My A1 printer calculates an incorrect pressure advance K-factor during automatic calibration for a standard PLA filament. It comes up with a K value of 0.059, which seems too high.
When I run a manual calibration print, I usually end up choosing values around 0.035–0.04. With higher values, I start seeing gaps between walls. Using the same filament on my P2S and running automatic calibration, I get a value of 0.032, which looks much more reasonable.
I haven’t been able to identify the root cause of this issue. In other forum threads, I’ve seen people reporting similarly high K values on the A1, and many of them eventually gave up and started using default values, saying that the A1’s automatic calibration doesn’t work properly.
Is there anything I can do to fix this, or should I switch to manual calibration for all of my filaments?
The values of PA shouldn’t be compared directly between printers, especially since the extruders are so very different between a1 and the p2’s servo based one.
That being said, I find the auto calibration to trend over, as well, but usually acceptable. I dont use bambus software anymore so the whole “saving back the K value” isnt a thing, and you just do the test. I like the test anyways since you can match it to the exact motion inputs of your outer walls (speed,accel,jerk) not just the extrusion output thats being measured in the eddy current thingy
I’m using the same hotends on both the A1 and the P2S, and when I run manual pressure advance tests, I end up with very similar K values on both machines.
However, when I use automatic calibration, the results differ significantly between the two. In my experience, the values reported by the P2S are much closer to what I observe in real prints, while the A1’s auto-calibrated values tend to be noticeably off.
You mentioned motor differences, but as far as I understand, the extruder motor itself shouldn’t directly affect the K value. Pressure advance is mainly influenced by print speed, hotend/nozzle diameter, filament characteristics, and filament moisture content. If my understanding is correct, these factors should matter much more than the motor type alone.
That’s why I find it confusing that two printers with the same hotend and very similar manual PA results can produce such different values when using auto calibration.