When To Stop Feed Line and Bubbles Question?

General Composites Discussions Composites Talk
#1

Hey guys,
So I remade the mold and received the epoxy infusion resin today. Man this stuff is thin and I see why you guys were saying to use it over polyester and regular epoxy. But anyway, I ran into a problem today while infusing.

Same setup…
Envelope bag the entire mold
2 layers of 5.7 oz cf 2x2 twill
Peel Ply B
Green mesh

Did a leak test for 30 minutes and it didn’t lose pressure (28.5 mmhg) so I went ahead and infused. The epoxy flowed quickly through the flow media and slowed where there wasn’t anything but peel ply. Infusion seemed normal, but I had a question regarding tiny bubbles being trapped between the infusion mesh. Is that OK? I assume so since it is above the part?

Also, when do you all shut off the feed line? Today I decided to infuse a little more than normal and cut the feed line just as one the epoxy reached the outlet (normally I cut it right after it passes the part). There was about a 2" peel ply break in between the mesh and the outlet. It seemed ok and went inside to eat lunch. 20 minutes later I checked on it, and there was some epoxy in my resin outlet line. So I just clamped the resin outlet line and shut the pump off. Is that normal? Or should I have stopped it right after it passed the actual part. I’m assuming I shouldn’t have done that because that extra epoxy was most of the epoxy that was infused?

Since my part is small, should I just infuse without the flow media? I’m a bit concerned that the flow media is causing the resin to move over the part to quickly causing lack of saturation?

Lastly, I’ve read some of you saying they control their resin feed line. How do you do that? With the hose clamps I use, it’s practically all or nothing. I’ve tried to slowly open the clamps but nothing happens. And once it the epoxy starts to be sucked up, it just flows normally.

#2

As I’ve said so many times already, clamp off your vacuum line at the end of the infusion. Unless you are using mti hose, you can’t leave vacuum line open, the resin will continue to be drawn out of the part after you have clamped the feed line. If you you want a resin rich part with a nice cosmetic finish, clamp the vacuum line just as the resin reaches it, THEN clamp the resin feed line (either straight away or after a few seconds if you you want it to be a bit more resin rich).

Use infusion mesh. If you’ve got a brake zone then you will be fine.

I use the same clamps as you and have no trouble controlling resin flow with it? Just undo the clamp, and when it starts flowing just tighten or loosen it to suit the speed you are after.

#3

How do you get the bubbles out at the resin front if you clamp the outlet line right after it passes the part? Although I degas, I notice that when I open the line clamp, it creates a choke point where the hose is crimped causing bubbles to form when it passes that point for a few seconds.

#4

There should not be airbubbles. Thats why you should degas the resin! Very tiny ones at the flow front will be there, but when infusion is completed they should not be there.
When you infuse with normal spiral you will have them again after some time. Thats because the air will expand and can push resin into the spiral.
If you start with infusion and want to prevent this our product the MTI hose will help you. Also read the MTI thread, mostly all problems in infusion are discussed there and we fixed a lot of problems members had here.
Don’t try to save money in infusion, even not at the beginning. This will end up in a lot of mess and is frustrating. Start with good material and follow the steps and tips in the MTI thread and you will get a very good part, and after some parts they will become perfect.

#5

Everything you say you did sounds normal, except clamping the resin line. You don’t do that. You can NOT suck out too much resin. If there are bubbles in your part, it is caused by a leak, gassy resin, or too fast infusion, and the bubbles are coming out of the tows.

Using a peelply brake zone is a good way to go. Clamp at the EndOfPart, or somewhere after the flow is in the brake zone. Bubbles IN the mesh are normal, especially during actual infusion. if you are part is SMALL, try one without mesh, or a slower mesh. This will allow the resin to flow INTO the fabric tows.

The only time NOT to clamp the resin line is when using a membrane, or this MTI hose (membrane wrapped vacuum line), because once resin fills the voids…no more can be sucked into the part…it just…won’t.

Oh, as for your second post in the thread. Try this: Open the resin clamp until the resin flows a few inches past that. Wait a few min to let all the air you had between the clamp and resin bucket to be sucked out. open the resin line slightly, to allow resin to fill ALL resin lines and spirals. Clamp and wait a few min to allow any trapped bubbles to escape. Then, infuse as normal…make sure you knock out any bubble points you see (pinch points, connector edges, etc)