$4tr setting for .5” ACME lead screw w/ 10 TPI.

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  • January 26, 2015 at 8:34 pm #7311
    mristau
    Member

    For $4tr, what’s a good setting for .5” ACME lead screw w/ 10 teeth per inch?

    January 27, 2015 at 5:27 am #7313
    chmr
    Member

    10 tpi (threads per inch, I would be worried if the screw had teeth 😉 means it will travel 1/10″ or 2.54mm per revolution. $4tr=2.54

    January 27, 2015 at 2:06 pm #7316
    mristau
    Member

    Thanks. Got it:

    Direct drive Z axis Stepper motor setup (with motor 4 as Z axis)

    1.8 degree per step motor = 200 full steps per 360 degrees
    set to 1/4 microsteps ($4mi=4) 800 microsteps per 360 degrees
    if using a 10 teeth per inch ACME lead screw, 8000 microsteps = 1 inch of travel
    $4tr=? (travel per rev in mm)
    convert to mm:
    1 millimeter is .0393701 of an inch
    or
    1 inch = 25.4 millimeters
    314.960 micro steps = 1mm of travel

    800 microsteps / 314.960 microsteps = 2.540 mm of travel per revolution
    $4tr=2.540

    January 27, 2015 at 10:01 pm #7319
    cmcgrath5035
    Moderator

    Well yes, but the only parameter being set is $ztr, travel per one revolution.
    If the pitch is 10 Threads per Inch, a nut, or the Z axis Lead Screw Nut, will move 1/10″ per revolution, or 2.54mm =$ztr

    tinyG does all the distance per step and distance per microstep calcs for you, based on the $_sa = 1.8 degrees ( which is 360 degrees/200 steps) and the $_mi microsteps per step parameter.
    If you want tinyG to use smaller steps, eg $_mi=8, you just set that parameter and tinyG computes a new distance per microstep,
    $_mi=4 is recommended because 1/314.960mm is already really fine precision for typical milling.

    Driving a laser engraver or a 3D printer may introduce additional considerations.

    January 28, 2015 at 7:18 pm #7322
    mristau
    Member

    Thanks again. Even clearer now.

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