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Old 05-12-2015, 01:02 PM   #11
Bioracing

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Originally Posted by susho View Post
Try a lightweight glass film as surface film (50-75 gram/m2). Try to extend the first layer beyond the rest of the stack, that will help extracting the air.
Sorry but I don't understand completely what you said, you mean putting a film directly on the mold, like a "release agent"? won't it wrinkle?
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Old 05-12-2015, 07:55 PM   #12
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hojo, i can't undestand this "for example 0mbar drop a the part in 10 minutes" I usually opened the vacuum tap helping the bag to don't bridge with my hand or with soft plastic tools, is it wrong? so the pressure drop was very quick, is it a problem?
I check for 0 mbar at room temperature, then i setted the oven temperature to 75, checking with an external thermometer the laminated temperature, the ramp time was usally 30 minutes, but this is quicker than what the supplier said to me (1C/3min) this is another mistake, right?
I've tried to stay at 70-75C for any kind of time but this doesn't change anything

my consumable stack is: (laminated) > peel ply (optional) > perforated film > breather
I hate the breather (and the peelply) beacause very often they bridge... And I have to do a lot of work to push down and press them when the bag is closed and sometimes this doesn't work.. any suggestion? I was thinking to intensifiers, but if i have to spend a lot of time on them why not a complete counter-mould? Maybe a soft sand bag pressed directly on the outside of the vacuum bag? or an alluminium microsphere bag that will be easier to heat and will expand with the rise of temperature..
Your technique of slowly applying vacuum and press in corners is correct. My point is that before you start the curing process you should confirm the vacuum integrity (leak rate, and pressure level) is good for the process. If you have a small leak, this will likely cause a poor surface in the part. You can try double bagging the part to increase your integrity, and lower the risk. What RIF system are you using? do you have TDS? You may find using a non perforated release film, with some try dry glass toes going to the breather to be a better technique.
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Old 05-13-2015, 01:27 AM   #13
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sorry hojo, what means "Rif System"? and TDS? sorry but I don't know what those acronyms means... :P

I may have understood what hojo said about the unperfored film: to put it behind the breather, before the vacuum bag, to let the stack slip into the mold, to avoid bridging, right?

Moreover I saw that with Zyvax semipermanent full treatment, I had better results in terms of surface smooth, so I'll surely use this in the new laboratory. Wax like "Ferro Mirror Coat" ar not good for me

hojo, I check my vacuum integrity looking at the manomether I don't like to pull out the mould from the oven, there is any kind of instrument to check for micro leak?
I'll surely try double bagging

really thanks to everyone of you, you are helping me a lot
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Old 05-13-2015, 10:04 AM   #14
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Originally Posted by Bioracing View Post
Sorry but I don't understand completely what you said, you mean putting a film directly on the mold, like a "release agent"? won't it wrinkle?
Company's like cytec, gurit, etc, sell "surface films"
It is basically what you are trying.

They come in a roll, where there is a resin film sandwiched in between a lightweight glass layer, and a thicker (300 gram/m2) carbon layer. It is one of the easiest materials to get a pinhole free result with.

So if I where you, I would try the same. Sandwich the film in between glass and carbon. The glass will become transparent, and will have no pinholes. because of the air extraction (important with dry fibres) above and beneath the film, pinholes in the carbon will get very rare, if air will become trapped. So try to get this layer in contact with the breather, by extending it 1 to 3 cm around the whole perimeter of the part. If necessary, on complex shapes for instance, trow in some glassfiber tows behind the first layer to the outside of the part, that will help too.

Then the trick is that there is enough resin in there for the whole stack (calculate), and a high vacuum, possibly around 97-98 percent.

If that gives a desired surface quality, you could do a test with out the glass layer, as the glass will be not as clear (although most won't notice the glass layer at all)
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Old 05-13-2015, 07:58 PM   #15
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Sorry, meant RFI (resin film infusion).. I suggest you use an absolute pressure gauge such as the GDH200-14. You should check the pressure level and leak rate before putting the part in the oven. You would want a pressure level at your part to be less than 20mbars, and a leak rate over 10 minutes to be zero would be ideal.
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Old 05-14-2015, 10:37 AM   #16
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My RFI system is from a company called 5M
I'll surely buy something like GHD200-14, thank you!

I've looked at the cytec's and gurit's websites, i think that cytec SURFACEMASTER will be a nice solution, what do you think?
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Old 05-18-2015, 12:23 AM   #17
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I think you should control the variable in your process first, then make changes to the process to achieve the results you are looking for. You can contact Vacmobiles for the GDH200-14.
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