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Black Box - Dual Y Motors - PNP Inductive Limit Switches

Discussion in 'CNC Mills/Routers' started by Forestbird Originals, Feb 19, 2020.

  1. Forestbird Originals

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    Black Box - Dual Y Motors - PNP Inductive Limit Switches

    Hello !
    I am planning my build and struggling with something I need to setup on my blackbox. It is common practice on many large bed CNC's to an endstop on each Y rail to make sure the machine returns to being square upon homing. My machine is a modified LEAD 1010.

    The blackbox has a single input for an endstop. I plan on running 12mm PNP Inductive Proximity Switches by switching the jumper to 24v. I would like to use these (if possible) on both sides for the y axis end stops. What I am struggling with is how to run 2 end stops when there is only 1 endstop spot on the blackbox?

    Is there a way I can run 2 sensors that would allow each motor to run independently until it triggers the associated end stop?
     
  2. Peter Van Der Walt

    Peter Van Der Walt OpenBuilds Team
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    If you have a v2.6 or later BlackBox you can: But it is quite advanced (and we don't recommend it: Square it mechanically instead, the motors stay in sync and its much simpler!)

    Refer to gnea/grbl for details, you'll have to compile it yourself for now (as mentioned above, the later hardware provides the jumpers to wire the second motor - but as we don't recommend it we are not providing precompiled firmware for this at this time. Do heed all the warnings in the linked section as well)

    With the LEAD, as its leadscrews, squaring it mechanically is a set-and-forget, the leadscrews will not be pushed out of sync just by the frame itself - spending a couple more minutes "building it right" makes more sense long term than having forces pulling on the frame all the time.

    Also read this Blackbox 4x v2.4 A3 and A4 pins. thread
     
  3. Forestbird Originals

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    I appreciate the reply. I have never run a lead screw based machine before. So in your experience, the 2 independent motors turning lead screws never gets out of square mechanically in cutting aluminum or other difficult materials? Part of my modifications to the design is to provide a more rigid Y and X rails that will resist twisting in drilling operations etc. Consequently my X gantry is about 7 or 8 lbs heavier than the stock one. Up the road, I plan on switching from v-wheels to linear rails.

    I know when trying to remain in the top 80-90% of available acceleration will be important with lead screws because the movement is much slower than belt driven systems I have seen. I want to make sure that if a step is missed that my hardware doesn't get destroyed or bent if possible. Unlike a belt driven system where a cheap belt breaks or it gets a little out of square.
     
  4. Peter Van Der Walt

    Peter Van Der Walt OpenBuilds Team
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    If it does, that will be the problem to solve (not squaring it again after it ran out, as by that time you've broken bits and ruined the job already). It shouldn't run out in the first place. And no, it won't - BlackBox is awesome, beefy stepper drivers, really won't go out of sync unless you have a real bad crash in the first place (i.e no longer square as a consequence, not cause) :)


    Which Dual Homing won't accomplish, it only "squares" the machine when homing, does nothing for you mid-job. But no, skipped steps is a thing with crappy drivers (; - get a Blackbox and don't worry about it
     
  5. Forestbird Originals

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    Thanks again for the reply. I have a blackbox and the high torque NEMA23's. So hopefully that should be sufficient.
     
  6. Peter Van Der Walt

    Peter Van Der Walt OpenBuilds Team
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    Oh yeah, golden! No need to worry, you'll be fine :)
     

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