What do I need to do here

I have this 'corrugated' surface. it doesn't look as bad as it does in a picture but its time to fix it. It seems to have become worse since tightening the belts recently. This a fairly small part, 20mm tall. Is this step resolution or something else? I have'nt checked to see what micro stepping the Ramps is set at but I am assuming its 1/16th. The x and y are driven by 16t gt2's. I have put a great deal of effort into making sure the machine is set up well and tight. Where do I go next?

Check that your extruder isn't overpowered. If it is, doesn't matter what microstepping is set at, it will jump to the whole steps if it's putting out too much power.
Here's a good guide.

---

Realizer- One who realizes dreams by making them a reality either by possibility or by completion. Also creating or renewing hopes of dreams.
"keep in mind, even the best printer can not print with the best filament if the user is the problem." -Ohmarinus

thanks Doc, I'm not sure it is the extruder. The reason I say that is because the flaws are inline vertically. It would seem if the extruder was to blame there would be some randomness. I print these smaller parts at 5-10mm/s. I'm more inclined to think the steps are being amplified into the part. If I knew how to tell what step rate it was in at that particular moment maybe I could conclude

Right, after looking again I realized how wrong I was.
Check that your X and Y motors are not over powered?
Also check your jerk settings, maybe raise them and see if that helps.

---

Realizer- One who realizes dreams by making them a reality either by possibility or by completion. Also creating or renewing hopes of dreams.
"keep in mind, even the best printer can not print with the best filament if the user is the problem." -Ohmarinus

That is an odd one. I would look for something machanical. some sort of binding on the axis, and maybe a little "slop" in a bearing/bushing. That is so slight, I dont know if you would be able to feel it.

If you shift the object on the build plate, or print more then one at a time, see what the lines do.

you could also print a block (maybe 3 mils thick, 5 or 10 mils high) the runs the length of the bad axis and to see where the lines are and then match up your carraige with the bad spots to see if you can identify the issue.

Eyeballing your part as 10mm wide, it seems to be about 0.25mm wavelength corrugation.

16T GT2 at 200 steps/rev gives you 16tooth/rev*2mm/step/(200step/rev)=0.16mm/step resolution, and /(16microsteps/step) would be 0.01mm/microstep. Both seem significantly smaller than the

Is it corrugated just on the curved areas? If the corrugation is in tune with the ends of the g-code line segments, it could be a relative pause due to acceleration or jerk. See [forums.reprap.org] is a good example of that.

If tightening up things mechanically made things worse, the slop in the mechanics could have been masking problems in the called-for motion.