My Week of Obsessively Printing Tiny Cubes
My other half thinks I’ve lost it. She walked into my office yesterday and found me staring intently at my sixth consecutive tiny plastic cube, holding it up to the light and muttering to myself. “Are you STILL printing those little squares?” she asked. I tried explaining these were vital calibration cubes essential to the perfect operation of my Prusa Mini. She just shook her head and walked out.
Look, I get it. Printing the same damn cube over and over doesn’t seem like a productive use of time. But if you’re into 3D printing, you know that feeling when your prints just aren’t coming out quite right - it’ll drive you absolutely bonkers until you fix it.
What The Heck Are Calibration Cubes Anyway?
For the uninitiated, a calibration cube is a simple 20x20mm cube with X, Y, and Z letters marked on the corresponding sides. You can find the model I used on printables.com. Nothing fancy, but incredibly useful for diagnosing printer issues.
These little squares of plastic tell you SO much about what’s going wrong with your printer - dimensional accuracy, ghosting/ringing, layer shifts, extrusion problems - it’s all there in that simple geometry.
I actually scaled mine up to 40x40mm because I’m getting older and my eyesight isn’t what it used to be. Also, the bigger size makes problems more obvious - what might be a subtle defect at 20mm becomes glaringly obvious at 40mm. I’ve found that diagnosing issues is easier when they’re literally staring you in the face.
My Cube Problems
My first test cube was… well, not terrible, but definitely not great either. Here’s what I was dealing with:
- Ghosting/echoing on the X axis (those little shadows after edges)
- Same ghosting issue on the Y axis (but slightly less noticeable)
- The bottom layers had these annoying gaps between lines
- The whole thing looked just slightly off-square - not enough to ruin a print, but enough to trigger my OCD
I’ve learned the hard way that trying to fix everything at once is a recipe for disaster. Change too many variables and you have no idea what actually fixed the problem (or more likely, what fixed one problem while creating three new ones). So I decided to tackle these issues one at a time like a sane person.
Squaring Up the Printer
First up: dealing with that slightly off-square print. This seemed like a mechanical issue with the printer itself, and Prusa actually has a fantastic knowledge base article on squaring up the Mini.
This process was surprisingly easy - no special tools needed, just follow their instructions and use the printer itself as a measuring tool. Clever stuff.
After spending about 20 minutes carefully measuring and adjusting, I found my X-axis was indeed a tiny bit out of square - only by maybe 0.5mm over the full travel, but in 3D printing, that’s enough to cause issues.
If you’re doing a full printer tune-up like I was, definitely do this squaring step first. Any other calibrations you do will get thrown off if you later square up the printer.
After squaring, I ran another test cube (cube #2 if you’re counting). The dimensional accuracy improved - my first cube measured 40.03mm on one axis, and now it was spot on at 40.00mm. Small victory! But the other issues were still there, so onward we go.
Belt Tension: The Art and Science of Twanging
Next up was tackling that ghosting/echoing on the X and Y axes. This is usually caused by belts that are either too loose (allowing movement to overshoot) or sometimes too tight (causing weird resonance issues).
There are two ways to check belt tension, and I’m a paranoid perfectionist, so I used both:
First, I printed this GT2 belt tension meter. Important note: this tool is calibrated specifically for Prusament PETG, so using any other material will give you wonky readings. Naturally, I ignored this advice on my first attempt and used some random PETG I had lying around. The readings made no sense. Don’t be like me - use the right material.
After reprinting with actual Prusament (cube-adjacent print #3), I used the tension meter to get the belts roughly in the right range.
Then I fine-tuned with Prusa’s belt frequency tool, which has you literally pluck the belts like guitar strings and listen to the tone. I felt completely ridiculous doing this, especially when my other half walked in right as I was strumming my printer and making serious faces about the sound.
“Is this some kind of printer ASMR thing?” she asked. I had no good answer.
Anyway, after tweaking both belts to the recommended tensions, I printed yet another cube (#4 for those keeping score). The ghosting was significantly reduced! Not completely gone on the X axis, but about 80% better. The Y axis looked perfect.
Cleaning a Very Unhappy Extruder
While printing cube #4, I noticed something concerning - the extruder was making this sporadic clicking sound. If you’ve been 3D printing for a while, you know that sound is the printer equivalent of your car making a weird noise on the highway. Nothing good.
The clicking usually means one of two things:
- The nozzle is too close to the bed, causing back-pressure
- There’s crud in the extruder gear mechanism
Since I knew my Z-offset was actually too high (remember those gaps in the bottom layers?), it had to be option #2.
Once again, Prusa’s documentation came to the rescue with their extruder cleaning guide. I followed it and… wow. The amount of plastic shavings that came out of there was embarrassing. I clearly hadn’t cleaned it in way too long.
I put everything back together and printed cube #5. No more clicking! And the prints were looking much more consistent. But those bottom layer gaps were still bugging me…
Z-Offset: The Final Frontier
The gaps in my first layer meant my nozzle was too far from the bed. This is adjusted through the Z-offset.
Instead of printing another full cube to test this, I created a quick 40x40mm flat slab that’s only 2.4mm high (I use 1.2mm for top and bottom shells, so this gives me a look at both). This printed much faster than a full cube, letting me iterate quickly.
I used the Mini’s built-in Z-offset calibration tool, which is super handy because you can adjust it live during the first layer. After about 4 test slabs (we’re up to approximately 9 test prints now), I finally got that perfect first layer where the lines squish together juuuust right with no gaps.
Time for the final test - one more calibration cube (#10 if you include the slabs).
And it was… perfect. Well, as perfect as my Prusa Mini can print. No ghosting, perfect dimensions, no gaps in the layers. All the issues from that first cube were gone.
Why I Tortured Myself With This Process
I typically do this full calibration routine every 500 print hours or whenever I notice quality issues creeping in. But this time I had an additional motivation - noise reduction.
My printer lives in my home office where I work all day, and the constant whirring, stepper motor sounds, and occasional random beeps drive me absolutely nuts during video calls. I’ve been muted more than once while frantically trying to explain that no, there isn’t a robot uprising happening in my house, it’s just my printer.
Getting everything perfectly calibrated means less vibration, smoother movement, and generally quieter operation. The long-term plan is to build an enclosure (another project to add to my never-ending list), but in the meantime, a well-tuned printer is a quieter printer.
Was It Worth It?
Ten test prints and several hours of my life later, was it worth the effort? Absolutely.
There’s something deeply satisfying about a well-calibrated machine. My prints are coming out better than ever, I’ve eliminated several annoying issues, and the printer does seem a bit quieter (though my colleagues on Zoom might disagree).
Plus, I now have a collection of increasingly perfect calibration cubes that make for a nice visual record of the improvement. I’m thinking of keeping them on my desk as a little trophy line-up, though I suspect only other 3D printing nerds would understand why I’m proud of a row of small plastic squares.
If you’ve got print quality issues that are driving you crazy, I highly recommend the methodical cube approach. Just maybe don’t tell anyone how many identical cubes you’ve printed. They wouldn’t understand.
Next project: making this thing as silent as humanly possible. My sanity depends on it.