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  • Dan Dubeau
    replied
    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.

    Leave a comment:


  • darryl
    replied
    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.

    Leave a comment:


  • jcfx
    replied
    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.

    Leave a comment:


  • jcfx
    replied
    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.

    Leave a comment:


  • Magicniner
    replied
    Originally posted by BCRider View Post
    Like 10 minutes or so.
    So was it 10 minutes or was it "Like" 10 minutes?

    Leave a comment:


  • BCRider
    replied
    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?

    Leave a comment:


  • MattiJ
    replied
    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)

    Leave a comment:


  • MichaelP
    replied
    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.

    Leave a comment:


  • Dan Dubeau
    replied
    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.

    Leave a comment:


  • boslab
    replied
    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

    Leave a comment:


  • jcfx
    replied
    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 ?

    Leave a comment:


  • garyhlucas
    replied
    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.

    Leave a comment:


  • jcfx
    replied
    I work with resins and rubbers all day long, mixing resins in a vacuum is probably over kill, when you can mix and vacuum the resin.
    Pot life is a consideration when vacuuming, the vac pump should have a CFM rating of 5 or higher, barometric pressure seems to
    have an affect on degassing materials, this is just from observation, I'm sure there is proof of barometric pressures effect on vacuum some where.

    Degassing the separate components to me is a waste of time since your introducing air when you combine the components, did that many eons ago
    and found no advantage.

    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.

    What sort of additives ? I would guess that the TDS for the additive would have vapor pressure data, that might be of use to figure out
    if you're losing anything, most additives I use ( dyes and pigments ) degassing has no effect.

    Leave a comment:


  • darryl
    replied
    Some of my applications will require a 'water clear' resin (which usually would be a 2 to 1 mix and have a longer working and setting time) and others will be using the cheaper and more available epoxies (which usually are 1 to 1 mixes and can have a working time as short as about a half hour). Currently I use a vacuum de-airing setup and a centrifugal setup- I was just wondering if the 'airless' system was being used at all. It has its advantages, especially for short working time materials.

    De-airing the separate components doesn't interfere with working time, but once mixed you're now on the clock. Warming the mixture helps with de-airing, but also shortens the working time. I was hoping to find a way to mix without introducing air into it- that would seem to be a progression of the state of the art.

    Leave a comment:


  • awemawson
    replied
    Yes Lew that was it !

    Working backwards it must have been 1969 that I was working with that stuff - a younger and fitter me !

    Leave a comment:

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