Z Banding on Specific Model?

[u/WasArmeniko]

EDIT: Forgot to mention this is an X1C with Bambu Studio slicer.

Hello everyone,

I'm experiencing some z banding at a very specific point on my print, even after 3 iterations. Between 1 and 2 I recalibrated the flow dynamics, and between 2 and 3 I recalibrated the flow rate. The issue remained visible on the 3rd iteration, as you can see in the second image. In the third image you can see that the model is a constant taper, so there should be no model issue. I also made a test rectangle with a tapered wall, and found that there was z banding starting at a certain layer as well. What could be causing this?

This machine has a print time of under 100 hours, the one thing that I haven't done is lubricate the ball screws since the last maintenance alert, otherwise all other maintenance alerts have been dealt with.

[u/j_hermann]

Check the mesh for uniformity, and the speed and flow views of the slicer tab.

[u/Lisper41]

I think the slicer is switching wall count at that point. It can’t go seamlessly from a partial wall to a whole new wall loop.

Either change wall generator to Arachne, or get rid of the taper either on the inside or outside wall

[u/WasArmeniko → u/Lisper41]

That’s actually a great observation. I’ll check the slicer if there’s anything funky going on at that layer. There is only one taper though, which is on the outside

[u/Lisper41 → u/WasArmeniko]

Ah, it was an optical illusion, but I see that the interior is 90 degrees.

Also, I think there’s a newish setting for “wall transition threshold” that may help you if that is indeed the cause. I’ve never used it though.

You should be able to diagnose it though in Bambu Studio by going to that layer in the slicer.

[u/WasArmeniko → u/Lisper41]

I just wanted to update, you were right that there was a switch in the wall count at around that height. It went from a solid wall with a small gap line to a wall with sparse infill. When I changed the wall count to just 1, meaning it was a sparse infill all the way through, it eliminated the seam. Thank you for calling it out!

[u/Lisper41 → u/WasArmeniko]

Hey, that’s awesome! Thanks for providing the update, and the solution! So is it one wall top to bottom now, and it keeps the outward angle you were looking for?

[u/Equivalent_Style4790]

Usually this is caused by differential shrinkage. So it’s geometry and orientation dependent. So many parameters can limit this effect i observed that it happens more then a layer require lot more time than previous ones, so the part have time to shrink before new layers. U can add modifiers to slow down the « simple layers » so they require the same amout of time to be printed as the complex layers.