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Machine tool design, linear ways

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  • #31
    Originally posted by wierdscience View Post

    I got a worse idea than that, next time your'e in China, pick up one of these-

    https://www.aliexpress.com/item/4000...ou_326459010.1
    Yeah, nevermind, forgotten how crappy of a design the Sieg X3 is, not worth it.

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    • #32
      Originally posted by RB211 View Post
      Just daydreaming, what else am I supposed to do, sitting in Turkey?
      Dummy. Have some hot beverages and enjoy the food. JR


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      • #33
        those casting kits actually look pretty neat. Not sure that you'd be that far ahead financially than buying an old mill to retrofit, but it looks like some thought has gone into the various reference surfaces. Looks like the've even drilled (and tapped?) the holes for the linear rails and bearings. In many ways they look like an easier option than a retrofit, simply because most if not all fo the machining has already been done.

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        • #34
          Originally posted by mattthemuppet View Post
          those casting kits actually look pretty neat. Not sure that you'd be that far ahead financially than buying an old mill to retrofit, but it looks like some thought has gone into the various reference surfaces. Looks like the've even drilled (and tapped?) the holes for the linear rails and bearings. In many ways they look like an easier option than a retrofit, simply because most if not all fo the machining has already been done.
          Do you trust the machining is accurate? I don't.

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          • #35
            The thing with software is that, even if your machine is out of square, you can compensate in the machine's parameters. From there it's accurate again. I remember my PCB software program that would let me calibrate my laser printer's accuracy by letting me correct the real measurements of a printed square to automatic reprint with the correct size.
            Helder Ferreira
            Setubal, Portugal

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            • #36
              Originally posted by RB211 View Post

              Do you trust the machining is accurate? I don't.
              Amen Brother !

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              • #37
                Originally posted by Noitoen View Post
                The thing with software is that, even if your machine is out of square, you can compensate in the machine's parameters. From there it's accurate again. I remember my PCB software program that would let me calibrate my laser printer's accuracy by letting me correct the real measurements of a printed square to automatic reprint with the correct size.
                Ture, geometry errors COULD be compensated for in software. Problem is that is only true IF the cnc controller software has those features or allows you to add them. Most cnc controller software is proprietary and limited in its compensation abilities. Compensating, ballscrews pitch error, linear error on a single axis, and such are common.

                Lets say the X axis linear rail is out of square with the Y axis linear rail (same if box ways). If you desire a pure move in the X direction, that will require the controller to do the trig and move BOTH the X and Y axis to arrive at the desired location of the commanded pure X move. That sort of compensation is NOT common on many/most controllers.

                I use linuxcnc and it is open source. It CAN do that sort of compensation and pretty much any compensation. That said, compensation is NOT the best way to handle such geometric errors, mechanically fixing the error is the best way if possible.

                Here is a good example of a BIG machine with a BUNCH of compensations going on in the cnc controller (linuxcnc).
                Here is a quote from another video of his " it is also fully geometrically compensated for all motion XYZAB - not just ball screw error but orthogonal error and pivot point error" https://www.youtube.com/watch?v=Nn1bJ3YAQdI&t=265s
                Last edited by Sparky_NY; 01-24-2020, 06:25 AM.

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                • #38
                  Originally posted by Sparky_NY View Post

                  Ture, geometry errors COULD be compensated for in software. Problem is that is only true IF the cnc controller software has those features or allows you to add them. Most cnc controller software is proprietary and limited in its compensation abilities. Compensating, ballscrews pitch error, linear error on a single axis, and such are common.

                  Lets say the X axis linear rail is out of square with the Y axis linear rail (same if box ways). If you desire a pure move in the X direction, that will require the controller to do the trig and move BOTH the X and Y axis to arrive at the desired location of the commanded pure X move. That sort of compensation is NOT common on many/most controllers.

                  I use linuxcnc and it is open source. It CAN do that sort of compensation and pretty much any compensation. That said, compensation is NOT the best way to handle such geometric errors, mechanically fixing the error is the best way if possible.

                  Here is a good example of a BIG machine with a BUNCH of compensations going on in the cnc controller (linuxcnc).
                  Here is a quote from another video of his " it is also fully geometrically compensated for all motion XYZAB - not just ball screw error but orthogonal error and pivot point error" https://www.youtube.com/watch?v=Nn1bJ3YAQdI&t=265s
                  If I was to purchase the full blown version of CNC12 with my Centroid Acorn, it will probe the vise and rotate the machine and work coordinate system to fix any errors. Think it is called coordinate rotation?

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                  • #39
                    Originally posted by RB211 View Post

                    If I was to purchase the full blown version of CNC12 with my Centroid Acorn, it will probe the vise and rotate the machine and work coordinate system to fix any errors. Think it is called coordinate rotation?
                    Yes, coordinate rotation. I did that on the cnc lathe I used to have with linuxcnc, it used gang tooling both in front and behind the spindle making rotation necessary to keep the toolpath display correct and avoid having to change X moves to minus X moves for rear tooling. It was a learning experience!

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                    • #40
                      Hey RB211,
                      I just checked out your youtube channel.
                      Some awesome projects you are doing there.
                      And very good explanations to boot.
                      Top notch.
                      --Doozer
                      DZER

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                      • #41
                        Originally posted by Doozer View Post
                        Hey RB211,
                        I just checked out your youtube channel.
                        Some awesome projects you are doing there.
                        And very good explanations to boot.
                        Top notch.
                        --Doozer
                        What is his youtube channel? I searched RB211 but came came up blank. Love to see his vids !

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                        • #42
                          I am not Clough42, but I do have some videos from long ago.
                          My old screen name, BillH308, have some videos, and I have some videos scattered on Vimeo.
                          Last edited by RB211; 01-24-2020, 07:09 PM.

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