G28 Z F750; Home Z
G28 Y F750; Home Y
G28 X F750; Home X
G29 S1
G92 E0 ; zero the extruded length
G1 X50 Y0 F750 ; go to the middle of the front
G1 Z0.1 ; close to the bed
M190 S[first_layer_bed_temperature] ; wait for bed temp
M109 S[first_layer_temperature] ; wait for extruder temp
G1 X100 E10 F200 ; make a thick line to prime extruder
G92 E0 ; zero the extruded length
G1 Z0.3 ; lift Z
G4 S2   ;wait 2 sec to bleed off excess pressure