Hi,
I have been doing the carbon inclusion for a while now, I have try many method but do not know what i have done wrong. ( still not perfect part) I have done like about 10 times now. The size of the part that is in the photo is 14cm in diameter and 4cm high. The step of doing is degas the epoxy before the infusion for about 5-7min. The mold has been wax for about 3 times.) Then I check for the leak of the bag. I have wait for about 30 min and there is no leak. So I start the process and set the vacuum at 30 inc.
Some time the part came out has less but some time is more of the white patch. The picture show the one that has the most. (so it can be seen easily in the photo) I try to set many value of the vacuum like i.e. 20inch but still the same problem.
Many thanks in advance.
Maybe you vacuum is not high enough or you suck too much resin out. Take a look at the MTI thread, there are a lot of pages, but some had the same problem than you and these problems have been discussed and now they don’t have the pinhole problem.
Many thank will look into it.
What do you use for a gel coat?
I’m assuming your vac is too high and you are sucking the resin out of the part.
Please post pictures of your molds and process for more help :).
Hi
This the mold that I use with. The other picture is the testing of how I do it. I have change the setting of the vacuum to about 40inc-50 inch. And I slower the resin to travel by having less mesh. The result is a little better but still having the white spot.
What is the requirement vacuum needed?
Many thanks
Have you read the MTI hose thread? It seems not. There was everything discussed, the vacuum, how to place the flow media…
Vacuum: the abs pressure should below 20 mbar / 0.06inHg
Flow media: all over the part, let it stop 2cm /1in before the fabric ends
If MTI hose no brake zone, if not min 5cm/2in peel ply as brake zone
You will get the best result if using MTI hose.
You may also have a leak in your mold.
Do i need to degas it every time before the infusion
thanks
Yes, always degas your resin, thos is very important. Even at amall parts.
looks like your gel is pulling from your carbon how long are you letting the gel cure . do you clear coat your parts if so just lay up with out a gel and you’ll be fine
Hi
I did gel coat the part and let it dry for an hour or so. When I try without the gel coat the part, it just leave the dry spot where the white patches are.
what the curing temperature?look like not enough resin at the surface.
It looks like air is being pulled into the part somewhere, somehow. Are you clamping the resin feed in a way that there is no possible way it can pull air in?
Also, maybe turning the pump off prematurely? I had the exact same problem and by leaving the pump on until the resin kicked solved the problem.
Hi
What I did when I test if there is a leak or not is by having it vacuum and clam it. i will for about 10-15 min or so if there is any leak by checking or pulling the bag to see if it is still stick to the mold. I try to switch off the pump before and after the curing it all turn out the same.
How long do your have your part at a low vacuum? I guess, because you are in Thailand the air humidity is high, so let the part longer in the vacuum until the water vapours. Then infuse. A quick guess, at least 30min -60min (with your part size) and lower vacuum than 20mbar!! Degas your resin.
Actually, its not enough to try to pull the bag to check the vacuum. You need to do a drop test to check the seal of your bag/mold.
The drop test would entail, pulling full vacuum that your pump can provide, at a pressure above the vapor pressure of water vapor at your ambient temperature, and then closing off the vacuum line and measuring the drop in pressure. If you have more than 1mb of drop in 5 minutes, you’ve got to check your mold/bag for leaks. Your mold seems to be very small, so you should think of 1mb in 15minutes or so.
Then infuse with a degassed resin at a vacuum thats say 10-20mb above the vapor pressure at your ambient temp.
hope this helps.
1 mb is 1/1000 of a bar.
I think it is impossible to reach such level of vacuum integrity.
Difficult to measure too.
not difficult, Use a digital absolute pressure gauge. its possible to hold much higher standards than what was mentioned (1mbar/5min)
I am just newbie over here, excuseme if im wrong, but could improve to have the entrance of resin at the center of the mold and the vacuum at the perimeter?
regards.
Antonio
Roberto,
Use high quality bagging materials, extremely high quality molds and vacuum equipment. If you have never been able to achieve this vacuum integrity, you need to work on it a bit more.
We regularly infuse parts, for production parts I have never seen us have a drop of more than 8-9mb over-night. Most often its 0mb, but the increase can happen after the reaction as well, that is where for some resins we get 8-9mb.
And yes, hojo, we use an absolute pressure digital gauge.