This is the most common Pro PCTG question we get. Plastic slowly collects on the outside of the nozzle, cooks, and drops onto the print as a dark blob, zit, or burnt speck. Large ones can knock a print off the plate or crash the toolhead.
Fix it in this order
- Slow down. Cut print speeds and acceleration in half, then step them back up until buildup returns. This alone fixes most cases. Fast, jerky direction changes tip the toolhead and scrape plastic off the previous layer onto the nozzle.
- Dry the filament. Moisture in the filament turns to steam in the hotend, and the steam pressure pushes out extra plastic. That over-extrusion collects on the nozzle. If the filament pops or hisses while printing, or the spool has been sitting out, dry it at 70°C for 6–8 hours. See Drying and storage.
- Calibrate pressure advance so the nozzle isn't oozing at corners. See Pressure advance.
- Lower the flow ratio 0.01–0.03 (for example, 0.98 to 0.96).
- Change the infill. Avoid grid and concentric; patterns that cross themselves in one layer drag the nozzle through fresh plastic. Use gyroid, cubic, or lines, and enable "Avoid crossing walls."
- In Bambu Studio, set Metal Stickiness to High in the filament profile so full retractions are used. Our current Bambu profiles already do this.
- Check temperature. Too hot cooks buildup into dark specks; too cold makes the plastic drag. Try 5–10°C either way.
- Start with a clean nozzle. Heat it to about 250°C and brush it with a brass brush before printing.
Good targets once it's fixed
- All features 150 mm/s or less; outer walls and top surfaces 100 mm/s or less
- Acceleration 2,000 mm/s² or less; outer walls and top surfaces 1,000 mm/s² or less (500 if buildup persists)
Only happening with one color?
Pigments change flow slightly. Run a separate pressure advance calibration for that color, dry the spool, and slow down a bit more.
Still stuck? Contact our support team with photos, your printer and nozzle, your slicer, and any changes you made to our profile. A project file (.3mf) helps most.
Comments
3 comments
Testing these settings on the H2D. I had noticed that the H2D when used with Bambu PETG builds up filament on nozzle at very high rate, was disappointed, got machine two weeks ago and been tuning in profiles for it.
Today, testing these settings for your PCTG and PLA Pro, first time I ever bought 3D Fuel, very exciting, looking forward to getting PCTG dialed in. These settings will come in handy for the PETG issue the H2D seems to have with buildup on nozzle, will tweak that profile similar to your suggested PCTG one to prevent build up on nozzle.
I also run a Qidi Plus4 but had over a year to optimize print profiles with that machine, it is a printing beast for PETG, ABS, PLA……..it still can outperform currently my H2D on final quality and speed. I have that machine dialed in like a Swiss watch, looking forward to testing and trying out your PCTG on it also along with your PLA+ which it appears I have dialed in nicely.
Running some prints now on H2D with these new settings on some test prints.
Update-
I cut the acceleration way down on the H2D and now have zero build up issues when running PETG and PCTG. This was key change that made drastic improvement.
Much Appreciated!
I have been calibrating and testing PCTG pro for weeks at this point and cant fix the nozzle build up problem. I used your newest process file, your filiment profiles, testing different temps, speeds. I tried just about everything and the nozzle gets absolutley caked up everyime. I have an H2D and want to use the materiel for a product I want to sell because the filiment properties are fantastic but it prints horibbly from my experiance. and yes i dried out the spools at 65c for over 24 hours. Does anyone know what im doing wrong or have the same problem? I have even tried calibrating the filiment per “factorian designs” “Filiment Calibration Masterclass” video and that still doesnt help. I tried tweaking retracking, wipe distance, and starting on the first layer it immediately starts buliding up. So frustrating.
I've spent time tuning settings for PCTG and PCTG Matte Black on my X1C. I was having a lot of issues initially with lines curling up during printing, which contributed to it building up on the nozzle. With my current settings, it prints nearly as smooth as PLA for me now. Here is what has worked for me, which are changes I've made to the PCTG print profiles provided by 3D-Fuel. My setup is X1C with 0.6mm hardened nozzle.
Takeaway is going slower (speed, acceleration), lower flow ratio, and optimal infill amount has unlocked PCTG for me. Along with having glass lid propped open to vent excess heat from chamber, and even front door cracked open. My PCTG curling and nozzle buildup issues traced back to too much heat/not enough cooling by the time the nozzle would come back for the next layer. With these settings I no longer have any issues.
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