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  1. #1
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    Nov 2020
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    DIY Fibre Concrete 40x30 CNC Mill

    Dear CNCzoners,

    below the link to my brand new video showing the highlights of the fibre concrete CNC built. I thought long about what materials best to use with the tools that I had at hand. I decided to experiment with fibre concrete. I am quite satisfied with the result. Enjoy the video!

    https://www.youtube.com/watch?v=3JwQ6bVTlHI

    Cheers

    TheTinkerLab

  2. #2
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    Jul 2018
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    2008

    Re: DIY Fibre Concrete 40x30 CNC Mill

    Hi Tinkerer - Well done. Peter

  3. #3

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    Jan 2020
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    36

    Re: DIY Fibre Concrete 40x30 CNC Mill

    Is concrete going to shrink during the following weeks and months as it cures completely?

    Sent from my SM-G970F using Tapatalk

  4. #4
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    Jul 2012
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    Re: DIY Fibre Concrete 40x30 CNC Mill

    Nice build.
    But I'm very sceptical about your measurements if you're claiming to have achieved 10 micron flatness by lapping concrete with a piece of MDF

    Also I would be worried that the concrete will shrink and move for many years.

    The UHPC for machine beds made by Durcrete needs 80°C curing during 48h to achieve stability after one week. If not cured at high temp, it needs at least 6 months to stabilise.

  5. #5
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    Nov 2020
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    Re: DIY Fibre Concrete 40x30 CNC Mill

    Quote Originally Posted by Nikolaguca View Post
    Is concrete going to shrink during the following weeks and months as it cures completely?

    Sent from my SM-G970F using Tapatalk
    Cement will shrink as it cures (how much?!) but not the aggregate. Depending on the grain size distribution (graining curve) and the cement there will be more or less shrinkage of the concrete, but it it will typically be in the range of a couple of 100 microns per meter (in comparison - thermal expansion of aluminium is about 260 microns per 10°C and meter). With epoxy coating as finish this becomes irrelevant for the final surface precision.

  6. #6
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    Nov 2020
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    Re: DIY Fibre Concrete 40x30 CNC Mill

    Quote Originally Posted by jackjr-123 View Post
    Nice build.
    But I'm very sceptical about your measurements if you're claiming to have achieved 10 micron flatness by lapping concrete with a piece of MDF

    Also I would be worried that the concrete will shrink and move for many years.

    The UHPC for machine beds made by Durcrete needs 80°C curing during 48h to achieve stability after one week. If not cured at high temp, it needs at least 6 months to stabilise.
    Thanks. You should be sceptical :-) I measured it with my dial indicator stuck to a peace of metal, since I don't have any flatness gage (https://www.youtube.com/watch?v=EWqThb9Z1jk). Even if it is double the error, I would still be happy given the cost of a grade B lapping plate! I was "lapping"/sanding epoxy BTW :-)

    How much do you think will it shrink after the first year? Consider a metal machine is most likely standing on a concrete floor as well.

    Thanks for the info and the feedback.

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