New Taz 5 - Issues with taller prints - consistent height ribbing / waviness (SOLVED)

Hi all,

I am a new Taz 5 owner (previously owned a Robo 3D R1) and am working through some initial issues but one issue I cannot seem to figure out is z ribbing / waviness on taller prints - this seems to occur at fairly consistent intervals or layers once I start to get higher than 5-6 inches.

Everything is stock on the machine, I am using Cura with the Lulzbot HIPS filament and Lulzbot HIPS Medium quality print profile.

Layer Height - 0.25
Shell Thickness - 1.0
Print speed - 50 mm / s
Bottom/Top Thickness - 0.8
Nozzle - 240 C
Bed - 110 C
Nozzle size - 0.5

As you can see on the attached pictures the quality toward the bottom of the parts are great but then start to really worsen. The fact that it happens at these intervals is what is curious. These 2 posts were printed side by side, with 1 of the 2 having significantly worse ribbing / waviness. The table that the printer sits on has a slight wobble but I didn’t think the consistent layer issue would to contributed to the table, am I wrong in assuming that?

I have also attached the STL and gcode but like I said its not just happening with this one model, it tends to happen with everything I have tried that exceeds that 5-6 inch height threshold.

I have spent some time searching the forums and I am not sure if I have seen this or am not searching for the right criteria, so I apologize if this is covered elsewhere.

Any insight is much appreciated!
HIPS_medium-quality_TAZ_single-extruder_0.5noz_cura.ini (10.6 KB)
Posts STL.stl (3.62 MB)
Posts STL.gcode (7.77 MB)

There is definitely something weird going on, but that actually doesn’t look like Z wobble. With Z wobble, you have an offset that is fairly constant up the entire part, that roughly matches the spacing of the threads on your leadscrews if you hold the part up next to it. In this case, you are having some offset issues, but only in occasional places, not regularly and matching the leadscrew threads, which means something else is probably going on here. It looks more like you might have a slightly loose setscrew or slightly loose belt in either the X or Y direction, that is allowing either the bed to shift or the X carriage to shift. I suspect it’s on the Y side since it is only showing up when the bed has sufficient additional mass on it, It could also be frame misalignment, a bearing that is gummed up and needs cleaning, fuzz in the bearing, etc. Also check the Z motor couplings and the Z motors themselves for loose screws Check those things and see if that improves things any. If not, let us know and we’ll look at other things.

Great, thanks so much for the suggestions.

The machine is less than a week old so I am hoping it is just something simple.

I’ll definitely take a look through all your suggestions and see if I get any improvements.

Ok so I ended up contacting Lulzbot support to talk through this issue and a couple others I was having and here was their suggestion which appears to have solved my issue here.

Locate x-carriage assembly with 4 allen screws on each side and loosen. (rectangle shape facing inward basically on threaded rods)
Auto home
Move z-axis almost to top of printer
Auto home
Move z-axis almost to top of printer
Auto home
Move x-axis to middle
Re-tighten all 8 allen screws (be careful not to overtighten)