Nozzle Size Indicator for MK3S

This nozzle size indicator is simple to print and only requires 2 parts, all of which can be printed.  The wheel includes indicators for 0.25mm, 0.4mm, 0.6mm, and 0.8mm nozzles. The base plate is designed to snap in place on the MK3S frame without any fasteners. The mounting location is on the upper corner of the frame just above the power supply, which makes the nozzle size indicator visible, yet out of the way.

I have printed it successfully with both PETG and PLA.  The design is not too sensitive to nozzle size, but was optimized for 0.4mm with 0.20mm layer heights.  The base includes a printed in place detent spring.  This spring arm has a gap of one layer which allows it to be broken free from the base once the print has finished.  Depending on how sticky the filament is, the best way to do this is to take a small screwdriver and lift up slightly on the arm once the part has cooled.

Initially the spring will be a little bit stiff, but will loosen some as the surfaces smooth themself. A small amount of dry lube will help the wheel to spin.

Print the wheel with the numbers facing down, for the best surface finish on the visible side.  If you want contrast between the numbers and the wheel, add a color change at 0.6mm height.