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IndustryArena Forum > CNC Electronics > Stepper Motors / Drives > Lack of Torque, Missing Steps
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  1. #1
    Member
    Join Date
    Mar 2008
    Posts
    1

    Lack of Torque, Missing Steps

    I'm looking for a bit of help on my motor setup. I have a hand built CNC simialr(ish) to the Gatton Sidewinder (40*26).

    I spec'd the motors and driver myself but I'm beginning to think I've made some pretty major mistakes when choosing. The machine doesn't have very much torque and on some test runs (cutting birch ply) it's missing steps. I'm running a two flute 1/4" downcut bit with a bosch colt router and doing 1/32" cuts at 39in/min and still missing steps as the peices are slightly off on measure and are not square.

    Here is the current setup:

    Stepper Motors (1x Z-Axis, 1x Y-Axis, 2x X-Axis)
    Model: 23HS9430B
    Pahse: 2
    Voltage: 4.8V
    Current: 3.0A/Phase
    Inductance: 6.8 mH/Phase
    Holding Torque: 280N.cm Min
    Detent Torque: 12N.cm Max
    Rotor Torque: 800g.cm2

    Driver
    Model: Geko G540
    Also I have a 3K ohm resistor wired at the driver connection for each motor. I forget where I read that this was required?

    Power Supply
    Model: S-600-48
    Output: 48V 12.5A 600W

    Lead Screws:
    1/2-10 RH ACME Rod, 5 Start

    This post has me especially worried: https://www.cnczone.com/forums/diy-c...25720-cnc.html
    Excerpt: "I see a lot of people buying the wrong motors because they think that 425 is better than 387. Larger steppers suck at higher rpm's and have high inductance, which means a large expensive power supply to drive them."

    At this point I'm just trying to cut a new gantry for the machine using the current machine without missing steps, I'm not concerned with speed.

    My initial thought was...
    Combined Motor Voltage 4.8*4 = 19.2
    Combined Amp Draw = 3.0*4 = 12

    But now I'm seeing that I missed out on the whole inductance thing...

    The G540 max voltage is 50 so, I'm up against the max for voltage already.

    I can buy new motors or a new power supply but, I'm just not sure what's best here. Humbly asking for any feedback or help you may have to offer to help me get this thing up and running.

    Would smaller motors help get me more torque and work with my current driver/power supply?

  2. #2
    Registered
    Join Date
    Nov 2013
    Posts
    904

    Re: Lack of Torque, Missing Steps

    Hi,
    low inductance motors are the key. In 23 size motors they should be 1-2mH, 1 mH preferred and reject anything over 2mH.

    Craig

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