Z Banding causes other than leads crew? (SOLVED)

I got my reprap printing yesterday, and I am noticing a very fine z banding on my prints, but they are not caused by the leadscrew (leadscrew is 2mm pitch, the bands occur at a much finer interval). Any ideas? The extruder isn't slipping or missing steps that I know of.

The picture is of a 15mm calibration cube.

Edited 1 time(s). Last edit at 07/23/2015 04:24PM by 1nxtmonster.

Ever tried prusa calculator for optimal layer height on z-axis vs lead screw?

Yes, and my layer height (.2mm) checks out. It says there is no error at that height.

Play in your X and/or Y axis, or a loose hotend, can cause banding if your slicer reverses direction at the completion of a layer.

How far apart are the bands?

The bands are about 1mm apart. I will try printing with a different layer height to determine if it is a mechanical issue (occurs every 1 mm) or a software/slicer issue (occurs every 5 layers).

I can't find the article, but it stated many causes for z axis artifacts. The few that I remember are thermal deformation of the heated bed, if using bang-bang method of heating the temperature swing can cause the pcb to warp in the bang-bang rhythm, moving it up and down. Depending on the time a layer is completed the z banding can change in appearance. Using PID for a more stable temperature and a good thermal connection between bed and sensor may help.

Extrusion flow can have some effect too, if the filament diameter changes over length, then that may translate into z artifacts too.

If you use auto bed leveling where the z axis moves continually, if it ovrrheats regularly it may stop for a while, also giving z banding. Abl is constantly moving the z axis back and forth, any slack/ backlash in the z axis nut will translate into artifacts. Another problem I encountered is that the x carriage locked up when the z axis moves down, the hole where the z axis goes through may be too small and locks onto the rod. Especially with bowden setups where the extruder motor is moved off the x carriage, the reduced weight doesn't push the x axis down on the z nut as much. There's a fix that I've seen with 2 nuts and a spring in between with a printed housing to reduce backlash. I'm planning to implement that at some point.

If the bearings of the bed are a bit loose or the construction is on springs the bed can tilt and bounce with rapid y movements squeezing and stretching filament in the z axis. This is more extreme with 3 fixture point beds than with 4 point beds. Since I use abl I've removed the springs, leveled as best I could with rings/washers/shims.

It's a lot of effort to work out the last bit of ribbing effect so I won't blame you if you call it quits

Edited 1 time(s). Last edit at 07/23/2015 03:16AM by imqqmi.

Thanks for the tips! I think I can rule some of those out because I don't have a heated bed, there is no auto level enabled, and my bed is glued down to the xy carriage (hbot)

I printed the cube at .1mm layer height, and the bands are twice as frequent. The bands are more prevalent in the corners so I am wondering if this could be caused (or at least accentuated) by the over extrusion that occurs in corners. I think I will try printing a cylinder next to see if the severity of the bands is lessened when there are no corners.

Also since the bands are occurring at the same time interval (.1mm is twice as slow to print as .2mm, and the banding is now twice as often) I will check the hot end and the PID and try a larger print to see what happens to the bands.

Edited 2 time(s). Last edit at 07/23/2015 08:27AM by 1nxtmonster.

On a larger cube the banding occurred at a finer interval. I am starting to think that it is not a z axis issue but an extrusion issue.

Edit: SOLVED!

It turned out to be an extrusion issue after all. After tightening the idler on the extruder the problem went away.



Edited 1 time(s). Last edit at 07/23/2015 04:22PM by 1nxtmonster.