Heating extruder and bed at the same time
This is a part of the start Gcode in my Prusaslicer. It heats the bed and when the bed is up to temp it heats the hot end. My printer PSU is capable of heating both bed and hot end at the same time. If I swap lines 2 and 3 will it heat both at once please?
M140 S[first_layer_bed_temperature] ; set bed temp
M190 S[first_layer_bed_temperature] ; wait for bed temp
M104 S[first_layer_temperature] ; set extruder temp
M109 S[first_layer_temperature] ; wait for extruder temp
RE: Heating extruder and bed at the same time
yes it will. However it usually takes much longer for a bed to heat up than the extruder so your extruder will sit there at its full temp while waiting for the bed to heat, that will cause it to ooze out and drip which can potentially mess up your printing later.
You could do a 2 step routine, set bed temperature and then set the extruder to 160-170. Thats a reasonable no ooze temp. Then you could wait for the bed to get to temp and then set the extruder to full temp and wait for it.
Thats similar to what some of us do to preheat for mesh leveling, we heat the bed, and extruder to an intermediate temp. Wait for the temps to equalize and give everything time to warm up fully. Then do mesh leveling with everything warmed up. Finally everything is set to printing temps