I have a vacuum set up with a tank that I made that allows me to pull down a certain amount of vacuum and the pump will shut off.
When the vacuum drops 7 to 8 inches of hg the pump kicks back on.
yesterday I layed up some plate material (wet layup, not infusion), The epoxy I am using is a 24 hour cure, It took about 2 hours for the vacuum to drop 7-8inches so it would kick back on and recharge the vacuum.
My question is: Is 7-8inches of vacuum loss an acceptable range when doing a wet layup, And then: Is 7-8 inches of vacuum loss acceptible when doing vacuum infusion.
The plate came out very nice but in the future I want to try to infuse and I need to know my equiptment will perform for me.
Thanks ,
Terry
Any noticeable vacuum drop is unacceptable in infusion. In vacuum bagging some vacuum loss is acceptable depending on how critical your part is but 3 or 4 would be more reasonable. 8 inches drop is a lot.
If you loss that much vacuum during infusion you would have air in your laminate. Your infusion should have no problem being disconnected from vacuum for a full day and barely see a drop, if any.
I was reading my gauge incorrectly. I loose 5" exactly before the pump kicks on and recovers. This takes an hour or two. I must have a small leak in my system (the pump or lines) but I just cant locate it. But if the bag setup is leak free think I should be ok.
Contiously run the pump while doing the infusion and pinch it off.
Thanks for the help.
I do have another question. I would like to infuse using a laminating epoxy with a viscosity of 1600cps(resin services HTR212). Is there a correct flow media that will allow something this thick to infuse? The part is 15"x22"
Thanks again
You should find all your leaks in your system first. pinch off your vacuum line, have a gauge on your vacuum pot. Find the location of the leak and fix it. Otherwise you will never know for sure if there isa leak in your bag or not.
Buy infusion epoxy, laminating resin is too thick to infuse correctly. Youll want a system below 600cps preferably.
ok, thanks for the help guys. Ill post when I give it a try
Terry
Indeed try and fix the leak. And keep in mind that everything is suspicious. I once had a leak in the vacuum gauge that I was using to find the leak…
Also the non return valve in your pump might leak. Sometimes the only solution is to use a leak detector.
As for the epoxy: You could infuse with that, but try and heat up the epoxy and the mould, and have patience. Infusion time is linear with viscosity.
In case you can’t find a leak in the bag and end up double bagging it and still covering all the suspicious spots with tape and you still have a leak, it might be the vac system like with me. I think it was Fastr that posted a pic along time ago where he had wrapped yellow bag tape around all his connections. I did this and it got rid of any slow leak I had. I can close off the valve to the pump and come back a day later to only see 3/4-1" drop from 29".
Instead of using tape, which usually gets messy, but indeed is a quick fix, you could also use some Loctite stuff. They have very nice sealants for threads. Do need to cure for a day or so, so plan ahead. (but much easier to use than teflon tape)
Always test your vacuum system. Just close it off, and watch the gauge. There should be no noticable drop.
I am having made vacuum sytems regularly. (I sell these). One of my customers decided he could construct one himself, and had the local smithy make a square tank, wheels, etc. This thing leaked in 106 places in the welds. (we counted them…)
I must admit that when installing a vacuum system at one customer, I found out that there was a tiny leak in a very odd place, hardly noticable. It was really just a pinprick. I squeezed in some sealant tape, and it is still there up to this point.