Help with resin infusion

[drtcmm]

I am new to the world of resin infusion and the small parts I have made seem to have voids! Am I not right thinking that if I get a bridge the void should fill with resin? On the part I am making, there is some lettering in the mould and the carbon cloth doesn't sit fully into it should the lettering not fill with resin? Is there any way of stopping the voids? I am using a vacuum pump and the gauge reads 28hg and when I turn off the pump it will hold that for 24hrs or more so I dont think I am getting leaks. Any help will be most welcome thanks!

[Herman]

The resin can run over the lettering without filling it. Has to do with cappliary action in the fibers, which lacks in the void.

You could pre-fill the lettering, or try with a higher vacuum.

[drtcmm]

how do i get a higher vacuum?

[Landlubber]

...., emmm, from my experiences with infusion, I would suggest that the lettering may have sharp edges, rounded edges seem to fill easily wheras sharp edges can leave fine lines of air along them. Maybe rounding the edges may help.

...you cannot simply raise the vacuum, I guess Herman means to get a better pump, but 28 is plenty for small parts anyhow.

[jim lee]

We've found..

Where ever there is any bridging, you get resin blobs. And -every- resin blob ends up having, or being, bubbles. They do -not- fill up with solid resin.

You can skin coat the part first to smooth out the hard edges? You can get really fancy with the glass packing? But bridging, we've found is always a disaster just as you've described.

28hg is fine. We've found that is doesn't seem to matter if you have the last n-th degree of vacuum. Its having a perfect leak free seal that's important. Leaks cause bubble streams that flush the resin out of your part.. Goes on and on..

Oh and be sure your using infusion resin..

Welcome to infusion!

-jim lee

[drtcmm]

would it help if I slow the infusion down?

[Herman]

I have thought a bit more:

-turn the mold so the lettering is vertical, not sitting in a horizontal plane.
-crank up the vacuum (better pump). Believe it or not, but higher vacuum DOES help. I was not aware of that untill I ran a couple of side-by-side tests. Last boat I did was at 98% vacuum, and turned out "really nice", instead of the usual "very nice".
-slowing down the infusion might help, in combination with the vertical placement.
-degas your resin. After the infusion, bubbles may form, and these tend to sit in the most permeable material, or in open areas (bridging, your lettering)
-keep a vacuum on the fabrics for a longer time, to get more moisture out. Moisture + resin = bubbles.
-change mold release. Some of the more repellant releases can cause more surface bubbles as well.

These are all hints that might all make a bit of improvement. All together they can produce acceptable results.

And indeed, welcome to infusion.

[Landlubber]

Herman,
-change mold release. Some of the more repellant releases can cause more surface bubbles as well.

I have not seen or heard this before, I did change my wax once as we ran out of the normal one and during my demo to the yard i was having problems not encountered before, like very fine aeration bubbles as the resin flowed out over the job, could this have been the wax, I never thought of it doing this?

[Herman]

Difficult to say. I could just answer "plausible" although other factors might have played a role as well.

A lot of aeration could also be caused by:

-water in resin
-water in curing agent
-water in glass
-violent mixing (without degassing)
-vinylester in combination with peroxide containing H202 (without some lag time and/or degassing)

[drtcmm]

so if I infuse vertical do I want the resin flowing upwards?

[drtcmm]

oh and thanks for all the help so far!

[CatBuilder]

Originally Posted by drtcmm

so if I infuse vertical do I want the resin flowing upwards?

From my reading, I know the answer to this question is "yes." You always want to draw resin from the bottom of a part up to the top of the part.

Otherwise, you can have some resin make its way to the suction tube before all of the resin has filled the part.

[Herman]

Indeed try and infuse from the bottom up. With complicated structures this is not always possible, but at least try.

[drtcmm]

Thank you very much! I will give it a go. What is a good cheap vacuum pump to buy?

[Herman]

Try contact www.eurovacuum.eu, see what dealer they have in the UK.