Changing filament mid print

Do I use one of these to stop/pause the print automatically so I can change filament?


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I personally used PauseAtZ in an attempt to pause my print at some arbitrary point. Upon selecting this script, it presents you with a dialog and I blissfully accepted the defaults which was a total mistake. It paused the print and then when I resumed it just ran the hotend through the top layers of my part, ruining it. Had to abort and lost the part.

Here is the thread in which I talk about the result. See "So well before the..."

I'm not sure what I'd suggest for automated pause-at-z which is bulletproof.

I do know that the native OctoPrint -> Settings -> GCODE scripts -> at beginning of pause

...does several things that seem to work well in conjunction with then restarting the job. The next time I intend to pause a job like this automatically, it will be because I've manually edited the GCODE file and inserted code inline at the right time.

 

If you're running the latest Marlin firmware, and you have an LCD controller, there is a "Change Filament" command under "prepare" if you're not printing yet, or "control" if you are. The machine homes X and Y at 0,0, retracts all the filament, and waits for you. It keeps the Z height it was last at, then continues back to its last location and resumes the print from there.

 

Cura has its post-processing scripts and OctoPrint has its pause plugin(s). If you use them, you should probably exercise them on a test part and the sooner (low Z), the better. I tend to favor the Cura approach because then I can review the GCODE before/after the addition to see what's different.

1. Slice with Cura without the pause post-processing script -> Before.gcode
2. Slice again with Cura with the post-processing script -> After.gcode
3. Bring both files into a program like WinDiff

I'll try to do this later when I'm at home.

With the OctoPrint version, the changes just happen in a black box. Who knows what they did?

 

On a somewhat-related note, I'm almost done with the version of the double filament run-out replacement for the C2 (which uses levered micro-switches). I also bought two opto switches but the interesting question would be from where to power those.

 

It's been fussy so far, maybe v3 now on the plastic design. I've dialed things in well over the iterations and making sure that this is easy without things like "now grab a drill and auger out that little corner..." and such.

And I'll later be further modding this so that my second bower motor will be mounted there as part of that mechanism. (You'll like it.)

 

Back to the original topic... I'm reading about Action Commands and it looks like you could:

1. Search your GCODE file for the appropriate layer
2. Insert a "M118 //action:pause" command on a line by itself
3. In OctoPrint, make sure that Actions Commands are installed as a plugin, noting that PAUSE is auto-defined
4. Send that to print

At Z=something, it should do the standard pause routine, as if you'd pressed the button on the LCD.

If this works, you could use the TweakAtZ in combination to add that M118 command as above if you didn't want to edit the file manually.

Hopefully this is in our version of the OctoPrint.

 

I wrote up a complete step-by-step process for the C2, with screen shots, so that no manual gcode changes are necessary. Works perfectly - just set each height of each color change. Process cleans out the old color so each layer is cleanly one color.

https://faqware.com/3d/robo-c2-multi-color.php