Changing Filament After Runout

I have a new Taz Pro and it’s working fairly well. However, estimating the amount of filament left on a spool to permit a print to go without running out of filament is a rather daunting exercise. Since the Pro has a runout sensor for both print nozzles on the Titan, is it possible to put in new filament of the same manufacturer and type and resume printing where it stopped? Is there a way to pause the printing and do this sort of swapping in new filament?

I’ll look at mine when I get a moment (probably not until this weekend). As I recall the filament run-out sensors can be placed in a disabled state (via the control panel) where they wont auto-trigger a filament change.

Normally a filament sensor will trigger a filament change (in g-code it triggers an M600 command). What M600 does is implemented in firmware. Typically it raises the print-head off the part, moves to a safe place, and waits for you to unload old filament and load new filament.

I recommend before just waiting for this to happen… deliberately trigger it to test how it works. Print a test part … then snip the filament just as it goes into the filament sensor … wait for it to run out and watch what it does.

M600 is a command which is sometimes used deliberately to change filament colors (when changing colors at a specific layer of your print for a multi-color part).

I think @altertalk is asking if you can load both nozzles with the same filament and have the Taz Pro automagically switch from one nozzle to the next when the filament runs out. I believe the answer to this question is no.

This would have to be a firmware assisted function because the slicer has generated the gcode based on the nozzle offset. It is possible to move that offset to the firmware with M218 but that still leaves the command to switch extruders (T0 / T1) and copying the E value between extruders.

As @TheVirtualTim pointed out, the runout sensor triggers an M600 command. Nothing in that command description allows for nozzle switching.

Yup, I do that all the time. It will make a sound and you walk over and hit the change filament menu item, it backs off the print and you replace the one that went out. It will then go back to printing. Be advised though its not perfect. You would do better to wait until its close and printing infill and hit the change filament there. If it runs out on a outer wall you can get a defect in the print.


@subnoize your suggestion worked! I let the printer run until the runout sensor identified a filament error. The printer went into a hold/pause state. I went through the LCD screen to change out the filament, swapped it quickly, and resumed printing. I did see that the printer was extremely slow at first when it resumed printing; not sure why that happens. Eventually, the printer picked up to its original speed and finished the part. I was fortunate enough to get the print to need new filament in the middle, where the hatching was occurring. In general, I really didn’t see that much of a difference. It will be interesting to see if the paused state of my Mini will enable me to do this as well. If it does, I can run out the filament until I get to a few centimeters instead of the .3m I have with the Pro. Thank you!

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Yay! Saves a great deal of money not wasting the ends of the spools. Oh! And you can tune the run-out to waste very little of the filament. Just figure the distance between the run out sensor and the print head and enter that value in the run out sensor menu. Be advised to leave enough to grab with a pair of pliers in case something goes wrong and it has trouble backing out the last bit.

@subnoize, I didn’t know you could set that distance for the runout sensor. As it is, I still have a small coil of PLA.

Yep, in the menu you can set how many mm before the sensor triggers. This is how many mm the extruder has pulled where the sensor hasn’t detected any movement. If you give it like 25.4 x 5 inches then it will pull for a bit before it gives up and will waste less filament. I would tell you the menu and how to get there but my Taz Pro is disassemble to try and resolve an issue. I think you can find it though. Just look for run out sensor and the setting is in mm.