Diagonal pattern / moire on object walls

[CrazyCoder]

UPDATE: possible solution can be found in this post.

I've noticed that all my prints have this weird symmetrical diagonal pattern on the outside walls:

diagonal-pattern.jpg

Does anyone know why it happens?

It's the same on X/Y axes, so it doesn't look like rigidity issue, it's also the same on all layers. On the left model it's different on different layers, probably because of the model specifics. The model on the right is just hollow 0.40 wall thick tower.

Could it be the extruder issue? Like every 2mm of extruded plastic there is some repeating unevenness in the plastic extrusion. Or is it a problem with the frame assembly/motors?

I found only one post that looks related. It has the following photo attached which look like my problem, but much more visible:

diagonal1.jpg

There is a suggestion to adjust VREF somewhere, but the original author reported that it didn't have any effect.

I'm puzzled, any ideas would be appreciated.

[CrazyCoder]

Objects from my photo:

http://www.thingiverse.com/thing:2064
http://www.thingiverse.com/thing:43179

Sliced with Cura suggested settings.

[Shiki]

Just to be sure, is your heated bed perfectly vertical, as the last appears to be inclinated towards one side.
To be sure, I suggest you use repetier or prontierface and set the cordinates using the commands and a sheet of paper in the heated bed to so you can move it to be sure about the tension which the extruder setting against the heated bed.

Syntax:
G1 X <Coordinate X> Y <Coordinate Y> Z <Coordinate Z> <= Moves the extruder to the desired coordinate

G1 X 0 Y 0 Z 5
G1 Z 0.1
G1 X 195 Y 0 Z 5
G1 Z 0.1
G1 X 195 Y 195 Z 5
G1 Z 0.1
G1 X 0 Y 195 Z 5
G1 Z 0.1

If any place touches the bed before the motor stops, your heated bed is uneven and you should adjust.

[CrazyCoder]

Thanks for the reply.

I've calibrated the heated bed pretty good, moving the extruder manually across the bed shows the same distance to the surface across all the bed. I was using A4 paper to calibrate and it's moving with the same tension in all corners/center under the nozzle. It doesn't look like a bed calibration issue to me.

[Shiki]

It really appears your filament is deposited unevenly, I mean your filament is being deposited, but the extruder deposits a litte more in some parts then a litte less later, so as your extruded filament goes out in variable quantities it gains different colors.

To fix it, you should measure it with a digital caliber and adjust one of the following parameters (filament diameter, extrusion multiplier or extruder temperature) at printer settings to solve it.

[Shiki]

[CrazyCoder]

Thanks, I already did it before the print, but I will try to adjust the extrusion speed and see if it makes any difference.

[sm0orb]

Two more things to check.
Settings for retraction. If to high it may cause the start of the next string to be sligthly thinner in the start.
Tha fans on the extruder. The one with the guide upwards is the one that shall be on all the time the one with the long guide pointing down can be started or stopped via software. Someone got the wiring wrong so they worked the other way around.

[CrazyCoder]

I've checked the fans and it appears that they are reversed. The one at the bottom that cools the extruder itself is off by default (controlled by printer). The one which is vertical and having the long guide to cool the filament under the nozzle is always on. I will swap the connectors and see if it helps.

[bolsoncerrado]

So far I think all of us got the fans the same way?? Ie the vertical one always on, the down one stop by default??

This is a mess!! (((