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IndustryArena Forum > CNC Electronics > UHU Servo Controllers > The UHU parts list, questions and improvement.
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  1. #41
    Join Date
    Aug 2006
    Posts
    2758

    Re: The UHU parts list, questions and improvement.

    There is a thread, somebody tried to make it work with steppers: https://www.cnczone.com/forums/mecha...-software.html
    No conclusion but it might give us ideas....

    You should keep on pursuing the DC servo/gearbox approach, the air-cylinder driven solution doesn't go well with using different types of tool holders, which will require complete disengagement from the drawbar. The torque limits (Vref) could be made to change via relays/mosfet-switches driven by the tool-change macro. But it still will require a way to align the drawbar square with the driven socket, some kind of drawbar position sensor or magnetic forced alignment, there is also the drawbar brake which must be handled by the macro too. It will be good to include a selectable impact phase to tighten the nut and release it without over-stressing the motor by stalling it.

    That Brushless CAN motor seems interesting too.

  2. #42
    Join Date
    Dec 2005
    Posts
    231

    Re: The UHU parts list, questions and improvement.

    That's exactly what I had in mind! He uses two air cylinders and has the spindle brake so he can turn the nut until it engages. That's been one of my problems with nut rounding happening when the impact wrench doesn't set the socket properly and then spins.

    Or, now that the nut is a bit damaged, jams when down and then pulls out of the 3/8" drive and stays stuck to the draw bar nut. Eventually I'll have to replace the draw bar nut.

    I don't have an encoder on it. Just one PPR pulse with hall sensor. I do have a sensor for socket all the way down.

    I've also whipped up a drawing and G-Code for a spindle lock but haven't actually made it yet.
    Here's a JPG of the assembly. The shape of the lock has changed a bit but you get the idea. Having a spindle lock will make even just manual operation easier.
    Attachment 483982

    And I had thought about using a DIP relay to switch in a different current limit resistor just as he did. But if I have a processor available that can do PWM or D/A then I have much better control over torque.

    I've been in contact with H.O. with respect to his MicroChip PIC version of the HP_UHU micro-controller. To see about adding a torque mode motion.

    I have some time. It will be a while before the planetary drive arrives. May turn out that 25:1 isn't going to be enough. I'll worry about that later.

  3. #43
    Join Date
    Dec 2005
    Posts
    231

    Re: The UHU parts list, questions and improvement.

    I've been looking at my HP_UHU boards and have a question. (A couple actually).
    My boards are marked Rev.10.b 12/2007

    R54 feeding the VR16 reference pot has been shorted out and there's a 1N4148 diode to ground. This matches 1.0d+ drawing except there's an R20 2.2K replacing that R54 and now 1.0d+ has two trim pots for references.

    There is one jumper on the top and some trace cuts near R55 and R16. Rev 1.0d schematic shows R16 is now connected to 15V instead of 5V. Why was that done? Something to change the behavior of the Slow Limit?

    There are 3 jumpers on the bottom which look like they add the Rev 1.0d+ change of connecting the O.C. LED to pin 2 of the 4013 instead of the U9A comparator.

    I never did change any of my boards to have the dual trim pots like in 1.0d+ or 1.0e.

    I don't think you ever made any Rev 1.0c, 1.0d or 1.0e boards right?

  4. #44
    Join Date
    Aug 2006
    Posts
    2758

    Re: The UHU parts list, questions and improvement.

    The latest PCBs I designed at the time were all Rev 1.0b 12/2007, the modifications on following revisions were made on those boards.

  5. #45
    Join Date
    Aug 2006
    Posts
    2758

    Re: The UHU parts list, questions and improvement.

    Quote Originally Posted by kreutz View Post
    ...... Look also at the mechanism of the automobile starter motor for inspiration, it engages and disengages on power up/down automatically.
    Look at: https://en.wikipedia.org/wiki/Bendix_drive and

    https://www.youtube.com/watch?v=kFsl5r34lCI

    The "flywheel gear" could be permanently attached to the drawbar nut, the bendix mechanism to the air rotating tool, dc motor, servo motor or stepper.


    Check also this: https://www.novakon.net/products/pow...-for-torus-pro
    They use a DC motor controlled by arduino.

  6. #46
    Join Date
    Dec 2005
    Posts
    231

    Re: The UHU parts list, questions and improvement.

    The Novakon is the direction I've decided to go but for now with a stepper motor and probably an encoder on the back of it.
    Click image for larger version. 

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    The 14mm keyed output shaft of the 25:1 planetary gear couples to a 3/8" socket drive.
    Click image for larger version. 

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    At slow speeds the torque will be there. Likely a relay to change the current limit resistors so CW torque is less than CCW.
    Biggest part of this project will be trying to use at least some of the original mounts.
    Click image for larger version. 

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    Meanwhile I am working on an HP_UHU to drive a DC servo but for that it turns out I need the 100:1 instead of 25:1 planetary drive.

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