Extruder nozzle keeps jamming and stops midway thru a print from SD

My technology teacher has a Lulzbot Taz 6 3D printer that has some issues.

First of all, the filament sometimes jams in the extruder nozzle and therefore preventing the 3D printer to print anything. I have tried heating the nozzle to around 220 degrees celsius (almost overheating the filament) yet the nozzle still jams for some reason.

Second of all when printing a .gcode file from an SD card the printer stops mid print for no apparent reason, but when printing from a Mac mini it prints just fine. I have no idea why it does this.

Ideas?