So I usually just infuse things so far without any resin degasing and have not really seen any problems or other with doing this but I was thinking to try it anyway since the vacuum catch pot is more than ok to do it quite easily.
Question is how long does it take to degas? I can’t see inside the catch pot so how long is a sufficient time to degas 500g of resin? 5 minutes??
If you can’t see your resin it will be hard to degas. It will expand a lot, so that will be a mess when you can’t see when to open your air valve.
Time depends on vacuumpump cfm, size bucket, resin, size vacuum chamber, vacuum, temp., ect.
When the resin has collapsed it takes mostly 10 or 15 min. Lett it be under vacuum until the foam / bubbles are gone on top of the resin.
Degassing your resin is just good practice, just like the cup transfer method where you pour your mixed resin into another clean cup. It’s not necessary but it helps you control as many aspects of your layup as possible. This is particularly important on structural parts.
Recently I worked on a project to make carbon fiber wheel shells using a resin infusion method. For this I degassed my resin for approximately 3-5 minutes after mixing it in my catch pot. Depending on your resin system you’ll definitely notice a difference.
(BEFORE)
(AFTER)
After degassing I noticed fewer micro bubbles in my resin which means less air in your final part. My advice get your self a designated degassing chamber so you don’t have to unhook your catch pot from infusion part and vacuum pump. I made one for about $50 using a kitchen pot and a 1/2" thick clear plexiglass plate.
Its best to have a clear top so you can observe the resin degas, as the pressure in the vacuum chamber decreases the resin will start to foam at the top. Once this top foam layer has collapsed you know your resin has been properly degassed. Depending on the resin system that can take anywhere from 2-5 minutes.
Couple things to remember, don’t leave the resin in the chamber for much longer than 5 minutes because it might exotherm too much. I usually give the resin a quick stir after degassing (being carful not to mix more air in) to even out the temperature. Finally drop and raise the pressure in the chamber slowly, like full vacuum over 30ish seconds, otherwise you might splash the resin out of the cup either by air rushing in too quickly or air foaming out of the resin too quickly.
Good luck!
Personally I don’t like opening the valve to stop the expansion anyway, as you’re introducing air to the process of removing air.
I prefer to place an object with a bit of weight to it on the top of the cup, and this then breaks the surface tension when the expanding bubbles reach it. Sometimes it still makes a bit of mess, especially if the pot isn’t big enough to allow for the expansion of the resin. Destroyed a vacuum gauge with one of these messes once…
I also don’t normally degass though, I don’t like it. I can see that perhaps from a purely structural point of view it might be better, but I have reservations about what the actual benefits are. Take care mixing your resin, let it self-degass in front of a heater for 5-10 minutes and there is virtually no air left anyway. Even expanded under vacuum the air is very little, and then most of that ends up in the flow mesh rather than the part.
I did the job without degasing and it went great.
Hanaldo you are right, if the resin is thin then most of the air comes out, then the inlet draws from the bottom of your pot too so there is no air there to even pick up.
When I was watching the resin flow in through the clear tubing you can see nothing but the smallest bubbles passing and not many either.
Yay, I thought I was the only one that did degas.