Sudden Z-banding issue

[Origami_Papercut]

Hello all,

I just got my Printrbot Simple five days ago. So far it has been churning out prints with exceptional quality and really smooth walls, but on my most recent project it has been giving some pretty severe Z banding.

Using Cura 15.04.6
In the picture, the left one is the first one printed at 205 using AMZ3D PLA, 30mm/s print speed, 0.1mm layer height, at 100% flow.
The middle one I increased temperature to 210.
On the third one, I tightened the X and Y belts, decreased temperature to 200 and decreased extrusion to 80%.

All of the setting tweaks seemed to do nothing to change the banding, so I'm suspecting a hardware problem. It seems too new for any wear to happen. Does anyone have some suggestions as to what I can do to fix this? I'm considering ordering the Z Lead Screw upgrade in case the lead screw is funky.

[Mooselake]

Those look like they're small. Did you print more than one at a time? With the cooling fan at 100%? The pictures are a bit fuzzy, but I'd suspect a cooling issue. 200 can be high for some versions of PLA (it's a spectrum, not a fixed plastic mix); I have spools that want 180 or so. Print a couple copies at a time, this gives the first one time to cool off before the next layer.

If not, look for something that came loose, pulley set (aka grub) screws, belt tensioners, linear rod/rail supports, etc. Your Z screws aren't under sufficient load to bend them while printing, so unless you've knocked the printer over (or similar damage) they wouldn't have changed. Check for wiring or similar that might have started getting caught in the mechanism, that your filament is feeding smoothly off the spool, anything that might be hanging up. Lube your rods (or these days rails), light machine oil or dry bicycle lube-type products.

Belts should have a "low bass note" when plucked, not so tight they sing soprano. Eye, er, ear ball it, no need to get out the violin tuner (although that'll work and has been done...). You're trying to get the slack out so they won't have any slop that affects direction changes (i.e. backlash), but too tight will cause increased wear and other problems.

I worked up some gcode to print a temperature test, should print on your simple. It should be big and slow enough that cooling isn't an issue

Kirk