Ripples on flat surfaces not from oscillation

When printing ABS on my TAZ 5 (upgraded from KITTAZ) I get these irregular surface ripples that start from the first layer and continue through till the end.

If you look at the bottom of the first layer there seem to be strange printhead jogs that are the source of these ripples.

The ripples are perpendicular to the direction of printhead travel. I’m using Lulzbot Cura 19.12 and the high detail profile on the Lulzbot website. Anyone have any ideas on what’s going on here?

Your initial Z height will be slightly too close to the bed. Essentially what is happening is there is not enough room for the filament to be extruded. This builds pressure within the hot end, and will slightly raise the hot end to release this pressure. Once pressure is released, it drops back down and continues to build again. As the bottom layer infill is so consistent, this pressure will build in approximately the same spot creating a “wave” type pattern. A 1/8th to 1/4th turn counter-clockwise of your Z axis adjustment screw should get you fixed up. Here is another example of the same issue:

Reinforcing the X and Y axis rods can also mitigate that effect. (Hardened or larger rods, or boxed rails - Openbuilds, etc.)

Thanks so much for your help. A quarter turn of the adjuster and everything is great.