Like Z Banding

[Ce72]

Hi Everyone
I’m looking for some help and suggestions to try and eliminate a Z banding like artifact on flat surfaces (shown in the pics). I’m running an AWD HevORT core XY with a Hemera XS Roto extruder on a Duet3D 6HC mainboard with a Pi5 SBC, on 3.6.0-beta.3 firmware.

To me it’s not mechanical as the 40mm tube pic shows no evidence of the banding.

What I have tried so far:
Bed heater P.I.D tune, Extruder P.I.D tune, Belt tension balanced, Extruder E-steps checked, Various PA values tried, Wall print speeds from 100-200mms And a few acceleration speeds 7000 – 10000 on outerwalls, all with no variation in frequency.

Any suggestion to what might be causing this or what else to try would be much appreciated.

[droftarts]

@Ce72 I think this is very likely to be an extruder issue. What extruder are you using? I'm guessing it is a dual-drive. Watch these two videos, particularly the second one:
https://www.youtube.com/watch?v=dL6u0UwPJOQ
https://www.youtube.com/watch?v=32dTLRNIYmw

Print this object and see if you get the 'woodgrain' effect: https://mihaidesigns.com/inconsistent-extrusion/

If you get the woodgrain effect, then you'll know if the issue is the extruder. If the lines line up, it's something in your X and Y movement.

If you do get a woodgrain effect, he explains calculating the extrusion distance between artefacts in the second video from about 1:50, which can help pinpoint what's causing the issue. From the look of your print, it looks more like the 'cogging' issue of the large drive gears (rather than cogging on the smaller teeth that push the filament), and varying the extruder teeth pressure (usually reducing pressure) may help.

Ian

[Ce72]

@droftarts Hi Ian, thank you for your response, and also for the great links. After extensive trawling I also found a helpful video from MirageC pointing me in the same direction.

I'm using the E3D HemeraXS Revo extruder so there's not a lot of wiggle room for modding or testing. I have odered a new set of drive gears to see if that helps, the only other thing I can think of is to try and make an undriven idler for the tension arm. But hopefully it won't come to that.

Once again thank you for the input.

[Notepad]

@Ce72 That is VERY interesting, I use HemeraXS's on multiple machines and have never seen that behaviour before. Just to double check, as your are using the HevORT printer, are you using the wobbleX decouplers?
I'm seeing two artefacts, one if the diagonal lines, the other looks like a repeated Z band patten.

[Ce72]

@Notepad Hi, I built my HevORT 3 years ago this year. Yes, I have been using the WobbleX rings for over a year now. I have even upgraded to the experimental 2.6 (I think) version on the wiki, that I remodelled to suit my setup, I have added the pic so you can see what I mean, But I did this upgrade back in September along with going to AWD and everything has been working fine.

To be honest I have only had this issue start around Christmas when I had to strip the bedplate off to reapply the bed heater as the old adhesive had started to let go. I have done multiple P.I.D tunes to try and see if that eliminates the problem and I have been chasing my tail ever since.