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  1. #11
    Removed.
    Last edited by Zorbit; 1 Day Ago at 01:15 PM.

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  3. #12
    Hi EZELab
    Welcome to the forum.
    I would like to point you to John McNamara's epoxy build( https://www.model-engineer.co.uk/for....asp?th=139042)
    A very thorough and informative thread.
    Kindest Regards
    Mike

    Sorry Guys didn't see the last couple of posts, was trying to find the link

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  5. #13
    m_c's Avatar
    Lives in East Lothian, United Kingdom. Last Activity: 15 Hours Ago Forum Superstar, has done so much to help others, they deserve a medal. Has been a member for 9-10 years. Has a total post count of 2,490. Received thanks 284 times, giving thanks to others 7 times.
    From the various builds I looked at while researching ideas, using an internal skeleton to essentially hold the key mounting surfaces in place was a method quite commonly used.
    However my concern was if the skeleton was too rigid, would there be any long term issues with the different materials and changing temperatures. It's not likely to be an issue on small builds, but over a 1m length, the internal stresses could get quite high.

    The common thing I found, was although different people used different methods, I never found any sort of academic/industrial papers that gave much practical scientific answers. It was more a case of people used what they thought would work for them.

    Personally I was swaying towards using embedded mounting surfaces that could be machined after casting, as it would be near impossible to keep accurately positioned surfaces in position within a large casting, however epoxying surfaces onto the main casting after curing can also be done (Chaz used this option on his big build which can be found on here).

    John's build was also one worth looking at, as he did do a lot of research, but the basics of his build did still come down to what suited him.


    Even looking at the commercial options, from what I gleamed from various sources, was they all seemed to have their own proprietary epoxy/granite mix, and seemed to use different methods for final surface accuracy, ranging from surfacing the cast EG, to embedding machinable rails. The techniques used all seemed to come down to what equipment they had available.
    Avoiding the rubbish customer service from AluminiumWarehouse since July '13.

  6. #14
    JAZZCNC's Avatar
    Lives in wakefield, United Kingdom. Last Activity: 15 Hours Ago Forum Superstar, has done so much to help others, they deserve a medal. Has been a member for 9-10 years. Has a total post count of 7,560. Received thanks 1,304 times, giving thanks to others 83 times.
    Personally I think a structural skeleton with the intention of adding strength is wasted money as it could have negative effects long term and interfere with resonances which is the main reason for epoxy granite. If the skeleton is to hold mounting plates etc and was a minimal wireframe affair then that's slightly different.

    Where I think most go wrong with Epoxy builds is not putting enough effort into the molds, I would Save the money for laser cut steel and put it into a better quality and strong mold which would hold mounting fixtures, etc and allow for good vibrating. This is how the Big boys do it.!

    Regards the Moving gantry or fixed then from the 2 you show then I'd say the Moving is the better stronger option. The fixed Gantry model has too much overhang on the table and when cutting at the outer edges you'll get vibrations.

    If you support the table better along its full width then the fixed Gantry is by far the stronger choice but not how you have it drawn.!
    -use common sense, if you lack it, there is no software to help that.

  7. #15
    Quote Originally Posted by mekanik View Post
    Hi EZELab
    Welcome to the forum.
    I would like to point you to John McNamara's epoxy build( https://www.model-engineer.co.uk/for....asp?th=139042)
    Thank you (:
    I checked it a couple of days ago, It's a great build, and learned a lot from him
    Actually, I searched the forum for any "epoxy granite" related topic and checked what others did with their builds


    Seems like the word "Skeleton" made some miss understanding here.
    I am not talking about a big chunk of steel inside, It will be a waste of money.
    I meant by skeleton is like any other EG build, some steel embedded inside the pour to provide some stiffness and mounting plates for stuff will be bolted on. Nothing more.
    Here's a quick sketch for what in my mind.
    Click image for larger version. 

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    Something like this, a thick 10mm steel on front for mounting rails & other stuff, And some 4 mm steel support inside the pour.
    Am I on the right track or not?

    And about the overall process, It will be not easy, I Know!
    I'll do my best in molding. My plan is cnc'ing the mold out of Melamine wood And lay them on an epoxy leveled flat floor.
    I don't have any hopes to get the Mounting plates flat after pouring on a big size like this. The base will go to a big milling machine to get everything flat & Parallel. Which will be another challenge since the estimated weight of this base around 600~700 KG

    I think I'll go with the fixed gantry design, I'll make the process easier than the other design


    Quote Originally Posted by JAZZCNC View Post
    If you support the table better along its full width then the fixed Gantry is by far the stronger choice but not how you have it drawn.!
    This was a fast drawing, And sure I'll make the table much more stable, Thank you.

    If anyone has any more suggestions, tips, Please share it (:

    Thank you All for helping

  8. #16
    Trying to stiffen an epoxy-granite structure with interlinked pieces of steel will only lead to issues due to the huge difference of thermal inertia. The steel will expand much faster than the EG.

    Forget about the bracing. If after calculation the beam is not stiff enough to your liking, increase the cross-section.

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  10. #17
    Removed.
    Last edited by Zorbit; 1 Day Ago at 01:16 PM.

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  12. #18
    Thank you guys, Got it.

    But, In John McNamara's build he put a LOT of enforcement inside, Like this base photo.
    Click image for larger version. 

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    I saw a lot of EG builds, most of them puts some kind of enforcement inside.
    Is there some way to do it right, Or should I just put plates on the surface for bolting ?
    Could someone please explain?

  13. #19
    Removed.
    Last edited by Zorbit; 1 Day Ago at 01:16 PM.

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  15. #20
    Indeed many hobby people put reinforcements in their EG structure. Probably because they don't really know the material and treat it like a regular concrete.
    Look at how the big guys do it. Studer/Granitan, Durcrete/Nanodur, Rampf/Epument, ... You will never see reinforcements in their castings.

    Only place inserts where needed to bolt things on.

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