Quick Dimensional Accuracy Calibration Print

I wasn't finding a calibration print that I liked for tuning my 'Horizontal Expansion" and “Hole Horizontal Expansion” settings in Cura, so I made one.  

And now, for the low low price of your own time and filament, it can also be yours! 🎊🎉🥳

There's really not a lot to this piece, but perhaps more than meets the eye (though it is not a ‘robot in disguise’, sorry).  There are 6 holes, two of which you can probably stick your fingers in (heyo!).  The numbers reflect the diameter of each of the holes.  You're probably going to find it difficult to measure 2.5mm with the inner side of a caliper, and the 1mm hole is more of a “can my printer do it” test.  Generally I measure the 5, 10, 15, 20 holes and then use those measurements to come up with an average value for ‘horizontal hole expansion’.  

But what about horizontal expansion!?

Yeah, ok, that's gets me to the disguised features.  The tool itself is 90mm x 35mm.  You can use that to get a rough average for horizontal expansion.

Ok whatever, any other uses? Sure!

• The model is 5mm tall, use it to check the dimensional accuracy of your z-axis*.
• Depending on the print orientation, I've used the model to check for horizontal consistency (seeing if and how the 35mm width varies across the length).

In both cases, I've used this to check for consistency (horizontal and vertical), which can help isolate mechanical issues (i.e. if the z-height or 35mm width is very inconsistent, maybe my gantry isn't square).

• If you put your index finger in the 20mm hole, you can twirl this thing around pretty fast and then huck it real far.  It's kind of fun, make a game of it.  I'm not responsible for any damage, lives lost, and the like.

Oh yeah.  The asterisk (*).  Don't use this tool to sit there and calibrate XYZ steps.  That's just a terrible way to tune dimensional accuracy on 3D printers.  Why?  3D printers tend to be hobby grade and there's only so much you can do.  At the end of the day, the mechanics are the mechanics and adjusting XYZ steps can really introduce some problematic variables when trying to dial in accuracy.  Additionally, different filament materials (ABS, ASA, PETG, PLA, etc) and even different brands of filament of the same material can vary in how they expand or shrink during/after printing.  Use the horizontal expansion, shrinkage settings, or scale your prints to account for this.  XYZ steps should be and are based mathematically on the physical properties of the printer mechanics.  Changing them would be like taking a ruler and stretching it like taffy, and then saying it still measures the same.

Good Luck!  If you feel so inclined to support my myriad of basement hobbies feel free to donate!