Problems with greenflow mesh.

General Composites Discussions Products Talk
#21

So the reason I feel confident in my vacuum level and integrity is because I’m using a 2 stage rotary vane pump, and I always drop test for more than an hour before infusing. If there is any indication that there is even a small leak, I will reseal and drop test again.

I do intend to pick up a digital gauge in the near future, and agree that it’s a waste/gamble to not have one, but I’d like to knock out all other alternatives first (especially because I feel like vacuum integrity isn’t the route cause).

My only knock against my vacuum system (as we spoke about over the phone) is that I have quite a length of PVC plumbing connecting my vacuum pump to my parts - over 50 ft. However everything is sealed up with loads of glue, and all brass fittings are tightly connected and threaded with Teflon tape. My analog gauge still reads 29" of vacuum at the bagged part.

#22

Yeh that could still be an issue though. I used to think my fittings and hoses were perfectly tight because they had clamps and sealant etc. on them, but when I built my ultrasonic leak detector I found that wasn’t the case at all. Still had very tiny leaks that were impossible to find but would be affecting my vacuum integrity.

That said, I agree with using a clamp to crimp the resin feed line to slow the infusion. Works fine for me.

#23

So I actually do have a squeezee from ddcompound, but I always have trouble regulating resin flow with it through my 1/4" ID tubing. It seems that when you clamp it close to being full closed, the resin velocity in that partially clamped section increases so dramatically that there is enough of a pressure drop to boil out any dissolved gasses that were left over in the resin (and this is after a full degas!). The air bubbles stay in the laminate stack until the resin front reaches the MTI hose and the pressure drops. Is this normal?

I’m considering inserting a small (1") section of .170" or .125" ID (.25"OD) tubing into my normal .25" ID tubing to see if that will act as an appropriate restriction for volume production. That could lead to a 46% or 25%, respective, drop in tube cross section, which I’m guessing will slow the resin down enough. I’m going to test this today with some .170 that I have, need to order some .125 (god I love amazon prime…)

#24

[QUOTE=craj1031tx;55881]So I actually do have a squeezee from ddcompound, but I always have trouble regulating resin flow with it through my 1/4" ID tubing. It seems that when you clamp it close to being full closed, the resin velocity in that partially clamped section increases so dramatically that there is enough of a pressure drop to boil out any dissolved gasses that were left over in the resin (and this is after a full degas!). The air bubbles stay in the laminate stack until the resin front reaches the MTI hose and the pressure drops. Is this normal?

Yes, this is normal. The good thing is that these airbubbles only exist in the resin front since there is max. vacuum but collapse as soon the system pressure increases. With the MTI system this is a self-regulating process, provided your setup is airtight.

#25

http://www.ebay.com/itm/Digit-LCD-Pressure-Gauge-Vacuum-Dial-2-5-30-Hg-0-psi-1-4-NPT-Case-ABS-Plastic-/331196228324?pt=LH_DefaultDomain_0&hash=item4d1cd562e4

would something this cheap even do the trick? vs an oil filled