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Thread: matching driver to stepper (help)

  1. #1
    *Registered User* pjkumpon's Avatar
    Join Date
    Nov 2018

    Default matching driver to stepper (help)

    I am in the process of designing my CNC wood router. I did my calculations and am comfortable with 380 oz-in steppers, which should give me a factor of safety of ~7. I've found many potential steppers on ebay, but I'm unsure of what other parameters that I need to look at before (1) choosing a final stepper and (2) choosing an appropriate set of drivers.

    Here is what I know:
    1. Lower inductance is better <2.0 mH - but there doesn't seem to be many around with an inductance this low
    2. the motor needs to have sufficient torque at my design RPM. I can read the motor performance charts, but I'm not sure what to do with the "1/2 step" (or other fraction) at the top of the chart - should I derate the torque chart based on this?

    Here is what I don't know:
    1. What do I look for in a driver ( should it be at least the max current of the motor? do I need to look at any other factors?, how to choose between unipolar, bipolar, etc? Is one better than others for CNC applications?)
    2. How to choose a power supply?
    3. I'd like to buy a set of 3 steppers, drivers, and a power supply for ~$200... does this seem reasonable?

    thanks for the help!

    pete in upstate NY

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  2. #2
    Community Moderator ger21's Avatar
    Join Date
    Mar 2003
    United States

    Default Re: matching driver to stepper (help)

    1) The driver needs to be able to deliver the rated current, and the voltage you plan on using. I'd want a little headroom on the voltage, so I wouldn't run 48V on a 50V rated drive.
    I don't think there are any modern unipolar drives.

    2) According to Gecko, 32 x square root of the motors inductance, in mH. With high quality drives, you can go even higher. The torque chart should have a voltage that it was created at. Higher voltages will give more torque at higher speeds, lower voltages will give less.

    3) High quality drives alone will cost more than that. These are a very cost effective option.

    And for larger motors, or higher voltages.

    Here's a slight smaller motor that may actually outperform the 380oz motors you were looking at.


    UCCNC 2017 Screenset

    Mach3 2010 Screenset

    JointCAM - CNC Dovetails & Box Joints

    (Note: The opinions expressed in this post are my own and are not necessarily those of CNCzone and its management)

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matching driver to stepper (help)

matching driver to stepper (help)