Calibrate Pressure Advance and Limit Volumetric Flow Rate

To resolve melt zone pressure instability, you must align the printer's extrusion behavior with the physical limitations of the flexible TPU 70 filament:

1. Open your filament settings in Bambu Studio and locate the Max Volumetric Speed parameter. Reduce this value to 2.0–3.0 mm³/s to prevent the extruder from pushing material faster than the hotend can melt it.
2. Navigate to the printer's maintenance or calibration menu to perform a Pressure Advance (PA) calibration.
3. Print the calibration pattern and identify the optimal K-value. For TPU 70, expect a significantly higher K-value (typically between 0.15 and 0.30) than what is used for rigid filaments like PLA.
4. Update the filament profile with the new K-value and the reduced volumetric flow limit, then save the profile and re-slice your model.
5. Perform a test print to confirm that the surface finish is consistent and free of the pulsing or zits caused by pressure fluctuations.