When the end near the hotend is discoloured, deformed or burnt, when there is a gap where it meets the nozzle, or when feeding feels rough. Tubes in the hot zone degrade with heat, and a damaged end causes clogs and stringing; cut the new tube squarely and seat it as the maker describes.
PTFE tubing guides filament smoothly, and the part near the heat wears out.
Where PTFE tubes sit in a printer
Bowden tubes run from the extruder to the hotend. Liners inside some hotends reach into the heat break. Tubes in or near the hot zone degrade over time.
Signs a PTFE tube is worn
Brown or black discolouration at the hot end. Deformed or narrowed tube ends. Gaps between tube and nozzle. Rough feeding or clicking on retraction. Recurring clogs at the same point.
Replacing a PTFE tube
Follow the printer maker’s procedure, with the hotend at the temperature it describes. Cut squarely with a tube cutter. Seat the tube firmly against the nozzle or heat break. Check the couplings that hold it, which also wear.
Heat limits of PTFE
PTFE tubing has temperature limits its makers publish. Printing high-temperature materials in a hotend with a PTFE liner shortens its life, which is one reason all-metal hotends exist.
Questions makers ask before buying
Why does the tube end need a square cut?
An angled cut leaves a gap against the nozzle where molten plastic collects and causes clogs. PTFE tube cutters make square cuts easily.
Does every printer have a PTFE tube?
Bowden printers use one between extruder and hotend, and many hotends have a short liner. All-metal hotends have none in the hot zone, as their makers state.
Last reviewed 15 September 2026