I finally got around to adding under bed insulation to my Robo. I’ve also added a purpose built Solid State Relay to avoid over heating of the RAMPS polyfuse and the mosfet. In my case the bed is the kickstarter 3mm thick borosilicate. Before the under bed insulation and SSR were added the heated bed was taking more than 10 minutes to get to 115C and struggling to hold temperature. To verify this @Galaxius has done a test on a unmodded Robo which shows it took 14 minutes to reach 115C and needed full power to hold temperature. The next screenshot shows that after the mod the bed temp profile from ambient (23c) to 115c is 6 minutes. Power to hold the bed at 115c is reduced to approximately 60 - 65%. TBH I was surprised by the dramatic improvement. The insulation material I used is a type of reflective foil used widely in the building industry (in Australia anyway). Brand names in Australia are Sisalation, HardieWrap and WallWrap. The foil is thin (less than 1 mm) but very tough and is attached underneath the bed foil side up using kapton tape. The reflective surface improves thermal performance without the need for any kind of bulk insulation (eg such as cork) which would interfere with the Y belt. The foil also has a high fire rating (ie low flamability) To get this better performance I also had to recalibrate the Marlin heated bed PID values in configuration.h. With the old PID values for the bed, the firmware paused the faster temperature rise way too early. To update the bed PID, make sure #define PIDTEMPBED is uncommented in configuration.h and use gcode M303 to run bed PID tuning and display the new heated bed PID values Kp, Ki and Kd. Update these values #define DEFAULT_bedKp ? #define DEFAULT_bedKi ? #define DEFAULT_bedKd ? in configuration.h, recompile and reflash the firmware. I’m very interested to hear any feedback from anyone using similar foil insulation.