Clogs on multicolor prints

Bambu Lab P1 Series Troubleshooting
1

I have a P1S with an AMS. The printer is only 2 or 3 months old. Most of the prints I have done have been single color but I have done a few multicolor prints. Over that past couple of weeks, every multicolor print I have done, the printer will print fine, cut the filament, retract it in to the AMS, bring the next one in, and tell me it’s jammed. Typically, I just tell it the problem is solved and it will try it again, repeat a few times, then it continues. Might get a couple more layers, might work for an hour or two, but then same thing.

It’s a P1S with AMS.

Bambu, Sunlu, Inslogic, Ziro brands of filament (does it on them all) PLA

Stock .4 nozzle that I have cleaned more times than I can count with the whole heat up the allen key, insert it from the back, heat up the nozzle, pull it out method that is on the Bambu wiki.

I’ve taken the extruder apart, it looks pristine still.

I have the AMS on a riser and the lid off, it does this with the door open and closed. It’s in the basement and I live in Michigan, there is a dehumidifier less than 10 feet from the printer. And this has been going on during end of winter and beginning of spring, so it’s pretty cool in the basement. It’s not an ambient heat issue but everything I read keeps saying “It’s heat creep because the area is too hot.” I even printed some spacers someone made to give better air flow over the heatsink specifically to eliminate heat creep. I’m so certain that it’s not an ambient heat issue as is evident from the side of my last print curling up on a brand new supertack plate, even while the extruder was getting jammed.

I did have a guide on top that the PTFE tube went through that was supposed to help prevent clogs and such, but then I see others talking about how that can actually cause them, so I removed it.

I have not changed the nozzle yet, that’s my next step, nor have I changed the PTFE tube yet, but I have checked both. I just switched off the printer during the latest clog mid print and am letting it cool so I can pull the hotend off and change the nozzle, but honestly I don’t think I have printed nearly enough to justify the nozzle having gone bad yet. I will then let it resume and see what happens with a brand new nozzle. But this is driving me crazy.

I am using Bambu Studio, all settings default from the people who make these models and such.

I’m not sure what other information I can provide.

Edit: Let me add that when it’s printing, and not clogging with a filament change, it prints great. It’s just when it changes filament during a multicolor print.

Edit 2: I thoroughly cleaned the nozzle, same thing on the very first layer. I replaced the nozzle with the spare that was sent with my printer, clogged on the second layer.

Edit 3: Replaced the PTFE tube inside the printer, it finished the rest of the print I had been working on. About 3 hours of printing, no problems. Started a new print this morning, clogged on the second layer during filament change.

1 Like
2

Hi, I had this same problem. I noticed that it did not happen with Hatchbox PLA. I am curious to hear what others have to say.

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Well my issue is happening not so randomly with several different brands, including Bambu, which is the primary brand I have. I would think their own filament should have the least issues.

4

It may be nothing, but I would check the filament cutting blade. There’s a spare in the box the printer shipped with so it should be a quick and easy fix if it looks beat up or damaged. Equally, you might get a confirmation of a problem if you pull one of the other filaments out of the AMS and check the end. It should be very uniformly cut and clean.

5

I actually looked at the blade when I removed the extruder yesterday and it looked fine, cuts look clean.

6

I guess you can’t edit the message after a day or two. So I printed the second print. After all of this it did print significantly better, but it still had multiple clogs on color changes in a 12 hour print, it had to be told to try again on clogs probably 10 or so times in several hundred layers. So yeah, changing the tube helped, but it’s still having a problem.

7

Still having this issue. After changing the PTFE tube almost a month ago the problem is significantly less, but it’s still happening. Working on an 8 hour print right now that is two color and it’s “jamming” after almost every color change. I tell it that it’s fixed, it tries again and works, but then jams again a few minutes later. This is incredibly frustrating and I would very much like a legit solution to this.

8

Did you observe the nozzle temp during the material change purging?
Sometime last year the filament change gcode received a downgrade by enforcing a 250°C nozzle temp rather than using the max temps in the filament settings. With a warm chamber, that may be enough to lead to heat creep.

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I did not. I only half way understand what you are talking about as I have only been doing hobbyist 3d printing for a few months. I will look for something multicolor to print so I can watch the temperatures during the filament change. I will say though that the chamber hasn’t been hot. This has been going on in a basement in Michigan during winter with the top off and the door sometimes open, sometimes not. It does seem to happen on a longer print and not a super short one though and only during filament changes of multicolor prints.

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Having a look at the nozzle temos reported from the printers screen or the Studio device tab can give some pointers. As can monitoring the chamber temp. But you’ll probably need to place a cheap thermometer in the chamber of the P1. There are plenty of holders to print on MakerWorld.
35-39°C is my sweet spot on my X1. However, above 35° with ironing, I get heat creep. I don’t use ironing much though.

Heat creep is a clog when the so called “cold end” gets to warm. Above the nozzle is the melting area. Above this, a heat break is intended to stop heat migrating upwards to areas where the filament needs to be solid. The part of the hot end above the heat break (i.e. below the filament cutter) is the “cold end”. If this gets too warm, the filament softends, expands and clogs the cold end of the hot end (yeah, I know this sounds silly :sweat_smile:).

Besides nozzle and chamber temps, one other factor can promote heat creep clogs:
Moist filament reacts much worse to heat than dry filament. Having travelled across the pacific (and made numerous stops), new filament, in bags that delay but do not stop moisture migration, is likely damp. It’ll behave better after drying.

11

So, I have a Sunlu filament dryer, I can try drying out my filament one at a time, but that is obviously going to take a considerable amount of time all in all. I have a new twist though. So I am attempting to print some drink coasters for my cousin. They are 3 and 4 color. I have done two and was working on a third. All three have had clogs. The coasters are only 10 layers and it’s an hour and a half print. I’ve had to manually clear clogs 3 times to get the two coasters to finish. I just cancelled the third one to do a test. It wouldn’t feed the next filament in during the print, hence the clog error. It kept trying. I cancelled the print and then heated the nozzle to 220 same as the print, and told the printer to extrude and filament extruded perfectly. Nothing changed, and it kept going until I stopped pressing the button. So why could I manually extrude it but the printer couldn’t? And again, this never, ever clogs at the beginning of a print or for a single color print. ONLY when changing filament from the AMS on a multi color print. If this was a true clog, then it shouldn’t have extruded when I manually did it through the screen after cancelling the print.

I do have a thermometer attached to the door on the inside. The chamber temp has been hovering around 27c. The nozzle temp for these prints has been defaults, which sits within the range of the assorted filaments I have had clogs with.

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The start of the hobby can be a bit frustrating as there are many different settings, components and failure cases.

What you are describing now indeed does not sound like true clogs.
BTW, you mentioned having done unclogging. Did you have a look at the tips after a cold pull? And did you do the “light” cold pull or the hot hex wrench cold pull? I have found only the latter to be reliable for me.

But back to what you are describing. If it prints by manual feed, there are a few things to check.

  • Starting at the spools in the AMS: Do they catch when you get the error? Is there some filament entanglement/entrapment? AMS savers from MakerWorld can help, as can Centre Spool Dessiccant containers.
  • Looking.at the AMS itself, is there a particular slot that is particularly troublesome?
  • Moving on: Are all PTFE ends cut neatly at 90°, are fully pushed into the couplers, have the shortest possible length with the largest possible radius? When using the default lengths on my X1, I had issues with the filament stopping just before the print head due to friction. So the thresholds are borderline. Shortening my paths eliminated that particular problem.
  • At the print head, things get a bit more tricky. A particularly annoying clog that can (rarely) occur is a travelling clog. Originating from a nozzle clog or heat creep, the extruder can abrade material which damages the filament tip, leaves residue in the teeth of the extruder, reducing its effectivity while also releasing debris into the nozzle for a new clog,… That is pretty much a worst case. Check the Bambu wiki for the nozzle (hot hex wrench!) and extruder clog removal and you are well prepared for the worst of clogs.

As for drying, I usually dry my rolls before putting them in the AMS. Plenty of dessiccant is usually good to keep at least PLA and PETG dry enough for months.

:four_leaf_clover: & :crossed_fingers:

13

Ok, let’s see if I can accurately answer all of what you said in this one.

I did the heating up, sticking it in from the back to bond with the stuck filament, then heating the nozzle and pulling the whole thing out.

I have no had any getting caught when I have a “clog.” As for AMS savers, I did actually print out some of the super popular ones but they actually caused me issues, not solved them. The would catch non Bambu spools and lift the spools out of the slots more. I ended up going with little button cover thumb savers, that’s what I’m using right now.

No particular slot.

I have not messed with any of the tubes inside the AMS it self. I replaced the one in the printer and that helped the issue considerably for a short time. The filament does feed all the way to the print head during one of these “clogs” and then retracts, feeds again, etc. Then gives an error after 5+ attempts. I did have a guide on top of the print head at one point, but not anymore and I’ve been having these clogging issues with and without it.

I can’t speak for this kind of clog at the moment. I do know that the last two “clogs” I cleared, I had to do the whole heated wrench thing more than once to get it all out. But on the last clog, that’s where I just cancelled the print and then told it to extrude and it worked fine.

I have dessicant holders in the AMS and in each spool and store them in vacuum bags when they are not in the AMS. I have not gone through and dried each and every spool of PLA that I have after opening them. I print pretty much exclusivly with PLA. I do have one single roll of TPU, which doesn’t apply with this, and 3 rolls of PETG that I rarely use, so I have not tested them but I’m pretty sure it would happen with them as well.

14

From the description, the issue occurs when the printer attempts to load a new filament. Old filament’s been pulled back successfully and the new filament has been fed, but either the filament hasn’t fed all the way or the sensor is flakey.

This is not a clog. If anything, it’s a “jam”. Clogs happen once the filament is being extruded. Jams happen when the filament can’t be loaded, or it loads but can’t be fed (the heat creep problem, which isn’t your problem since that keeps the filament from being extracted, too).

If the filament feeds but doesn’t actually make it all the way to the extruder, the problem could be at the point where the PTFE tube meets the extruder, a mechanical misalignment. Maybe the coupler is loose or busted. The other possibility is that the PTFE tube is offering too much resistance and the filament gets stuck upstream of the extruder someplace.

You’re going to have to watch it through the top (so you can see the filament feed through the PTFE). If it doesn’t, PTFE paths need to be adjusted. The AMS is pushing from a long way back, it’s not just the tube inside the printer where resistance can cause the filament to bind.

If it makes it all the way to the extruder and you’re sure the coupler isn’t tweaked somehow, the remaining possibility is a flakey sensor. I’m not sure how you’d diagnose that to prove it, though.

Oops. I took too long to write this and you posted an update with more details. Doesn’t really change my message, though you’ve already thought of some of it…

15

So I can’t see far enough in to know for absolute certainty that it makes it all the way to the feeding teeth of the extruder, but since it works every time for single color prints, I assume that’s not the case…? I can say that many times I have sat on a stool right in front of the printer and I watch the filament go through the PTFE tube all the way to where I can’t see it anymore in the top of the print head/assembly/whatever it’s called. From what I can see, it makes it all the way in, but since it’s all metal and plastic, I can’t tell past the point where the tube enters the housing.

What makes my brain explode is that this only happens on a multicolor print and not every time. All of these potential issues sound like they should be just general problems that I would have regardless of single color or multicolor. And who knows, maybe it is and just the frequencey of changes with multicolor, therefore the chances of it happening are a total fluke that it’s not been a single color problem as of yet. I don’t know.

All I know is that the whole reason I bought a Bambu printer is because they are supposed to “just work” for the most part and this is incredibly frustrating because I have been aware that things do happen (I was a computer tech for just under 20 years) and maintenance is certainly a thing, but I expected to get at least a year or several years before having what I consider a major reoccuring issue.

If it was something relatively simple, like when I changed the PTFE tube, fine, even though that also wore out too soon in my opinion. But of course I never get the easy issues. The curse of having worked in diagnostics before, nothing is ever simple for my own personal property.

This feels to me like a fault of some kind. Either software or hardware, it feels like it is a flaw in my printer rather than a worn part. Nothing to base that on besides my gut, but there it is. The question is what now? Should I contact Bambu directly and see if they can send me some replacement component or whatever, since this is so far eluding the community as well?

16

OK. Here’s a question - when you run a single-color print are you always using the same AMS slot? Are the colors that don’t always load in the other slots?

It worked better when you changed to a new tube, maybe because that tube had a “set” (it was bent a certain way) that was favorable to the filament path but after going through a few heat cycles it has now taken a different “set” that isn’t favorable.

I’m pretty sure the printer monitors motor current when driving the filament in order to detect when it’s not feeding. So straightening out as much of the PTFE between the AMS and the printer might help.

The issue might just be that the circuit that senses if the motor is slowing down too much is too sensitive.

17

I tend to keep my most commonly used two filaments in the first two slots of my AMS, but I regularly use all the slots of the AMS. I just don’t change those two as much. Like the first slot has my black filament. Because of how frequently it’s used, my most common clog/jam is in transition from or to black, but it happenes between other colors in other slots of the AMS as well.

The old tube did have a pretty defined curve to it. My printer had the lid on with the AMS on top of that until I could print a riser, I think that was part of it since the tube rubbed against the glass the whole time.

I just double checked and the tubes are about as straight as they can get outside of what is in the AMS inner workings. I forgot that I do have a 3d printed y-splitter on the back so that I can feed filament in from the outside of the AMS. That splitter has been on the printer for months though and I honestly don’t think it’s an issue. I loosened the screws on the printer end very slightly and am going to try another print. If that fails, I’m going to remove it all together just as a test run but I really don’t think it’s the cause.

18

I agree that it does not sound much like a clog anymore.

Just to be sure, I’d check the ends of the PTFE to the print head. They do tend to fray after a while.

Following the filament path, the print head filament sensor’s PTFE coupler can cause very similar issues as you are describing. Annoyingly, it is not a coupler you can just order. However, the coupler is identical to the one on the same PTFE at the back of the printer. You can also order the 3 PTFE couplers from Bambu as you can break out the same couplers from that.

That may help if the filament does not make it to the extruder. If it does however, we may need to look at the extruder and nozzle at the same time. Just in case the extruder gears contain residue which may be travelling down to the nozzle.

https://wiki.bambulab.com/en/x1/troubleshooting/extruder-clog