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Converting an old 3-axis router to blackbox controller

Discussion in 'CNC Mills/Routers' started by philipforget, Sep 9, 2019.

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  1. philipforget

    philipforget New
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    I'm converting an old Probotox v90 fireball machine (leadscrew 3 axis cnc router) to use the openbuilds blackbox controller / GRBL. The machine has three NEMA 23, high torque, 280 oz-in, 1.8° resolution steppers, data sheet available here.

    I believe the original controller for it ran on 36v as the power graph for the motor in the data sheet illustrates. I have a few questions regarding using them with the blackbox controller:

    1. It seems like wiring them in parallel would exceed the blackbox's per-motor amperage rating. From the datasheet it seems like wiring it as a unipolar motor drops the torque but keeps the max speed higher. What would be the best way to wire this particular motor?

    2. Is it OK to run these motors of a 24v power supply?
     
    #1 philipforget, Sep 9, 2019
  2. Peter Van Der Walt

    Peter Van Der Walt OpenBuilds Team
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    1) BlackBox supports only Bipolar motors. Wiring two motors in parallel would not be needed, there is a Slave axis: OpenBuilds BlackBox 4X Documentation
    2) BlackBox only supports 24v. It should run the motors in 2.1a/phase bipolar wiring configuration. You can try the 4.2A wiring scheme too and see how it differs in the real world (although getting a little less current, the bigger picture is about more than just current (switching speed determined by coil inductance, back EMF characteristics, and many more come into play) They may not run as well as our motors, but since you have them, try them first. If they don't deliver satisfactory results, you can upgrade the motors later.
     
    #2 Peter Van Der Walt, Sep 9, 2019
  3. Peter Van Der Walt

    Peter Van Der Walt OpenBuilds Team
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    PS: Stepper drivers are current limiting, you can run 4.2A motor on a 3A driver setting for example, driver will just deliver 3A to it (or whatever driver is set to)
     
    #3 Peter Van Der Walt, Sep 9, 2019
  4. philipforget

    philipforget New
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    Ah thanks for the response Peter. I'll give both bipolar wiring configurations a try and see how they behave. As for parallel, I meant wiring the windings in parallel vs series.

    In the documentation it also states to adjust the current on each driver until it can no longer stall. Are the default values good to start with considering that I'm not using the openbuilds steppers they are meant to drive?

    Thanks again for the quick reply!
     
    #4 philipforget, Sep 9, 2019
  5. Peter Van Der Walt

    Peter Van Der Walt OpenBuilds Team
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    Yeah, should be get to get you moving.
     
    #5 Peter Van Der Walt, Sep 9, 2019

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