3d printing bad surface finish

HI,

I'm using Prusa i3 and my firmware is marlin with dual extruder enabled, nozzle J head 0.4mm, filament 1.75 mm PLA, slic3r and host octoprint.

I was getting reasonable quality prints from machine, but for a few weeks I'm getting prints with bad surface finish. In some cases I get some layers with smooth surface(not very smooth) and some others with rough surface and this happens alternatively in a single object.

This what I've done so far,
1. oiled the smooth rods and z axis threaded rod
2. Changed the temperature by 5 degrees( tried both increasing and decreasing range 190-240)
3. Changed speed(now running at half the speed of default value)
4. tried with different layer height.
5. replaced nozzle(new one)


Sometimes I could see that material is not coming from the nozzle properly(In this case perimeter width in single movement of nozzle is lower than normal, and they are extruding kinda porous), Some layers are not properly sticking to the bottom layers.I'm already using cooling fan and they are at full speed.

One anothe thing I notice is that, my no. of solid layers is 6 (Print settings >> layers and perimeters >> horizontal shells for both top and bottom) , and in these layers as far as I've noticed filament is extruding properly and getting better prints but when print stars for remaining layers all the above problem happens.

Files are too large to upload here , please see the link below

images

Why is this happening?

Could this be due to material damage ? I don't have any other material to test

Thanks

Edited 2 time(s). Last edit at 05/19/2016 06:18AM by athul.

Watch the extruder when this occurs. It could be the filament is slipping or not feeding off the spool, the stepper motor for the extruder is skipping steps or the stepper driver is overheating. Also, it could be the gear on the extruder stepper motor is slipping.

Quote
stephenrc
Watch the extruder when this occurs. It could be the filament is slipping or not feeding off the spool, the stepper motor for the extruder is skipping steps or the stepper driver is overheating. Also, it could be the gear on the extruder stepper motor is slipping.

Hey, thanks for the reply. I couldn't see any issues with stepper motor and it's not skipping steps also I when printing I loosened the material from the spool to avoid the jamming of it.


Could moisture content in material cause this?

It could be that your filament has absorbed moisture. PLA can print badly when it has moisture and if one side of the real got more than the other that would also explain the banding. Put it into an air tight container with an ample amount of the desiccant bags and leave it a day or two and see if that helps.