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ChrisPrefect

Start heating bed and extruder and level bed at the same time

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Posted (edited) · Start heating bed and extruder and level bed at the same time

Hi!

 

I tried to add some gcode to the start gcode section in cura, but apparently that code only gets executed well after the bed and the extruder has reached it's temperatures.

I want to start heating the bed and the extruder at the same time, without waiting for one to reach it's temperature. There is enough power in the power supply to do so. And I want to simultaneously start leveling the bed with the BLTouch sensor.

 

These three gcodes can run at the same time. Why can't I set that in the start gcode section?

 

Thanks!

Edited by ChrisPrefect

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Posted · Start heating bed and extruder and level bed at the same time

I have noticed the same problem. I thought it was made this way due to the fact that it takes much more time to heat the bed than the extruder and if started at one time the nozzle will stand hot and ooze.

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Posted · Start heating bed and extruder and level bed at the same time

For an Ultimaker? There is just enough power to do so, but due to tolerances, it can happen that there is not enough power available (thus causing a shutdown). There is of course also the issue of oozing, but this can be fixed with a prime pruge.

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Posted · Start heating bed and extruder and level bed at the same time

It's for an Ender 3 with 24V power supply. There is more than enough power. I frequently manually heat up the bed and nozzle at the same time.

Ideally the nozzle and bed would heat up at the same time and as soon as the nozzle reaches 185 degrees it would retract 20mm. And the Bed-Leveling would start immediately while heating the bed and nozzle.

How can I set this up? Why does Cura execute "hidden" gcode before the manually entered gcode in the start section? Can I override this in a settings file from Cura or something?

Thanks!

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Posted · Start heating bed and extruder and level bed at the same time

CuraEngine adds its "hidden" gcode (as you call it) heating up your bed and nozzle because Cura does not see you adding your own.

 

As soon as you add the string "{material_print_temperature}" somewhere in your start gcode, Cura will know it does not have to add it by itself. Same with "{material_bed_temperature}".

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Posted · Start heating bed and extruder and level bed at the same time

OK nice! I tried it with this start gcode but it does not work. Cura first heats the bed, then the nozzle and then executes this code, overwriting the temperatures set in the slicer settings. It should be the other way around. Cura should set the temperatures from the slicer settings after the start gcode was executed.

M140 S60 ; start heating the bed to 60 degrees Celsius
M104 S200 T0 ; start heating T0 to 200 degrees Celsius

M280 P0 S160 ; BLTouch alarm release

G4 P100 ; delay for BLTouch
G28 ; home
G29 ; auto bed leveling


Does Cura only look for the code M109 or should M104 also work?

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Posted · Start heating bed and extruder and level bed at the same time

Cura looks for neither M109 or M104, it looks for the text {material_print_temperature} (including curly braces)

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Posted (edited) · Start heating bed and extruder and level bed at the same time

Oh now I get it.

OK but even if I add "{material_print_temperature}", will cura still set the temperatures for the initial layer and the following layers etc?

So this should be in my start gcode section:

 

{material_print_temperature}
{material_bed_temperature}

M140 S60 ; start heating the bed to 60 degrees Celsius
M104 S200 T0 ; start heating T0 to 200 degrees Celsius

M280 P0 S160 ; BLTouch alarm release

G4 P100 ; delay for BLTouch
G28 ; home
G29 ; auto bed leveling

And then Cura continues to heat to the set temperatures in the slicer, for example 215 degrees?

Edited by ChrisPrefect

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Posted · Start heating bed and extruder and level bed at the same time
6 minutes ago, ChrisPrefect said:

Oh now I get it.

No, not quite.

 

M280 P0 S160 ; BLTouch alarm release

G4 P100 ; delay for BLTouch
G28 ; home
G29 ; auto bed leveling

M140 S{material_bed_temperature} ; start heating the bed to what is set in Cura
M104 S{material_print_temperature} T0 ; start heating T0 to what is set in Cura

Feel free to change the order, but the idea is that the {material_bed_temperature} (as is, including curly brackets) gets replaced by Cura.

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Posted · Start heating bed and extruder and level bed at the same time

Ah! Those are variables! OK makes much more sense! Then the exact required temperatures are set automatically.

OK I will have to add "M109 S{material_print_temperature}"  at the end so the printer waits to actually reach the temperature if it takes longer than the bed leveling requires.

I will try. Thanks a lot!

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Posted · Start heating bed and extruder and level bed at the same time

It works perfectly! Thanks a lot! 😄

 

The printer used 249 Watts while heating the bed, nozzle and doing the bed leveling at the same time.

 

Bed leveling with the BLTouch and 9 points is finished before the nozzle has heated up completely, so I don't loose any time for bed leveling anymore.

 

This is my whole start gcode for reference:


M140 S{material_bed_temperature} ; start preheating the bed WITHOUT wait to what is set in Cura
M104 S{material_print_temperature} T0 ; start preheating hotend WITHOUT wait to what is set in Cura

M280 P0 S160 ; BLTouch alarm release
G4 P100 ; delay for BLTouch
G28 ; home
G29 ; auto bed leveling

M190 S{material_bed_temperature} ; start heating the bed to what is set in Cura and WAIT
M109 S{material_print_temperature} T0 ; start heating hotend to what is set in Cura and WAIT

G92 E0 ; Reset Extruder
; M92 E97 ; esteps hard set
G1 Z2.0 F3000 ; Move Z Axis up little to prevent scratching of Heat Bed
G1 X0.1 Y20 Z0.3 F5000.0 ; Move to start position
G1 X0.1 Y200.0 Z0.3 F1500.0 E15 ; Draw the first line
G1 X0.4 Y200.0 Z0.3 F5000.0 ; Move to side a little
G1 X0.4 Y20 Z0.3 F1500.0 E30 ; Draw the second line
G92 E0 ; Reset Extruder
G1 E-2 F1800 ;retract 2mm at 30mm/s
G1 Z2.0 F3000 ; Move Z Axis up little to prevent scratching of Heat Bed
G1 E1.8 F1800 ;retract 2mm at 30mm/s

 

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Posted · Start heating bed and extruder and level bed at the same time

Let me just give you one last reason not to do leveling and heating things up at the same time. Things expand when they get hotter. Not by an enormous lot, but they expand anyway. The nozzle will likely be slightly taller when hot, and your bed will probably warp ever so slightly differently when it is hot compared to when it is cold. If the top-left of your leveling procedure is done with a cold extruder and bed, and the bottom-right with a hot extruder, your leveling data will be skewed.

 

The distortion may be smaller than the precision of your printer, or the convenience of a faster print start may outweigh the imprecision. This is up to you to decide.

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Posted (edited) · Start heating bed and extruder and level bed at the same time

I did some tests with bed leveling before, during and after I heated the bed and nozzle and the differences where inside the margin of error that the bltouch produces even when I do two measurements right after each other when the bed is cold.

I have a glass bed, I think the thermal expansion coefficient of glass is fairly small.

I did a calculation: A glass bed of 5mm thickness would expand to 5.0012mm when heated from 20C to 60C 😎

Edited by ChrisPrefect
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Posted · Start heating bed and extruder and level bed at the same time

I would not worry about the thickness of the glass, but warping of the glass and the (alu) part that holds the glass. But since you tested and meassured, I guess you know what works for your printer.

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