I recently bought one of these large, fast, printers but have a problem getting it to print.

After levelling the bed, heating hotend and bed, loading filament and a GCODE file, the machine "homes" and centres but before starting to extrude the bed drops by about 35 - 30mm and I end up with "spaghetti" on the bed rather than a print.

Can anyone offer a reason or better still, a solution ???