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IndustryArena Forum > Mechanical Engineering > Epoxy Granite > CNC table with epoxy granite
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  1. #1
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    CNC table with epoxy granite

    Hi,

    I am creating a medium sized CNC router, the table will have 1320mm x 1000mm (around 52" x 40"). My machining will be on aluminum and steel parts. I want to use coolant system with great flow.

    The big problem is if I use wood for the table, even if it is waterproof, in a few weeks or months I will have problem with the large amount of liquid.
    If I make an aluminum table, it will be very expensive in my country. If I make a steel or granite table, it will be extremely heavy.

    So after much research on the subject and reading various forum topics, I believe a table made of granite epoxy is the best option. I would like your opinion and how I could do with thread inserts.

    I read in some topics that it is impossible to have a good fixation of thread inserts directly on the surface of epoxy granite, that the correct is to have a steel plate or aluminum inside the surface, is that correct? how should i do?

    Something like that?


    my cnc:

  2. #2
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    Re: CNC table with epoxy granite

    Hi Vital- Have you looked for a local granite kitchen top supplier or a stonemason. Granite tops come in 20mm, 30mm and 40mm and would make a great machine base (and they come flat!). Buying granite or synthetic rock is cheaper then making your own EG. Epoxy is very expensive. I would use a std concrete thread insert. This is either placed when cast or drill and place once cast. Do not expand them! Just bond them in. Backing plates are not really needed. Bolts are epoxied into concrete directly. Look up chemsets. If you cast a bolt in or use threaded rod to create a stud then you don't need the insert. This can be cast in or post drilled and cast. Look up any concrete insert type Ramset etc for how they do it.

    I have made a couple of machines and have come to the conclusion that casting EG is the solution as well but I intend to make timber moulds and make epoxy alumina parts....cheers Peter

  3. #3
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    Re: CNC table with epoxy granite

    An epoxy-granite table like that will be just about as heavy as a natural granite one. And you'll still have problems attaching things to it. But with a machine like the one in your picture, where the table is stationary and the gantry moves, the weight doesn't matter too much anyway.

    In my opinion, by the way, you're kidding yourself if you think you're going to be machining steel on that machine. Round rails mounted on aluminum extrusions with a tall wobbly gantry will make it difficult to machine aluminum effectively, let alone steel. Think of projects you can do in wood - for which a wooden top will be fine.
    Andrew Werby
    Website

  4. #4
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    Re: CNC table with epoxy granite

    Quote Originally Posted by peteeng View Post
    Hi Vital- Have you looked for a local granite kitchen top supplier or a stonemason. Granite tops come in 20mm, 30mm and 40mm and would make a great machine base (and they come flat!). Buying granite or synthetic rock is cheaper then making your own EG. Epoxy is very expensive. I would use a std concrete thread insert. This is either placed when cast or drill and place once cast. Do not expand them! Just bond them in. Backing plates are not really needed. Bolts are epoxied into concrete directly. Look up chemsets. If you cast a bolt in or use threaded rod to create a stud then you don't need the insert. This can be cast in or post drilled and cast. Look up any concrete insert type Ramset etc for how they do it.

    I have made a couple of machines and have come to the conclusion that casting EG is the solution as well but I intend to make timber moulds and make epoxy alumina parts....cheers Peter
    I don't talked yet with the kitchen top supplier or a stonemason, but that is a good idea.
    I researched about the granite kitchen, the surface with 15mm and one square meter has 47kg, so my cnc table will have 62kg. It's a nightmare to handle (put on and take off when servicing machine), maybe I can do 3 or 4 pieces and put them side by side to make it easier.

    About the thread inserts, I found that germany product and also a similar on the aliexpress




    Quote Originally Posted by awerby View Post
    An epoxy-granite table like that will be just about as heavy as a natural granite one. And you'll still have problems attaching things to it. But with a machine like the one in your picture, where the table is stationary and the gantry moves, the weight doesn't matter too much anyway.

    In my opinion, by the way, you're kidding yourself if you think you're going to be machining steel on that machine. Round rails mounted on aluminum extrusions with a tall wobbly gantry will make it difficult to machine aluminum effectively, let alone steel. Think of projects you can do in wood - for which a wooden top will be fine.
    This is my second cnc router, I created a similar one in the past and the aluminum machining was very good for a cheap home cnc, several pieces had only 0.01mm error (that's a good result to me, I'm a cnc hobbyist =) haha)

    About steel, I think I forgot to mention that they are 1~2mm thin sheets, I don't intend to create large and complex parts, I know my CNC doesn't support this

    But let me know, what do you think I could improve on in the future?


    I want to machine 9~12mm aluminum sheets, sometimes small blocks of aluminum, acrylic and thin steel sheets

  5. #5
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    Re: CNC table with epoxy granite

    Hi Vitali - The inserts look very good. To go from cutting alum to steel is about a 3x or 4x increase in stiffness of a machine. Prefer more. Doesn't matter whether its 2mm or 20mm. So think it through and keep beefing up. A multi piece top will be a nightmare. Others have tried and come to that conclusion. Maybe a plastic top? A slab of acetal would do it 1400kg/m3 vs 2700kg/m3 for granite half weight? Look up G10 fibreglass. It comes in 25mm and 32mm thick for electrical applications. I make slabs of it on window glass for various things. 1800kg/m3 very stable. Peter

    https://www.google.com/search?q=g10+...qnLl5MYq9TM8M:

    By the way G10 fibreglass plate is same stiffness as granite yet less dense. If you can find a supplier that maybe the way to go vs granite as its an industrial product and should be cheaper. I make similar stuff for machine parts.
    https://cncrouterkits.com.au/tetrium/

  6. #6
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    Re: CNC table with epoxy granite

    "But let me know, what do you think I could improve on in the future?"

    The best single thing you could do would be to replace those round rails with profile rails and trucks. Next best would be some triangulation in the gantry supports.
    Andrew Werby
    Website

  7. #7
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    It depends on each purpose, but I would definitely suggest to visit this website ( here: https://www.woodroutersreviews.com/ ), if you need some advises about cnc routers as well. They have some comparison tables, and useful tips how they works in different situations. A non-stop updating blog of new and cool stuff of DYI sphere.

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