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Thread: How to: Duplicating a radio bezel.

  1. #71
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    Quote Originally Posted by Graywolf
    You sir, are my new hero.
    Awesome..

    And I was right.. the resin arrived today.


    But I'm not going to show you the resin... so there!




























    Just kidding.

    The 4-pounds of resin arrived in 2 1-quart bottles, and is mixed in equal parts of each in a 1:1 ratio by either weight or volume.

    I estimate that I've probably got enough for at least 2-3 pours.
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  2. #72
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    Pressure-loading the mold.

    The two halves of the mold weren't sticking together as tightly as I would have liked, so I took some pieces of plywood and some rubber bands and strapped some reinforcement across the front.

    The horizontal pieces of plywood are loaded across each end with some rubber bands tied together, which go around the back of the box.

    The vertical piece of plywood is the only piece touching the posterboard underneath, and is the piece that's actually applying pressure to the box.

    If I had more pieces of plywood, I would have used three pieces vertically to spread the load better.


    This ensures that the two halves of the rubber mold press against each other with enough force to make a good seal.

    Next, I'll measure out the resin, mix it up, and make the pour.
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  3. #73
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    cant wait to see the result!

  4. #74
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    Quote Originally Posted by dannn
    cant wait to see the result!
    Unfortunately, I can already see the result of this first pour - I got a messy puddle of uncured resin surrounding the box.

    I must have not sealed the edges well enough, because of what I poured, most seemed to come out the bottom.


    I'm going to have to wait about an hour or two for the remaining resin to cure, and then take it apart, clean out the cured resin, seal the edges of the mold with tape, and then re-assemble the box..

    Gah, what a mess.

  5. #75
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    Failure #1...

    Ok, I peeled apart the mold, and I can see where the resin escaped, and probably why.


    The weight of the rubber probably caused the bottom edge to spread open, causing the resin to flow out and cause a mess.


    After I let the remaining resin cure enough so I can peel it off, I'm going to take the mold out, and make something new to keep it together.


    What I should have done was to cut two large posterboard pieces that fit the front and back shape of the mold, and then taped those two pieces together, kind of like a posterboard-rubber sandwich.

    The two pieces of posterboard on the outsides would have taken the load of the weight off of the rubber, and the tape would have evenly applied pressure around all sides.

    That, and taped the edges of the rubber to prevent leaks..
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  6. #76
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    Successful Pour...

    Ok, I think I got a good pour this second time around.

    I cut out two large pieces of posterboard to fit the front and back of the mold, sandwiched the mold in between them, and taped the edges together nice and tight.

    I also taped around the entire bottom and side edges of the mold, so nothing could leak out, and then covered that with plastic wrap.


    A little excessive, but it's working..

    I mixed up 500 grams of resin, which actually was too much, and made the pour - it went in slowly, but I got resin coming back out the venting channels at the top, so I think it worked.

    I think I could have gotten by with 300 grams of resin, but I'll know for sure after it's all cured and I can weigh the newly cast part.

    There's some resin still left in the mixing bucket I made, and in this picture you can see the resin's color prior to curing, which is yellow in color.


    In the time that I took to write this post, the resin in the bucket has cured to a white plastic.

    The resin in the mold is just starting to cure, however.
    It'll finish its cure in about 16 hours, and you bet I'll let it sit there in the mold for at least that long.


    The reason the resin in the bucket cured so fast is that there's a large amount of resin in the bucket, so the curing process generates more heat, which causes the "kick" to happen sooner.

    The "kick" is when the resin goes from a liquid state to a solid, and you can actually see it happen in the bucket..

    Sometimes it happens very quickly, which is why you have a limited time to pour the resin once you mix the two parts together.


    Tomorrow afternoon, or about 16 hours later, I'll cut the tape off and open up the mold.

    You can be sure there will be more pictures..
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  7. #77
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    Check www.freemansupply.com They have a 2 part silicon tooling mix that lets you make a nice flexible silicon mold. Needs no release agent, and has a smoother fill and mold surface.
    It's expensive to start, but a gallon of the silicon will go a long way.
    Dave

  8. #78
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    Quote Originally Posted by big_cali_dave
    Check www.freemansupply.com They have a 2 part silicon tooling mix that lets you make a nice flexible silicon mold. Needs no release agent, and has a smoother fill and mold surface.
    It's expensive to start, but a gallon of the silicon will go a long way.
    Dave
    Thanks for the link.

    The stuff I used is pretty much the same, a silicone molding rubber, and is very flexible and non-stick.


    I got mine in a 1-gallon bucket for about $86.

  9. #79
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    Success!

    The resin actually is at a solid cure at about 1 hour, but I let it sit for 4 hours before I opened it up.

    And it was a near perfect pour.. excellent.


    I sliced off the tape, and peeled off the back part of the mold, and I can tell I got a nearly perfect pour.


    The picture shows the back side of the part, and as you can see, there's some flash (thin resin) around certain sections, but that's to be expected.

    I don't think any of it leaked out at all, this time..


    I'm going to wait another 8 hours or so before actually pulling the piece out of the mold, because I don't want it to deform if I pull it out while it's still soft.


    But as you can see, it's looking good!
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  10. #80
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    Did I say 8 hours?

    I meant 8 minutes.. 'cause that's about all the patience I had left.


    I gently pried the mold away from the part (note: not the part away from the mold.. there's a difference), and as you can see, it looks pretty good.

    There's a few air bubbles cast into the plastic on the bottom edge of the opening, but otherwise it's looking good.

    A little trimming, some putty, and it'll look just the same... until I start chopping it apart to extend it.
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