The project of converting my 3DR Simple to use magnetic ball joints caused me a lot of grief. Despite the apparently successful video, I was never able to get the thing to print reliably when the print head was attached. Rods would always randomly pop out and cause havoc. Proceed at your own risk. Magnetic effector plate and carriages for 3DR Simple that uses countersunk circular magnets and steel ball-bearings attached to the rods. Watch it move here. Effector has slots for nylon wire ties for wiring tidiness. Carriages have removable sections to make attaching and removing spectra line easier (change the carriage without cutting the spectra line!). Work in progress.