preparation pre-processor adds bad code

[mrvn]

The preparation pre-processor turns on the heater and runs G28, which makes the head end up in the center of the build platform 5mm over it. Due to the heating some filamanet will (should) come out. It then lowers the head down to the bed, depositing and squishing the extruded filament right in the center of the build platform, where naturally your object would be.

Please move the printer head into a corner for heating and maybe move the head from left to right while lowering so the filament blob is deposited out of the way and not squished between the nozzel and bed.