Z Ribbing Issue

I'm having problems with Z Ribbing on my i3. I've tried a few different layer heights (namely 0.2, 0.18, 0.15, and 0.14) and none seem to work. Each layer height I've tried has the ribbing occurring at intervals (ie, not random), but the intervals are different depending on the layer height, so I know it's ribbing. Here's some photos of th .2mm and .14mm layer height test prints:

0.2 layer height

0.14 layer height


What's weird with the 0.14 layer height is that it doesn't start ribbing until a little ways up, it skips the first rib. Why would that be?

If the ribbing doesn't match up with the pitch of the z-axis lead screws, it could be problems with the hobbed bolt in the extruder, if the hobbing isn't consistent, the extrusion wont be either. Try printing 2 cubes at a time, if the pitch of the ribble doubles, it is most likely an extrusion issue.

Tried printing 2 cubes at the same time, ribbing distance is the same as with 1 cube. What could that indicate?

Are your z leadscrews straight?

Bend z leadscrews can lead to non linear motion, which again leads to inconsistent layer height, which is seen as ribbing, since some layers is overextruded and other layers is underextruded.

Bend leadscrews can also move the x-carrige around in circles, preventing layers from being stacked nicely on top of each others.

Alternatively it could be your steps/mm not matching the layer height, if you increase microstepping on the z-axis this will become less of a problem, alternatively find some layer heights that matches your steps/mm.

There are some debate whether running micrstepping on z, can cause syncronization problems with two z motors, personally I run 1/4 microstepping (800 steps/rev), and I don't have these problems. Your milage may wary..

What mode do you use to power heated bed? PWM or Bang Bang

Quote
Ralf
Are your z leadscrews straight?

Bend z leadscrews can lead to non linear motion, which again leads to inconsistent layer height, which is seen as ribbing, since some layers is overextruded and other layers is underextruded.

Bend leadscrews can also move the x-carrige around in circles, preventing layers from being stacked nicely on top of each others.

Alternatively it could be your steps/mm not matching the layer height, if you increase microstepping on the z-axis this will become less of a problem, alternatively find some layer heights that matches your steps/mm.

There are some debate whether running micrstepping on z, can cause syncronization problems with two z motors, personally I run 1/4 microstepping (800 steps/rev), and I don't have these problems. Your milage may wary..

The leadscrews WERE bent, but I bought some replacements that are perfectly straight and still have the ribbing issues.

The steps should be perfect, I'm using metric leadscrews so they are very easy to calculate for.

How would I go about increasing the microstepping?

Quote
karabasf
What mode do you use to power heated bed? PWM or Bang Bang

Normally I use PWM, but the heated bed has been off for a few weeks now because of a broken MOSFET. I've got a new one on order, but in the mean time I've been printing without a heated bed. I still have the ribbing issues whether or not I'm using a heated bed though.

Quote
GtwoK
How would I go about increasing the microstepping?

Depends on your electronics and firmware, typically you just have to move some jumpers, maybe also rebuild the formware, in Marlin you can use M92 to adjust steps/mm.

Quote
Ralf

Quote
GtwoK
How would I go about increasing the microstepping?

Depends on your electronics and firmware, typically you just have to move some jumpers, maybe also rebuild the formware, in Marlin you can use M92 to adjust steps/mm.

I've got all 3 jumpers on each of the drivers in my Ramps, if that would do it. Or is there more to it than that?

Quote
GtwoK
I've got all 3 jumpers on each of the drivers in my Ramps, if that would do it. Or is there more to it than that?

That is 1/16 microstepping, that should be more than sufficient for the z axis.

Quote
Ralf

Quote
GtwoK
I've got all 3 jumpers on each of the drivers in my Ramps, if that would do it. Or is there more to it than that?

That is 1/16 microstepping, that should be more than sufficient for the z axis.

It's been at that point since I initially built it though, and still have the problem. IS there anything else that could fix it?