Cura 4.8 - how do I stop preheating?

[war4peace 1]

Here's the problem I am facing:
Every time I start a print using Cura sliced g-code, the bed preheats and then the nozzle preheats before the pre-print code is run.
My pre-print GCode does a full bed mesh checking using G29 (25 points), then homes once more, then prepares the actual print with a priming line etc.

During all this time, the nozzle is preheated by Cura and oozes filament pretty much everywhere.

I have found a setting called "Initial Printing Temperature" which I assume controls the initial temperature of the nozzle before the G-Code is being processed. Am I correct in my assumption? For example, if I set it to 100 degrees Celsius, would it mean that there's no more oozing and fully heated nozzle while pre-print GCode is being processed?

Thank you for your answers!

[tricky2k 3]

For a bed mesh check you want the bed and nozzle hot, otherwise it's pretty much useless since it won't count for heat expansion. When the nozzle is heating up, retract the filament a few milimeters by hand, that should do to stop oozing

Edited November 13, 2020 by tricky2k

[war4peace 1]

Actually the nozzle being hot or not won't matter at all, the expansion is very small. Furthermore, you only have to do it once.
Mesh bed leveling helps in case the bed moves a tiny bit because of the springs and there is no need for nozzle to be hot at the time. The bed, yes, but not the nozzle.

Other slicers don't preheat the nozzle if I tell them not to. Cura seems to add the M109 command before even processing the pre-print G-Code. So far I have resorted to editing the GCode every time and removing the offending part, but I want to find out whether that can be done through the slicer rather than manually.

 

This is the part I am talking about:

 

;Generated with Cura_SteamEngine 4.8.0
M140 S85
M105
M190 S85
M104 S230
M105
M109 S230

 

 

[tricky2k 3]

That was the other thing I was going to tell you, to edit the gcode, but yes, it's annoying and not for noobs. Can M109 be modified in the Start GCODE in machine settings?

Edited November 13, 2020 by tricky2k

[war4peace 1]

Well that's the issue, the preheat GCode is inserted by Cura before the "Start G-Code" entries in Machine Settings.
One thing I have done is dialing back the temperature to undo Cura's preheating, but there is still a little bit of filament buildup in the nozzle.

 

Here's my Start G-Code:

 

M201 X500.00 Y500.00 Z100.00 E5000.00 ;Setup machine max acceleration
M203 X500.00 Y500.00 Z10.00 E50.00 ;Setup machine max feedrate
M204 P500.00 R1000.00 T500.00 ;Setup Print/Retract/Travel acceleration
M205 J0.01 ;Setup Jerk
M220 S100 ;Reset Feedrate
M221 S100 ;Reset Flowrate
M104 S120 ;Set temperature back to 120 degrees to mitigate Cura preheating
G28 ;Home First
G29 ;Create New Mesh
M104 S{print_temperature}
G28 ;Home
M420 S1 Z2 ;Enable ABL using saved Mesh and Fade Height

G92 E0 ;Reset Extruder
G1 Z2.0 F3000 ;Move Z Axis up
G1 X10.1 Y20 Z0.28 F5000.0 ;Move to start position
M109 S{print_temperature}
G1 X10.1 Y200.0 Z0.2 F1500.0 E15 ;Draw the first line
G1 X12.4 Y200.0 Z0.2 F5000.0 ;Move to side a little
G1 X12.4 Y20 Z0.2 F3000.0 E30 ;Draw the second line faster
G10 ; Retract
G1 X14.4 Y20 Z0.2 F5000.0 ; Move a little bit more to mitigate stringing
G1 Z2.0 F3000 ;Move Z Axis up
G1 X14.4 Y200 Z2.0 F5000.0 ; Move a little bit more to mitigate stringing
G11; Unretract
G92 E0 ;Reset Extruder

 

[ahoeben 1,948]

  

3 hours ago, war4peace said:

M109 S{print_temperature}

This is the wrong replacement pattern. Use this and Cura will not have to prepend its own preheat sequence for your extruder:

 

M109 S{material_print_temperature}

Similarly, include this to stop Cura from having to preheat the bed for you:

 

 

M190 S{material_bed_temperature}

[war4peace 1]

2 hours ago, ahoeben said:

  

This is the wrong replacement pattern. Use this and Cura will not have to prepend its own preheat sequence for your extruder:

 

M109 S{material_print_temperature}

Similarly, include this to stop Cura from having to preheat the bed for you:

 

 

M190 S{material_bed_temperature}

Thank you, that did the trick. Turns out I had the wrong variable. All good now, thanks again for fixing this!