high gloss orange-peel-free surface. The IMC can be polished if it's slightly hazy. Semi-permanent releases will sometimes get hazy after many molding cycles. This haze can be easily removed on the part by using a Swirl Remover and few minutes of hand work.
2) The layup contains voids. Voids cosmetically will not look good even if the IMC is spanning them. The IMC is also prone to breaking if it's spanning a void.
3) The resin and curing technique do not eliminate fabric print-thru.
4) If the part is too big to be filled with dry material and infused within the open window.

For the rest, nothing but good things about it.
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Old 02-01-2013, 07:00 AM   #28
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I have demold 3 hours ago. I have a lot of print-thru, but I was a vandal with the cure....infusion at about 30C, then oven @ 50C for 20 mintues, then without ramp 70C for 25 minutes and then 10 min @ 80C, 5 min. to cool down until 60C and demold


A question about print-thru and class A finish surface... Class A surface is 100% print-thru free? Yesterday I see Gurit sprint prepreg and a test piece make with this...it's class A surface finish, used by Aston Martin to make hood, fender and rear hood. It has some print-thru
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Old 02-01-2013, 07:53 AM   #29
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Then it is not Class A, but marketing BS.

Class A is like a mirror, and a very good one.

Even the tempered glass sheet we use for testing already has some waviness. Enough not to call it class A.

Do the ruler test. Position a ruler on the part, and see up to how many cm or inch you can read the markings on the ruler. The more, the better.
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Old 02-01-2013, 08:26 AM   #30
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Quote:
Originally Posted by herman View Post
Then it is not Class A, but marketing BS.

Class A is like a mirror, and a very good one.

Even the tempered glass sheet we use for testing already has some waviness. Enough not to call it class A.

Do the ruler test. Position a ruler on the part, and see up to how many cm or inch you can read the markings on the ruler. The more, the better.
If I understand right, class A surface in automotive isn't a mirror surface, but a surface ready to paint.
This is the prepreg
http://www.gurit.com/files/documents...re-2011pdf.pdf
with a single layer of this prepreg they made the outer side of the bonnet, front wheel arches and rear tailgate.
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