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Old 04-14-2014, 08:53 PM   #1
Gilbert

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Default Surface finish issues

I posted on here several weeks ago about my finished surface having resin voids, pinholes, and not having a good resin to fabric ratio. I do wet layup vacuum bagging. I am having issues with major resin voids and pinholes on my surface side. I have tried putting another layer of resin on my fully cured part and letting that cure. Once it has cured I noticed that it bleed through the entire carbon fiber panel. My methods I have tried are putting a layer of resin in the mold and letting tack up then laying fabric in and wetting out. Then I use perforated release film with bleeder cloth. I put that under full vacuum and leave running until cured. When the part is cured my bleeder cloth is fully saturated and I feel like too much resin is being pulled from the carbon fiber. Next method I used was wet lay the fabric and then lay it in the mold and follow my bagging process. I had the same finished product this way as well. Also, having the pinholes I try to clear coat or add a layer of resin and it bleeds completely through the panel. I am very frustrated at this point and don't know what to do. I am ok with tiny pinholes but I want a smooth finished surface that looks presentable and where I am able to put a clear coat finish on it to make a better end result. I use west system 105 epoxy resin and 5.7oz twill carbon fiber. Would it be better to put a regulator on my pump and pull less vacuum to try and keep more resin in the fabric? Would that reduce my pinholes and cut back on print through? Any help would be greatly appreciated.
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Old 04-15-2014, 06:11 AM   #2
Wildcard

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I remember your original thread about print through. I've never heard of a part draining epoxy that sits on the top. Can you show some pictures so we can better help ?
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Old 04-15-2014, 06:15 AM   #3
sammymatik

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what release are you using?

Also have you used non-perf release film?

Pictures would be helpful
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Old 04-15-2014, 09:10 AM   #4
Gilbert

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Here is a picture of the back side of my panel. The shiny part shows where the automotive clear bleed through the entire panel to the back side.
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Old 04-15-2014, 09:17 AM   #5
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Here is a picture of the front of the panel. I have already started sanding it but you can see that the clear bleed through and made piles on the finished side. This panel is only 2 layers thick of 5.7oz fabric but I have had the same issue with 4-5 layers thick. When I take the bleeder cloth off it is fully saturated. When I watch videos most people just have small circles of minor resin on the bleeder cloth. Am I pulling too much vacuum? I have never made a panel that has a smooth surface, always print through or pinholes with even small areas with no resin. I use frekote along with partall wax for my release agents. I have always used perforated release film. I started with peel ply first then release film, then I cut out the peel ply and I am still having the same results.
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Old 04-15-2014, 09:22 AM   #6
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This is a panel right out of the mold. I tried sanding and buffing this and it has so many pinholes that the rubbing compound stayed between the weave and I can't get it out.
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Old 04-15-2014, 09:24 AM   #7
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This is the same panel and here are the resin voids. On the flat parts it just has pinholes all over it and print through.
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Old 04-15-2014, 02:03 PM   #8
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i was in the same boat a few weeks ago. i used perforated release film as well. But I've since abandoned this method.. I personally think you need to lower the vacuum. Its very deceiving as ive here anywhere from full vacuum to 10-15 (from uscomposites) which makes sense in my mind. IF youre at full vacuum until cure, the pump will just keep sucking resin out so you will get a part with resin starvation..

Another tip people kept telling me, is if you can not do a wet layup without pin holes, then your baggin will still have pin holes. apparently thats the trick, which takes a lot of practice...
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Old 04-15-2014, 02:35 PM   #9
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Okay, here's my thoughts... after looking at your old thread, the print through issues in that thread could be fixed by allowing a gelcoat layer of epoxy to cure until it is tact free... then start your layup.

The issue of whether you are pulling too much vacuum because videos that you saw only have a few drops on their bleeder cloth, is not how you should be deciding how much vacuum to use. I have done many vacuumed parts and the bleeder is completely saturated with resin, and I used perforated release film. So, focus on making sure that you have sufficient vacuum to press the cloth into the contours of your mold, and not on the fact that your bleeder cloth is more saturated than this guy over here. There are many factors, how much resin used, perf or non-perf film, etc. etc..

2 layer of 6.5 oz for a finished part is a very light part. It is possible for that light of a part to have areas where there are gaps between the carbon tows that are areas without any fabric. You can check this by holding the part up to the light, you may see some spots where light shines through. Usually, these spots are filled with epoxy, but perhaps sanding might have broken them open.

I've never seen a part bleed through like that, usually clear may roll off of the edges and migrate to parts of the back of a part, but there are parts that are darker that are not by the edge, so I'll take your word for it that it is draining material through holes. I would suspect that the drainage is due to what I mentioned in the previous paragraph. Try using more layers, and orienting the different layers at different directions.

Pinholes are something that we all deal with. Coat on the first layer of clear with a brush, then sand it. Then you can continue spraying with clear.

I don't understand your release agent strategy. You are using frekote (sealer or release agent, or both) along with partall wax? I'm confused because you are supposed to remove any wax from the mold to use frekote, so i'm completely lost with how you are using both together. I'm sure this is not causing your issue, but one should be eliminated to save cost in the future.

The last picture, that is just a void that can be filled with epoxy and sanded back down. Place either flash tape or release film on the epoxy and pull taught. Then after it is fully cured sand back down.

Since you have your vacuum setup, you may want to add a resin trap and give infusion a try.
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Old 04-15-2014, 04:11 PM   #10
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Wildcard, when you say put a layer of resin in the mold and let it become tack free do I need to sand it prior to laying the fabric to make it adhere to the fabric? I ask this because I tried doing this and when I went to demold the layer of resin stayed in the mold and it delist adhere to the fabric so I have a ruined mold.
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