As I had difficulties getting the supplied IR sensor to function properly I made this modification to the design by iamburny I've made a small alteration to the one-piece fan/heatsink duct, allowing swapping the IR sensor with a microswitch. And it WORKS - I've printed the last 10 prints or so without any problems. When homing z this mod drives the nozzle into the bed until the duct pivots and activates the ms. Homing the x axis takes advantage of the bulb present on the acryllic xrib. Cudos also has to go to KimBrown (father of bigblue http://www.thingiverse.com/thing:448906) for giving the inspiration to use a ms.This mod requires a bit of changes. First off the ms needs to be wired into the duet as seen on the wiring diagram. Secondly the homing gcodes has to be changed (found last in this note). This can surely be done smarter than what I've come up with, as the x is homing it rams the hotend into the far end of the x axis if the starting point isn't relativly close to x = 0. Dosen't harm anything - just isn't smooth. homez: M109 S195; Set Extruder temp to 195. Avoiding frozen platic to get in the way. G90 G1 X30 Y30 F1500 G1 Z-220 F200 S1 G1 Z2 F50 G1 Z-220 F5 S1 G92 Z-1.6 ; Has to be changed to match the nozzle height relative to the activation of the ms G1 Z0 G90 homex: G91 G1 Z5 F200 G90 G1 X80 F2000 G1 X-240 F2000 S1 G92 X6 G1 X3 F200 G1 X-30 S1 G92 X-13.8; set relative to the activation of the ms G91 G1 Z-5 F200 G90