Best posts made by nhfoley

@Phaedrux said in Horizontal banding defect, non-kinematic. Need some help!:

Are you not able to control the bed heating loop via the Duet so you can PID tune it?

I have the parts for that in hand, but was holding out with the hope that I could use the off-the-shelf controller for a few months and learn firsthand whether something more sophisticated (like a system with independently controlled quadrants & super well isolated AC) was the better path. Seems like I at least need something of a middle ground to start.

Ugh, solved. The primitive bang-bang controller of the AC heated bed system was causing enough temperature oscillation to generate slow-moving thermal expansion waves that caused this time-dependent layer variation. I'd initially dismissed this as the cause because the temperature variation didn't seem high enough to explain things, but since there are two independent AC zones running bang-bang, the two cycles were probably going in and out of phase with each other to double the amplitude. I ran one of the same prints after unplugging the at-temperature heated bed, and the finish is basically flawless. Time to build a more sophisticated controller for the heated bed...