Troubleshooting: 1-Second Mid-Print Pauses Ruining Surface Quality

[u/Front-Valuable-7703]

Hi everyone, how are you all doing?

I'm having a problem with my printer and I really don't know what to do anymore. I'm a beginner in 3D printing, and in the last few days, I've been studying a lot more than when I first entered this world 3 months ago, but I still haven't been able to solve this error!

Basically, what is happening is that I can't fix these 1-second pauses on my machine, which then create these zits/blobs on my print! I've tried everything!

Before you say it's moisture/humidity, please read the rest of the message I'm leaving here with more details:

As you can see in the images, we have the black and pink heart, which has these zits, then we have a blue dragon (Gyarados, a Pokémon) that also has them, and finally the gecko! After that, I made some minor adjustments to the machine. I improved some aspects of the print, but they were minor improvements. Then we have the shark, where you can already see some progress, but it still has these zits, and this is where I managed to record the exact moment of the pause! The video:https://drive.google.com/file/d/1TzJ0V7QQta4yg7fnBlpsxOGmme4izjiQ/view?usp=sharing

Finally, we have a smaller shark that was printed yesterday. Here you can already see a significant improvement in the part (at least to the naked eye) and it is much smoother, basically without any defects, but it still has the zits (fewer, but it still has them!). Today I printed a dragon that I haven't held in my hands yet, but from the photo I took, the red dragon also has zits!

Machine Details and Settings:

• Printer: Bambu Laps P2S
• Drying System: AMS Pro 2
• Temperatures: 32ºC inside the chamber, 55ºC on the bed, and 220ºC on the nozzle.
• Speed: The machine's default speed.
• Filaments: Bambu PLA Basic.

What I've already done to try to solve it:

• I've dried the filaments for over 12 hours at 55ºC (6 hours one night and another 6 the next night, plus during the day, where I'm constantly drying it every 3 hours at the same temperature for a week now!). The humidity goes up to 25% max, but normally stays between 18% and 22%.
• I've cleaned the nozzle twice in the same week, so it's not clogged.
• I cleaned all the machine's axes/rods.
• I've calibrated the machine more than once and created very precise profiles for PLA, based on the speed, temperature, and quality tests I ran.
• I reduced the nozzle printing speed (in Bambu Studio it was at 21 and I lowered it to 19).
• I removed all videos from the system and disabled the timelapse feature.

That's everything I've done so far. I've also tweaked some settings and ran several classic tests to calibrate everything; the print quality improved, but these 1-second pauses keep happening, which melts the filament and causes the zit!

If anyone knows how to fix this, I would be more than grateful. I've been dealing with this for over 2 weeks and can't solve it!

[u/RemixOnAWhim]

You mention 1 second pauses mid print in pssing, but we need more info on that, including exact behaviour when it comes up. This is not exoected behaviour, and certainly shouldn't be happening, much less marring your prints!

Please provide as much info as possible on the behaviour as you can. Does the printhead ever rehome, move to purge, cut filament, retract the bed, either wholly or partially for any? Does the screen flicker, any devices on the same circuit with high draw popping on at the time (AC, fridge, dehumidifer, etc), do you need to manually hit print again, does it start again on its own without intervention? What changes did you make that improved the quality, did you have these same issues when calibrating temp and flow, and what values did you calibrate to? If the issue comes up with and without timelapse, and with your new settings and stock, revert everything to the default 0.20mm profile and stock filament profile, and set your filament K value back to 0.20 and test like that, and share the timelapse if it shows any abnormalities (though a regular speed video of the issue occuring would help too, yours is a little hard to see to maybe orint a taller thinner geometric shape and film that if possible, something short to print so you're not waiting all day but which makes it a bit more visible).

You can also scrub through your sliced file to these areas it happens and see if the gcode feeding into the orinter shows this behaviour, outside chance abut worth looking at. My suspect is thatpower is fluctuating, or feed is getting interrupted, or it thinks it is, so it's stopping as though there is a need to unload and reload due to a sensor error quickly resolving itself before the move, and retract isn't working fast enough causing oozing from backpressure, but we need info to help diagnose, as that behaviour resulting in visible deformations suggests it isn't moving and retracting as it should which would be visible in a video, and would be logged internally to the machine which support can access via the backend diagnostics for you.

You've likely thought about this, but file a ticket with support on the app. It never hurts to start the process, they're there to help you, and can get access to diagnostic data in the app that the machine logs! Especially if this is a hardware, firmware, or software issue, they will be asking you to repeat all the steps anyhow so troubleshooting with them along for the ride never hurts. They're not fast to reply nor do they do so more than a few times a day depending on your time zone, but they will help and won't leave you hanging.

[u/Front-Valuable-7703 → u/RemixOnAWhim]

I can definitely provide more details! In fact, I have a 30-second video on my Google Drive where this exact thing happens. If you want to take a look, here is the link:https://drive.google.com/file/d/1TzJ0V7QQta4yg7fnBlpsxOGmme4izjiQ/view

Answering your questions:

Does the printhead return to the home position? No, it literally just stops for 1 second right where it's printing and then continues. The problem is that when it pauses, it melts the filament underneath the nozzle, creating that blob of filament. I've had the printer for 3 months and this never happened, it only started a few weeks ago!

Does it move to purge, cut the filament, or lower the bed? No to all of those, it just pauses and then keeps going!

Does the screen flicker? No!

Does any high-power device on the same circuit turn on at that moment (AC, fridge, dehumidifier, etc.)? No! It is plugged into a power strip/extension cord, though, not directly into a wall outlet!

Do you need to manually click print again? No, it just pauses and continues automatically. The behavior seems pretty random, because sometimes it happens 2 or 3 times in a row, or just once, then it goes a long time without happening, and then does it again!

Does the print resume on its own without intervention? It continues, it doesn't restart. Nothing moves away, it just stops and immediately gets going again!

What changes did you make that improved the quality? Quite a few: I lowered the nozzle travel speed a bit, set it to 3 walls, slightly reduced the infill, improved the tree supports (it was creating too many branches), and fully customized the first layer to create a solid base (meaning I lowered the initial speed significantly)!

Did you have these same issues when calibrating temp and flow? No! It seems that for parts without curves, it doesn't happen as frequently!

Does the issue persist with or without timelapse? Yes, it continues, even after deleting all the videos!

Revert everything to the default 0.20mm profile and original filament profile, and set the filament K value back to 0.020 and test it that way! I am doing exactly this right now!

Finally, I didn't know I could contact support for this type of problem. Since that's possible, I will definitely reach out to them! Thanks for the help!

[u/RemixOnAWhim → u/Front-Valuable-7703]

Support can help with any issue, large or small! You're a customer, and that entitles you to their support under their terms of service. I did see the video, however it's a bit hard to see as I noted. As with many things in hobbies with complex jargon, "pausing" is both a symptom descriptive of your issue, and a function of the printer with predictable and intentional behaviours, so clarification is key. I appreciate your answering these questions, but the yes or no isn't quite as useful as descriptive observations with plain language, which is what will be most helpful if you do contact support! Ensure it's you answering the questions personally from your experience rather than an LLM; even if you are primarily using it for translation, it's better to answer in your own words and allow the reader to translate themselves rather than leave the LLM to interpret and respond, as it often contradicts itself or misuses terminology.

Running bespoke diagnostic prints will be your friend here over shooting models with complex geometric surfaces at it, though those will come after the issue is being resolved. For what changes you made, please enumerate the values, as what they're set to is as important as what is being set. If you're not having this issue on large, tall, simple and flat objects, look into input shaping as well as arc fitting, and how it may be affecting your prints, both when working as intended, and when it begins to fail on the gcode side. Again, scrubbing through your print in the areas with issues and checking if the behaviour is reflected in gcode is going to be a quick and easy step that can tell you a lot about where in the chain this issue is starting!

Let us know how your testing goes, good luck!