Practical Project Guide

A thin cleaning pin held up beside a Bambu P1S, with a stretched strand of molten plastic hanging from its tip.
The top-side probe came out like this: the pin coated in molten PCTG, trailing a thin strand. It didn’t clear the clog, but it told me what was in there.

Partway through a six-hour PLA print, the nozzle on my Bambu P1S clogged.

It was the first print-halting clog in about a year of heavy use, with PLA, PETG, PCTG and PA-CF all going through the same 0.4 mm hardened-steel nozzle. I did have a spare complete nozzle and hotend assembly on the shelf, so swapping it would have been the easy answer. I wanted to see if I could get the one I already had working again.

I could. This is what I did, in the order I did it. It’s one recovery, not a procedure, and I’ll be clear below about the parts that were specific to my situation.

At a glance

PrinterBambu Lab P1S
Nozzle0.4 mm hardened steel (recovered, not replaced)
ProblemClog during a six-hour PLA print, right after a PCTG print
OutcomeNozzle back in service, several good prints since
Root causeNever confirmed

What Bambu says first

Bambu publishes an official nozzle-clog troubleshooting guide that walks through thermal extrusion, the unclogging pin that ships with the printer, and heavier fallbacks. They also publish a cold-pull procedure for the P1S: heat to 230°C, cool to 70°C, then pull the filament out by hand. They recommend cold pulls as routine maintenance, especially when you switch filament types.

I didn’t do a cold pull this time. Start with Bambu’s instructions for your printer; what follows is only what happened on mine.

What I did

1. Bottom pin at 270°C. The nozzle had just run PCTG, so I suspected leftover PCTG rather than a plain PLA jam. That’s why I went hotter than I would for PLA, and used Bambu’s cleaning pin from the bottom.

2. Probing from the top. I tried the same pin from the top of the nozzle. This did not clear it. The pin came out coated in molten PCTG with a thin strand stretching off the tip, which is the photo at the top of this post. It was useful evidence, but not a fix.

3. PCTG fed from the top at about 265–270°C. I kept feeding PCTG through until a steady, full-diameter stream came out. That’s the sign the path is clear.

The Bambu P1S toolhead above the blue build plate, with a thin strand of filament extruding from the nozzle and coiling on the plate.
Checking the extrusion after the PCTG purge. A steady, full-width strand is what I was waiting for.

4. Real prints. I declared it clear when the stream was steady, but the proof was in printing. It went on to complete several good prints, and I confirmed again the next day that the cleaning had held.

The temperature wasn’t a recommendation

270°C and the 265–270°C purge were chosen for this incident, because PCTG residue was my suspect. They are not a PLA unclogging temperature. If you have a plain PLA clog, match the temperature to the filament actually loaded and follow Bambu’s guide.

What I still don’t know

I never pulled out a piece of plastic or identified the cause. PCTG residue from the previous print is my working theory, which is why I treated it that way. Heat creep is another possibility. If this clogs again, I won’t assume it’s the same cause.

What worked and what didn’t

  • Worked: the bottom-pin attempt followed by a same-material (PCTG) purge at a temperature chosen for this specific situation, and not stopping after the first attempt failed.
  • Didn’t work: probing with the pin from the top.

Safety

The hotend, the pin and freshly extruded filament can all cause burns. Keep your hands clear of the nozzle area while it heats and extrudes, use the printer’s own temperature controls rather than handling hot parts, and follow Bambu’s current instructions for your model.

Sources

Leave a Reply