Bobbin for a sewing machine. Size 20x12 mm, with undercut. It is printed out as one solid part which does not require gluing. External support is integrated into the model, additional support is not needed. For the correct printout, it is necessary to activate the functions (in Cura): Outer Before Inner Walls and Print Thin Walls.
After printing, remove the external support by pulling at its end, remove the burrs and the bobbin is ready. The bobbins have been tested, they work perfectly.