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  1. #1
    Join Date
    Jul 2018
    Posts
    6254

    How stiff is your machine?

    Hi All - I'm designing a new router and I'm trying to determine what machine stiffnesses are out there. I'm currently using 10N/um or 10N/0.001mm as a guide. This is the stiffness at the bottom of the Z axis at maximum extension or say at the bottom of the tool clamp. Anyone know their machine stiffness or can you measure it? Ta Peter

  2. #2
    Join Date
    Jul 2018
    Posts
    6254

    Re: How stiff is your machine?

    Hi All - I've done some research and there are machines out there from <10N/um to 100N/um. Mainly good info on vertical machining centres. Found some theoretical works and some practical. Still going with the 10N/um at the moment. Peter

    I also found a reference to a Kuka robot that had 1N/um stiffness and it mentioned typical VMC at 50N/um so where in the ballpark.

  3. #3
    Join Date
    Jan 2014
    Posts
    126

    Re: How stiff is your machine?

    Unsure what size or type of machine you are going to be building, but you'll be surprised how hard it is going tot be to reach any of those figures. If you've ever gotten to push on a robot arm, even a small one, you'd be amazed at how rigid they are. Not sure if my benchtop machine (more rigid than a router for sure) would even make the 1N/um stiffness. Just trying to keep things in perspective.

    But looking at the theory is quite fun and required for industrial machines.

  4. #4
    Join Date
    Jul 2018
    Posts
    6254

    Re: How stiff is your machine?

    Hi All- found this on a UK forum. Router gets 1N/um maybe 3N/um

    stiffness measurements cnc mk3

    Hi mcardoso - I used to program industrial robots and they are quite stiff. Search for Maximus in this forum, can follow its development if you like. So far I'm at 10N/um but thats theoretical. Got to shot somewhere. Found some article on a machine that was +100N/um was a very precise mill.

    discussions here on 3-5N/um
    Planet CNC • View topic - Machine rigidity.

    So far I think 10 is a good target
    Attached Thumbnails Attached Thumbnails machine stiffness.JPG  

  5. #5
    Join Date
    Jan 2014
    Posts
    126

    Re: How stiff is your machine?

    After much reading on the topic thanks to this post, I agree with your number to shoot for. Certainly going to be tricky, good luck!

  6. #6
    Join Date
    Jul 2018
    Posts
    6254

    Re: How stiff is your machine?

    Thanks Mcardso - 10 is a good number, would be great if someone out there had a real number from a known machine like a CNC RP machine or shopbot? Peter

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