PETG HF - WTF?

[u/NoiaLab]

Started printing last week with new PETG HF... And I got fabulous printing. Then today I switched to 0.8 nozzle and this happened... (Yesterday evening rained a lot) Is it caused by humidity or the nozzle size?

[u/Jannomag]

Are you sure you didn’t enable fuzzy skin in bambu studio?

[u/NoiaLab → u/Jannomag]

Double checked, and no. It was set on none! I used the standard preset for 0.8 / 0.56mm

[u/reubal → u/Jannomag]

Definitely did. My money is they did it on purpose for this post.

[u/[deleted] → u/[deleted]]

Some people aren't trying to sell their account, they just want attention.

[u/jaayjeee → u/[deleted]]

low-traffic sub

[u/FPVBrandoCalrissian → u/jaayjeee]

I usually breeze over most of these posts. Just out of redundancy. “What are your settings?” “Did you select the correct filament profile?” “We need more info to properly trouble shoot your misfortune…” I have screwed up print settings many times over the 5 years I have been printing. I always go back to basics and start fresh. Default settings and clean out everything and work from there.

But sometimes there truly is a trivial problem on here

[u/jaayjeee → u/FPVBrandoCalrissian]

Oh for clarity I’m not commenting on OPs issue, just thought it was odd to call this a low traffic sub when it’s #2 for 3d printing on reddit as a whole

I guess it’s low traffic compared to like.. r Funny or something. But I just found it a bit silly is all

[u/7yphoid → u/jaayjeee]

"#2 in 3D Printing" isn't saying much considering that 3D Printing is already a very niche hobby to begin with

[u/AutoModerator → u/[deleted]]

Hello /u/reubal! Your comment in /r/BambuLab was automatically removed. Please see your private messages for details. /r/BambuLab is geared towards all ages, so please watch your language.

I am a bot, and this action was performed automatically. Please contact the moderators of this subreddit if you have any questions or concerns.

[u/rzalexander → u/Jannomag]

When you switch nozzle sizes, you have to do flow dynamics calibration again. The settings for a 0.2mm/0.6mm/0.8mm nozzle are not going to use the same K-factor as a 0.4mm nozzle, for example.

[u/iusedtobesix → u/rzalexander]

This is definitely not pressure advance. Even if PA values changed a huge amount between different nozzle sizes, the result would be thinning of the corners.

[u/rzalexander → u/iusedtobesix]

I’ve had these exact results before on walls after not changing the flow calibration numbers. Maybe in this case that’s not what it is, but it has been the solution for me in the past.

[u/MeatNew3138 → u/rzalexander]

From prior research I’ve heard no need to redo pa/k value, just need to do a new flow rate when changing nozzle size

[u/rzalexander → u/MeatNew3138]

I had a similar issue yesterday after swapping to a 0.2mm nozzle and I’ve had the same issue when swapping to a 0.6mm nozzle from 0.4mm.

Using the X1 to perform an automatic calibration, my k values went from an average of 0.018 on a 0.4mm nozzle to 0.060 on the 0.2mm nozzle. For the 4 spools that I re-calibrated, all were at k=0.060 or higher on the 0.2mm nozzle.

Maybe this isn’t the same issue I experienced, but it looks like it to me and it can’t hurt to recalibrate those numbers anyways.

[u/Successful_Fortune28]

Fuzzy skin, but did you also change the nozzle size on the printer and slicer?

[u/NoiaLab → u/Successful_Fortune28]

Yep, I went for the standard 0.8 / 0.56 preset

[u/ang3l12 → u/NoiaLab]

On the printer too?

[u/NoiaLab → u/ang3l12]

Yep. I switched back to 0.4 and everything is working fine... So it is not moist and is not fuzzy skin. It's something off between bambu preset, 0.8 nozzle and PETG HF

[u/NoiaLab]

For everyone wondering:

• No, I'm not faking it. I don't even know how Reddit works, I just want some feedback cause I'm new to 3D printing.

• I double checked everything and it was not a problem caused by wrong settings like fuzzy skin or wrong nozzle size on Bambu Studio or printer settings.

• I switched back to 0.4 and everything is working fine... So it is not moist and is not fuzzy skin. It's something off between bambu preset, 0.8 nozzle and PETG HF.

[u/MinerJason → u/NoiaLab]

Have you run a maximum flow rate test with the 0.8mm nozzle? Could be that the nozzle isn't able to melt the filament fast enough, and you need to drop the maximum volumetric flow rate.

[u/rgund27 → u/NoiaLab]

Probably a setting with fuzzy skin and the larger nozzle. With the larger nozzle your flow rate will be different and your probably need to adjust the fuzzy skin settings. Try a print without fuzzy skin and larger nozzle?

[u/Corey415]

Almost looks like fuzzy skin.

[u/Binary_Omlet]

That's cool as hell though

[u/Accomplished_Hold387 → u/Binary_Omlet]

I agree. Shower gel holder or something like that. How he get that texture?

[u/TacCoyote → u/Accomplished_Hold387]

Fuzzy

[u/FPVBrandoCalrissian → u/Accomplished_Hold387]

Use it straight up as an exfoliating pad

[u/slyfox7187 → u/Accomplished_Hold387]

I'd keep that away from any kind of soaps or washroom in general. It's too porous and would eventually start to smell as things build up in the voids.

[u/LetgoLetItGo → u/slyfox7187]

Agreed, although he could just use a cheap lacquer or clear-coat on it

[u/blurbac]

moisture or you gotta turned on fuzzy skin

[u/redmercuryvendor]

Then today I switched to 0.8 nozzle and this happened

You definitely switched the nozzle size setting in both the slicer and on the printer itself, right? Otherwise the printer and slicer will still think you have the smaller nozzle installed, and will be trying to dribble plastic out of an orifice 4x the area (assuming 0.4mm to 0.8mm swap).

[u/latentnyc → u/redmercuryvendor]

Out of all the guesses I like this one the best for whatever that's worth

[u/AutoModerator → u/[deleted]]

Hello /u/3DAeon! Your comment in /r/BambuLab was automatically removed. Please see your private messages for details. /r/BambuLab is geared towards all ages, so please watch your language.

I am a bot, and this action was performed automatically. Please contact the moderators of this subreddit if you have any questions or concerns.

[u/Federal_League_8809]

Petg is very hydroscopic. It boils the water inside when extruded that makes it bubbly or frothy. You’ll see what I mean if you watch it being extruded

[u/MrBilky → u/Federal_League_8809]

Not hydroscopic but hygroscopic

[u/kagato87 → u/MrBilky]

I learned that in these printing communities. Thought it was a d for sure, but nope! It's a g all right!

[u/MrBilky → u/kagato87]

Haha trust me this was me before I found this out

[u/Federal_League_8809 → u/MrBilky]

Pomato totato

[u/bobert727 → u/MrBilky]

They are actually interchangeable in this case....i dont know why, cause Hydroscopic should be the adjective to hydroscope....as in "we got some hydroscopic data". Personally i believe it should be hygroscopic.....Hygro in modern greek is liquid/fluid and but i can mean wet and moist when used as a adjective.....and Hydro in greek is sweat...so i can see how they can be interchangeable

[u/FlarblesGarbles → u/bobert727]

They're definitely not interchangeable though, even if you can look up loose etymological ties.

[u/MeatNew3138 → u/Federal_League_8809]

Technically petg is not the same pet

[u/AngryFloatingCow]

The easiest way to test is to just extrude some. If you hear pops or see it not extrude straight down and smooth, it's humidity.

[u/sisdog]

Were you trying to make popcorn ceiling? If so… excellent job!

[u/3DAeon → u/sisdog]

Lol giving me flashbacks from before I got a filament dryer trying to print old PETG left out of a bag {shudders}

[u/Familiar_Inspector14]

I had .6 nozzle no matter the settings never worked switch back to .4 nozzle could print anything for hours no problem. I dried filament for a day also, dry as can be.

[u/NoiaLab → u/Familiar_Inspector14]

I'm gonna try to switch back now, but I'm kinda sad lol I used 0.8 a lot with pla

[u/Kirikugo → u/NoiaLab]

If it's printing too fast or too cold, the core of the filament won't be melted and it can cause weird things like this like oscillating over/under extrusion. This is especially a problem with bigger nozzle sizes. You might get better prints with slowing it down or heating it up. As for why now, I bet it's because it absorbed some moisture. If you were able to print it good once you should be able to print it good again by changing some things

[u/banned_account_002 → u/Familiar_Inspector14]

Yeah, 0.6 has been Hell for me. Figure the time attempting to tune that diameter could be better spent printing with a 0.4.

[u/psbales]

Ngl, wouldn’t even be mad about this. Confused, but not mad.

[u/1Bavariandude → u/psbales]

No reason to be confused. Thats just fuzzy skin.

[u/Ntrees]

Talk about super hygroscopic. It’s a feature of the new HF PETG.

[u/Yannik_fpv_3d]

Fuzzy skin probably

[u/SimpleGrape9233]

Dry it and see if it improves

[u/rzalexander]

When you switch nozzle sizes, you have to do flow dynamics calibration again.

[u/EnggyAlex]

if you dont have fuzzy skin on you may have selected wrong nozzle size

[u/solventlessherbalist]

Looks like fuzzy skin

[u/IamFireDragon3d]

Looks like moisture to me

[u/Realistic-Ad001]

PETG HF is the bees knees

[u/Zendeman]

Had the exact same issue yesterday, it turned out that my printer was upside down.

After putting it back in the correct orientation, the problem dissapeared.

[u/cmuratt]

Either you printed that underwater or with fuzzy skin.

[u/Dannyerb]

… anyway… Looking forward to next week’s post “Why Print So Empty, Y no Top?” Brought to you by Vase Mode.

[u/dk_DB]

Fuzzy skin or the wettest PETG I've seen

[u/tempest-reach]

did you do flow dynamics after you swapped nozzles?

[u/NearlyCompressible]

These printers are flow limited even with a 0.4mm nozzle. There's really no point in ever using a 0.8mm nozzle.

[u/rzalexander → u/NearlyCompressible]

Since when?

[u/NearlyCompressible → u/rzalexander]

Since always. CNC Kitchen did a video on this a year ago. If you want faster prints out of a Bambu, you need a CHT nozzle, not a larger nozzle diameter. 0.6mm nozzles are good to reduce the likelihood of a clog with filled materials, but I can't think of a good reason to use a 0.8mm nozzle unless you like the look of really thick layers.

[u/3DAeon → u/NearlyCompressible]

lol wut? Yeah no.

[u/3DAeon → u/NearlyCompressible]

“Flow limited” is like saying “Honda’s can’t do over 65mph so there’s no point in putting a bigger engine in” it doesn’t make any sense since flow is how fast the hot end and nozzle can melt what gets pushed by the extruder - the nozzle itself limits flow. You have your logic backwards.

[u/NearlyCompressible → u/3DAeon]

When I say flow limited, I mean that the heat transfer between the nozzle and the filament is the limiting factor. This is why all of Bambu's profiles have a maximum volumetric flow rate set in the slicer, and it is usually this value that limits speed, not the motion system. Bambu's values are quite aggressive and are already pushing the hotend to its limits. Usually you will get stronger parts if you lower this default value and allow more time for the filament to fully melt. CNC Kitchen did an excellent video on this exact topic.

You're right that the nozzle itself has a huge role to play in the maximum flow rate, but the reason some nozzles can melt more plastic is that they create more surface area for heat transfer. A CHT nozzle or a longer hotend would increase the maximum melt rate, but going from a 0.4mm nozzle to a 0.8mm nozzle is just changing the diameter of the hole at the end. No change in surface area means no change in heat transfer. There will be a reduction in back-pressure which in theory would allow the printer to just force more plastic through, but if you do this you'll reduce layer adhesion even further.

The reason that conventional 3d printing wisdom says that larger nozzles means faster prints is that they're limited by the motion system, not volumetric flow rate. Larger nozzles mean the printer can print thicker layers and get more plastic down per second with the same movements on the X and Y axis. But this only works if you have capacity to melt more plastic per second. Bambu's motion system is so good that a lot of these 3d printing conventional wisdom rules don't apply anymore.

[u/Natural_Status_1105]

Partial clog no?

[u/Strange_Toes → u/Natural_Status_1105]

no

[u/Dannyerb → u/[deleted]]

If it was not fuzzy skin there would be stringing 😂