TinyG skips lines of Gcode

From the original Synthetos forum (2011–2025)

Started by geroswen on Jul 15, 2016 in TinyG Support. 2 replies, last activity Jul 23, 2016.

geroswen Jul 15, 2016 #

Hello,

I'm having an issue with TinyG skipping lines of gcode when i have multiple homing commands G28.2 Z0 in the same program.

I'm using M8 and M9 commands to control the probe tool.

What would i expect it to do:
lift Z axis 20mm
extend probe tool
wait 2 seconds
home Z (until Z min switch is hit)
set this as new Z0 point
take back probe tool
wait 2 seconds
and repeat same steps one more time

What is actually does:
first ~9 lines are executed as expected. Than it skips all the lines until 2nd instance of G28.2 Z0 and runs G28.2 Z0 again. No matter how many lines of code I add before 2nd instance of G28.2 Z0, TinyG skips all of them.

G21
G90
G92 x0 y0 z0
G0 Z20
M8
G4 P2
G28.2 Z0
G92 z0
M9
G4 P2
G0 Z20
M8
G4 P2
G28.2 Z0
G92 z0
M9

Programs with one instance of G28.2 Z0 command work fine. But I'm having issues whenever I use more than one instance of this homing command. (it the example shown above the probe tool will not extend before 2nd homing sequence)... I need to home Z axis before every cut to properly set pierce height of plasma torch. Thank you for helping me.

cmcgrath5035Staff Jul 18, 2016 #

Have you reviewed the Wiki, particularly

https://github.com/synthetos/TinyG/wiki/Homing-and-Limits-Description-and-Operation

Z axis homes to Zmax, not Zmin.

Available support for M8 and M9 behavior may not be what you need, see

https://github.com/synthetos/TinyG/wiki/Gcode-Support

geroswen Jul 23, 2016 #

[image: zHome.jpg, no longer available]

My Z axis homes to Zmin when i use settings as shown on the screenshot. I dont think that is the problem here, because first few lines of code are executed correcty (including Z homing cycle).

I could replace M8 and M9 commands with anything else and I'm pretty sure that program wouldn't work correctly. I'm using M8 and M9 to control 3,3V arduino relay, which further controls 12V air valve to move probe tool down and up (enabled, disabled).

I'm currently trying to replace G28.2 with G38.2 for Z probe. It fixed the problem with skipped lines, but I'm having issues with X and Y axis going out of workplace. I will try to figure that out.

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