Vacuum infusion - reducing wasted resin

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#1

We’re making some pretty big parts in fairly simple shapes.

The current one is 8’ x 14’, with a layup of 2 plies 1808, a 1/2" core (perf’d), and 2 more plies of 1808. Infused in one shot. The FR resin we use is fairly slow to flow, and when it kicks, it kicks fast. So we use flow media over the entire surface, stopping it just a couple inches from the edges.

When we weigh the final part, our cloth/resin ratio is great… on a 175lb finished part, the cloth is about 80lbs, gelcoat about 12lbs, foam core about 22 lbs, which means about 60lbs of resin actually used in the part. But we’re using over 100 lbs of resin in the infusion. Thats’ expensive! Very little actually left in the bucket, or going into the catchpot. So its all in the lines and the flow media.

Looking for suggestions to bring this down in future.

  • RTM Lite? with a Bmould that has flow channels in it?
  • similar with a silicon bag with flow channels?

Help…
Phil

#2

I’m just throwing out ideas here. Once your calculated amount has gone through. Is there something you can switch to (say water or vegetable oil or something) to keep pulling a vacuum until your epoxy is in your mold.

If you knew 65# of epoxy was in your line and you then switched to say vegetable oil it would still pull your epoxy into the mold and you wouldn’t waste the extra epoxy.

#3

may i ask why infuse and not wet layup and vacbag ?

#4

we’re going to weigh all the “consumables” (peel ply, flow media, etc) before/after and see if we can better quantify where the excess resin is going.

Why infuse? quality, fabrication speed, work environment, …

#5

i wonder how much of your weighed resin is in the perforations? Or in the foam it self?

Did you weight the feed lines? THat’s where I’d think the resin would be. That and as you mentioned flow media/peel ply, etc.

#6

40 lbs of resin not in the part? Holey smokes.

Could you use a core that is scored as well as perfed and acts as flow media? Work with the resin supplier to reduce the viscosity of the resin?

#7

Dear Phil, I don’t think you can do much to prevent the wasted resin in tubes and in flow mesh; if infusion is preferred for your application. Even peel ply captures some resin. I observed around 700 grams per square meter wasted resin with the airtech’s non woven greenflow and econoseries peel-ply. This number changes with; different flow-mesh, different vacuum pressure, with different peel-ply, with different resin, even with different vacuum bag! Yeah that’s right if vac-bag is thinner and stretchier; less resin is wasted because thinner bag collapses better in to the flow gaps thus less room left for resin to fill in. In conclusion; you can reduce the amount of the excess waste by using short tubes, low profile mesh, thin peel-ply, but no way to completely eliminate it with vacuum infusion.

#8

Thanks for that.

I want to talk to VectorPly (and others) for infusion-specific laminates that could help reduce the need for flow media. There are also some alternatives to traditional spiral tube for the flow channels that may result in less waste.

#9

Don’t you think the cost difference between (cheap) spiral tubing and (more expensive) flow channel media will cancel out the expense of the wasted resin in the spiral tubing? From what I can tell, the additional cost of the flow channel media is worth it only for parts where you want to avoid the imprint patterns of spiral tubing. (Being a lower profiled product, it is also less likely to puncture the bag). But maybe I’m wrong, have you researched the price difference?