Vref adjustment for parallel stepper motor in Y axis

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  • April 30, 2015 at 5:46 am #7683
    tornwing
    Member

    Hi Synthetos

    I just bought gshield board to assemble shapeoko 2 before a few months.

    As you know, Y axis is driven by two stepper motors.

    I looked up some discussion on net, if I wanna make stepper motor work efficiently, I have to adjust Verf on Gshield for rated current of stepper motor.

    According to Shapeoko forum, I got the caculation for I=Verf/0.8.

    The rated current of my Nama 17s is 1.3A, so I adjusted Verf become 1.035 V (Iref=1.29).

    However, in parallel, the currency will become larger. I remember gshield just serve 2.5 A. Once the Nama 17s are paralleled, the total currency (Iref in Y) will become 2.58A to damage Ti8818. Do I get wrong?

    Thanks for youur help.

    May 18, 2015 at 6:49 am #7714
    alden
    Member

    Putting 2 NEMA17’s (or NEMA23’s) in parallel will not damage the driver. Adjust the Vref until the driver runs smoothly. If the drivers take too much current – as might be the case with very large NEMA23s – the driver may go into thermal shutdown but should not be damaged. In that case we recommend fan cooling.

    May 24, 2016 at 10:53 pm #9711
    alienrelics@yahoo.com
    Member

    To clarify, the Gshield limits the current no matter how many steppers are paralleled. So two in parallel does not double the current, instead it splits it between the stepper motors.

    The stepper motor cannot take any more current than what the Gshield is set to supply. It is a chopper drive, which means it is a switch mode current regulator, using the stepper motor winding as the inductance.

    I would also strongly suggest you run the motors at no more than 80% of their maximum rated current. The maximum is just that – a maximum. You’ll likely need to place fans on them to run them at 100% of their maximum rated current. An overheated stepper motor can partially demagnetize and then become very weak.

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