Need help on ribbing issues

I got struck by ribbing issues which I never encountered before and I'm unsure how I'm going to solve this. What I did was try to check on which acme rods that I used and it is TR8*8 (I think?) with 8mm lead per revolution, put 400 steps/mm on 1/16th microstepping, used 0.2mm layer height during printing which was actually the optimal layer.

Here is the series of images about the ribbing issues I'm having [imgur.com].

I also gone back to the aluminum spring coupler and printed the square tower, still the ribbing occured. I am using the slic3r pe 1.39.1 for that. The file for the square tower was used again.

Can it be due to not lubed up for the acme rods?

I would appreciate if there's any solution to this problem.

Thank you in advance.

What about the smooth rods and linear bearings? Do they run smooth?

Edited 1 time(s). Last edit at 05/05/2018 11:41AM by o_lampe.

Yes, because I've been using the anti-wobble printable tr8*8 nut that will support as a pad for the x axis gantry from the bottom. I actually didn't notice this ribbing issue until I printed a tall object. Most of which I print small and short.

Apparently, the problem lies in z motor mount for the 2020 frame where the screws were loose and caused the motor itself to wobble. I've reverted back to the aluminum spring coupler, remodeled the z axis top bracket not to constrain the acme rods by giving margin on the bracket, used the blue filament holder in the picture and finally, tighten the screws for the z motor mount.

Summary, z-motor mount screws became loose and solved by tightening it again.