Why does Prusaslicer set the final temperature in two steps?

Question

I'm using PrusaSlicer 2.5.0 and printing the sliced G-code on a Creality CR-6 SE via a USB-connected OctoPrint/OctoPi. As you can see, the slicer sets the temperature by G-code commands in two steps (final temperature is 205 °C). This seems strange to me, as the printer can go directly to the final temperature. Also, this screenshot shows the case where I'm switching filament, therefore I have to heat up the extruder and when I start printing, the hotend cools for some time, because the target temperature is way lower set by PrusaSlicer.

Is there a setting for configuring this in PrusaSlicer? These are the first few lines in the G-code file:

; generated by PrusaSlicer 2.5.0+win64 on 2023-01-18 at 12:15:56 UTC
;
; external perimeters extrusion width = 0.42mm
; perimeters extrusion width = 0.44mm
; infill extrusion width = 0.44mm
; solid infill extrusion width = 0.44mm
; top infill extrusion width = 0.40mm
; support material extrusion width = 0.36mm
; first layer extrusion width = 0.42mm
M201 X500 Y500 Z100 E5000 ; sets maximum accelerations, mm/sec^2
M203 X500 Y500 Z10 E60 ; sets maximum feedrates, mm / sec
M204 P500 R1000 T500 ; sets acceleration (P, T) and retract acceleration (R), mm/sec^2
M205 X8.00 Y8.00 Z0.40 E5.00 ; sets the jerk limits, mm/sec
M205 S0 T0 ; sets the minimum extruding and travel feed rate, mm/sec
M107
;TYPE:Custom
G90 ; use absolute coordinates
M83 ; extruder relative mode
M109 S180 ; set temporary nozzle temp to prevent oozing during homing
M190 S70 ; wait for bed temp to stabilize
M140 S70 ; set final bed temp
G28 ; home all axis
G1 Z50 F240
G1 X2.0 Y10 F3000
M104 S230 ; set final nozzle temp
M109 S230 ; wait for nozzle temp to stabilize
G1 Z0.28 F240
G92 E0
G1 X2.0 Y140 E10 F1500 ; prime the nozzle
G1 X2.3 Y140 F5000
G92 E0
G1 X2.3 Y10 E10 F1200 ; prime the nozzle
G92 E0
G21 ; set units to millimeters
G90 ; use absolute coordinates
M83 ; use relative distances for extrusion
; Filament gcode

score 7 · Accepted Answer · edited Jan 18 '23 at 14:24

Since the bed usually takes longer to heat than the nozzle, the nozzle is in a pre-warmup stage so that it doesn't ooze filament waiting for the bed while homing and/or finding the Z limit.

Once the bed is warmed up and the Z limit is reached the nozzle heats up to the final temperature and the print starts.

If you go to the Printer Settings tab of Prusaslicer and click on Custom G-Code, you'll see the initial temp in the Start G-Code section. Mine even says:

M104 S150 ; set temporary nozzle temp to prevent oozing during homing

A temperature of 150 °C is low enough that the filament doesn't melt but close enough to the final temperature so that you're not waiting for a full heat cycle.

Why does Prusaslicer set the final temperature in two steps?

1 Answers1