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Old 06-27-2015, 02:54 PM   #1
Centri

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Default glossy finish both sides

Hello everyone,

I recently got into making carbon fiber and I am currently experimenting with making parts. I am noticing the longer I have the epoxy sit on the mold before I lay the first layer of carbon fiber down the shiner that side gets. I am using a perforated release film on top of the carbon, then breather, then vacuum bagging it. The non mold side comes out very dull and bumpy.

What are some of the ways to make this side shiny like the mold side? I need both sides of the piece to look glossy.

Also, I am noticing sometimes on the mold side, there are small areas where the resin does not appear along with the rest. I added some photos to help show what I mean.


Thanks for any suggestions or tips.

-Brian

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Old 06-27-2015, 04:02 PM   #2
Hanaldo

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If you are making anything other than flat sheet, then only way to make the reverse side glossy with typical wet lay vac bagging is to refinish that side once it's cured. This means sanding that side smooth (touch easier if you use peel ply but still a bit of work), and then clear coating the back with lacquer or resin. You'll probably then need to flat back at least once more before polishing. It's a tedious task, so decide how much you really need that reverse side to be glossy.

As for the problem in your photos, that is caused by too little resin. Either you aren't putting enough in, or you are drawing too much out. I like to make the first layer quite resin rich if it's a cosmetic part, and then do the rest as per normal.

How hard a vacuum are you pulling? You can actually squeeze out too much resin if you apply too high a vacuum (assuming you are using absorber of course). With wet lay vac bagging, I try not to draw more than 80% vacuum. You'll end up with a more resin rich part, but at the end of the day, does that matter? A few grams extra weight is normally worth it for a perfect cosmetic finish.
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Old 06-28-2015, 07:16 AM   #3
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Hanaldo,

Thanks for the detailed explanation. I am probably pulling too much of a vacuum so I will try to pull it a little less next time. A few oz doesn't matter at all for what I'm making.
What type of clear coat would you recommend? I would probably want something thicker so that it doesn't run down the part since its curved.

It's crazy that to get the back side glossy requires that much work. Does anyone else have any tips or suggestions to help get the back side glossy without going through the whole sanding and clear coat strategy?
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Old 06-29-2015, 08:27 AM   #4
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Hi Centri,

you can obtain a shine side on back surface of the part if you use a back mold made by siliconic gum for example or fiberglass, but you have to change manufacturing system to vacuum injection
https://www.youtube.com/watch?v=yTsXKGUdtCE
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Old 07-06-2015, 06:29 PM   #5
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Interesting approach to the problem. Thanks Simontech
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Old 01-14-2017, 09:12 PM   #6
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Can Vaccum infusion be used on a closed mold.. injection equipment is super expensive!
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Old 01-15-2017, 05:26 PM   #7
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Quote:
Originally Posted by gentlegiant View Post
Can Vaccum infusion be used on a closed mold.. injection equipment is super expensive!
To a degree.

With infusion you need some form of flow media to allow the resin the move through the laminate. You obviously can't go the regular route of having the flow mesh on top of the stack, as this will ruin the aesthetics of the B-side. So the only option is an internal flow media. Materials like Soric would work if your part can be thick enough to utilise a core material, but other than that the only option would be to use a flow mesh that can be left inside the laminate without affecting interlaminar bond strength. The other problem being that flow meshes tend to use a lot of resin and not contribute any strength, producing a heavier part without any structural gain.
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Old 01-15-2017, 09:05 PM   #8
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Thank you hanaldo, following up with another question, planning on using lantor soric in between the laminate, need two sheets of sizes 2 and 2.5 mm.
What i would be doing is engraving credit card business card holders into the laminate, with the soric in between would it by any any affect the final result. The 2mm sheet will have a 0.76mm depth engraved into it by CNC.
Any experience cutting or engraving these kind of laminates?
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Old 01-15-2017, 10:32 PM   #9
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Are you OK with having the core exposed at the cut out? If not, you'll want to make sure your laminate skins either side of the core are at least 1mm.
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Old 01-15-2017, 11:30 PM   #10
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not okay with the core exposed unfortunately, but will test working out how i can manage the skins properly, so vacuum bagging with soric as core sounds good, what about the b side mold, mylar? what do you think will be the best to get a nice surface finish.
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