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  1. #76
    Join Date
    Aug 2010
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    Glenbrook NSW Australia
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    swisscheese I have not done the epoxy leaverlying as yet, but it made sense to me that it would work. I was looking at a fgi laminating epoxy and putting on around 4-5mm thick as I have this on hand or look at one of the casting epoxy but I will look into the West system. Good point about bolting it down first....
    All the best for your exams..
    R
    vapourforge.com

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  3. #77
    Join Date
    Oct 2013
    Location
    melbourne
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    Quote Originally Posted by rusel View Post

    swisscheese I have not done the epoxy leaverlying as yet, but it made sense to me that it would work. I was looking at a fgi laminating epoxy and putting on around 4-5mm thick as I have this on hand or look at one of the casting epoxy but I will look into the West system. Good point about bolting it down first....
    All the best for your exams..
    R
    Hi

    Did a bit of looking for you. It looks as though that epoxy should work fine IF you use the slow epoxy hardener. If used it has viscosity of 50-100 cps. Using the faster hardeners raises this to 1000-2000 cps, which is around the viscosity of honey, no good. For comparison the west system I used was 400-500. Yours should work good.

    info: http://www.nuplexcomposites.com/nz/f...volume%202.pdf

    How are you going to make the channel? Are you leveling the whole cross section of the top of the frame or just the sections where the rail runs(with some kind of joining channel between the two)?

    After the epoxy has dried you will no doubt have high sections along the edges. Are you drilling holes before or after the resin?
    The highs on the edges are easily removed with a power drill and sander attachment. If you decide to drill holes before, you will get high spots around where the screws are. Once dry and with screws removed the easiest way to remove those high points is with a large drill bit, say 10mm for m5 screws. Just use your hands and drill the holes out a little. Is quite easy.
    Good luck

  4. #78
    Join Date
    May 2003
    Location
    Perth WA
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    3,784

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    I am offering a different perspective for other builders so don't think you have to defend the epoxy method of levelling. In engineering to get a perfectly flat surface the process is to first mill the surface, then machine grind, then manually scrape using a surface plate as a datum. I don't see how poring resin and letting gravity determine the final surface is going to achieve a flat surface. What deters from this method is the accuracy of your dam walls with other factors such as capillary action of the resin, voids, air bubbles and setting the parent material perfectly level in all directions. Frankly it is a big ask to do all this and I believe the original plate is probably more accurate than the finished resin surface. I happy to be challenged on my opinion as this is how we all learn. Chris sorry if it has steered your thread a bit OT.
    Cheers,
    Rod

  5. #79
    Join Date
    Aug 2010
    Location
    Glenbrook NSW Australia
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    705

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    I am guessing that you would have to make the epoxy tracks at least twice the width of the rail and use no filler in the resin so as the get no meniscus upsetting the surface tension of the resin.
    The bolt holes I was thinking of having them drill and tapped and filling them with wax before the pour and then drilling the epoxy cover out after. ( can use rail as drill guide) this would leave no raised edge.
    rodm you have a point as to the accuracy of this verse the original surface, but I see the RHS as not the truly flat surface especially after welding. And the aluminum tube for the gantry would be a lot better....
    As for leaving it up befor the pour it's got to be close but not perfect, The resin will do the rest. I think it would be harder getting the gantry at right angles to the frame and the rails bolted down in a straight line.

    Sorry Chris bit of a hijacking taking place here.....

    R
    vapourforge.com

  6. #80
    Join Date
    Feb 2008
    Location
    Australia
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    988

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    I don't mind


    It's taken a long time to update but it's finally ready for its first cut. Had to shim the angle brackets as it was pulling the gantry top forward, but according to the dial gauge it came out perfect with just a 0.09mm shim from a solo can.

    X axis ballscrews needed a shim one side and had to remove some material from the other, also re-cut the end mounting brackets so they were adjustable up and down.


    Still needs a lot of work but now I'll be able to finish re-cutting plates for my smaller machine and a couple of other projects I want to finish up.
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  7. #81
    Join Date
    Oct 2013
    Location
    melbourne
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    Ch4is that's a great build.

    With respect to the resin personally I believe its the way to go for diy steel framed cncs due to inherent warpage ect. 99% of people making their own cnc don't have access to the heavy machinery to face mill a frame, so I think its the next best thing.

    What deters from this method is the accuracy of your dam walls with other factors such as capillary action of the resin, voids, air bubbles and setting the parent material perfectly level in all directions.
    All these concerns can be removed.
    Dam walls don't have to be accurate, you just want a 5mm space between wall and anything that you want to be flat, so you can sand down the resin from capillary action as you said. I didn't experience any air bubbles or voids. It can take some time to get the frame level within reason before doing the resin but it is achievable.

    Here's a very good build with the resin technique used. Shows how accurate you can do it. Go down the page a bit and you'll see some graphs of error and also some pics of the process.
    BUILD LOG: A sufficiently strong machine

    Anyway that's enough ruffling of the feathers for now.
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  8. #82
    Join Date
    Feb 2008
    Location
    Australia
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    988

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    Added the mid table support, machined up some T-slot nuts from 25mmsq stock, got started on re-machining the Y/Z axis (finally found a use for that 1" plate that's been hanging around)

    Cut up some yellow tongue, bolted it down and started cutting some new plates for my smaller machine. It's good to see it finally running 1.5 year build time so far
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  9. #83
    Join Date
    Apr 2013
    Location
    Loganlea Queensland Australia
    Posts
    1

    Default Like the post & picks

    I am a Newbe,,
    Just a question what have you done with the old one, Still looking for a machine to go with my 900 by 600 laser.
    Projectx

  10. #84
    Join Date
    Feb 2008
    Location
    Australia
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    988

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    Quote Originally Posted by Projectx View Post
    I am a Newbe,,
    Just a question what have you done with the old one, Still looking for a machine to go with my 900 by 600 laser.
    Projectx
    Had to sell it off a long time ago, as I don't have much room to spare in the garage, went off looking pretty decent once I'd re-cut most of the plates, should still have some sketchup files somewhere if you want to build your own.
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