Troubleshooting — Assembly Issues
This page provides solutions for common problems encountered during PrintExo assembly.
1. General Assembly Errors
Incorrect Part Orientation
| Symptom |
Cause |
Solution |
| Parts don't mate |
Flipped or rotated incorrectly |
Check CAD reference, reassemble |
| Asymmetric fit |
Left/right parts swapped |
Verify part labels, reinstall correctly |
| Holes don't align |
Part upside down |
Disassemble and flip part |
Missing Components
| Issue |
Checklist |
| Spacers missing |
Verify BOM, check packaging |
| Washers missing |
Use BOM checklist before assembly |
| Bearings forgotten |
Disassemble and install before continuing |
Tip: Lay out all parts and cross-check with BOM before starting assembly.
Screws Not Aligning with Holes
| Cause |
Solution |
| Print warping |
Reprint affected part with brim |
| Wrong screw length |
Verify screw spec against BOM |
| Hole not drilled/tapped |
Ream and tap before assembly |
| Parts shifted during tightening |
Loosen all screws, realign, retighten evenly |
2. Planetary Gear Assembly Issues
Planet Gears Not Rotating Freely
| Cause |
Solution |
| Bearing not seated |
Press bearing fully into housing |
| Debris in bearing |
Clean with compressed air |
| Bearing seized |
Replace bearing |
| Gear teeth binding |
Check sun gear centering |
Sun Gear Misalignment
| Symptom |
Cause |
Solution |
| Uneven rotation resistance |
Sun gear off-center |
Use planet gears to verify centering (see Assembly Guide) |
| Clicking during rotation |
Partial tooth engagement |
Reassemble with proper alignment |
| Premature wear |
Continuous off-axis loading |
Disassemble, inspect, realign |
Caution: Even slight misalignment causes binding, uneven wear, or gear failure. Always verify centering before installing ring gear.
Ring Gear Installation Problems
| Issue |
Cause |
Solution |
| Won't seat fully |
Planet gears mispositioned |
Rotate planets to align with ring gear teeth |
| Tight fit |
Print tolerance |
Lightly sand ring gear outer surface |
| Loose fit |
Oversized housing |
Use shim or retaining compound |
3. Fastener Problems
Stripped Threads
| Cause |
Solution |
| Over-tightening |
Reprint part, use thread insert (heat-set) |
| Cross-threading |
Back out, realign, restart carefully |
| Repeated assembly/disassembly |
Install brass thread inserts |
Over-Tightened Bolts
| Symptom |
Result |
Solution |
| Bolt won't turn |
Threads seized |
Apply heat carefully, back out slowly |
| Part cracked |
Excessive torque |
Reprint part, use lower torque |
| Head stripped |
Wrong tool size |
Use correct hex key, replace bolt |
Prevention: Tighten until snug, then 1/4 turn more. PLA does not require high torque.
Cross-Threading
| Symptom |
Solution |
| Bolt goes in crooked |
Back out completely, realign, restart |
| Resistance increases suddenly |
Stop immediately, check alignment |
| Threads damaged |
Re-tap hole, or reprint part |
Bolt Length Issues
| Issue |
Cause |
Solution |
| Bolt too short |
Wrong spec |
Check BOM, use correct length |
| Bolt too long |
Bottoming out |
Add washer, or use correct length |
| Bolt protrudes dangerously |
Incorrect part stackup |
Verify assembly order |
4. Bearing Installation Issues
Bearing Won't Press In
| Cause |
Solution |
| Hole undersized |
Ream carefully with appropriate bit |
| Bearing cocked |
Align squarely, press evenly |
| Debris in hole |
Clean hole before installation |
Bearing Falls Out
| Cause |
Solution |
| Hole oversized |
Use retaining compound (Loctite 648) |
| Housing cracked |
Reprint part |
| Wrong bearing size |
Verify bearing spec against BOM |
Bearing Doesn't Spin Freely
| Cause |
Solution |
| Over-pressed |
Bearing deformed — replace |
| Contamination |
Clean with isopropyl alcohol |
| Wrong bearing type |
Verify bearing spec (must be appropriate type) |
5. Post-Assembly Functional Checks
Perform these checks after completing assembly:
Gearbox Rotation Test
| Check |
Expected |
If Failed |
| Rotate output by hand |
Smooth, consistent resistance |
Check gear alignment, bearing seating |
| Full 360° rotation |
No binding at any position |
Look for debris, check tooth mesh |
| Backdrive input |
Should rotate with gear ratio resistance |
Verify all gears engaged |
Hinge Alignment Test
| Check |
Expected |
If Failed |
| Inversion motion |
Free movement, no binding |
Check hinge pin, clear debris |
| Eversion motion |
Free movement, no binding |
Verify hinge components aligned |
| Return to neutral |
Smooth return |
Check for friction, misalignment |
Shank-to-Actuator Connection
| Check |
Expected |
If Failed |
| No wobble |
Rigid connection |
Tighten fasteners, check mating surfaces |
| Aligned with output |
Straight torque transmission |
Reassemble with proper alignment |
Shoe Interface Check
| Check |
Expected |
If Failed |
| Rigid mounting |
No play at connection point |
Tighten bolts, verify fit |
| Lace tension |
Even across all guides |
Relace following guide pattern |
| Plantar guides secure |
No looseness |
Verify installation |
See Also