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Positioning spindle (end mill) manually

Discussion in 'CNC Mills/Routers' started by DavidCNC2017, Mar 25, 2021.

  1. DavidCNC2017

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    Hello,

    On my previous CNC machine I used arduino with Synthetos gShield V5. It was possible to adjust the position of the spindle manually by means of rotation appropriate axis manually, using rotary knobs.
    It was very useful, especially when adjusting Zero of Z axis using sheet of paper.

    Now I switch to cnc controller and real drivers like DM542 and CNC controller (GRBL). When I make connection all motors gets locked and it is impossible to rotate axis by hand. Only by software .

    Is it possible to unlock the motors ( without switching off the connection) to move them manually by hand?
    And why it was possible using gShield and arduino and is not possible using DM542 drivers and cnc controller (GRBL)?
     
  2. Alex Chambers

    Alex Chambers Openbuilds team
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    That's not a particularly good idea - when you turn a motor by hand it becomes a generator creating back emf. This can be very high voltage spikes and can damage your stepper drivers. Much better to use the controller to move an axis - it should be possible to set jog move to very small increments for accurate positioning. What control software are you using?

    Alex.
     
    Peter Van Der Walt likes this.
  3. Peter Van Der Walt

    Peter Van Der Walt OpenBuilds Team
    Staff Member Moderator Project Maker Builder Resident Builder

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    You can checkout gnea/grbl but it will have the side effect that any time the machine is idle, axis can move by hand, also unintentionally (gravity making Z droop down etc)
    Secondly, moving motors by hand, can make them act like generators, backfeeding the drivers, which can damage the drivers.
    Best to just adapt to jogging in Software.

    If you use CONTROL, you can use your Phone as a Handheld wireless pendant: Wizards and Tools > Mobile Jog Widget

    upload_2021-3-25_14-9-56.png
     
    Alex Chambers likes this.
  4. DavidCNC2017

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    Thank You for reply.
    I am using different soft, mostly Openbuilds Control. I know about emf, but never had damaged drivers on gShield. May be because this hand adjustments were very slow and mainly were performed to zero the Z axis.

    Ok, I will try to change my habits and try to adjust spindle position only by soft using onscreen cursors or whatever.
     
  5. DavidCNC2017

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    By the way, if moving motors by hand is so dangerous what is the purpose of Openbuilds part JOG KNOB?
    Or stepper motors with double shaft?
     
  6. Peter Van Der Walt

    Peter Van Der Walt OpenBuilds Team
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    People use OpenBuilds's modular system for all kinds of assemblies - sometimes woodworkers build jigs like box jointers, or router sleds, that use leadscrews, but no electronics

    Centrally mounted inside a machine, with a driveshaft off to each side. Typically used in Laser cutters to ensure the two Y belts are ALWAYS syncronised as going skew with flying optics is disasterous.

    upload_2021-3-25_15-2-37.png
     
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  7. ljvb

    ljvb Well-Known
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    Or adding rotary encoders..
     
    DavidCNC2017 likes this.

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