Announcement

Collapse
No announcement yet.

airless resin mixingq

Collapse
X
 
  • Filter
  • Time
  • Show
Clear All
new posts

  • #16
    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)

    Comment


    • #17
      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?
      Chilliwack BC, Canada

      Comment


      • #18
        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 ;-)

        Comment


        • #19
          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.

          Comment


          • #20
            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.

            Comment


            • #21
              Degassing on a shallow plate seems like a good idea. It would require a wide enough pot, and that's going to mean more air to remove. Pump down would take longer. My system includes a 100 gallon vacuum tank, so I can probably go down to 2 or 3 lbs in seconds, then switch the tank off and let the pump suck the remaining air from the vacuum pot. After that the valve to the pot is closed and to the tank is opened again. The pump runs more or less continuously to bring the tank pressure back down.

              It's a vacuum capacitor system- unrelated to the flux capacitor

              I need to revisit my centrifuge. The throw-away cups I was using don't fit the holders very well, and the pressure when it is spinning just wrecks the cups. I'll have to find a disposable cup that I can get lots of at any time, then rebuild the holders to suit.
              I seldom do anything within the scope of logical reason and calculated cost/benefit, etc- I'm following my passion-

              Comment


              • #22
                Originally posted by jcfx View Post
                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.
                I was planning on drying the wood items, then puting them in a vacuum chamber in a stabilizing resin bath. Once stabilized they will be set in a mold and resin poured around them and then set in the pressure pot to cure. Then they'll be turn on a wood lathe. I'm unsure on which type of resin to use, but I'll make sure they're both compatible with each other (I think the stabilizing resin is just polyurethane). Sorry, didn't want to highjack the OP. My knowledge on all this is 100% gleaned from you tube, so it's a bit hard to get some of the important details sometimes. Thanks for the info. I'm just trying to make some interesting Christmas gifts for some of the kids in the family, while learning something, and adding some new tools and capabilities to my shop (vacuum pump/chamber, and pressure pot) while not breaking the bank, or turning it into a career.

                Your advice to play around with it on a small scale is noted. I think that's probably best before I waste a bunch of money doing full pours. Thanks.

                Comment

                Working...
                X