Hi reprap community - thanks for putting together such an excellent resource in this forum. I've been working on a plastic / filament extruder build for the past few months to do large scale robotic 3d printing and have come up against an issue with uneven heating of the extruder's barrel. We are using a couple of cheap REX C100 PIDs with K type thermocouples to control 75mm band heaters. We'vby gstrooder - Plastic Extruder Working Group