Post-processor: setup and commands

The post-processor translates calculated paths and operation settings into the commands expected by the machine controller.

Choose and edit a post

Choose the process before creating operations. The supplied Laser XY, Waterjet XY, Plasma XYZ and Router XYZ templates are starting points; Router also has an inch template. They are not certified profiles for every machine. Match units, axes, power/spindle commands and clearance heights to your controller.

Import .gpp loads a Gardos post. Import Vectric .pp converts supported definitions; review all diagnostics and the resulting .gpp, because not every Vectric feature is supported. Edit post opens the editor. Validate checks the syntax and produces a 10 mm square sample. Apply uses the valid post in the job. Save as writes a separate .gpp copy; export and generated sample text require activation. Save the project to retain its post settings.

After any post change, inspect existing operation values and calculate again. A successful Validate checks the post syntax, not the suitability of every command for your machine. Plasma templates do not configure probing or torch height control; the router template assumes a fixed tool and does not implement automatic tool changes.

How a .gpp is organized

Sections use [BRACKETS]. Settings use Key = Value. A line beginning with # is a comment. Command sections contain the text to output; values in {BRACES} are replaced automatically. Keep section names, keys and variable names exactly as shown, regardless of interface language.

Operation defaults

When command sections run

The six base command sections are PROGRAM_START, RAPID_MOVE, PATH_START, LINEAR_MOVE, PATH_END and PROGRAM_END. Add the XYZ, arc and Punch sections required by your capabilities. Typical XY sequence: start program -> rapid -> process on -> cutting moves -> process off -> next path -> end program.

Variables inserted in commands

G-code commands used by the templates

Example: from template to movement

[LINEAR_MOVE]
G1 X{X} Y{Y} F{FEED}

G1 X48.000 Y40.000 F1200.0

The first two lines define a post section. The last line illustrates its output for a destination of (48,40) and feed 1200 in a millimeter job. The braces disappear; the actual coordinates and feed are inserted. This excerpt is not a complete machine program.

Arcs and full circles

With Arcs = Yes, provide ARC_CW and ARC_CCW with X/Y/I/J/FEED and also Z for XYZ. PROGRAM_START must contain G17 and G91.1. Only XY arcs with incremental I/J are supported; radius R format, other planes and absolute arc centers are not supported. Settings > Curve output chooses arcs or G1 segments. Full circles use two semicircles. Arcs = No causes linear fallback.

For a circle of radius 10 centered at (0,0), starting at (10,0), the two example G3 moves below return to the start. Each I/J pair is measured from the start of that particular semicircle. Check that your controller supports the declared arc-center mode; if it does not, use line segments and a suitable line-only post.

G21
G90
G17
G91.1
G94
G0 X10.000 Y0.000
G3 X-10.000 Y0.000 I-10.000 J0.000 F1200.0
G3 X10.000 Y0.000 I10.000 J0.000 F1200.0

This is a geometry example, not a production-ready program: process start/stop and machine setup are intentionally outside the excerpt. The controller manual is the authority for supported commands. Reference definitions: LinuxCNC G-codes and M-codes, https://linuxcnc.org/docs/stable/html/gcode/g-code.html and https://linuxcnc.org/docs/stable/html/gcode/m-code.html . Using these references does not make a template a verified LinuxCNC machine profile.