check out our work on making a heated build platform for MakerBot. The primary goal was to make it as light as possible since the stage is actively moving, so that means just some nichrome, a thermistor, and some silicone as a carrier. The silicone is also an insulator (very important!!) so no kapton tape is needed and we can see clearly what’s going on inside because the silicone is also clear. we currently use a reprap motherboard and extruder to drive the heat, looking at simpler electronic design soon (but this setup has the excellent PID in the extruder firmware 1.6!).