So the '5 has been running nearly non-stop over the COVID lockdown for that last few months and quality was starting to go downhill. I was getting a lot of hanging up/skipping. I printed some towers to check Z cals and they were too tall (76.5mm vs. 75mm) My Z steps were at 408 steps/mm. Lowering steps/mm make the hanging/skipping worse and increase meant I had to extrude more to have good layer adhesion. I decided to replace all of the bearings and Z lead screws as they were making a lot of noise and developing stop. I installed those anti backlash lead screw pieces. That took care of the hanging/skipping. Movement is much smoother in all directions. I am presently printing at 402 steps/mm which gets the Z distance just about spot on over 75mm.
However, both before and after the maintenance, I get this odd striated pattern as you can see in the pictures below. The part itself is very strong. The hot end temp is very steady at 240 +_ a few degC. Bed temp is 100C. step/mm cals are X80 Y80 Z402 E407. Accel is 100, jerk is 5, speed is 80mm/s with walls at 40mm/s.Retract is 2mm at 60mm/s.
I have cleaned the lower frame of debris to ensure the Z belt is clear.
I am stumped on this one. Could the Z motor be bad?