Suddenly started under extruding

[ng1]

Hi All.

Hope any of you can give me some advice regarding an issue that has developed with my X1C.

It has 341 hours on it (bought around easter this year), and has suddenly started under extruding during prints.
It has so far only printed with plain PLA, so I don’t expect the issue to come from there, yet.
You can see 3 examples of the issue in the pictures below.

What I have done so far:

1. Ruled out the AMS setup, by feeding filament directly in to the print head without any tubes connected.
2. Ruled out the Slicer (Orca Slicer 2.1), by printing a pre sliced object from the printer.

So far I have tried to see of there was any foregin objects in the hot end, I did a cold pull of the tool head, by doing that I seem to have pulled out some PTFE shavings/fragments, which seems to have come the PTFE tube connector in the tool head, as there were a lot around the tube when I pulled it out of the PTFE connector.
But haven’t seen any improvement in the print out, see the PA tower picture below.

What I have planned on doing next is to do a hot pull as described on the bambu lab wiki, and take apart the extruder mechanism to see if there should be any issues there.

Do you have any other ideas what the issue could be, firmware issue maybe ?
I know it printed fine on 1.07, currently on 1.08, is there anyway to try to downgrade the firmware ?

I any case, thank you for your time.

Her is an example of the calibration lines, they are not connected as you can see.

Here is an example of a pre-sliced print from the printer it self.

Here is an example of a preassure advance calibration tower which contains lots of holes in the walls.

[Olias]

Yeah that one should be an easy one to diagnose and remedy. You have a feed problem somewhere in your filament flow. So the straightforward troubleshooting method I might recommend in order of easiest and fastest is this.

First, I would start with only performing a first layer test and default filament settings.

1. Make sure the spool is unwinding in an unencumbered manner. You said you eliminated the AMS so maybe trying another spool of a different manufacturer is also not a bad idea.
2. After step one, check your PTFE tube for wear and possible snags. You may want to look at the head movement during printing to see if the under-extrusion coincides with the tube’s position at a particular bend or stretch point.
3. After those to steps comes the more technical part and that’s looking at:

• Hotend Nozzle. Look for clogs or do a cold pull. Here is the WIKI for that.
• Extruder itself for wear and tear. In particular, look to see if the teeth are worn down. Here’s the wiki on that.

[ng1]

Hi @Olias

Thank you for your reply.

Your step 1 & 2 have already been covert in the steps I have already done (My step 1).

Regarding your step 3 is in progress and already partly done:

@ng1

So far I have tried to see of there was any foregin objects in the hot end, I did a cold pull of the tool head, by doing that I seem to have pulled out some PTFE shavings/fragments, which seems to have come the PTFE tube connector in the tool head

I have just ordered new gears for the extruder and a new hotend so that I have some spare just in case I find any issues with them when I take it all apart.

Thanks again for your time

[Olias]

Good luck and please let the community know how you faired. This is important for the next people who run into this issue.

[ng1]

A progress report for those interested, I have now taken the extruder apart and cleaned it, there was a lot of buildup and filament dust in there, see the pictures below.

Pre clean:

Post clean:

I used a q-tip with IPA initially to remove the loose stuff, but for the stuff in the teeth I had to use a wooden stick (q-tip without the cutton) and press it in to them and twist it to get it loose.

Now onto a test print and see how it goes, if it still fails then I’ll try a hot pull on the hot end.

[ng1]

That didn’t work either, am now in the process of printing a test print after taking out the hot end and doing a pull, but couldn’t see anything obvious in the filament that came out.

So next step would probably be trying some other filament, have the sample spool of BBL filament that came with the printer.

Else do a factory reset of the AMS/Printer ?

Any one else got some ideas what to try other than what I have mentioned above ?

[ng1]

Okay, progress…

Tried to print the PA calibration tower with a BBL filament, and it came out nice.

So now I’m down to:

1. Filament issue
2. Some kind of configuration issue/incompatibility of filament settings

To resolve point 2, I’m printing the same Calibration tower with the print job from the printers cache that used the BBL filament, lets see how that goes.

[Olias]

Thanks for the updates and best of all the clear photos. It sounds like you’re making progress in narrowing down the root cause.

I haven’t taken my extruder apart in months after I installed the stainless steel extruder but I don’t recall there being this level of dust in the original extruder. It almost seems like for whatever reason, your filament is being dragged against its will into the hotend. Of course that’s only conjecture, this could be standard high volume wear and tear.

I do have to wonder though who much drag an AMS puts on the extruder. Since I don’t own and AMS, I’ve love to hear from folks who may have explored this.

One other question. Do you have the stainless steel extruder? or the original one? If not, maybe that might be your next upgrade.

[JonRaymond]

Check your thermal paste and see if it has dried up.

Thermal Grease: Small Cause -> Big Effect on printing results

Since most Bambu Lab printers are the same age, I can imagine that this problem could affect several people here in the forum. My printer has been producing imperfect prints from time to time lately. After 3 weeks of vacation I wanted to use it yesterday and this is what I got as a result: [IMG_0421 2] So I cleaned the nozzle according to the instructions and was in good spirits when the next print looked pretty decent at first glance. When the printer stopped extracting filament after a …

[johnfcooley]

Kinda curious about that extruder gear. Blowing it up, it looks like each grove has filament within it, efffectively making it smoother. Could just be the lighting.

I have to wonder if the bearings have become clogged with gunk as well. This would limit it’s motion. Trying to imagine what would be causing this and I’m struggling with what I think. Almost looks like the extruder wasn’t moving and the filament was being shoved through, shaving off pieces as it goes. This would maybe be caused by the extruder not tight enough on the filament.

I have an AMS but to be honest I don’t know with how much force it pushes. If the gears were further apart and/or not moving as well, and it pushed through then that could explain it. I’m only guessing.

Could replace with a hardened as Olias has suggested. The Bambu one is great as is one from Fystec (AliExpress). I use the latter, but have run both.

[ng1]

Hi @Olias

My guess is that the amount of deposits in the extruder gears comes from my first steps into 3D printing back around easter, where I had a couple of jams with white filament, so wouldn’t personally say that that is normal wear and tear, just my in experience

Regarding the hot end, it is the standard 0.4 mm hardened steel that the printer came with.

[ng1]

Hi @JonRaymond

Thanks for the heads up, I’ll keep that in mind for the future.
He had around 1350 hour on his printer before it stopped working, so I hope that I’m still good for around 1000 hours more

Do you by chance know if anybody ever has tried silicone pads or similar for this, hey are used a lot in the electronics industry to transfer heat from transistors to a heat sink, and basically newer dries up ?

[ng1]

Hi @johnfcooley

That is the result from my own stupidity back when I started with 3D printing around 3-4 months ago, where I had a couple of times done something stupid which caused an external to the printer “knot” on the filament so the extruder would still try to pull in the filament, but the filament was stuck.

It was pretty tightly packed in the teeth of the gears, had to force it out with some wood, but it still had pretty good pulling power on the filament.

When I had reassembled it again I tried turning everything by hand, and it all felt smooth, didn’t feel like the bearings had taken any damage.

[ng1]

As I noted in my last “Diary” entry I printed the filament with the same sliced print job from the printers cache, and it came out really nice just like with the BBL filament, so that rules out option 1 above.

And yes, it definitely is option 2, still trying to wrap my head around it.

But so far it’s a combination between my expectations, how BBL printers work, OrcaSlicer and custom filament settings.

But I’ll keep this updated with what I find, may result in a OrcaSlicer bug report/regression, as there is definitely some strange behavior going on there.

[ng1]

I have now completed full calibration on the black filament, but something is strange, because the PA/K value is rather high at 0.073, and just started calibrating a white filament and it has a value of 0.060, which I believe both were down in the 0.030 range when I started using the printer.
And the Max Volumetric flow is also rather low I believe it was around 15-17 mm³/s before and is now at 9,83 mm³/s which is also below the manufactures specified 12 mm³/s.

When I receive toolhead parts from BBL today, I’ll try swapping out the hot end and see if that improved the matter.

What a learning experince

[ng1]

Have now installed a new hot end, and the PA/K values are now 0.038 for black and 0.032 for white, think the issue has been found.

While it was printing the automatic calibration, I took apart the original hot end, and the thermal grease, the little there was, came of in flakes, so it seems to already have dried up

I’ll try to rebuild it with new thermal grease, and see if everything is fine again, then see if I can find a quality brand so I don’t have to do this every 4 months, maybe even some of those thin silicone heat transfer pads can do it, they never dry up

EDIT:
I have found some thermal pads that I want to try out and see how they behave, you can see the list and datasheets via the link below.

https://www.digikey.dk/short/m5q8b2p0

But the high temperature used in the hot end (300+) limits the selection quite a bit.
And don’t know how well the temperature PID control loop will behave with this, but we will see how it goes when it arrives in a couple of days.

[johnfcooley]

Be careful. There’s not a lot of clearance between the heating element and the clip that holds it and the thermistor in.
You can bend it, but I don’t know how that will affect the clip in regards to holding the thermistor. The pads may be too thick.

Try this. A tube should last you and your children, maybe even your grandchildren.

Boron Nitride Paste (5 cc) by Slice Engineering | Improve Conductive Heat...

[ng1]

Hi @johnfcooley

Yeah, I have extra heating elements and thermistors for the hot end, just in case.
The thermal pads are between 0.05, 0.2 mm in thickness, so I hope one of them fits

Was about to order that thermal grease too had found another link for it in the link @JonRaymond mentioned.

EDIT:
I have ordered the Boron Nitride paste from Slice Engineering, but it’s apparently not available in the EU, so have to import it, so it will first arrive in about 14 days

[ng1]

I have received the thermal pads, and am now preparing to test them.
I’m going to use the spare hot end that came with the printer so I have a brand new one to test with, and I have new heaters and thermistors, I only have to borrow a fan, for that i have the failed hot end I can steal from.

Do you have any recommendation about test procedure ?
I was thinking of using the Volumetric speed test in OrcaSlicer to stress the thermal transfer.

I will test them in the order of thinnest to thickest thermal pad, so that if the retention clip should start to deform, it will always be used with increasing pressure.

The order will be:

Thickness [mm]	Part no.	Speed [mm³/s]
-	Standard hot end (New)	24,95
0,05	TG-P10050-150-150-0.05-1A	23,665
0,07	EYG-S091207DP	?
0,09	TG-P10090-150-150-0.09-1A	?
0,10	EYG-S121810	?
0,02	EYG-S0204ZLSN	?

I don’t have any more of the BBL Thermal paste, so I will use GCS-060-GS-20G which I also ordered together with the thermal pads, for the thermistor.

Update:
After I have run the first test, I can’t get the heating element off again, I suspect that the graphite material has embedded itself into the the ceramic heater, so it is now kinda “glued” in place now, which I didn’t expect, this means that to continue with further tests, I will have to order more parts from BBL and build more hot end’s, but I fear that when I go over a thickness of 0,07 I can’t get the retention clip on because of the thickness of the pad.

What do you think, should I order more parts and try the other thicknesses ?

Currently I’m planning on using the 0,05 mm pad and see If I can get the failed hot end up and running again, because after adding new thermal paste to it, it performed badly, else I’ll probably scrap it.

The conclusion I have so far is that it’s not worse in thermal transfer than the thermal paste used by BBL, and it will never dry up, but removing the ceramic heater may be destructive to the heater.

Which brings a new question, if the heater can be removed without destroying it, can it be reused ?

[ng1]

I have tried the 0,05 on the failed hot end as well, and I think something in side of it is defective or partly blocked, or maybe I have damaged it during cleaning earlier, because the thermal paste application seems to have covered the contact area nicely.

Here are some results with the following hot ends used:

1. New standard out of the box hot end
2. Old hot end with new thermal paste from BBL
3. Old hot end with 0,05 thermal pad
4. New hot end with 0,05 thermal pad

I Have only tested with a volumetric speed test

No.	Speed [mm³/s]
1	22,5
2	9,55
3	9,57
4	23,67