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Servo motors 850oz for knee mill conversion

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  • Servo motors 850oz for knee mill conversion

    Do you all think servo motors 850oz. reduced 2:1 or 3:1 would be strong enough for my knee mill. Steel is 90% of the material when milling.
    Location: The Black Forest in Germany

    How to become a millionaire: Start out with 10 million and take up machining as a hobby!

  • #2
    Hang weight off the hand crank and see what kind of power it takes to lift the knee.

    Counter balance cant hurt either....

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    • #3
      Originally posted by Black Forest View Post
      Do you all think servo motors 850oz. reduced 2:1 or 3:1 would be strong enough for my knee mill. Steel is 90% of the material when milling.
      No idea, what is the kw rating of the motors. I knew a guy who direct drove a knee with a 750 brushless motor.

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      • #4
        The OP was inquiring about a knee mill retrofit, I think he is referring to driving the X/Y on the table, nowhere did he mention automating the knee itself. Assuming he is talking about the X and Y on the table, then yes 850oz servos do it nicely, it has been done many times.

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        • #5
          Originally posted by Sparky_NY View Post
          The OP was inquiring about a knee mill retrofit, I think he is referring to driving the X/Y on the table, nowhere did he mention automating the knee itself. Assuming he is talking about the X and Y on the table, then yes 850oz servos do it nicely, it has been done many times.
          Hey Sparky aren't you physic? Everyone else on here knew I meant to drive the knee also!!!! Man, take your tinfoil hat off!

          I did mention or question about using the knee in another thread. So you have no excuse!
          Location: The Black Forest in Germany

          How to become a millionaire: Start out with 10 million and take up machining as a hobby!

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          • #6
            My interact in the thread in here has 1100oz/inch units in 2:1 drive ratio driven now by dm860a chinese stepper drivers, and I'm still not entirely happy with how fast it moves one of the axis's before it misses steps but I have a issue somewhere possibly and I'm still only driving a 80v capable motor and driver with 60v.
            The steppers were spec'd by sir john for it and it arrived with them, so I went with them, I figure he knows a thing or two about what steppers to use and you can buy larger steppers with driver packages quite reasonably.

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            • #7
              I have fixed the problem with my X and now they all run very fast with the 1100oz/in units if that helps. It had a mechanical issue. You may be able to use the 850's sucessfully.

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              • #8
                Whereas Servos retain their torque through the rpm range better than steppers maybe they will be better than steppers in my application. Meaning moving the load better at higher rpm's.
                Location: The Black Forest in Germany

                How to become a millionaire: Start out with 10 million and take up machining as a hobby!

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                • #9
                  Originally posted by Black Forest View Post
                  Hey Sparky aren't you physic? Everyone else on here knew I meant to drive the knee also!!!! Man, take your tinfoil hat off!

                  I did mention or question about using the knee in another thread. So you have no excuse!
                  I servo'd the knee on my series one bridgeport. It ran 100 ipm with a very low following error without any gas strut or similar assist. Its not brain surgery, but does require a tinfoil hat.

                  Also, if the 850oz motor referred to is the typical chicom variety, then its 850oz peak torque, steady torque is in the area of 225oz. I have used those motors in retrofits and although fine for some things, they are not up to the job of a 700lb knee at any reasonable speed. 3:1 would not work. They are approx. a 350 watt motor.
                  Last edited by Sparky_NY; 02-16-2015, 08:03 PM.

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