I’m trying to make carbon fiber plates but everytime I vacuum bag the parts I end up getting a heavily textured surface. The flat plate side is great but the breather seems to leave wrinkles on the top. Below are the details of my build.
Layer order from top to bottom
Vacuum bag
Bleeder
Bleeder
Perforated release film
Breather
Perforated release film
Carbon Fiber/Epoxy
Metal Plate
According to my vacuum gauge the pressure pulled was 68.5 cm (~27") hg or 13.3 psi
The side that faces the metal plate gets wrinkled or the rear side (perforated release)?
a photo of the problem would help a lot.
I don’t think you need to have that first release, breather, second release, and then bleeders. I think the best bet is to have part, release film, bleeder/bleeder…if you really want, add another breather on top if your bleeder gets really soaked.
Wrinkles are going to happen when you have a plastic film on the surface of your part. Even with prepreg, where layups are only a flat plate. Plastic film = wrinkles. You can try adding a layer of peel ply on the part surface…somehow that many times eliminates the wrinkles, howbeit, will leave the entire surface rough (for secondary bonding). Or just do your best to tape the release tighter, and not have any excess film that can bunch up.
Are your breather and bleeder materials different? Shouldn’t need so much, or the extra perf film between them.
Without a caul plate however, one will always have an imperfect B side to some extent. To improve this, a stiffer perf film can be used, a thinner bleeder/breather (just 1 ply), and the material can be taped tightly onto the tool surface. Wrinkles in the bag itself don’t affect surface finish unless they’re bunching up material under it when vacuum is pulled.
The breather and bleeder materials are the same, polyester felt I believe but I’m not sure since it’s second hand material. I’ve linked pictures for TNT but my TET and riff42 answered my questions.
http://flickr.com/gp/canyon289/zR027L
Thank you for the help
oh yeah, that surface is beyond normal for using breather on top of a part!!!
for flat plates, you can use a plate (same size as part) on top, and infuse between the 2 tool surfaces.
Or wetlayup, just place a plate on top of the part, and apply vacuum.
obviously release coat everything!
I’ve got a quick question about the release coat.
I have PVA and I want to be able to spray coat my molds. However I don’t know what type of spray gun to buy. I bought one of those small spray bottles from Target but the PVA is too thick to nebulize.
Are there any cheap suggestions for mist coating PVA? Manual pump is fine.
youll get a much better surface if you just a wax or semi- permanent release agent. PVA isnt neccessary and just creates an extra step that takes away from the quality of the surface of your part. but if you really want to use pva you should get a gravity feed spray gun.
I’ve been using PVA because it was leftover by a previous student and at the time I had no other knowledge of release agents. What wax would you suggest? And also what are semi permanent release agents?
I prefer semi permanent release agents over wax. They chemically bond to the mold surface and if the mold is treated right you can many pulls before reapplying a coat. If you decide to go to release agents make sure you get a good mold cleaner, sealer(very important) and release agent. There are many different companies that are good. The most well known is Frekote.
if you wanna spray pva, get an automotive airbrush, needle size 1mm, spray at around 1 bar pressure (hvlp)
i have even sprayed with 1.6 mm needle with a non hvlp gun at 2 bar with excellent results.
Hey HoJo…do you suggest mold sealer on metal molds? We always use 700 and 55NC on our tables/plates, and have success. However, there is a once and awhile happening, that something sticks BAD. I figured the mold sealers are for epoxy or spray coated molds. What do you think?
All the techs I have talked all suggest that both metal and glass should be sealed. Do you rerelease every pull? One the most important things to remember with release agents are that they chemically bond to the surface of the mold, so if you lay up on that mold too soon the release agent will actually become an adhesive and bond the two together. I think if you are having sticking problems I would strip down the surface with cleaner then seal it and release it several coats. Make sure you wait proper time between coats as it can attack itself too if reapplied too soon. Also I would say the most important is that you keep your release containers sealed up very well, air will make it go bad quick.
“We always use 700 and 55NC on our tables/plates, and have success.”
What are 700 and 55NC?
Caynon: it’s the type of Frekot. they have a bunch of types, of specific applications. Hysol (Henkle) makes it.
HoJo: with our common tools and tables, I acetone clean, and then add 2 more layers. New molds, about 5-6. Baked afterwards according to the directions. All of our dispensers are those squeeze bottles with the tube out the top…I can see how it could go bad, since the bottles get buggered up after awhile. I’ll tell our guy to order some sealer, and see what happens.
why do you acetone the surface? thats going to strip your frekote surface down I would think. your surface gets that dirty everytime you need to clean the surface? I would look in to a solvent that is ment to clean mold surfaces without stripping the release off if you really need to clean the surface. It may be that when you clean your surface with acetone you leave a puddle that sits on the surface for too long and removes too much release? How long you waiting between coats? Also its not the squeeze bottle you need to worry about, its the gallon or 5 gallon containers that its packed in. Often time people just hand tighten the cap on. You should use channel locks to get a tight seal. Just dont over tighten and strip the threads.
It looks like you’re making a composite soup more than a laminate. You need way less resin.
Haha, Aw man your comment made me laugh
That was an early part I made when I was practicing. I (think) I fixed my process. For that part I measured by just pouring into a cup on a scale, which turns out didn’t really work too well. I now use syringes to more accurately mix resin