Reel Spool Keeps for Wanhao Duplicator

Being tired of having to babysit my printer when using a new spool of filament I made two discs to fit the spool shafts and fitted a 30mm ID spring to keep the spool tight to the cabinet and prevented the filament spooling up and jumping the drum which then knots up and stops the print.

Also adds a small amount of back tension on the filament stopping it from spooling of the drum