Simultaneous heating of extruder and bed at start of print

  • I notice that if I print from Cura without preheating the printer, it will first raise the bed temperature and then raise the extruder temperature. The G-code it generates is:

    M140 S55     ; set bed temperature to 55 C
    M105 ; report temperatures
    M190 S55 ; wait for bed temperature to reach 55 C
    M104 S210 ; set hot end temperature to 210 C
    M105 ; report temperatures
    M109 S210 ; wait for hot end temperature to reach 210 C

    The "Preheat" feature of Cura presumably send the "set temperature" commands without the corresponding "wait" command.

    Wouldn't it be more efficient to do something like this:

    M104 S210    ; set hot end temperature to 210 C
    M140 S55 ; set bed temperature to 55 C
    M105 ; report temperatures
    M109 S210 ; wait for hot end temperature to reach 210 C
    M105 ; report temperatures
    M190 S55 ; wait for bed temperature to reach 55 C

    Then the bed and extruder heat up simultaneously, and we wait for the higher temperature one first assuming that the other will reach its target temperature in the meanwhile.

    If this is sound, is there a way to set this in Cura, or would I need to submit a patch?

    No patch needed, just add it into your start G-code, works fine. I've been using it for a while using place holders in Cura. I'll post an answer when I'm behind my desktop computer. Note that Slic3r allows arithmetic on place holders, that is even more powerful. I allow my bed to heat up to 75 % and then start heating the hotend while the bed continues to 100 %; this results in bed and hotend to reach their final temperature at the same time.

    The bed is usually much slower, its temperature sensing less accurate and has no adverse effects if it stays at the target temperature for a while, while the hot end warms up quickly and will start leaking plastic as soon as it is warm. Sequencing the warmup phase allows the bed temperature to stabilize, and allows printing to start immediately.

    FWIW in my experience (Ender 3 with PLA, TPU, and PETG) both take roughly the same amount of time. With PETG the extreme bed temp can make bed take slightly longer. This might indicate I should tune PID for hotend better, as the last 10 degrees of hotend heating take inordinately long.

    I agree with Simon Richter. The time adds only a few minutes to the total that is usually hours. It prevents the hotend from oozing and also heating up the material for too long, which can start clogging. The bed temperature and enclosure temperature stabilize and also the printer power supply is less stressed.

  • 0scar

    0scar Correct answer

    2 years ago

    This can be achieved with start G-code adaptations, this requires no software changes. Cura, and most slicers, have the ability to use placeholders (basically variables or maybe better: constants). These placeholders are substituted with the correct value upon slicing.

    To sequentially heat the bed and hotend you would need to add the following into your start G-code:

    M117 Heating bed 1st...
    M190 S{material_bed_temperature_layer_0}
    M117 Heating core 1st...
    M109 S{material_print_temperature_layer_0}

    For simultaneous heating you need to add:

    M140 S{material_bed_temperature_layer_0}     ; set bed temperature to e.g. 55 °C and continue
    M104 S{material_print_temperature_layer_0} ; set hot end temperature to e.g. 210 °C and continue
    M190 S{material_bed_temperature_layer_0} ; wait for bed temperature to reach e.g. 55 °C
    M109 S{material_print_temperature_layer_0} ; wait for hot end temperature to reach e.g. 210 °C

    Note that Cura is very limited in using placeholders. E.g. Slic3r allows for arithmetic using the placeholders. The following example shows heating the bed first to the bed first layer temperature minus 10 degrees Celsius; then the hotend starts heating and heatbed starts further heating up to the final temperature. For my machine this results in the bed and hotend being at final temperature at the same time; so no time is wasted and printing can start.

    M117 Heating bed...
    M190 S{[first_layer_bed_temperature]-10}
    M140 S[first_layer_bed_temperature]
    M117 Heating core...
    M109 S[first_layer_temperature_0]
    M190 S[first_layer_bed_temperature]

    Yes, I'd forgotten this is an option too and probably a better one for folks using Cura through the GUI since it doesn't require rebuilding anything from source.

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Content dated before 7/24/2021 11:53 AM