Layer Consistency

I have a Taz 6 (about 6 months old).
I am having an issue with layer consistency and could use some input.
Image1 shows a cross section of a single wall test cube from the Taz 6. The layers are not consistent leading to a rough surface finish. Interestingly there seems to be a repeating pattern. Pla white, .5mm nozzle, .2 layer height, Cura
Image2 shows the same cross section, same material, different printer. This printer has a direct drive, no gear reduction, extruder. It shows very consistent layers and a smooth surface finish.
I’m thinking the problem is errors in the printed gears. Is there anything I can do about it?

Try tightening the idler arm tension bolts, and make sure the small gear setscrew isn’t slipping. you can also adjust the gear mesh by unbolting and moving the gear mesh tighter. The printed gear should be fine unless you have one with a noticible wobble. Usually the pulsing like that is either due to under or over extrusion in the profile (usually due to incorrect fillament settings, incorrect starting layer height, or improperly calibrated extruder) or mechanical feed slipping usually caused by idler bolts not being tight enough. Start with around 7mm distance between the two washers on either side of the springs on the idler arm and see if that helps.

edit: looking at this further, it’s most definitly underextrusion. THe layers that are narrower are also thinner. That means you aren’t getting enough material there. I was suspecting Z wobble or deflection for a second, but this is almost certanly underextrusion, either software or mechanically derived.

Thanks for the reply!
I will try out all of the above.

I have a TAZ 6 and am always concerned with whether I have this tension correct. Is there a disadvantage (or obvious symptom) if the idler is too tight?

Too tight and it places strain on theidler arm. It can also theoreitically cause an issue by causing a pinch point at the hobbed bolt bearing interface and causing grounding, but generally it’s better to be too tight than too loose there.

If the idler is too tight and you have a bunch of retractions in a short period of time, it can wear down the the filament in one area and cause a strip out. I have found that it is better to be a little tighter rather than looser overall. Just make sure you don’t fully compress the springs.

Thanks nopick. So far I haven’t experienced anything like that since I’ve started keeping it tighter. I’ll assume the torque settings in my thumb and forefinger are right on :wink: