This is a part designed for testing your printer tolerances to help calibrate for the filament being used. More detailed instructions can be found here on how to calibrate your filament: https://www.thingiverse.com/thing:2502677
As shown in the images load the object twice and orient one of them 90 degrees from the other. This will test the tolerance matching of the X and Y directions. Do this for each head on your printer.
Testing of the clips is accomplished by printing the set found in the single STL file and flipping one of the clips upside down on top of the other to test the fit of the features. If the clips are loose then you are under extruding and need to lower the nominal diameter of the filament or increase the extrusion multiplier. If the clips are too tight then you are over extruding and need to increase the nominal diameter of the filament or decrease the extrusion multiplier. When the clips fit easily together with no wiggle and stay put you have precisely calibrated filament.
After adjusting the diameter of your filament to the right size the parts will snap together easily and be snug. When using two heads the different filaments should produce parts that are interchangeable. No post processing should be required.
The files include the source file which imports with the object units in mm's with the scene units in inches. The CS file is scaled for direct import into Cura.
The test part was designed around PLA assuming the printer can hold a tolerance of 0.1mm but should be able to be used with any filament. Calibration is made by adjusting the measured diameter of the filament being used until the surface is smooth when printing with no over extrusion or under extrusion. I have added an image showing the part before and after calibration.
For example the orange filament was set to the standard of 1.75 mm but the Grey was set to 1.9mm. Used a print speed of 40 and a bed temp of 60 C for the entire first layer and then reduced it to 45 C during the second layer for the remainder of the print. Part cooling fans came on at the second layer.
More detailed instructions can be found here on how to calibrate your filament: https://www.thingiverse.com/thing:2502677
TIP: I flip one of the clips over when fitting them together to ensure that the squished sides from the first layer are facing out. How tight you level the bed will affect if this is beneficial or not when determining the fit.
If the fit is perfect and you still get an occasional gap (maybe on one edge only) between the outer shells I bump the temperature up by 5C and the gaps disappear.
I also write on the clip what filament diameter and temperature they were printed at.