# Printer with two extruders but one as a backup

I'm trying to make a printer that will have a second extruder as backup for when the primary one clogs or runs out of filament. It is an ongoing project I'm doing to make a 3D printer as reliable as possible. How could you implement this.

• This question should be reworded to clearly ask specific points, opinions are not allowed on this site, see help section.
– FarO
Oct 21, 2020 at 8:32
• @FarO Indeed, I initially overlooked the part in the body, I've reworded the body as the question (use of a spare tool) has value to retain for the future.
– 0scar
Oct 21, 2020 at 12:30

You could use a "filament runout sensor" and combine it with a "filament running sensor". If either fails the controller needs to be notified by a signal. If you configure the Configuration.h filament runout setup such that it doesn't call M600 but instead a series of codes to park tool 0, activate tool 1, home tool 1, prime tool 1, and commence printing, you are near a solution.