LayerStack printer layer stacking test

This is a semi-objective test to determine your printers accuracy in laying down layers on top of each other.

It's useful to compare printers and especially to determine if changes to your printer make layer stacking better.

The general procedure is to print a test cube and sand down one of the x sides and one of the y sides until all layer lines are scuffed. A measurement of the amount removed using a micrometer or calipers and a little math determines a LayerStack score.

Procedure:
- Slice and print layerstack_cube.stl. Slicer settings are given below.
- Measure and write down the distance across the cube, 1/2 way up, aligned with the three marks along X and Y, yielding 6 numbers. See picture for a cube marked with the points to measure.
- Using 240 grit sandpaper on a smooth surface (a mirror works well), drag the cube on the X face across the sandpaper across the layer lines. Rotate the cube 180 for each pass so you don't favor one side or the other. Continue