Sorry if I’m getting a bit repetitive 
Thought I had it perfectly tuned, but these appeared after around 30 hours of printing. Any ideas? It looks like z wobble except the amount of wobble oscillates. MakerFarm 10" i3v with an E3D v6. Added contrast to show the ribs.
Sorry to get off your topic, but what are you doing for a mount for your E3d, I was going to get the i3v 10" without a hotend and go with the E3d, but wasn’t sure how I would mount it
@Todd_Morris I had to print a mounting plate. if you buy it with a hotend it includes one, but otherwise you might need to have one printed for you. Maybe ask Colin to include one.
@Alex_Lee I’m not sure what you mean, the artifacts are on the Z axis where the infill doesn’t change between layers.
@Alex_Lee Nah, I think those are artifacts of too much acceleration.
It is too late to check, but it could just be variances in the filament diameter.
@Wylie_Hilliard That is very possible, and would make complete sense since the ribs are more visible on larger prints.
@Alex_Lee No problem, I’m not incredibly experienced either so I’m happy to help!
Could also be attributable to PCB bed flexing under temperature expansion. This caused a Z-wobble that drove me nuts for a long time. PID or PWM bed control should fix it. Repetiers dead time control is quite nice also.
@Sanjay_Mortimer Mine actually drove me nuts for a while too, but I’ve got an SSR for my 10" bed and PWM enabled now. Thanks for the suggestion!
If the bed is definitely not the cause then I would look at (in order):
Filament diameter varying
Spool tension changing. (can pull up on Z axis)
Leadscrew nasties or inconsistencies.
Temperature fluctuations in ambient environment
Thanks! I think you’re on the right track. I’ve been messing with the filament and I think it’s either diameter or spool tension.