Dialling In with Calibration Cubes
Calibration cubes are not exciting, but they are incredibly useful for chasing down print quality issues. A standard calibration cube is 20×20 mm with X, Y, and Z on the corresponding faces, and the model is easy to find on Printables. I scaled the cube to 40×40 mm to exaggerate defects, which makes them easier to see and fix.
Troubleshooting process
Printed a cube, noted every problem, then tackled them one at a time:
- Ghosting on X
- Ghosting on Y
- Gaps in the base
- Slightly off-square
Working on a single variable at a time keeps the cause and effect clear.
Squaring the Prusa Mini
The first step was to square the printer using the Prusa guide, which can be done without special tools. The knowledge base article is here: Prusa KB. After squaring, another cube confirmed dimensional accuracy was corrected, even though it had only been out by a tiny amount before.
Belt tension
Next came X and Y belt tension. Belts that are too loose can cause ringing, belts that are too tight can do the same by feeding back vibrations. Two tools were used together:
- The printable GT2 belt tension meter to get into the right ballpark
- The belt frequency tool to fine tune by strumming the belt and matching the target frequency
After tensioning, another cube showed no X or Y ghosting and the square remained true. It is worth rechecking squareness after belt work.
Cleaning the extruder
During a print there was clicking from the extruder. That usually means debris in the extruder or the nozzle too close to the bed. Since gaps in the first layer were visible, the latter was unlikely, so the extruder was cleaned using the steps in the Prusa KB. The next cube printed cleanly apart from slight gaps in the base.
Z-offset
The remaining issue pointed to Z-offset being a touch high. Using the built-in first layer test, Z-offset was adjusted live. For faster feedback a 40×40 mm slab at 2.4 mm height was used, which aligns with a typical 1.2 mm top and 1.2 mm bottom shell configuration. After a few runs on the smooth plate, the first layer was dialled in.
Another cube confirmed it. All issues identified at the start were gone and the printer was ready for real work with confidence.
Next steps
The plan is to repeat this routine roughly every 500 print hours or whenever problems crop up. The follow-on project is to reduce noise, since the printer lives in a work room. An enclosure is the long-term goal, but any gains that reduce noise before that are a win.
Thanks for reading. If you have a reliable calibration routine or a favourite Printables model for first layer tuning, share it so others can compare approaches.