These GRBL configuration constants seem to work well with the DW660 router in the MPCNC gantry:
$$ | |
$0=10 | |
$1=255 | |
$2=0 | |
$3=2 | |
$4=0 | |
$5=0 | |
$6=0 | |
$10=1 | |
$11=0.010 | |
$12=0.002 | |
$13=0 | |
$20=1 | |
$21=1 | |
$22=1 | |
$23=0 | |
$24=500.000 | |
$25=2500.000 | |
$26=250 | |
$27=3.000 | |
$30=30000 | |
$31=0 | |
$32=0 | |
$100=100.000 | |
$101=100.000 | |
$102=400.000 | |
$110=8000.000 | |
$111=8000.000 | |
$112=3000.000 | |
$120=2000.000 | |
$121=2000.000 | |
$122=2000.000 | |
$130=635.000 | |
$131=465.000 | |
$132=103.000 | |
----- | |
$n | |
$N0=F150 | |
$N1=G10L2P1X-633Y-463Z-3 | |
----- | |
$# | |
[G54:-633.000,-463.000,-3.000] | |
[G55:0.000,0.000,0.000] | |
[G56:0.000,0.000,0.000] | |
[G57:0.000,0.000,0.000] | |
[G58:0.000,0.000,0.000] | |
[G59:0.000,0.000,0.000] | |
[G28:-418.670,-282.016,-3.000] | |
[G30:-628.000,-3.000,-3.000] | |
[G92:0.000,0.000,0.000] | |
[TLO:0.000] | |
[PRB:0.000,0.000,0.000:0] |
The overall XY travel is slightly smaller than the initial configuration, because the router sticks out further than the penholder I’d been using. Increasing the $27
Homing Pulloff distance to 3 mm leaves a comfortable space beyond the limit switches after homing to the positive end:

Adjusting the $13[01]
XY travel distances and switch positions on the other end of the rail leaves a similar comfort zone at the negative end:

Both switches now live on the rear X-axis rail and appear as seen from behind the bench; they just look backwards. The Y-axis switches are on the left rail and look exactly the same.
The XY travel works out to 630 × 460 mm = 24.8 × 18.1 inch, which is Good Enough.
Some fiddling with the Z axis limit switch tape mask produces a nice round 100 mm = 3.9 inch vertical travel. The Z-axis rails just barely clear the table at the lower limit and just barely stay in the bottom bearings at the upper limit, so it’s a near thing. In practical terms, the rails or the tool will smash into the workpiece sitting atop the table before the limit switch trips.
Setting both $20=1
Soft Limits and $21=1
Hard Limits may be excessive, but I vastly prefer having the firmware detect out-of-range moves and the hardware forcibly shut down if the firmware loses track of its position, rather than letting it grind away until I can slap the BRS. The steppers aren’t powerful enough to damage anything, of course, so it’s a matter of principle.
The $N0=F150
sets the initial speed, as the default F0
seems to (sometimes) confuse bCNC’s auto-level grid probing.
The $N1=G10L2P1X-633Y-463Z-3
sets the default G54
coordinate origin to the front-left corner, with Z=0
at the home position up top, so as to prevent surprises. I expect to use G55
for most work holder touchoffs, although we’ll see how that plays out.
The G28
and G30
settings depend on the tool change location and the Z-axis probe location, so they’re still not cast in concrete.