Using Lightburn with a GRBL controller. The controller Alarms when the limit switch is pressed but lightburn continues to drive the axis. Is there something in lightburn I have not set properly. secondly the Grbl controller has a Z-Axis but the table is only an X & Y axis. How do I get a get controller software that does not have a Z-Axis?
No. Homing is done in firmware, LB only sends the “start” command. So the problem is your firmware configuration.
What do you mean? Most controller boards feature a z-axis control option, but if you don’t need it, don’t use it. It’s that simple.
The catch is that (some) GRBL versions have Z axis homing enabled, which means they will home the Z axis before homing X and Y.
If the controller firmware tries to home the Z axis, but the machine does not respond because there is no Z axis hardware, the homing sequence fails and the controller sits there with a “not homed” error.
Depending on the controller hardware, the only way to not home the Z axis is to recompile the source code or flash precompiled firmware with the Z axis disabled. The former can become what they call a “learning experience” and the latter may be an Easter Egg Hunt for the proper combination of hardware & options.
We’d probably need to know a lot more about your controller to be able to help.
If you’re willing, please type the following report requests into the Console window in LightBurn (pressing Enter after each one):
$$
$i
?
Feel free to, Select and Copy text from the Console window in LightBurn and Paste it directly into a reply here.
If he’s not driving the Z axes and the X or Y axes move, then it’s not trying to move the Z axes. Otherwise it wouldn’t fault with the home/limit switch activation…
The Z axes is supposed to pull away from the work area and it fails to home on Z, then the machine usually quits, it should not move either X or Y axes because it doesn’t know where the Z axes is.
That’s my line of thought… I’m thinking the addition of the Z axes data was a last thought and is really a red herring … ?
He didn’t imply he built it, so it’s likely to have the proper firmware and settings to operate…
I hope @Harold went through the Lightburn Grbl Setup…?
The homing function in the controller starts with Z then X then Y. If there is no Z homing fails. I’ve tried a switch to simulate a Z but still cannot get it to work. I suspect its my controller software. Not sure how to get new software.
This may be way out there, can you disconnect the wires into your Z axis drive? Trigger the home switch by hand if necessary.
Timing is everything, because GRBL expects the switch to trip twice during the home sequence:
- First trip = during the relatively fast movement to find the home switch
- The axis moves away from the switch to release it
- Second trip = during the slow movement to precisely locate the switch
Manually closing the switch once won’t work, nor will tripping the switch twice during the fast movement.
At least one person rigged a cam on a tiny stepper to fake a Z axis, rather than figure out all the intricacies of grafting it onto the actual laser.
GRBL $22=0 means homing is disabled and GRBL will not attempt to perform automatic homing using the home switches.
When homing is disabled, the controller assumes the position at startup is the home position.
If you turn it on when the laser head is not in the home position, then all future positions will be incorrect.
This seems to be a configuration problem, not a homing problem.
Have you tried setting $22=1 to enable automatic homing?
The GRBL doc may be helpful:
That is the documentation i have for the controller.
I have enabled $22=1. and set a manual switch for Z. When i send a $H and press
Z wait and press Z a second time nothing happens. I expected X to start searching for the X switch.
Any suggestions?
As I said, timing is everything. The machine does not have any hardware on the Z axis, so you cannot manually press the switch when the firmware is expecting it to happen.
To make automatic homing work, choose any one:
- Find firmware matching your hardware without Z axis homing
- Recompile the firmware to not have a Z axis
- Gimmick a fake axis with a motor and a switch
Or you can disable automatic homing again and use the machine without switches by following the manual homing procedure every time you turn it on: