Post Process¶

In one sentence: Run the selected post-processor on the active Job and write the G-code output to a file.

Overview¶

Workbench: CAM
Menu: CAM → Post Process
Command: CAM_Post
Shortcut: none

Calls the post-processor Python script for the active Job and writes the G-code to a file. The post-processor translates FreeCAD's internal path representation to the G-code dialect of a specific CNC controller.

Intuition¶

FreeCAD stores toolpaths in a machine-neutral internal format (always metric, always absolute coordinates). Post Process applies a post-processor script — a Python file that knows your machine's specific dialect — to convert this to the G-code your controller actually accepts.

When to use it¶

When you are ready to cut and need the G-code output file.
When testing post-processor output during setup.

When NOT to use it¶

Don't skip Sanity Check first — run Sanity Check to catch configuration errors before post-processing.

Step-by-step¶

Run Sanity Check to verify the job.
With the Job selected (or active), choose CAM → Post Process.
A file dialog opens — choose the output path and filename.
Click Save. FreeCAD runs the post-processor and writes the G-code.

Post-processor arguments¶

Post-processors accept command-line style arguments in the Job's PostProcessorArgs field:

Argument	Effect
`--no-show-editor`	Skip the G-code preview editor
`--inches`	Output in inches instead of mm
`--comments`	Include human-readable comments
`--header`	Include file header block

Arguments vary by post-processor. Run the post-processor with --help to see all available options.

Common mistakes and pitfalls¶

Output file is empty

All operations may be disabled, or no operations produce a valid path. Run Sanity Check and verify at least one operation is active.

G-code coordinates are wrong scale

The post-processor may be outputting in inches while the machine expects mm, or vice versa. Check the --inches argument and verify with G20/G21 in the output file header.