I am working with vacuum bagginf and i would like to ask you if there is any specific technique to make a part with both it’s surfaces smooth and shiny.
Usually the surface facing the mould is shiny and the other surface gets the texture of the peel ply.
One solution would be to not use peel-ply at all, but most times the perforated film cannot be laid on to the laminate perfectly and it forms some ridges.
Does anyone have the same problem? Any solutions? Thanks in advance!
caul plate or RTM
I was looking for an easier method.
For example, is there any way to make the perforated film temporarily “sticky” so we can lay it up on top of the laminate without forming any ridges? Then lay the bleeder up and continue the usual vacuum bagging method?
you CAN use perforated release…but 1: the surface will conform to the weave, no matter what. 2: will have tons of wrinkles and mini-resin rich spots. 3: be full of holes where the perfs are.
Same with pre-preg. Using a release on top still leaves a rough surface, and conforms to the weave…but at least it’s SHINY 
so, like hojo said. caul plate, RTM, or RTM lite.
OK, you’re right.
One other idea is to use two moulds (one mould for the outer surface, the other for the inner surface) put the laminate on one mould then “close” it with the other mould, and finally put all them into the vacuum bag…
The excess resin could be drawn by some quantity of bleeder fabric on the perimeter of bouth moulds…
Do you think this could work?
I too have been unhappy with the results when using perforated release film so yesterday I tried a similar process to the one you suggested above. I created a “matched mold” using vinamold, a re-usable vinyl rubber. I laid up the part then covered with peelply( I’m not too bothered about the texture that the peelply leaves because a quick rub over with 400 grit leaves a nice smooth surface. It’s the wrinkles and ridges created by the release film I’m trying to eliminate) I then laid down the rubber top mold and covered with breather ensuring the perimeter was fully covered. This was then placed in a vacuum bag. I have de-molded the part today and the results were a partial success. The back of the part is much smoother with none of those nasty wrinkles and ridges, the only problem was that a few minor resin rich areas are showing on the face of the part, I guess this is due to the lack of good path to draw out the excess resin… Back to the drawing board :sad:
I don’t think you need the peelply unless you are bonding to it later. The peelply might be stretching and causing the bridging and leaving the resin rich areas. I’m guessing you are doing wet-layup?? If so, yeah, you might not be pulling enough resin out. Maybe make sure less resin IS in those areas?
I used the peelply for 2 reasons, I thought that the peelply would at least soak up some of the excess resin and may even act as a pathway for the resin to reach the breather around the perimeter of the mold, secondly, the Vinamold top mold did not have a perfect finish to it because it could not be poured all in one go. I would have preferred to have used a brush on silicone but I had the Vinamold available, so I used that instead. Yes, it was a wet lay up.
Marc, how you make the vinamold back mould?
I think that an easier process could be -instead of vinamold- to use a GRP part (after making it using the main mould) quite thin so it will be flexible and easy to follow all the surfaces of the main mould.
I want to learn more about the vinamold and why you chose to use it.
Vinamold is a very easy product to work with, it comes in a big block and you just need to cut it up into small pieces and place these in a pyrex jug and pop it into the microwave for a few minutes until it melts. You then just pour the molten rubber over whatever you want to mold. I would not recommend doing this to molds that have not been vacuumed and post cured though, I have done that in the past and it causes small blisters in the mold surface where there has been trapped air(the vinamold is at 150C when molten).
I used the Vinamold because it was much easier and quicker than creating it in GRP etc. If I had of chosen to use GRP I would have had to allow for the thickness of my part, ie using sheet wax etc. Using rubber means that is not necessary because the rubber will conform to the part and its dimensions are not so critical. I suppose it all depends on the mold being used, if it is a relatively simple shape without compound curves, lips, protrusions etc then it would be better to use GRP etc. Every mold is different and each requires a different approach to sort these problems out… it’s all part of the fun 
I hope this helps.
Very interesting Marc, thanks for the info.
Would it be a good idea to pour some vinamold on the surface of a glass plate, so you don’t risk the main mould’s integrity?
I ask because i don’t know how flexible and easy to conform to shapes this material is.
I understand that for simple shapes with very smooth curvatures this would be a good solution but not so good for a complex part with large protrusions etc.
Thanks anyway!
Yes, I suppose you could pour the rubber on a glass plate if you are worried about your mold. The molds that have blistered on me were not a big problem to repair, I just rubbed them dowm with some 600 w&d, then 1500 w&d then repolished with T Cut. This material is very flexible and easy to conform to different shapes. There are 2 different types of Vinamold, red & yellow, red being the softest and yellow the hardest. I have used both but prefer the yellow one.