G91               ; relative positioning
G1 H2 Z5 F6000    ; lift Z relative to current position
G1 H1 U275 F1800 ; move quickly to X axis endstop and stop there (first pass)
G1 U-5 F6000       ; go back a few mm
G1 H1 U275 F360  ; move slowly to X axis endstop once more (second pass)
G1 H2 Z-5 F6000   ; lower Z again
G90