Steppers not moving during Homing

LightBurn Hardware Compatibility GRBL
,
1

I just installed 2 normally closed (NC) limit switches on my DIY Aliexpress Laser. When I try homing with $5=0, the stepper motors get powered, but won’t move. The Laser stays on “busy” for a while, followed by:
“ALARM:9
Homing failed. Limit switch at search distance could not be found. Defined as 1.5 * max_travel during search and 5 * pull-off during search phases.”

When setting $5 to 1, I immediately get:
“ALARM:8
Reference run failed. The cycle could not clear the limit switch when pulling off. Try increasing the pull-off setting or check the wiring.”

The board I’m using is similar to this one: Bachinmaker Neue Produkt Pcb 2 Achse Circuit Control Board Für Laser Gravur Maschine Und Schreiben Elektrische Controller Panel - Buy Control Board For Laser Engraving,Pcb Control Board,Pcb 2axis Circuit Control Board Product on Alibaba.com . When using console commands, the stepper motors work fine. My home position is bottom-left.
My settings:
$$
$0=10
$1=10
$2=0
$3=1
$4=0
$5=1
$6=0
$10=1
$11=0.010
$12=0.002
$13=0
$20=0
$21=0
$22=1
$23=1
$24=25.000
$25=500.000
$26=10
$27=1.000
$30=1000
$31=0
$32=1
$100=100.000
$101=100.000
$102=100.000
$110=5000.000
$111=5000.000
$112=100.000
$120=100.000
$121=100.000
$122=10.000
$130=350.000
$131=420.000
$132=200.000

$I
[VER:1.1h.20190825:]
[OPT:V,15,128]
Target buffer size found

$#
[G54:0.000,0.000,0.000]
[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]
[G28:0.000,0.000,0.000]
[G30:0.000,0.000,0.000]
[G92:0.000,0.000,0.000]
[TLO:0.000]
[PRB:0.000,0.000,0.000:0]

$G
[GC:G0 G54 G17 G21 G90 G94 M5 M9 T0 F0 S0]

2

That says $5=0 is the correct setting.

Despite the “2 achse circuit control board” in the title, the PCB has three stepper drivers and I’m (almost) certain the GRBL firmware was compiled with all three axes active.

As a result, the firmware is trying to home the Z axis and failing, because your machine does not have a Z axis motor or home switch.

You can confirm that by wiring up a third switch to the Z axis input and manually tripping it (twice) immediately after starting the home cycle. If the X and Y axes start moving, that’s the problem.

The least awful way out is to flash a version of GRBL compiled without Z axis homing

3

Agreed.

Looks like the board being used is Arduino based. In that case the easiest way to do this is to use LaserGRBL. It contains multiple flash images, has one specifically tailored for 2-axis lasers, and can be flashed from the program itself.

Flashing Grbl Firmware – LaserGRBL

Use the one called “v1.1h, custom, XY Homing 20190830”.

1 Like
4

Ed, that might prove difficult. Looking at the web link provided it would appear that the “Z” axis does not have a limit switch input, just “X” and “Y” (even though it has a “Z” axis driver).

5

Bonus: Ship 3-axis firmware on a board that can’t run it. :grin:

Now, to be fair, the board may have two Y axis drivers in parallel, rather than a Z axis driver, but you (well, I) sure can’t tell from the pix.

Trust, but verify …

6

Thank you all very much for the quick help!
I modified the firmware according to LaserGRBL (v1.1h, custom, XY Homing 20190830) and the stepper motors now move. $5=1 somehow ended up being the configuration that works. I also had to set $23=3, but $3=1.
@bionicback321 My board only came with 2 drivers (x, y), but this configuration is no longer available on the sellers website.
@ednisley I have to take the blame for the wrong firmware, since I updated it, not knowing about this caveat.

7

Experience is what you get when you don’t get what you wanted … :grin:

8

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