If you have the , you can modify an existing 3-axis Fanuc or Haas post to support a 4th axis. 4 axis post for mach3 - Forums, Autodesk

If you can tell me your (e.g., Haas VF-2) and your controller type (e.g., Fanuc Oi-MD), I can help you find a more specific download link or configuration guide.

: If the G-code generated is incorrect, revisit the post processor configuration and ensure all parameters are set according to your CNC machine's requirements.