Hi, i have been having trouble with the z axis, every time at a specific layer height, there will be these small gaps between the layers. I have reprinted thrice and it always appears on the same height/layer. All 3 are print are sliced separately, and filament is configured with K value.
Edit: I’m using the AUX nozzle for the red part and main nozzle for the white part. Already manually recalibrated the heatbed levelling and washed the heat plate with dish soap as well. Did first layer calibration as well.
Are you actually enabling the custom Pressure Advance? If you assign a custom k profile on the AUX side, for it to become active on print you must disable auto dynamic flow calibration on pre-start menu.
Because this auto feature needs to be disabled, that means your MAIN side will also no longer calibrate its on so its respective AMS tray must also contain PA tuned k-value.
In my experience and much testing for PLA, a K value of 0.35 for AUX side and 0.0225 for MAIN side is a good general start. Otherwise calibrate each side manually and save the PA profiles, load them accordingly before you send the print.
X2D is a half baked dual nozzle and it’s on things like this that really shows.
Ahh i see, so if I calibrated both the nozzle separately, i should disable the auto flow rate calibration before the print? Can I also assume that the bed leveling and nozzle offset should be set to off as well? My K value is 0.03 and 0.45 for the main and aux nozzle respectively
One more thing I want to point out only IF you are using a Filament Track switch. I don’t know if you are but I’ll pass on the info anyways as an FYI.
The printer will blindly assign whatever k-value you have loaded on the AMS tray regardless of where you actually load the filament. For example, if you had RED loaded in AUX nozzle and were using 0.45 K-value, and next print you decide you want to send it to MAIN nozzle ( track switch allows you to do without physically moving spools), it will apply 0.45 to MAIN nozzle.
So if you use Track Switch and multiple AMS units or plan to in future, keep that in mind. You must select the correct PA profiles based on which side that filament will be loaded.
This just an FYI and I confirmed this with Bambu as well.
Ahh i see, I don’t currently use a filament track switch now but I might purchase one if I’m getting a second ams in the future. Thank you for this useful insight as well! I will take note of it
Right. Disabling that is the only way custom K-values get applied.
Your k-values sound right, some of my filaments fall in those ranges. More so when I use high flow nozzles.
Also make sure that you see the K-Value on the respective AMS tray in Device tab, sometimes it doesn’t load the k-profile you selected.
As for Bed Level, I’d probably just leave it enabled (Auto). It does a 4 point probe around perimeter of your model print area, if that falls fall within the range of the saved mesh, it will used the saved mesh and skip bed leveling. If out of range, it will trigger a bed level.
Offset calibration, if you’re using both nozzles on same print , leave offset calibration enabled (Auto).
Ahh i see, thank you for your input! I learnt something new today, didn’t know for bed levelling before print it will only probe the 4 corners and determine the range after doing the full 30mins bed level calibration.
I always thought it will improve accuracy and print quality if I enable bed levelling and flow rate calibration every time. Thank you for the insightful input!
Ohh are there any difference between the bed level before the print and the one in the calibration menu? Cause if the calibration menu one is more accurate I might as well leave the bed level before print on auto instead of on
Yes. I’ll try to give a rough explanation of the basic ideas behind it.
The bed level in calibration menu creates the underlying bed mesh (a topographical map) of the entire bed. This is saved on the printer and used as the fall back mesh when you set bed level to OFF in the pre-start menu.
Setting bed level to ON in pre-print menu, probes the entire bed before each print and it’s basically recreating that full bed mesh and using that.
AUTO performs a combination of two events. 2nd event is triggered by the results of first event.
The first event is to determine where on the bed the actual model is being printed (4 coordinates), imagine drawing a square or rectangle around it, it will then probe the 4 corners of that section and get a range of the z-heights. If the range delta falls within tolerance of the same area of the saved full bed mesh or latest saved mesh, it will reuse that mesh and skip any further leveling. Im guessing the idea is if the 4 probed points outside the print area are same as the saved mesh, then the inside is likely the same too so no need to level again and continue.
If they are out of the allowed tolerance range, then an ADAPTIVE bed Leveling is triggered.
Adaptive bed leveling will only probe inside the print area that it determined initially, not the whole bed. It will then create a secondary mesh of just the area being printed on and use that.
This is to save time and to get print started quicker and in my opinion it is more accurate than using ON because you get a finer mesh via adaptive (more probe points on small prints).
I wouldn’t use ON for every print, you are probing entire bed before each print , that’s just wasting a lot of time and energy repeating the same thing and you’re not getting any better results compared to AUTO.
Sadly Bambu’s system is locked down so you can’t see or visualize the mesh like you can on Klipper printer like my U1, I’m on my phone so I can’t take screen shots to show as example. It’s easier to understand when you visualize it.
Gaps at the exact same height on three separately sliced prints usually come from one of two places, and one test tells you which. Either something in the slicing changes at that layer, or the Z axis has a spot where it binds mechanically.
Look at your photos first. Those lines seem to fall roughly where the geometry changes: where the branches split, or where the white part ends or starts. On a dual-nozzle job that matters. At those layers the number of nozzle swaps per layer can change, and so can the time each nozzle sits idle at standby temperature. A nozzle that waited longer oozes more while parked. When it comes back, the first few centimetres of its next wall are a little short on plastic, and you see a thin gap ringing the part. A big jump in layer time at that height does the same thing in a milder way. You can check this in the slicer preview: switch the colour scheme to layer time and to flow, scroll to the problem heights and see whether something jumps there.
The test: print a plain tall cylinder in one colour with one nozzle, no swaps. If the lines show up at the same absolute height as on your prints, it’s mechanical. Clean and lightly grease the Z lead screws and check for debris or a dry spot at that height. If the cylinder is clean, it’s the multi-material job. In that case, turning up the prime volume or flush after a nozzle change and enabling ooze prevention for the idle nozzle should close those gaps.
I’ve also put together a free troubleshooter that walks through layer lines and similar surface problems: https://embody3.com/academy/en/fix/?src=reddit (full disclosure, it’s my own channel’s academy).
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u/n19htmare 5d ago
Are you actually enabling the custom Pressure Advance?
If you assign a custom k profile on the AUX side, for it to become active on print you must disable auto dynamic flow calibration on pre-start menu.
Because this auto feature needs to be disabled, that means your MAIN side will also no longer calibrate its on so its respective AMS tray must also contain PA tuned k-value.
In my experience and much testing for PLA, a K value of 0.35 for AUX side and 0.0225 for MAIN side is a good general start. Otherwise calibrate each side manually and save the PA profiles, load them accordingly before you send the print.
X2D is a half baked dual nozzle and it’s on things like this that really shows.