I’ve been helping folks get their X-carve machines up and running. I’ve learned a lot. One of the things that I have noticed is that the grbl parameters seem to be inconsistent, especially when the Arduino has to be re-flashed.
Long story short I wanted to find out exactly what the defaults should be.
I took a new Arduino and used the EEPROM clear example program to clear the contents of the EEPROM (1024 locations), compiled the source code for Grbl 0.9j, downloaded to the Arduino, then ask for a $$ report,
Here are the results for a 500mm X carve with the ACME Z axis screw:
Grbl 0.9j [’$’ for help]
$0=10 (step pulse, usec)
$1=255 (step idle delay, msec)
$2=0 (step port invert mask:00000000)
$3=3 (dir port invert mask:00000011)
$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=3 (homing dir invert mask:00000011)
$24=25.000 (homing feed, mm/min)
$25=750.000 (homing seek, mm/min)
$26=250 (homing debounce, msec)
$27=1.000 (homing pull-off, mm)
$100=40.000 (x, step/mm)
$101=40.000 (y, step/mm)
$102=188.947 (z, step/mm)
$110=8000.000 (x max rate, mm/min)
$111=8000.000 (y max rate, mm/min)
$112=500.000 (z max rate, mm/min)
$120=500.000 (x accel, mm/sec^2)
$121=500.000 (y accel, mm/sec^2)
$122=50.000 (z accel, mm/sec^2)
$130=290.000 (x max travel, mm)
$131=290.000 (y max travel, mm)
$132=100.000 (z max travel, mm)
As you bring up your unit there are settings that will change. Most of the changes will be simple and usually are for homing/limit switch use. Some people have changed the steps per mm values to fine tune the accuracy of the machine.
For those who are bringing up their machines for the first time, many problems can be avoided if you check these values after you have run the machine setup procedure in Easel. You can do that with a terminal program like HyperTerminal or Putty. In Easel you can use the Machine Inspector to view the parameters.
If your machine is working the way you want it to then you don’t need to check this, but if you are having problems that don’t appear to be mechanical issues then this is a good place to start looking for the problem.
This link can help you decide what changes, if any, you would like to make to the Grbl settings: