Infill Setting
The first thing to change is to make sure that you're not using Grid infill.
Grid infill tends to be one of the worst patterns for nozzle contamination and material buildup because of how the toolpath forces the nozzle to interact with already-laid filament.
Grid infill creates self-intersections in the same layer
Grid is essentially two sets of straight lines at 90°.
Unlike gyroid or lines infill, the nozzle physically drives across previously extruded strands within the same layer.
What happens physically:
First pass lays molten filament.
Second pass crosses over it while it’s still warm.
The nozzle scrapes and reheats the first strand.
That scraping action causes:
✅ softened polymer to smear onto the nozzle
✅ tiny strings to wrap around the nozzle tip
✅ additive/filler particles (CF, mineral, pigment) to accumulate
For materials like your Pro PCTG or PET-based copolyesters, which stay rubbery longer than PLA, this effect is amplified.
Vertical pressure points = “micro plowing”
When the nozzle crosses an intersection:
Z height is constant
But the filament bead underneath is not perfectly flat
So the nozzle experiences localized upward force.
This causes:
slight extrusion backpressure changes
micro under-extrusion after crossings
molten filament pushed up around the nozzle shoulder
That molten collar is the start of nozzle boogers.
This is why you’ll often see:
clean print → suddenly a blob forms mid-print → drags across surface
Grid infill is basically a repeated blob generator.
Heat + dwell time increases stickiness
Grid infill also has more:
sharp direction changes
deceleration points
dwell time at intersections
Those pauses let material:
stay hot longer
oxidize slightly
adhere to brass or hardened steel tips
PETG/PCTG especially likes to stick during slowdowns — something you’ve likely seen on the X1C with certain profiles.
Why gyroid, cubic, or lines behave better
Patterns that reduce buildup share one trait:
👉 No direct same-layer crossings
Examples:
Gyroid – continuous flowing motion, minimal scraping
Lines – parallel passes only
Cubic – intersections happen across layers, not within one layer
Result:
Less nozzle contact with warm plastic
Lower contamination rate
More stable extrusion pressure
Speed and Acceleration Settings
One of the biggest settings you should change that will cut down that buildup you're experiencing is to drop your acceleration rates in your Process settings under the Speed tab. (in Bambu Studio or Orcaslicer, for reference)
Bambu Studio defaults to 10,000 mm/s^2. I recommend dropping that to 500 or 1000 mm/s^2.
The reason this makes a difference is due to the fact that the toolhead does not have balanced mass above and below the gantry and when it makes a dramatic direction change with fast acceleration rates, it causes the toolhead to tip ever so slightly.
Because Pro PCTG is a viscous material, it stays where you place it. This means that the previous layer of the print can have a "crown" to the extruded material and the tipping of the toolhead causes the very top of that crown to be scraped and then build up on the nozzle.
We really need to address this via a Process profile for Pro PCTG, as this setting is not a part of our Pro PCTG Filament profile.
I hope that this feedback helps you to be more successful in printing Pro PCTG.
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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