Z banding (Possibly extruder problem)

Hey, everybody. I just remodeled my z-axis on my CoreXY machine making it a lot stiffer. I have been having trouble removing an artifact from all of my prints. First, I got the classic thread pitch banding which aligned perfectly with my 1/4" ACME lead screw.

This shows the thread banding on the left and something I cant' figure out on the right. The same problem exists in both prints. It is some low frequency issue that appears to be lower frequency than any z-axis problem (the dark and light banding suggesting some thinner and thicker layers). I decided to print something witha different amount of filament layed down per layer to see if the frequency changed and it seems that it did.

Could this be an oblong hobbed bolt in my old Gregs extruder? Or maybe some temperature fluctuation? Please help, this is last thing I have to solve before I can achieve near perfect prints (in my eyes ). Thanks

Isn't that fascinating. The period looks too long to be the extruder I think. You could double check by calculating the length of extruded filament per turn of the hobbed bolt, but I can't imagine it's anything like you're seeing. Plus, extruder related issues tend to produce diagonal artifacts which change angle fairly dramatically as you change print parameters like extrusion width or layer height. Your banding seems to be mostly (but not quite exactly?) horizontal.

I'm wondering if it is a heat-bed related thermal artifact. Is it possible to try a print with the heat bed off? Or maybe at least drop the temperature half way up the print and see if it impacts the banding as the bed cools.

could it be a temperature problem. some filament changes color at different temps

Are you using PID to control the bed temperature? There's no good reason not to.

---

Ultra MegaMax Dominator 3D printer: [drmrehorst.blogspot.com]

Hey, guys I forgot to check the forums for awhile over the holidays and saw that I had some replies. I don't actually have a heated bed. Sorry, I forgot to mention that in the first post. I print Esun PLA at 195°C. I was running PID for the hotend but never did the Marlin autotuning. I just did the autotuning today and it took away the artifact in the cylinder (or seemingly lessened it) but the artifact is still visible in the square cylinder. After JamesK mentioned it I noticed the slight diagonality of the dark band. Do extruder problems usually appear at angle? I am working on a direct drive extruder to try to rule out extruder problems and just update my printer in general.

Edited 1 time(s). Last edit at 01/04/2017 01:02AM by jtoombs.