+x

 

Chris Rogers - 11/25/2019 7:25:37 PM

I totally agree that digital gauges are a huge help with infusion but an important thing to consider when pulling really high vacuum levels is that you get into the problem of volatile materials - mostly water - boiling off in your bag.  A lot of the problems you see on a drop test are moisture related once you have a really good bag.  If you drop test an almost perfect bag (sub 15-20 mbar) and then let it sit under high vacuum for a few hours you should notice that your drop test results look a lot better if you drop test again after time to evacuate the moisture.  In the sub 50 mbar range most high vacuum pumps can only move a very small volume compared to their rated free-flow capacity so it takes a long time for moisture (because when something becomes a gas it gets huge!) to get sucked out.  

Last week I wrote a post about troubleshooting infusion which goes all over this:

https://explorecomposites.com/2019/11/19/troubleshootin-vacuum-infusion/

and you should check out this info from Vacmobiles which explains moisture issues really well:

https://www.vacmobiles.com/vapour_pressure.html