HELP!!! I’m getting desperate. Can anyone tell me what is wrong here. I’m printing BambuLab PLA-CF. It has been dried (20%), calibrated to K number and Flow Rate. I’m using Tree support. I’ve tried all 3 different tree supports and the prints are all showing same/similar flaws. I’ve tensioned the xy belts (twice) done machine calibration and self check. The print starts immediately above the top of the tree support. Grateful if you can help 
What’s the "access violation message " about? Do your printer shows a “violation” message? If it does, when does it show, what does it say, and have you checked with Makerworld Wikipedia to see if someone else has been confronted with a similar or identical situation?
It sounds like you’ve tried a lot of different things, which can make troubleshooting a lot harder as one cannot know what is having an affect or not.
Rule #1 of Troubleshooting:
Change only one variable at a time. This approach will help you identify the issue more accurately.
Here’s what to do next:
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Isolate the Problem Areas: It would help us help you if you can post clear screengrabs of the model from different angles and images of the sliced model. This will help the community understand your goals and identify potential issues. Art the moment, all we can see is what looks like a bar with holes in it. It’s impossible to infer what the output was intended to look like.
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Use the Cut Tool: Trim a section of the model where the errors occur. Focus on reproducing the error on a smaller scale by experimenting with different cut sections. This will allow for quicker test prints and save time and filament and allow for quicker experimentation.
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Go Back to Basics: Before tackling the complex model, print simple test shapes such as a Benchy or a Vorlon, Orca test cube. This will help confirm if your printer is properly calibrated and rule out any setup issues as everyone here in the community knows what those shapes are supposed to look like and can all weigh-in on what they may see as issues.
If you can upload the 3MF model. Others can then also take a crack at your exact model and see if they can reproduce it. Use the new upload tool in the toolbar at the top.
If you can’t access that tool, you may have to go back to the forum help screen and take the forum’s short tutorials which are required before some features are made available to newer users. This is an anti-spam measure to ensure that humans are posting and not bots.
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This is the 3mf file if you could take a look and let me know what needs changing. The model is a yacht rudder with tubercles.
21.09.24,1xV3,vert,200x65x7,vlh,normshaft.3mf (611.7 KB)
Many thanks for your help and advice all, and Olias in particular.
We’re making progress! Thanks for sharing the 3MF file; this will help us move forward quickly.
The current configuration of this 3MF file won’t allow the model to print properly.
I recommend combining the two objects into an assembly before conducting further diagnostics.
To save time and filament, try cutting the assembly into a smaller piece using the cut tool. Then, re-run your print to see if any undesirable artifacts appear. If they do, you’ve successfully created a good test model, and real troubleshooting can begin.
Based on the original photo, here’s the recommended cut. This should reveal the part of the model that’s causing issues.
To conserve even more filament, you can lower the model below the build plate. The less of the model above the plate, the quicker the print. Don’t hesitate to start with just a 25mm high model and gradually increase the height until the artifacts reappear.
Drag the z-axis arrow to move the model below the build plate like this:
If you see this error, don’t worry—it’s a known bug in the slicer, which misinterprets the object before the cut. The model should still slice and print correctly, and you might not even encounter this error.
The goal here is to isolate a specific section of your model for testing. This will allow you to optimize without wasting time and filament.
To bring your profile back to a ‘known’ state, I suggest resetting all defaults. This way, you follow the primary rule of troubleshooting: change only one variable at a time. Right now, there are over a dozen modifications to your profile, making diagnostics very difficult.
Lastly, before making any further changes, if the test model still shows errors, that’s actually a useful result. It allows us to rule out mechanical issues and focus on filament problems. The best way to do this is by using Basic PLA test filament that you know works well. If the errors persist, then it’s time to inspect for mechanical issues before tweaking filament settings.
BTW: I can’t tell from your photo, but can I assume it’s from this section of the model? If so, apply the steps above but make the test cut horizontally instead of vertically to isolate the problem area.
Good Luck. 
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I tried your 3MF, just in plain PLA settings though.
Correct me if I am wrong here:
You are printing this fully vertical and the main issue is those nice bumps that come out messy ?
Rounded overhangs like these are a total pain with most filaments.
Using 4 or more walls and a lower layer height of like 0.12mm would help but is probably not a good idea with CF filament.
I tried to export the STL for the part but Bambu made a total mess out of it - it it wasn’t a mess already.
The part, in my Cad program looks as if it was put together and joined from several individual parts rather than being designed as one piece.
Lots of inconsistencies that make working with it too hard and time consuming.
Assuming you properly merged and fixed the two parts in your design program:
Cut this impossibly thin edge off!
Make the edge a 0.4 to 0.6mm flat edge, than extrude this by 8 to 10mm - this addition you can later just cut off cleanly to get the desired edge, no need for this cylinder.
Also angle the part a bit more…
Not sure if you are aware but at least the exported STL is not flat on the plane which means supports below would be required or a raft.
I found an added angle of 20 to 25% provides sufficient change to print those noses without mess.
Fantastic response! I will do as you suggest and report back. Again 
Vertically yes as I have found printing this way the surface finish on the “bumps” is better than horizontal. It is a rudder so water needs to flow across the surface as smoothly as possible. The bottom 65mm is 99% “solid” as there is a hole for a rudder shaft that needs to be strong. The rest is infill to keep weight down. The sharp, thin edge is a very important part of the design and cannot be eliminated. I’ve oriented the print so that the sharp edge is vertical and can be supported by the cylinder.
The cylinder is there as support as near the top the print was wobbling and causing issues.
The 3mf file does include a support tree which is in the original pics posted.
I have printed many of these without the flaws pictured earlier so something has changed fatally.
I will try angling the print 20 to 25 degrees (?) as you suggest. Many thanks
OK Olias, I will do as you suggest. I’m expecting a new E3D diamond nozzle in the post and was going to switch that in to see if it’s the nozzle (Obxidian 0.4mm)
BTW I printef off the Bambu V2 cube last night and it’s a mess!
But it may be something else so will concentrate on those other things.
I’ll report back.
With a cube like this I suggest you check the filament calibration.
No wonder if the rudder fails if the cube is already such a bad mess.
I have run flow rate and flow dynamic but I can run it again. The Cube was printed after the problem flaws with the rudder. I wanted to establish if the Rudder GCode was at fault.
how do you measure the dryness of the filiment?
The quickest and easiest way to get a handle on how dry your filament is is to drop the spool into a poly box like these with a hygrometer, close it up, and let it sit a couple of hours before reading the hygrometer. No desiccant. Just spool and hygrometer and also know best results will be with full to mostly full spools. Too little filament or if these are cardboard spools can throw the results.
The humidity value it stabilizes to is in effect a measure of moisture in the filament but is modified by filament type. The numbers won’t mean the exact same so if you start doing this only compare numbers of similar filaments. PLA to PLA, PETG to PETG, etc. (Added - it could be they all behave pretty much the same too but no data yet to support saying you can compare across filament types. We just don’t know yet.)
A properly dried spool should cause the humidity to plummet. On my filament they all go to 10% RH pretty quick. That has been good for all my printing. Any numbers above that and there’s more water in the filament. Undried PETG HF has had numbers like 40 and 42%. After drying, 10% or less. (I don’t know the actual humidity when they display 10% - just that it’s 10% or below since that’s as low as my hygrometers go.)
Something to also keep in mind is we don’t have a good handle on how low is necessary. It could be 20% is good enough, but if you see numbers above 30% it’s probably getting iffy. Anything higher is worse. But I don’t see moisture effects now with numbers at 10% or less.
OK. Now that we have a reproducible ‘known’ model to observe, we can offer clearer observations and possible fixes. This is why it’s crucial to return to basics when troubleshooting: start with a known factor and avoid changing multiple variables at once.
I don’t think changing the nozzle will fix this problem. In fact, you’re breaking the #1 rule of troubleshooting: change only one variable at a time.
This cube shows classic signs of a flow problem, which should be addressed first. The two main causes of flow problems are incorrect temperature/flow settings or filament feed issues. Adding a new nozzle is an unnecessary expense and might not solve the issue. Will it help? Maybe, but you’ll still have the underlying flow problem, and you’ll be out of pocket for something that might not have been needed—unless you wanted that nozzle for other reasons.
Here’s a new checklist:
- If you’re using an AMS, remove it from the feed and perform a single-spool print test of the cube.
- If the problem persists, inspect the PTFE tubing for wear. Although unlikely, a feed issue can cause erratic filament flow. I don’t see signs of this in your photo, but it’s important to rule it out.
- Try printing with a different filament as a reference. If the same problems occur, it could indicate a nozzle issue.
- Clean the nozzle. Remove the PTFE tube and manually feed a section of another filament using the control panel. Choose a contrasting color of a filament that has been tested to produce a clean model and check for any residual filament. The contrasting color will show any contaminants which can be used as an indicator of when the nozzle is complete purged. In your case, white would be ideal given the dark filament you’re currently using. Set the nozzle temperature to above 250°C.
Here are a couple of quick tests to diagnose flow problems:
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Perform a max flow rate calibration using Orca, or set a very low flow rate in the settings—around 10 mm³. Then rerun the cube test and if there are differences in the outcome, you have likely found the culprit. A max flow calibration test using Orca Slicer will help you optimize the filament settings. Bambu Studio does not have this test.
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Reduce the overall speed by setting the printer to silent mode after it starts printing. This will slow down all head movements. Use the printer control panel, and make sure the button press is registered. Bambu firmware can be unreliable with this function, and speed settings only take effect after bed leveling, purging, and the start of printing.
Hi Mzip,
I am very careful about humidity. I have the latest Sunlu 4 reel dryer which I mostly use for printing out of instead of the Bambu AMS which I find troublesome with PLA Carbon fibre. My failed prints have been with Bambu PLA-CF but I have had mostly successful prints with this material before.
I also have 2 Solvol 2 reel dryers which I use to maintain low humidity.
Hi Olias, very sensible advice and I will follow it. I’ve removed the nozzle (E3Ds’ Obxidian 0.4mm) as part of a big maintenance programme.
As you can see it was hidden under the silicone sock and removing the sock reveals a bit of a mess! I have a spare new one so I will change it and repair/renovate the one removed.
I have downloaded Orca slicer which I have not used before. I will give all the tips a go and report back.
BTW the new nozzle printed a Cube and disc test perfectly (with Basic PLA)
Many thanks again for all the time and trouble you are taking.
See pics attached!!
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Why did you put the hotend on the BBQ together with the meat ? 
That will take bit of work to get the E3D back to a good shine and clean surface…
But could also explain a lot of your issues with the prints.
While their hotends are really great and fast - they are NOT ever lasting.
Once this inner coating wears off, like it does with abrasive filaments over time, I find their benefits quickly quickly disappearing.
I use the E3D for ‘nice’ filaments and cheap hardened steel ones for those filled filaments.
It’s back to almost new condition now (not sure about the innards though). As you said it did take quite a time to clean up. It was seriously carbonised!
New nozzle fitted (E3D DiamondBack) and this is what the print should look like!
Thanks all for your time, interest and help.
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I have found when my filament starts getting to 20% or higher that is when I start noticing issues.
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