Layer Striping

Greetings,

I've built a few printers now but have never seen this error or even know what to call it. I googled, yahoo'd, and bing'd my little heart out to no avail.



When i print my outer walls are getting this fairly defined striping pattern to them.
The pattern is very regular which led me to believe my Z-axis screws or ways had something to do with it, I took it all apart ran a die over my lead screws inspected my bearings and rods and found nothing out of sorts. put everything back together and ran a small print with the same issue. I've also tried slowing the print and double checked my extruder steps.

Has anyone run in to this in their builds and fixed it? Does anyone have any other ideas?

Thanks in advance

That looks like Z wobble to me. It's hard to see when you're lifting by a layer height at a time, but if you move the Z axis from top to bottom in a single command, you might be able to detect a bit of wobbling of the X ends. That's called Z wobble and it results in print patterns like this.

It's a difficult thing to get rid of entirely, but there are things you can do to mitigate this. You should refer to this thread for more information

It's difficult to see if that's Z axis wobble or a Z layer height that's not an integer multiple of the Z full step height.

The wobble comes from having the screws constrained rigidly enough to influence the carriage despite the smooth rods (or whatever your ways are).

The full step height issue comes from the repeatability of fractional steps being different from that of full steps. If your layer heights always stop at the same fractional step position (whole step layers), then the position error will be consistent. If not, then the error will increase for some layers and decrease for others, leading to a cycling under/over extrusion condition. The banding looks like Z wobble, but doesn't follow a helical pattern around the part.

So i took everything everyone gave me and did a lot more research. I printed up some parts to allow the drive nut to essentially float free. It help some but not a ton IMO. any other ideas?

I do use full steps for my z-axis. I have 5/16-24 rods and i use 0.1958 for a layer height. Im going to get some M8 x 1 on order and see of that helps.

Just shot in dark...try lowering acceleration to about 1500.
Another thing... check your pulleys and belts, do they match? It happened to me once that i had 2.5 belts and 2.0 pulleys.

jmarasch:
Can you post link to the objects you printed for the top z axis holder ? i got a little z wobble too, i found something that helped me alot, but still having some left, maybe those will help.
Heres what helped me: [www.thingiverse.com]

Ill have to look at what my accelleration is currently set to, thanks for the tip.

As for the top z axis holders my machine is setup for m8 or 5/16th drive rods and probably wont work if your using m5 rods.

What i dont like about the anti wobble device your using is that it only pushes the axis up it wont draw the z-axis down and then your relying on gravity.

you can find my design files here

Edited 1 time(s). Last edit at 01/29/2014 10:20PM by jmarasch.