Feature request: M302 support

Features
1

Hi. I think it’ll be useful to have M302: Allow cold extrudes support. It will be used for filament load and unload to not need to preheat the filament, but still watching for too low temperature during normal printing.

2

Rn you could just set the min extrude temp to something like 10°, restart, do whatever you need and then set it back to your original temp

3

Setting the minimum extrude temp during print is impossible, but that will help these load / unload macros

4

I have implemented M302 in my fork of klipper.
You can check it out at: https://github.com/Zeanon/klipper/tree/m302_final
Please tell me if there are any bugs since I copied it from my heavily modified version of klipper and I’m not sure whether I forgot something

1 Like
5

Hi. Thanks for your time designing it! I’ll try it after this weekend and tell you about it

6

No Problem, let me know how it goes or if there are any bugs.
I also added a doc, would be cool if you could tell me if it was understandable(I’m not really good at writing doc XD)

7

Hi. I found the first issue - it works for negative extrusion, but not positive:
image

[gcode_macro UNLOAD_FILAMENT]
gcode:
    # G1 E-738 F3600
    COLD_EXTRUDE HEATER=extruder ENABLE=1
    G1 E-620 F3600
    COLD_EXTRUDE HEATER=extruder ENABLE=0


[gcode_macro LOAD_FILAMENT]
gcode:
    # G1 E738 F2400
    COLD_EXTRUDE HEATER=extruder ENABLE=1
    M118 cold extrusion enabled
    G1 E600 F3600
    COLD_EXTRUDE HEATER=extruder ENABLE=0

If it’s intended however, I think it should work the same with extrusions as well as retractions, because M302’s purpose is to load and unload filament (both directions)

8

I fixed it, I forgot a return when cleaning up the code, just get the newest version(but from this branch: https://github.com/Zeanon/klipper/tree/m302_final [I created another branch to do a proper PR])

9

ok, it’s fixed :). I’ll test it over the week and see if it causes any other issues, thanks :smiley:

10

Hi. I spotted that the same issue happens from time to time. I pressed on the LOAD_FILAMENT macro, first time it told that extruder is too cold, second time worked. Maybe there’s some issue with the M302 implementation?

11

The only explanation I have is that it needs a small amount of time to register.
Klipper has an internal variable called can_extrude which gets updated every time the temperature_callback function of a heater is called.
What I essentially did was update that from self.can_extrude = self.smoothed_temp >= self.min_extrude_temp to self.can_extrude = (self.smoothed_temp >= self.min_extrude_temp or self.cold_extrude)
(which is the most sensible way imo as it does not break any safeguards and is the least invasive way to do it)
so of course as long as temperature_callback is not called, the can_extrude variable will still be false.

EDIT: everything I wrote before is not important, I am still going to leave it there for anyone wondering what I did, but I just realized, I can just update can_extrude when setting cold_extrude…
Don’t mind me, I was dumb

2 Likes
12

Please, I have the same problem with chocolate printing so I need temperature 36 degree on nozzle. I try M302 gcode not work(( Can you help? What need to change ?

13

M302 is not implemented in Klipper, I opened a PR for it but it was dismissed
You can use force move though
Or manually add the code from my PR: