NOTE: This is not a finished design, do not print it as it is! If you want to design your own spool holder for the Ultimaker 2 series, here is the complex part of the holder. It is designed to print well with minimum of material and support structures, yet be strong enough to support heavy spools. Continue designing your own spool holder by adding an extrusion that fits the spools you intend to use. For really heavy spools you might consider higher infill than default settings in Cura. Use supports "touching buildplate"!