Hi, I am very new at 3D printing and have the same issue: I am building a dual extruder printer using solenoid valves and RAMPS 1.4. I tried to change the Marlin code so that it would stop extruding when changing extruder or when no E was present in the gcode line (or E=0) but seem to have failed. I am now trying to make a program taking the g-code from Slic3r as an inout and going through the cby gogo2 - RAMPS Electronics