Session 10: Post-Processing & Troubleshooting
Session 10
Post-Processing & Troubleshooting
A Clean Simulation Isn't the Finish Line
Fusion's simulation shows the toolpath. Your machine needs its own language to actually run it.
The Post-Processor
Translates Fusion's generic toolpath into the specific code your exact machine's controller understands.
Different Machines, Different Language
A ShopBot and a Makera don't read the same code — the wrong post-processor produces code your machine can't run correctly, even from an identical simulated toolpath.
Where It Lives in Fusion
Actions → Post Process. Pick the post configuration for your machine, set an output folder and filename, and Fusion writes the file the controller actually reads.
The Post field is empty, and so is NC extension. That is not a broken screenshot — it is the dialog before you choose. The extension is not yours to type; it appears once you pick the post, because the post is what decides it.
A ShopBot post writes .sbp, not the .nc G-code you may have heard of. Different machine, different file extension — that alone tells you the post did something real.
Your Machine
Fusion ships two ShopBot posts — ShopBot OpenSBP and Handibot OpenSBP. Both write .sbp. Picking the wrong one still produces a file, and the file still looks fine.
So confirm which post your specific machine and controller take, with your instructor, before running anything for real.
The Diagnostic Clinic
From here on, most problems show up as a symptom first — you work backward to the cause.
Symptom: Didn't Cut All the Way Through
Likely cause: stock thickness entered wrong, or final depth set short.
Symptom: Part Came Out Undersized
Likely cause: wrong profile offset — Session 7's exact problem.
Symptom: Part Shifted or Came Loose Mid-Job
Likely cause: no tabs, or tabs too small — Session 8's exact problem.
Symptom: Bit Broke
Likely cause: step-down too aggressive for the material.
Symptom: Machine Errored or Moved Strangely at Startup
Likely cause: wrong post-processor, or zero point not actually verified — Session 4's protocol.
Notice the Pattern
Every one of today's symptoms traces back to something already taught — nothing here is a brand-new idea, just the same ideas showing up as real-world failures.
Two Things to Remember
A symptom rarely has just one possible cause.
Check the most likely explanation first, but don't stop looking if it turns out wrong.
Two Things to Remember
A pre-cut checklist beats fixing mistakes after material's already ruined.
Everything on today's list is cheaper to check before pressing start than after.
Next Up
Week 4: The Practice Build.
Design a small item, program it, actually cut it — everything from these four weeks, in one small project.
'F' → Fullscreen
Build
Step 1: Match Symptom to Likely Cause
| Symptom | Likely Cause |
|---|---|
| Cut didn't go all the way through the material | |
| Part came out noticeably undersized | |
| Part shifted mid-job | |
| Bit broke partway through a deep cut | |
| Machine behaved strangely right at startup |
Step 2: Write Out One Real Fix
Pick one symptom above. Write the actual fix — not just the cause, but the specific correction you'd make in the CAM setup.
Step 3: Build Your Pre-Cut Checklist
Write a personal checklist of everything you'd verify before pressing start on a real job. Pull from all four weeks so far — safety protocols, offset direction, tabs, step-down, stock thickness, WCS origin, post-processor choice, zero point. You'll use this checklist for real in Week 4.
Two of those are new as of today and easy to forget, so write them in explicitly: did I post with the right configuration, and does the machine's zero match the WCS origin I set in Fusion? A perfect toolpath posted against the wrong origin cuts a perfect part in the wrong place.
Checkpoint
Before you move on, confirm your pre-cut checklist includes at least one item from each of: safety (Session 4), CAD/offset (Session 7), and pocket/tabs (Session 8).
Reflection
Answer these on your own. Reflections are individual, even when the rest of the session was team work.
- Every symptom today traced back to something from an earlier session. What does that tell you about how these skills actually connect, rather than existing as separate topics?
- Session 11 starts your own practice build — your design, your material, your toolpaths. Name one thing you'll deliberately keep simple, and say what would go wrong if you didn't.
Submit
Submit your symptom-matching table, your written fix, your pre-cut checklist, and your reflection.