FreeCAD - Which postprocessor? LinuxCNC or GRBL?

Just wondering which is the best postprocessor to use in FreeCAD. Since Onefinity’s controller is a fork of Buildbotic’s controller and Buildbotic’s controller understands code which is patterned after the LinuxCNC dialect, I first though I should use the LinuxCNC postprocessor (Path workbench → Job → Output tab → Processor). But Carl and Lynn uses the GRBL processor, possibly because of this?

I thought I’d seen an earlier post asking a similar question that also got zero replies. Maybe it’s a faux pas? IDK. Anyway, I tried it and:


  • I’ll be using GRBL

More …

  • Running LinuxCNC output file starts with a prompt to hook up the probe. Once it gets a touch and you click continue, it begins cutting.
  • The GRBL output doesn’t prompt for the probe - it moves straight into cutting.

Although it looks like the actual motion portion of the generated gcode was identical in the 2 files, the differences are:

GRBL GCode inserts the following on every line

K0 - Turn off Linear Advance

LinuxCNC preamble

G54 - sets the work offset zero location
G49 - cancel tool length compensation
G80 - cancel all active canned cycles
G40 - turn off cutter compensation
M5 - stop spindle rotation
M6 T2 - Toolchange

LinuxCNC postamble

G54 G80 G40

I’ve been using the LinuxCNC post processor for over a year. I didn’t mess with the post amble (G54 G80 G40) but I have on occasion gone into G-Code files and modified height settings for the milling bits - only reason being is my negligence in properly defining all the detail for the mill bits, depths & heights in the job.