Infusion problems

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#1

Hi all,

My first post on this forum !

Since 1 year, I made stratification composite with vaccum bagging. My results was really nice, no pinholes, perfect surface.
But after saw many videos on the infusion, I wanted try this technic. I bought infusion mesh and resin for infusion.

So I have made a mould, using black gelcoat with aluminium. I polished it, put 1 layer of PVA and 5 layers of liquid wax and polished it again.

This is the result of my mould:

A guy who is suscribed on this forum, helped me for my first infusion.

We put:

1: 1 fine layer of spray glue
2: the first layer of carbon (193gr/m2)
3: a second layer of carbon
4: 2 layer of kevlar
Each layers have been glued with the spray
5: 1 layer of peelply
6: 1 layer of perforated film
7: 1 layer of infusion mesh
8: 2 demi circular spiral tube, 1 for resin, 1 for air.
9: 1 layer of vaccum bagging

My vaccum pump only give me -0,75 bars.
We make the vaccum and we prepared the resin. We have put the resin pot under the level of the mould and clamp the tube. The tube for air and resin is Ø6 mm.

This is the moment to remove the clamp on the tube, the resin entered in the mould and after 10 minutes, all the mould was full of resin. The excess is gone out on my catch pot. After several minutes, I have clamped the air and I have put my part in my oven for 12 hours at 60°.

I have demoulded this morning, two layers was too thin so I break my part, so it’s only a test !
I have try to release the rest of my part from the mould. The result is not good, I have many pinholes. We don’t understand why because the guy who helped me for this test make some beautifull parts with success with the same technic, so where’s the problem ?

Is my pump don’t give not enough vaccum ?
What I’m doing wrong ?

Thanks.

#2

-more vacuum
-degass your resin
-infuse slower
-let the fibers sit at -0,98 at least, to get rid of moisture. Make sure you infuse at lower than -0,98.

#3

Your vacuum level should be 20mbar absolute pressure for infusion. Than it is important to degas the resin. That can be done by using an exsikkator.
Infusion speed seems to be ok, the pinholes are created because the resin is not degased and so the enclosed air starts to expand when you close the feed line.
May be the MTI hose is interesting for you. In the product talk is a thread about the MTI hose.
Do not clamp the air line, let the vacuum work until the resin is cured.

#4

Thank you for your reply.
I have find a vaccum pump that correspond to those caracteristics, I will take it next weekend.

I will make a new test and show you the result.

#5

I have make a new test with my new vaccum pump.
For the vaccum, it’ better. I have -0,97 bars in my mould … but … my new result is worst than the first !
I don’t understand why.
My infusion is too slower or too faster ?
I have degassed my resin before.
Here is the result:

#6

Infusion is too fast. Slow it down. You need more resin.

#7

I am sure you do not work with the MTI hose. So you need a brake zone and you have to reduce your vacuum. your brake zone should be 2" / 5cm peelply and reduce vacuum to about 500 mbar after infusion.
Are you sure that your vacuum is tight?
Wich resin do you use? Dont use any additives like a degasing additive, degas in a vacuum chamber / exsikkator!

#8

The infusion time is approximatly 10 min, my part makes twenty centimeters of diameter.

What is the “brake zone” ?

My vaccum seems to be tight, I will control it better next time.

I use HP textiles products, my infusion resin is HP-E3000RI. I use PVA and HP-BM17 for liquid wax.
My carbon fabrics is a 193gr/m2 and I use peel ply and infusion mesh from HP textiles.
I degas my resine in a vacuum chamber.

#9

193 grams is very open, leaving lots of room for pinholes. Do they have a heavier fabric, for instance 245 grams?

#10

in my opinion the infusion is too fast.
i had this problem with too fast infusion, or loss of vacuum after infusion.
your first problem is the first, no time to impregnate completely fibre

DDcompound…why recude vacuum after infusion? I have try this, is better for pinholes, but there is more resin in the piece. I usually degas and infuse at about -0.95 bar, then i maintain this vacuum

#11

10 min is more than slow enough, you can infuse it in 1 min and there will be no problems. The 193g/m2 is a a bit open, but that should be no problem if the process works.
A brake zone slows down the resin flow front, it is needed to saturate all layers. ( It is not needed if you work with MTI)
Maybe the capillary forces suck the resin out of the fabric wich will produce your pinholes. This happens because the resin can travel in you evacuation hose.

#12

what is the ambient temperature?
I had this problem with

  • too fast infusion (especially with perforated realease )
  • loss vacuum after infusion
  • too low room temperature—> high viscosity of resin
#13

-0,95 IS reduced vacuum. Try and reach a vacuum of -0,98 or even -0,99 (an absolute-vacuum measuring vacuum gauge is needed to see the vacuum level decently)

#14

Festo SDE1 works perfect and shows it fine scaled digital.

#15

Checked the datasheet for the SDE1, but it measures relative pressure (relative to ambient pressure) which is not so good for very low pressures, around the boiling point of water (some 20 mbar abs at 23C)

There are simple analogue gauges, which measure pressure relative to a built-in barrel with very deep vacuum (near to absolute vacuum).

#16

To resume:

1/ The vacuum value, in the ideal should be 0 absolute ?
Much vacuum you have, better results you have ?

2/ The brake zone temporises and regularises the resin before infusing the part to having an homogeneous resin.

I have seen videos on internet and it’s seem to have many technics to make infusion.
Sometimes they use PVA, sometimes they use dry fabrics without spray glue, sometimes they use gelcoat … It’s not an exact science ?

I make my infusion in my garage and actually the temperature is 14°, I know that it’s low and the resine is less fluide. I already seen peoples who heat the resin to 35-40° to fluidize it.

#17

Absolute 0 is too low, but 10 mbar absolute is what I would like to see. This gives me the assurance that moisture is gone. After infusion, raise to 50 mbar. The voids that are still in the laminate (there should be hardly any) will get a lot smaller by doing that.

About using PVA: The release agent has not too much influence on the infusion. PVA is nice, but not easy to apply correctly, and will never give an out-of-the-mould shine.

The only applications I recommend PVA for:

-mould making on someone else’s delicate but water resistant object.
-on Gibco Flexmold
-in a new polyester mould, for the first 2 products
-on sanded parts (I once made a trailer mould on a grit 80 sanded boat, using PVA)

For the rest: wax or semiperm.

Dry fabrics without spray glue: Whenever you can do without, do not use spray glue. It solves one problem, but can create many new ones. If you do not need it, do not use it.

Gelcoat: again, hardly any influence on infusion. It is a matter of personal preference. Which gelcoat works for what is a whole chapter in itself.

Now to the real point: 14 degrees C: That is really low. Heat up the workshop before doing another infusion. That really makes a huge difference. The wetting capabilities of epoxy resin at 14 degrees are not so good.

#18

Hello , Can anyone help me with a idea I have to infuse resin into a mould cavity.
Any help would be appreciated.