GRBL Stuck with latest Lightburn 1.0.01

Hi everyone !

I’m using LightBurn version 1.0.01 on a CNC 3018 with GRBL v1.1h. Recently the CNC got easily stuck on some path. Like it start a path, but the CNC motor just stop working, and nothing move after except if you click on stop and restart the job.

What i tested:

  • Tried different usb cable, but all of them are shielded, no changes.
  • Tried different version of GRBL, no changes.
  • Tried different speed (even if it was working), no changes, even at very low speed.
  • Tried using synchronous instead of bufferring, it worked.
  • Tried to export the gcode and using candle to send it, buffered, it worked.
  • Tried an older version of LightBurn i was having (0.9.20), it worked.

I captured with wireshark/usbmon the serial traffic, and the card just stop answering “ok\n” at some point, but as soon as you click stop, character is “\x18”, it unlock the machine and start receiving all the others “ok\n”. Does it make sense ? Not at all. Why candle would work and not LightBurn on the same gcode ?

Then, by checking the gcode, i figured out something. I tried exporting the same shape (i messed up the scale) in gcode and check. See below. The LightBurn version 1.0.01 emit sometimes 3 digits after the comma like G1X5.033S330.
Even the description “Scan+Cut” have 1000.002 mm/min.

I am aware about the -d on the latest LightBurn version, but this doesn’t provide output on 0.9.20. I can provide pcap if necessary.

How can i prevent 3 digit generation on LightBurn ?

LightBurn 0.9.20

; LightBurn 0.9.20
; GRBL device profile, current position
; Bounds: X0 Y-0 to X30.53 Y30.46
G00 G17 G40 G21 G54
G91
M4
; Scan+Cut @ 1000 mm/min, 33% power
M8
G0X13.8Y0.18
; Layer C05
G1X2.93F1000S330
G1X0.81Y0.1S0
G1X-4.52S330
G1X-0.64Y0.1S0
G1X5.76S330
G1X0.5Y0.1S0
G1X-6.71S330
G1X-0.43Y0.1S0
G1X7.54S330
G1X0.39Y0.1S0
G1X-8.31S330

LightBurn 1.0.01

; LightBurn 1.0.01
; GRBL device profile, current position
; Bounds: X0 Y0 to X30.81 Y30.74
G00 G17 G40 G21 G54
G91
M4
; Scan+Cut @ 1000.002 mm/min, 33% power
M8
G0X14.926Y0.119
; Layer C05
G1X0.93F1000S330
G1X1.37Y0.1S0
G1X-3.67S330
G1X-0.65Y0.1S0
G1X5.033S330
G1X0.543Y0.1S0
G1X-6.154S330
G1X-0.437Y0.1S0
G1X7.06S330
G1X0.4Y0.1S0
G1X-7.896S330

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