unfamiliar with vacuum bagging, I usually infuse. Surface voids form on the mold surface after 30-60 min. It seems the resin is absorbed by the breather, leaving the laminate too dry.
Vac bagging at around 12-15 in hg. and holding until cure.
resin viscosity 600 cps
4 layers 6 oz.
2 layers breather
Should vac bagging be at full vacuum?
Are surface voids common?
Without a gel coat I’ve never been able to get rid of pinholes when vacuum bagging. There was another thread that had a similar question about the breather absorbing resin. Maybe it’ll help!
http://www.compositeforum.werksberg.com/showthread.php?t=3894
didn’t catch that thread thanks
you mean wet layup vacuum bagging? If this is what you are trying to do, use a perforated release film between the part and the breather, or it will suck all the resin out!!! Also, full vacuum of 26-29" would be the best if you can. If not, maybe make a degassing jar and degas the resin before you use it…granted, soaking it into the fabric will make lots of air, but it might help.
But yeah, don’t put breather right on top of the part (even with peelply)
forgot to include the perf release film, just assumed
and yes wet layup vac bagging
If you don’t mind me asking why did you switch to vacuum bagging if your usual method is vacuum infusion?
ah…in THAT case…
more vacuum? Degas the resin?
I ended up having to vac bag with peelply, no perf release film, just some breather around the side of the solid release…ended up not only having VOIDS, but the surface was the fabric tows. It’s like the resin filled the tows, and I didn’t even have vacuum. Odd.
For this part the resin is viscous with a short cure time, for this particular part using a squeegee to apply resin is very easy. Also I wanted something with a little less setup time and more leak tolerant.
for a low viscosity resin such as you are using, the release film needs to be small pinprick such as p3. And with such a low viscosity resin you are using you may find that you would need to use a non-perf release film and try pull air from the edge such what you would do with a net-resin prepreg system. Either way there are many variables that you will have to control in order to get a pinhole free surface. That is why infusion is usually chosen over vac. bag. the quality and properties are much better and easier to control.
I was under the impression vac bagging was foolproof. Wasn’t even aware of different hole sizes.
There are many variables, control is the key.
takes time and patience to get a pin hole free part, I unually also find that pulling the vac slowly also helps reduce pin holes, not sure exactly why, I guess it must have something to do with the resin having time to move and any small bubbles within the resin moving to the vac bag surface slowly? or it could just be co-incedence!