Good evening, everyone! I am using a vacuum press that I have built for bagging hand layups, but it maxes out at 25".
I have read a lot about the infusion process, and it does appear to make some fine parts. Of course, I would like to join the club, but is 25 going to get me there?
Thanks, everyone for the help!
This is the vacuum press.
The layup in that mold is an exhaust shroud for a DR650 by the way.
I live at 5,000 ft elevation and can only get 25" Hg. I have successfully infused many parts.
That is why absolute pressure is important, not relative pressure with ambient as reference.
For an ultra-high-surface-quality infusion you want to get very low in absolute pressure, say 5 or 10 mbar. Regardless of ambient pressure. If you wantto fight pinholes, after infusion you let the absolute pressure rise to 100, 500 or even ambient pressure. Any pinhole that might have existed collapses in the process.
But it would not hurt trying with what you have. Max out the pump, infuse, and let the pressure return to ambient.
Only thing is that you will probably not be able to degas your resin, which again helps in surface quality.
Trying to degas some resins with 25" Hg is futile.
That’s a nice looking set-up but are you sure the pump is working properly? I also have a double membrane pump and get 28.9"Hg.
[COLOR=Green]Hi guys! Thanks for replying!
As far as I know, the pump is working just fine. It was purchased through joewoodworker.com for $100. It’s not new, but he does sell them freshly rebuilt. The pump performs exactly as the website said it would, pulling 25" consistently.
I have been using the US Composites 635 thin resin for most of my projects.
The resin appears to be fairly thin, but the US Composites website doesn’t offer a data sheet on it, so I’m not sure how it compares to other infusion specific epoxy resins.
I could try an infusion with this resin unless you guys think that it would fail. If so, where should I go from here for resin?
I have just started an experiment with making my own epoxy surface coat to test how it might be used as a surface coat for molds. I’m using this bowl as a plug.
And vacuum bagged the following layup on the bowl for best quality of the “test” mold.
What I would like to do is pull this mold tonight, trim it up, and maybe set up my first vacuum infusion with CF in this mold. Any setup tips on the infusion setup for the bowl would be great.
BTW, is MTI hose available in the states? It seems to only be available in the UK.
Anyway, thanks for having me everyone! This forum is a great resource!
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US Composites 635 is pretty thick compared to a true infusion resin. It’ll work just fine for small parts but larger infusions will probably stall.
What is your elevation? Elevation will effect the max pressure.
Yes MTI hose is available in the US. Just private message DDCompounds or Designbikes and they can fix you up.
Thank you, Ro Yale, I’ll get in touch with those guys.
Is the MTI hose the way to go and make a huge difference, or would spiral tube be OK?
MTI hose takes quite a bit of engineering out of infusion. Especially for first timers I highly recommend it. Also great for optical quality infusions.
For extra lightweight infusions you need to keep an eye on things, or do some extra rigging, and gain some experience.
Definately highly recommended material.
Hi,
the MTI-hose is available in the USA and Kanada. Take a glance at www.german-advanced-composites.com. On that website you can watch an animated video and read a lot about vacuum infusion and the transformation to MTI.
25 inches Hg would be close to absolute at 5000 feet, and only about 85% at sea level.
But with that kind of pump you will always only be able to create 85% vacuum. So you can not pull a absolute vacuum on 5000ft hight.
For first trys a cheap ebay vac pump works, they cost about 70$ and create a 99.95% Vacuum.
And do not use a stretchable vac bag, they often leak. Use a multilayer bag with polyamide (PA) and make pleats.
Use only good materials, nothing is more expansive than a mess part.
So now that I have the MTI hose taken care of, it appears that I need to start looking for a quality vacuum pump for infusion. I would really like to purchase something new that is robust, powerful, and will pull down to max vacuum for my altitude. I have read about lots of vac pumps mentioned on the forum, but if you were going to buy the last vacuum pump you ever would need, what would it be. I would probably build it into a system like the one above.
DDCompound, you mention using a multi layer bag with polyamide. I have heard of double bagging; is this the same as a multi layer bag, and what is polyamide?
Thank you everyone for your help!
By the way, the epoxy surface coat experiment that I was doing with the bowl in the above pics worked out well. I’ll certainly be using an epoxy surface coat on future projects.
Check out the surface of the resulting mold in the pic below.
Polyamide is nylon, a multilayer bag usually is a laminate of nylon and polypropylene. It is different thandouble bagging, which is using 2 bags.
If I were to buy my last pump, it would be an idustrial oil lubricated rotary vane pump, such as made by many, like Becker, Leybold, Rietschle, and many more. Like this for example:
http://www.vacuumsystemen.com/losse-vacuumpompen/ev-serie/ve-0010nm.html
These run forever, even with minimal maintenance.
I would buy a Busch pump. Most professional shops I know use them, my favorite is the Busch R5 series.
How soon after infusion should you release the pressure?