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Q about adding powered cross slide as an attachment to a large wood lathe

Discussion in 'Concepts and Ideas' started by auto.pilot, Nov 28, 2015.

  1. auto.pilot

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    I am working with a Powermatic 2442 wood lathe. It can handle up to 24 inch diameter work and 42 length. I would like to add a powered cross slide cutter and have some questions: I will need no more than 1000 mm for my X axis and nothing more than 250mm for the Y. My plan is to attach it to the lathe bed at the proper height so that no Z axis is necessary. Obviously, there will be lots of wood chips and saw dust flying around. Would I be better with a V Slot or a C Beam set up? I would ideally like to control the X and Y using some sort of joystick or switches. Both X and Y need to move very slowly.

    Ideally, I don't want to hook any of this up to a PC. Is it possible to simply run the stepper motors with current alone and no CNC set up? What do I need to make this happen?

    Both X and Y need to move very slowly, but I'd like to vary the speed via turning a knob.

    I am totally new to this and would appreciate any thoughts...

    Here's a link to the lathe....
    https://images-na.ssl-images-amazon.com/images/G/01/th/content_26/Q4_2009/jet-B0002ZHWDQ-1-sm.jpg

    Thanks in advance for any advice.

    Jim
     
  2. David the swarfer

    David the swarfer OpenBuilds Team
    Staff Member Moderator Builder

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    Hi
    Stepper motors are driven via electronic drivers that are driven by 'step' and 'direction' inputs. The direction pin is either on or off, on giving one direction and off giving the other direction. The voltage used is normally 5v, the standard for logic circuits, though 3.3v is making headway in modern stuff.

    The step pin is pulsed at varying frequency to give varying speed of rotation. A computer (or other control device) gives the right frequency and number of step pulses to make the motor turn the right number of steps to go the programmed distance. Stepper motors cannot instantly accelerate so they have to start slow and ramp up to speed.

    So, what you need is a device that produces variable frequency pulses from the position of a knob, a switch to select which axis the pulses go to, and a switch to select the direction of the selected axis. (BTW lathes use X-Z axes, the spindle being equivalent to the spindle on a mill).

    So, here is the pulse generator
    555 stepper pulse generator - Electronics-Lab
    and now all you need is your local electronics guru to wire it up with switches to your stepper drivers.

    The stepper drivers will need 5 volts for the logic section, and 24 to 40 volts for the motors themselves, depending on the driver itself. Read about stepper motors https://www.geckodrive.com/gecko/images/cms_files/Step Motor Basics Guide.pdf for the details on why the motors run on high voltage (despite the label saying 2 volts or so!).

    As for dust, there are various methods of creating 'bellows' to cover the leadscrews, and you should definitely be rigging a vacuum hose to the tool holder to suck up the dust at the source, primarily for your health, secondarily to preserve the machine. If you can use a tool that cuts rather than scrapes (like the skew chisel and gouges do) then you get much less dust.
     
  3. JustinTime

    JustinTime Master
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    Jim, besides David's excellent advise, why would you want to go to all that trouble and then do the cutting manually? Isn't the whole idea of stepper motors, and so on, to have it done by a machine that can make it much more precise and repeat it over and over without any variations?
     
  4. auto.pilot

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    Thank you. I have much to learn, but you have pointed me in the right direction.
     
  5. auto.pilot

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    The lathe is in a rental space. Storage for my attachment is limited. However, my primary reason for this simple set up is that I am cutting a flat surface (cylinder). ideally, I would like to have a lightweight device that attaches to the lathe bed. Thanks
     

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