I just got my K40 setup and successfully created a couple of smaller engravings. I uploaded a larger one and started the raster engrave and stepped out of the garage for a couple of minutes.
Sadly, when I returned I noticed a fire in the box so shut everything down. Apparently, the belt on the Y (left to right) arm of the gantry fell off and the laser was focussed on a single point for an extended period of time. I also noted that my power was jumping between 10 -15 even though it was set for 5.
I managed to get the belt reattached and replaced the parts that melted (thank goodness for 3D printers) but I now have the problem of the laser not homing properly. The bar moves to the upper end but the laser is not moving to the upper left corner AND my laptop no longer recognizes the engraver. Any ideas/suggestions?