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Balazs Szikszai
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+xJust to clarify the thing on keeping the pump pulling on the bag through the cure - it's like a syringe applying suction even if there is no clear air path. The laminate stays under pressure even if no air is flowing - and it takes up any slack if you have leak or vapor issues. Also, you should avoid sucking resin into your catch pot - with a proper resin brake and holding back your flow media you should have no need to suck resin in - especially with small epoxy parts. Just fill the part, dial back the vac and clamp the feed. I'm sure it can be done - to shut off the pump as soon as the part fills - and maybe I'll try it someday to satisfy the curiosity. But I can't see any benefit beyond power saving - and the risks of ruining a part are huge. Literally nobody - tech reps, infusion consultants, bosses, peers - nobody I have ever discussed this with has shut off the pump before the resin has gelled - totally unheard-of in the professional composites world. This forum seems to be the only place this has come up. But as Hanaldo suggest, if you have a leak - all bets are off - even a tiny leak can overshadow all the other technical tweaks that make for better infusions. That clears things up a little, thanks. I've got a feeling (and am hoping) that the infusion speed and vacuum are the main problems here. I'm keeping my fingers crossed that with a resin break and the other tweaks here it starts working. It looks like my vac tube and gland fittings wont arrive till Monday now so I'll have to wait til next week. I'll update the thread regardless of the outcome.
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Lester Populaire
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I'm on Hanaldo's site here. To get reliable and reproducible results with vacuum infusion your bag needs to be perfectly airtight. And then you do not need the pump to apply pressure on the laminate, pressure remains the same during curing.
With a decent size resin break you won't pull air out the system either. And when switching the pump off, you don't get into problems with the resin off-gazing volatiles.
And i know plenty of professionals working in the industry for years who turn off the pump once infused...
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KLComposites
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Im a strong advocate for MTI hose. The first infusion I ever did was with a 2 to 3 inch resin break and MTI hose with great results. Simply lock down the inlet hose the moment all the peel ply is saturated and leave the pump running. As long as the bag successfully drop tests prior to the infusion, you’ll end up with a good result. We never de-gas the resin, and we use the pro-set epoxy infusion resin system exclusively.
What I believe I see in these photos is the result of an air leak, but I also don’t see a resin break which is extremely important.
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Chris Rogers
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MTI hose is awesome! I agree with KLComposites and have had great results with Proset too. Here's some evidence from the Easy Composites documentation on infusion that Google found for me. It contradicts the video (which I just realized is the source of this pump turning off bit) - it worked in the video but it is a bad idea in general. Videos are otherwise excellent! https://system.eu2.netsuite.com/core/media/media.nl?id=59028&c=3937524&h=ed6c113ff018e812d5f3&_xt=.pdf Here's one more great infusion resource from Vacmobiles in NZ: https://www.vacmobiles.com/resin_infusion.htmlI'll be interested to see how your infusion goes when you try again. Next time I'm unclicking the "Notify me of replies to this post" button!
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Warren (Staff)
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Both methods work fine. Pump on and good resin break will work well, as will pump off on a sealed bag. It can be hard to get a great resin break if the flanges aren't that big which means the part would end up a little dry as some resin would still suck out during the cure process until it gels. This is avoided by clamping off and switching off the pump - however you need vacuum to hold to a very high level until the resin has gelled.
So both techniques can be made to work and some people get on with one versus the other better.
Warren Penalver
Easy Composites / Carbon Mods - Technical Support Assistant
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Hanaldo
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I think it is also important to keep in mind that suction is not the driving force behind infusion (or even a syringe for that matter), it is pressure differential. When you draw resin through the laminate, it is being pushed in from the feed side through to the lower pressure outlet side, it isn't being sucked through. So in order for the pump to draw any air out in the case of a leak, that air has to be pushed through the entire laminate by the higher pressure ambient air to reach the low pressure front. It just isn't possible for the pump to draw out air post infusion if there is a continuous leak or even volatiles outgassing - at some point the air can't be pushed through the laminate anymore and it just remains in there as voids. Sure if you happened to develop a leak in a location where the air could go straight to the pump without having to go through the laminate (ie, the brake zone) then the pump will be able to maintain pressure, but the likelihood of that is so small it doesn't seem worth doing.
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Balazs Szikszai
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So I set up another infusion late yesterday to try all of the changes, and so far, the results look promising. As suspected the resin had a huge amount of moisture to boil off and doubled in volume for about 5 min under vac. This was was definitely worthwhile trying! The resin break also slowed the flow down through the whole process, and I cracked a tee piece on the vac line to reduce the vacuum towards the end to control any further boiling. Not sure if it was a combination of all or one thing specifically, but the resin flow through the bag was almost completely devoid of bubbles, and the reduction of vac towards the end seemed to remove the post draw boil that used to fill the catch pot. Its only been about 12 hours and the temps overnight were in the low 20s so I haven't been able to de-mould just yet, but I have removed the bag to have a closer look... I'm excited for this afternoon! Resin boiling off  Boil-free flow!  Debagged 
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Balazs Szikszai
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Update: The A side is completely flawless and there doesn't appear to be any aeration through the part, so gold star. BUT I'm still getting the surfacing on the peel ply side. Looking at it under a magnifier it actually looks like the peel ply is ripping resin off the top of the part, exposing the reinforcement... I'm thinking this resin may not be entirely compatible with basalt fabric (or is just rubbish). I might switch back to CF after this. It's is super frustrating as this one should have worked properly! Here is a closeup of the surface where it looks really obvious: 
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Balazs Szikszai
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So the theory is confirmed. The epoxy didn't seem to bond to the basalt fabric well enough and was being ripped off in places by the peel ply. Made up a CF test piece using the same technique as the basalt before (degassing, resin break, keeping compressor on till gelling), with the same resin, and the results were as they should have been all along. After this I might just use CF and not bother with the basalt until I can find a compatible resin, or a better quality fabric. Thank's everyone for the input and assistance.  
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Hanaldo
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Was there a reason you were using basalt?
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