Z banding / wobble when printing straight edges, but not circles?

Z banding / wobble when printing straight edges, but not circles?

Printer is a Printrbot Frankenbot - so I’m not expecting perfection as I may have issues with how centered and true the threaded rods and vertical steel rods are aligned.

I printed some 25mm OD hose adapters (vertical tube, with walls 3mm thick - so multiple loops and 10% infill). I was surprised at how well they turned out - virtually perfectly straight verticals. Essentially no trace of Z wobble or banding. Sliced with Cura, 0.2mm layer height.

Same printer, but using KISSlicer to slice at 50% layer height (of a 0.4mm nozzle), so 0.2mm as well. I’m printing a 100mm x 100mm box and I’m seeing banding on a regular basis - tell tale sign of z wobble.

Why would circular paths suppress / hide the wobble?

Swap the leadscrews out. The TR8 from eBay Work excellent for me. Love Printrbot but their leadscrews never worked for me

I think they suppress the wobble by approximately constant side loading, vs. the more sudden acceleration from corners. I saw something similar on my hictop i3 mutated clone, and I bought single-start T8 to replace the M5 and it totally resolved the problem. (Single start moves slower than the more typical four-start, but I appreciate the resolution and Z stability.)

The only reasonable sources of single-start T8 I ever found to order were a few weeks of shipping from various far east countries, but recently saw a link to https://www.zyltech.com/ who carry it at least for the US for reasonable prices. I don’t know whether they ship to Canada and I haven’t ordered anything from them yet; they’re just the first US-based source I’ve found. Wish I’d found them before my most recent purchase! :stuck_out_tongue: