CHT nozzle problem with seam

Bambu Lab X1 Series
1

Hi all,

I have being using a CHT nozzle for a while without problems. Not to break any records. I hope the better flowing abilities will help the print quality (I print mainly @ 0.08 layer height).

Then I tried to print a simple cardboard spool adapter in BB PLA @ 0.2 standard profile (AUX off). The seam of the outer wall was wide open, but only on the outer wall of the upright part. The inner seam and the seam of the base looks ok.

This happens only with the CHT nozzles. A hardened stainless steel BB nozzle does not have the problem.

Has anyone had this problem? Any ideas what might cause this?

Files and photos below.

Print file:
https://www.printables.com/model/351187-polymaker-cardboard-spool-adapter-for-bambulab-ams/files

The pictures below show:

  • white ring printed with an old and proven 0.4 CHT brass Aliexpress nozzle
  • grey ring printed with new 0.4 CHT brass Aliexpress nozzle
  • green ring printed with 0.4 hardened steel BB nozzle

PXL_20230525_075105672 (Large)
PXL_20230525_075105672 (Large)1434×1080 235 KB

seam of outer wall

PXL_20230525_075702656 (Large)
PXL_20230525_075702656 (Large)1434×1080 240 KB

seam of outer wall base

PXL_20230525_075805981 (Large)
PXL_20230525_075805981 (Large)1434×1080 177 KB

inner seam

1 Like
2

Low Filament temp comes to mind. It is hardening up and not getting enough adhesion during the layer change. READ - the nozzle makes contact and starts moving, dragging the initial contact along until the new extruded filament sticks to the previous layer.

Maybe too much cooling.

3

Hm, printed @ 220° without the AUX fan. If the filament did not adhere and was dragged along, I would have expected a bigger blob when it finally sticks.

I will print it @ 230° and see what happens.

4

Did you re-calibrate the filament flow rate and pressure advance when you changed to the CHT?

1 Like
5

I did for the BB basic white. I found the orca flow and PA results where the same as for the BB hardened steel nozzle.

Do your flow and PA settings differ a lot between BB and Ali CHT?

6

For me. Yes. Flow and PA are lower with the CHT nozzle

Neon-Orange PETG from Extrudr:

Stock 0.4 - Flow: 1.03 / PA: 0.042
CHT: 0.4 - Flow: 0.9785 / PA: 0.032

1 Like
7

Hi all,
Found some time to look into the CHT seam problem.

Thanks to the new automatic calibration tool of the latest Bambu studio/orca a better PA was found. It is significantly lower then for the Bambu stainless steel nozzle.

Filament: PLA BB basic grey @ 220°

Stainless steel standard:
Flow - 0.97
PA - 0,021

Brass Ali CHT:
Flow - 0.97
PA - 0,016

Thanks julie777 an cl33