Post-Processor Verification Checklist: 10 Mandatory Checks When Modifying a Fusion 360 Post for HAAS VF-2 or Fanuc Robodrill

Many programmers who use Autodesk Fusion 360 with HAAS VF-2 or Fanuc Robodrill machines end up customizing the post-processor (adding macros, changing tool formats, handling coolant, WCS, operation order, etc.).

The problem is that even a small change to the post can generate unexpected behaviors on the real machine: wrong coolant, WCS not activated, out-of-sequence tool changes, aggressive rapids, or movements that Fusion's internal simulation does not show.

This 10-point checklist allows you to systematically verify the generated G-code and use Eureka3X to confirm that the behavior matches what is expected on the machine.

1. Always Reinstall the Modified Post-Processor

After every change to the post:

• Completely close Fusion 360
• Reopen and reinstall the post (or update it from the post folder)
• Generate the G-code again from scratch

Never trust a G-code generated before the modification.

2. Check Coolant Activation

Verify that the following appear correctly in the G-code:

• M08 / M09 (flood coolant)
• M07 / M09 (mist coolant) if used
• Any custom commands (e.g., M88, M89 on HAAS)

In Eureka3X, check that the coolant is visually activated and deactivated at the right points in the cycle.

3. Verify Work Coordinate Systems (WCS)

Ensure that:

• The G-code contains the correct G54 (or G55-G59)
• There are no sudden WCS jumps
• The reference system matches the one set on the machine

In Eureka3X, you can clearly visualize which WCS is active during each phase of machining.

4. Check the Order of Operations and Tools

After a post modification, the order can easily change:

• Out-of-sequence tool changes
• Operations executing before they are needed
• Unnecessary tools being called

Use the "Order by tool" or "Order by operation" function in Fusion and verify the result in the G-code.

5. Check Tool Changes and Tool Length Offsets

Verify that:

• Txx M06 is present and correct
• G43 Hxx (or G43.4 on more advanced machines) is applied after every tool change
• There are no unnecessary tool changes

In Eureka3X, you can clearly see the tool change and the length application happening in real-time.

6. Check Rapids and Clearance Heights

After post modifications, rapids can become too aggressive or too conservative. Check:

• G00 values and positioning
• Clearance Heights / Retract Heights
• Z-axis movements before long rapids

7. Verify Fixed Cycles and Canned Cycles

If using drilling, tapping, or pocket cycles:

• Check that the cycle parameters (e.g., R-plane, depth, peck increment) are correct
• Verify that the post has not broken the cycles in strange ways

8. Check Safety Exits at the End of the Program

At the end of the program, there must be:

• Coolant OFF (M09)
• Spindle OFF (M05)
• Return to a safe position (usually G28 or G53)
• M30 or M02

9. Compare the G-Code with a Previously Working Version

If you have a version of the post that worked well, compare the two G-code files using a diff tool (like Beyond Compare or VS Code) to quickly spot the differences introduced by the modification.

10. Simulate the Complete G-Code in Eureka3X

This is the most important check. Open Eureka3X (with the HAAS VF-2 or Fanuc Robodrill model already ready) and:

• Load the G-code generated by Fusion
• Run the full simulation
• Check for collisions, over-travels, abnormal tool changer and WCS behaviors
• Verify that the behavior matches your expectations on the real machine

Only after this verification can you send the program to the machine with peace of mind. Read more about Fusion 360 Machine Simulation vs Eureka 3X Pro.

Conclusion

Modifying a Fusion 360 post-processor is often necessary but introduces risks. The combination of a rigorous checklist and real G-code simulation with Eureka3X drastically reduces the possibility of costly errors on your HAAS VF-2 or Fanuc Robodrill.

For more complex scenarios, don't forget to check out our enterprise solutions at eureka-sim.com.