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Thread: airless resin mixingq

  1. #11
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    Mar 2013
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    We use a fiberglass tank/building that is vacuum bagged in the mold and the resin comes in at the bottom corners and is pulled all the way to the top of a 11' tall tank by vacuum. Big tanks 12 feet wide, 50 feet long and 11 feet tall.

  2. #12

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    That's quite a setup for vacuum infusion, just curious on how long it takes to set up the fabric, peel ply and channel layers ?

  3. #13
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    If you really want to stir under vacuum it’s fairly easy to stick the vacuum chamber on a magnetic stirrer if the chamber is small with acrylic top and bottom, seen it done in the lab I worked at a few times, what the chemists were making I dread to think, looked like coffee to me, glad I only had to repair things myself.
    We did have a vacuum induction furnace that would melt about 4 or 5 tons max that had a stirrer made of graphite if needed the shaft went through a dublin (company name I think) swivel fitting that leaked so much we plugged the hole, we used to make steel and iron standards in the furnace so they had to homogenous, turned out stirring didn’t help much anyway the stirred standard and unstirred were about the same different in the middle to the outside as a result of solidification, just like iron or steel castings
    Mark

  4. #14
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    Dec 2008
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    Quote Originally Posted by jcfx View Post
    If your casting clear resins, pressure casting is another option, a paint pressure pot with 80lb of pressure does nicely, caveat on
    pressure casting is that your resins shouldn't be mixed to a froth, I use a Jiffy mixer to introduce the least amount of air into the mixture.
    And the big caveat with pressure casting is that the rubber mold material must be degassed, otherwise the trapped air in the cured rubber will
    compress and cause bumps and warpage on the cast part, even leakage since the rubber is deforming.
    .
    I just picked up a pressure pot for that purpose. I have some gifts I want to make from resin and "waste wood" for some friends kids. I learned about that technique on you tube, and am anxious to try it out in a couple weeks. Any advice from a resin casting neophyte? I plan to vacuum stabilize the wood first before casting resin around it. That resin is not cheap up here and I don't want to spend any more money on the learning curve than I have to.

  5. #15
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    Sep 2008
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    Dental labs and some offices use vacuum mixers for certain materials.
    I'm not sure if the cost and cleanup efforts will be worth it for you if you use one for resin.

  6. #16
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    Dec 2016
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    Helsinki, Finland, Europe
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    Quote Originally Posted by boslab View Post
    If you really want to stir under vacuum it’s fairly easy to stick the vacuum chamber on a magnetic stirrer if the chamber is small with acrylic top and bottom, seen it done in the lab I worked at a few times, what the chemists were making I dread to think, looked like coffee to me, glad I only had to repair things myself.
    Mark
    Or if the resin is too thick for typical magnetic stirrer just place the mixer motor inside the vacuum pot. Preferably brushless induction/bldc motor so it doesn't spark..
    Wires are easier to seal than rotating shaft (not that it would be hugely difficult for moderate vacuums like here)

  7. #17
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    Chilliwack, BC, Canada
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    The thing with resins that have shorter working times is that the cure process is such that when the exothermic part of the mixing kicks in and heats up the container of resin it can reduce the working time a lot more than you think. When I've worked with resin that has a two hour working time with the bulk in a small cup I had it kicking off in well under an hour due to the exothermic reaction in the cup even with it being just a couple or three ounces of resin.

    My response to that was to mix the resins well in a cup and then pour the resin out into a shallow plastic tray. For batches the size I used a plastic food plate with raised sides for holding in baby food meals worked like a treat. And being spread out and then put into a vacuum chamber any air bubbles will have a lot shorter path to freedom since they rise.

    So if you get to that point perhaps hit up the dollar store for baby plates?

  8. #18
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    Jun 2004
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    Quote Originally Posted by BCRider View Post
    Like 10 minutes or so.
    So was it 10 minutes or was it "Like" 10 minutes?
    If you benefit from the Dunning-Kruger Effect you may not even know it ;-)

  9. #19

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    Quote Originally Posted by Dan Dubeau View Post
    I just picked up a pressure pot for that purpose. I have some gifts I want to make from resin and "waste wood" for some friends kids. I learned about that technique on you tube, and am anxious to try it out in a couple weeks. Any advice from a resin casting neophyte? I plan to vacuum stabilize the wood first before casting resin around it. That resin is not cheap up here and I don't want to spend any more money on the learning curve than I have to.
    I've never done encapsulating items in resin, so I'm not sure what you mean by 'stabilize',
    but sounds like a good idea if by stabilizing you're drying the wood, epoxies aren't that moisture sensitive
    polyurethane resins are very moisture sensitive and if the wood bits aren't dry as a bone
    you'll get bubbles where the polyurethane resin reacts with moisture or inhibition.

    Depending on the type of resin you intend to use ( epoxy or polyurethane ) it would be wise to mix a small batch and paint
    some on scrap pieces and pressure cure to test for issues in curing and appearance before doing full pours.

  10. #20

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    Quote Originally Posted by BCRider View Post
    The thing with resins that have shorter working times is that the cure process is such that when the exothermic part of the mixing kicks in and heats up the container of resin it can reduce the working time a lot more than you think. When I've worked with resin that has a two hour working time with the bulk in a small cup I had it kicking off in well under an hour due to the exothermic reaction in the cup even with it being just a couple or three ounces of resin.

    My response to that was to mix the resins well in a cup and then pour the resin out into a shallow plastic tray. For batches the size I used a plastic food plate with raised sides for holding in baby food meals worked like a treat. And being spread out and then put into a vacuum chamber any air bubbles will have a lot shorter path to freedom since they rise.

    So if you get to that point perhaps hit up the dollar store for baby plates?
    One thing to point out in degassing materials is make sure your container is at least 3x the volume of the mixed material, otherwise the
    material will overflow the container as the air 'boils' out. I can cheat since I use a clear domed vac chamber, I can monitor the level and jog the vacuum
    so I don't get overflows.

    In one of your earlier posts, the fellow's vacuum pump sounds like it might have been a Sargent-Welch pump, I worked with one at a studio eons ago
    and they were the bees knees, his was probably not working well or was too low a CFM capacity if it took him 10 min to degas resin.
    There is a point where the viscosity of the resin just won't release any more air, strangely,if pot life allows, when the resin is brought back to
    normal atmospheric pressure the left over bubbles seem to either break or go back into solution.

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