GRBL device always hits end stops when it starts to run job

LightBurn Hardware Compatibility
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I have designed and built a laser cutter for balsa parts. The bed is 3 feet long by 4 inches, with an Arduino Uno using GRBL. Being in a dusty workshop, I’ve been using a Raspberry PI running Universal GCode Sender and sending GCode files to it from Lightburn on a windows machine up in my inventing room. A few teething issues but it is working well.

However, running Lightburn and UGS seems overkill and I’ve decided to purchase a refurbed laptop to run Lightburn connected directory to the Arduino UNO and remove UGS.

I’ve hit a problem and having read various support articles can’t see an understood way forward. My machine homes in the top right position and any moves into the workspace are negative. When using Lightburn to run a job, it moves in the positive, causing my endstop switches to triggers and setting off an alarm.
I tried changing the origin in Lightburn for my machine to bottom left, the green dot on screen shows in this position and now my jobs on screen shows bottom left as well. I thought that was going to resolve the problem, my machine would home bottom left (there are end stops at the end of each axis) so positive coordinates would not trigger an alarm. It still homes top right and hits the end stop as soon as the job starts.

I’ve done some reading, and can see in GRBL setup it states If your machine uses negative workspace coordinates you’ll need to apply a workspace offset (G10 L2 P1 xx yy). However I’m not sure if that is the correct fix, how to implement it, or there might be something simpler to do. Does anyone have a solution or could point me in the right direction? I’d very much like to use Lightburn directly with my machine rather than UGS.

Thanks in advance

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which board? i am running a wemos esp32 d1 r32 for the same thing. instead of max make the limits zero?

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Hi John

Thanks for your response. I’m running it using an original Arduino Uno. A bit behind the curve, where do I make the limits zero, is that a machine setting?

All the best

Howard

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I have sorted this problem, by setting the homing mask on GRBL to 7 which reversed X & Y. Now it homes to the bottom left. This has produced another problem but will open up a fresh topic for that. Cheers

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I finally got to the bottom of this issue. Too much enthusiasm and not enough reading on my part. Don’t change the homing position on GRBL. GRBL provides a negative coordinate system whilst Lightburn is positive. Simple solution is to apply an offset. This page explains it all very clearly.
Grbl Settings
If that is not clear for you read this as well
[Negative Coordinate Machine Setup]

I’m very please to have swapped from Uinversal Gcode Sender to Lightburn.

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