GRBL Settings For My IndyMill Build

As it turns out there is some math required to figure out some of the GRBL values! Although GRBL is no longer being developed, its still very popular and Nikodem used this for the orginal IndyMill so not about to re-invent the wheel for a domain in which I have very little understanding!

Most of the below is straight from the docs

Misc

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$0=10         (step pulse, usec)
$1=25         (step idle delay, msec)
$2=0          (step port invert mask:00000000)
$3=6          (dir port invert mask:00000110)
$4=0          (step enable invert, bool)
$5=0          (limit pins invert, bool)
$6=0          (probe pin invert, bool)
$10=3         (status report mask:00000011)
$11=0.020     (junction deviation, mm)
$12=0.002     (arc tolerance, mm)
$13=0         (report inches, bool)
$20=0         (soft limits, bool)
$21=0         (hard limits, bool)
$22=0         (homing cycle, bool)
$23=1         (homing dir invert mask:00000001)
$24=50.000    (homing feed, mm/min)
$25=635.000   (homing seek, mm/min)
$26=250       (homing debounce, msec)
$27=1.000     (homing pull-off, mm)

Cartesian – [X,Y,Z] steps/mm

Stepper motor steps:

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motor_steps = degrees_in_a_circle / stepper_motor_step_angle
motor_steps = 360 / 1.8
motor_steps = 200

Driver micro steps:

(typically 1, 2, 4, 8, or 16). Using high microstep values (ie 16) can reduce your stepper motor torque, so use the lowest that gives you the desired axis resolution and comfortable running properties.

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microsteps are calculated based on the dip switchs on the stepper drivers
mine is pre set to 8

MM per revolution:

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1605 ball screws for x,y
05 means 5mm for 1 full rotation

the z has is 8mm on the trapezoidal lead screw

Finally some math:

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steps_per_mm = (steps_per_revolution*microsteps)/mm_per_rev
steps_per_mm = (200 * 8) / 5
steps_per_mm = (1600) / 5
steps_per_mm = 320

steps_per_mm = (steps_per_revolution*microsteps)/mm_per_rev
steps_per_mm = (200 * 8) / 8
steps_per_mm = (1600) / 8
steps_per_mm = 200

Now the resulting GRBL:

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$100=200       (x, step/mm)
$101=200       (y, step/mm)
$102=320       (z, step/mm)

Also see grbl settings 101 a how to guide

Rates

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$110=635.000 (x max rate, mm/min)
$111=635.000 (y max rate, mm/min)
$112=635.000 (z max rate, mm/min)

Acceleration

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$120=50.000 (x accel, mm/sec^2)
$121=50.000 (y accel, mm/sec^2)
$122=50.000 (z accel, mm/sec^2)

Maximum Travel

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$130=225.000 (x max travel, mm)
$131=125.000 (y max travel, mm)
$132=170.000 (z max travel, mm)