Local under extrusion

[Johnh76]

Having an X1 Carbon with 670 hours print time. Recently I have seen problems with under extrusion in the innermost area of the print bed and along the right side.

I haven’t seen it before, although I rarely print in that area. But I needed to print something that makes use of the entire build plate.

I immediately thought: print bed, so I did a manual bed tramming. Then did a new flow and flow dynamics calibration, but it didn’t help.

The filament is Bambu black basic PLA (through the AMS) and using Bambu’s own settings. 0.4 nozzle. The machine is completely stock.

I tried both the cool plate and the textured PEI plate with very similar results. Tried both Bambu Studio and Orca slicer with no difference between them.

I’m not sure how to proceed as the rest of the print looks fine. It’s only the innermost area that looks bad, but it causes bad warping in the print a few layers later.

Any ideas are most welcome.

[EnoTheThracian]

Mhm, strange. Usually, the Auto Bed Levelling should take care of bed induced changes in nozzle distance…
If it was only the back, I would hazard a guess as to draft influences but there should then not be anything on the right side. Do you also get that with a higher temp plate like tje smooth PEI?
Finally, it may help to run through the full recommended maintenance. Bambu Lab X1 Maintenance Recommendation | Bambu Lab Wiki Not that it’ll help directly, but it’ll rule out a lot potential root causes like the Lidar.

[Johnh76]

Yes, it’s really strage. I have never seen anything like that before.

I don’t have the smooth PEI plate unfortunately. But I could try the engineering plate.

I have gone through most of the mainyenance suggestions, but I will go through the rest as well. Thank’s for the tip!

[Olias]

1. Does this sort of rippling occur in the same location on the build each time?
   
   
2. How thick is the test sample, are we looking at a 0.20mm first layer test?
3. Does it happen with all filament types?
4. Have you tried testing without the AMS and used a direct feed? Does the result vary at all when you do this?

If at all possible, is your camera capable of doing a macro closeup of the ripples? If so can you post both a regular photo and a macro closeup of the same area?

[Johnh76]

@Olias

• Does this sort of rippling occur in the same location on the build each time?

• How thick is the test sample, are we looking at a 0.20mm first layer test?
• Does it happen with all filament types?
• Have you tried testing without the AMS and used a direct feed? Does the result vary at all when you do this?

1. Yes, always the same place on the plate
2. 0.2mm, first layer test. I printed a real part this morning, that showed bad warping in the same area.
3. I have only tried PLA and PETG, as it was what I have at home for the moment.
4. No, I havent tried this yet. I assumed (probably incorrectly) that since the under extrusion doesnt happen everywhere, it probably isn’t the AMS. But increased friction in the AMS could of course create problems anyway. I guess, when the print head is in the innermost areas of the printer, the resistance in the filament path is at it’s highest (bent tubes, etc.). I will try that too.

Z-axis wobble?

[Olias]

Thank you for providing close-up photos and answering questions; this detail is very helpful.

There are two possible culprits here and this is what I might suggest as a troubleshooting tests to see which one is more likely the case:

Possible Cause 1: Filament Calibration

To start, I normally don’t trust the factory settings, you may what to check filament calibration. Since under-extrusion occurs at the end of nozzle strokes, it could point to a calibration issue, which is usually easier to troubleshoot. Also note that since you’re system has 700 hours on it, if you are relying on auto calibration, you may want to clean the lidar or disable it to see if it affects the test model. While you’re at it, check to see if there’s accumulation of filament under the silicone sock. Sometimes this can interfere with temp sensors.

Troubleshooting Step 1

It might be simpler to first rule out a second possible cause, which may align with your suspicions. Try using the slicer’s cut tool to isolate the problematic section of the model. This will let you see if under-extrusion persists with the model section when printing a smaller area. If it does, a mechanical issue becomes more likely.

Possible Cause 2: Mechanical Issues

An easy test here is to switch the first layer’s flow pattern to circular. By using a circular pattern instead of linear, you’ll observe if under-extrusion occurs at the same points. Consistent issues with a circular pattern suggest a mechanical problem.

If you’re unfamiliar with changing the flow pattern, here’s how: In your slicer settings, set the top layers to 0 and bottom layers to 1 for the concentric pattern to take effect. In the example shown, I’m using a 50mm square on the first layer to make nozzle stroke changes more visible.

Default version

[Johnh76]

It’s I who should say thank you. I’m very thankful for the time you put in to help me

I will start with going through the maintenance list. Then I will try both of these suggestions. Before seing this, I already tried without the AMS. The AMS isn’t the culprit, it seems, as the result without it is exactly the same.

I normally don’t use the auto calibration. I use the manual calibration in Orca. I was running on my own profile until the problems srarted. When I couldn’t resolve them, I did a factory reset and tried with no changes. When that didn’t help, I did an auto-calibration.

[Johnh76]

The order became a different one. I tried your suggestions first:

The cut version showed no clear improvement.

The result of the concentric pattern test was interesting though. Although the result isn’t perfect, the improvement is huge. The far right corner still shows small issues, but everything else looks fine.

The pattern looks a bit funny though… I hadn’t expected to see what looks like seams in so many places.

I will do all the maintenance checks now.

[Olias]

Those are very interesting results; however, I don’t think they give us enough data to draw a conclusion. When I mentioned cutting out a section, I meant to include part of the model that was smooth as well. Sorry if I wasn’t clear. Here’s what I meant:

Expanding the section to include both the clear and distorted areas helps determine if this issue is mechanical. Look for size changes in the distortion, did it get bigger or smaller? If there’s no change in size and the areas with good and poor flow are the same in both dimensions and location, that’s more conclusive. If the extrusion problems recur in the exact same location, this likely rules out the nozzle running out of molten filament due to travel distance and points us back to mechanical issues.

Another point—the circular test here doesn’t show the full travel pattern. Sticking to a symmetrical model print in circular pattern, like before, may yield better insights. This missing notch makes the test ambiguous and loses its value as a test.

Two Possible Alternate Theories

Theory 1: Bed Temperature Fluctuation

This is a long shot, but it’s worth ruling out. If you have an IR thermometer, check the build plate’s temperature consistency at the edges with and without the bed attached. ±5°C of variation is acceptable; greater deviations might suggest plate contact issues, affecting print quality.

If you don’t have an IR thermometer, they’re helpful for diagnostics and available for under $10 on Amazon or at auto parts stores.
https://www.amazon.com/s?k=ir+thermometer&s=price-asc-rank

Theory 2: Bed Warpage

There were early reports–most were debunked–some earlier beds had bowing issues. But Bambu did offer some folks bed replacements. Contact support and see what they think. The bed calibration was supposed to correct this, but it’s worth verifying that the bed itself didn’t warp. Try laying a steel ruler across the bed and look for any light peeking through. A small gap is normal, but a middle bulge causing the ends to drop by 1mm or more is not.

BTW: I know you said you ran the original initial bed calibration but have you repeated it?

Retro Test Using Painter’s Tape

Before heated beds, painters’ tape was commonly used for adhesion. Applying tape over the problematic area might offer additional clues. If you see improved filament adhesion with the tape, this leans more towards a mechanical cause.

[Johnh76]

I understand. I have done those tests again, but the results are not entirely conclusive.

1. New print containing both the “bad” area in the corner, but also an area that was good.

2. New print without the cutout in the corner. Maybe still not good enough as the print is rectangular due to the unprintable area in the ourer left corner of the build plate.

The interesting thing now, is that both prints look completely fine. I can’t understand why…
Only the tiniest signs of scraping, but that’s kind of normal.

The temperature looks fine @35 degC. There is only a difference of 0.2-0.3 degC over the whole build plate. @55 degC I see about 2 degC lower temp in the corners. @90 degC it doesn’t look good, with 10-20 degrees lower temp in the corners and half of that along the sides. That would likely be a problem if printing ABS or nylon, but for PLA it shouldn’t be of any concern I guess.

I haven’t checked with the ruler yet, but I will do that as soon as I get the chance.

[Olias]

At least you’re making some progress by achieving uniformity. I still suspect mechanical issues, but I also see possible flow rate inconsistencies in your filament.

Are you using the original extruder that came with the printer? There could be wear in the extruder itself causing flow issues. Filament calibration can compensate somewhat, but the ultimate solution would still be to clean or replace the extruder.

Check out this recent post where someone had similar issues. They shared images of their worn extruder. Their problem involved wall gaps, but the solution might apply to your case as well.

When they finally checked their extruder, this is what they found. It may help to check yours as well. Once they replaced their worn extruder, the issues were resolved.

[Johnh76]

Yes, it’s the original extruder. I would expect more life out of an hardened steel extruder than roughly 600 hours. But I will take ot out and have a look at it. I will be going through all the maintenance points so it makes sense to do that too.

To be honest, this printer has been somewhat of a lemon so far so I can’t exclude that this has been there from the beginning.

I just printed the full first layer rectangle again (linear pattern) and the problem is back. The right corner looks ok, but more or less the whole inner side is of poor quality.

[Olias]

@Johnh76

To be honest, this printer has been somewhat of a lemon so far so I can’t exclude that this has been there from the beginning.

I totally get it—that feeling of disappointment when a product doesn’t live up to its promise, especially when you’ve invested in what’s supposed to be the “leading-edge” option. Bambu may be ahead in the turnkey 3D printing space, but as you’re experiencing firsthand, there’s a massive gap between where this technology should be and where it currently is.

It’s not just you; for all its hype, the tech simply isn’t as polished or reliable as other modern desktop equipment we’re used to. When you’re sold on ease-of-use and end up troubleshooting half the time, it’s beyond frustrating. Hopefully, your experience with this “lemon” turns around, but you’re definitely not alone in feeling the way you do.

[Johnh76]

I’m an engineer so I don’t expect a turnkey experience. 3d-printing may never reach that level. My first two printers were Creality’s. With them, you could kind of assume that nothing was straight and almost nothing was tightened . Then I went to Prusa and it was the complete opposite - it just worked once it was set up. But it was slow and the build volume barely usable.

When i went for the X1C it was for the larger build volume, the enclosure and the speed. But at that price point I had expected the stability of the Prusa. The X1C hasn’t been stable and when problems are around the corner, tougher to fix than with the Prusa, partly because of the more closed ecosystem.

I mainly print large engineering parts for my hobby so the tolerances need to be tight.

Many thank’s for your valuable help. Very much appreciated.
I will continue to fault trace and if I find the culprit I will post the solution here, for others to benefit from.

[Olias]

@Johnh76

I mainly print large engineering parts for my hobby so the tolerances need to be tight.

I recognize that chair. That’s one serious hobby. I don’t see a screen in front of that chair so I’m assuming VR? What sim do you use?

[Johnh76]

I’m rebuilding it at the moment so it’s not prectical to have the screens in there due to space restrictions.
I use a Pimax Crysal headset and, when not in VR, 3 55" LG C4 TV’s.

Mainly ACC, iRacing and AMS2. But also dome flight simming on occasion.

[Johnh76]

The extruder gear is fine. It looks like new. No visible wear at all.

The images don’t do it justice.

Replaced the hotend with a new one while I was at it.

[Johnh76]

No luck unfortunately. I have done all the maintenance, cleaned the extruder, replaced the hotend. The result is better, but not good. It looks fine everywhere except in the right corner.

I am considering to feed the filament directly into the extruder, skipping the ptfe tube, to see if that helps. The tube is at its most bent state in the right inner corner.

Apart from that, I have no more clue on what to test. I do think this is mechanical.

[Olias]

@Johnh76

I am considering to feed the filament directly into the extruder, skipping the ptfe tube, to see if that helps.

That’s a sound diagnostic step.

Also, if it wasn’t mentioned, reach out to Bambu if you haven’t already done so. If they suspect a hardware issue like perhaps a failed heat bed, they may offer you one for free. It has happened before.

[EnoTheThracian]

What @Olias said.

When contacting Bambu, it may be helpful to have some of those bed shape pics ready. And probably include a link to this thread.

Also, but that is really grasping at straws, do you have local differences on the reflectivity of the plate? The Lidar is helpful for leveling but if the Lidar can not get a reading, it’ll just use the nozzle sensor reading. That is usually more than good enough but if there are small errors in the Lidar reading which do not trigger that fallback…
But @olias already suggested using the other side of the build plate or a different one, so … probably just me grasping at straws…