1. Know your controller
The controller decides the dialect. Mach3 and Mach4, grbl and grblHAL, LinuxCNC, Syntec, WinCNC and Centroid all read G-code but differ in comments, arcs, tool changes and supported codes. ShopBot uses its own OpenSBP language. Industrial panel machines from builders such as Biesse, SCM, Homag and Felder often use their own formats or software. Start from a post made for your controller family.
2. Configuration checklist
| Setting | What to check |
|---|---|
| Units | mm or inch, matching the controller default |
| Arcs | I/J/K absolute or incremental, helical arcs allowed, planes supported |
| Spindle | Controlled by M3 S, or manual; speed range and warm-up |
| Tool change | Manual with pause and re-zero, automatic changer, or single tool |
| Z zero | Top of material or spoilboard, matching how Fusion setups are made |
| Work offsets | Whether G54 and others are supported |
| Extraction & vacuum | Codes for dust collection, vacuum zones and pop-up pins |
| Feed limits | Maximum feed and rapid speeds |
| File format | Extension (.nc, .tap, .gcode, .sbp), line numbers, comments |
3. Example output (grbl-style)
(Pocket - 6mm flat)
G90 G94 G17
G21
M3 S18000
G0 X0 Y0
G0 Z5
G1 Z-3 F600
G1 X100 F2400
G1 Y50
G1 X0
G1 Y0
G0 Z15
M5
M304. Manual tool changes
Many routers have no tool changer. The post can stop the spindle, move to a convenient position, pause with a clear message, and wait while the operator changes and re-zeros the tool. Alternatively, it can output one file per tool, which is often safer on simple controllers.
5. Automatic tool changers
Routers with linear racks or carousels need the right tool change code or macro, and sometimes spindle and dust hood handling. Aggregate heads and drill blocks on panel machines need special output that the builder defines.
6. Sheet work and nesting
For nested sheet work, the post should handle vacuum zones, onion-skin or tab strategies set in Fusion, and a safe park position for unloading. Program order also matters: small parts cut last to keep vacuum hold.
A router post that matches your controller saves more time than any feed-rate tweak.
7. Personal-use licences
Fusion for personal use limits some post output, such as rapid moves and automatic tool changes. For commercial work, a commercial licence gives full post output.
Router post services
See Fusion CNC router posts and Fusion 3-axis posts, and read 3-axis CNC milling post processors.