What is causing this creaking sound?  

RE: What is causing this creaking sound?

Are you talking about the clicking?  That is your extruder grinding on the filament.  It could be a partial jam.  

RE: What is causing this creaking sound?

Yes, to me it sounds like the extruder is having difficulty pushing the filament through, but the print seems well established at this point, so it's doubtful there is a Z axis clearance issue. Can you feel the clicking if you hold your fingers on the filament as it feeds into the extruder? If not, try light finger pressure on the X/Y drive belts and trouble shooting accordingly. Does the print none-the-less complete successfully? Are there any visible defects or blemishes?

RE: What is causing this creaking sound?

Ok. After print finished I checked few things before going to bed.
1. This is not extruder!
2. I "clicks" when moving X axis by hand.

Here is video of me moving it by hand.
https://1drv.ms/v/s!Aj3AAyCJJc-agcEm4VCtGOmCXXuA4w?e=NAjfP2

Printer didn't do it for first 2 weeks. It started doing it recently.

I would add this information to first post. But I can't seem to be able to edit it.

RE: What is causing this creaking sound?

Edit windows on the forum are very short.  You cant edit once beyond that.

If you are getting 'clicks' moving an axis by hand then it is likely to be the bearings.  I'm sorry to tell you this but even though Prusa state the bearing come pre-lubricated, in fact they arent.  They come with shipping grease inside them to prevent corrosion during storage and transport.

While many people seem to go for awhile with it, many also find they start having problems anything from 2 weeks to a few months in.  Its why many of us on the forums recommend cleaning them out and properly re-greasing them prior to assembly.

Its also possibly the idler wheel bearings but the main bearings are far more likely.

You can check if it is that by apply a few drops of a light machine oil to the rods and working it past the dust seals by moving back and forth until some works its way inside.  If that helps the problem then its almost certainly the cause.

Remove your build plate before applying oil and wipe off any excess afterwards as you don't want it on the build surface.

RE: What is causing this creaking sound?

@neophyl

I'll check it after work. I'll completely remove tension from x belt to check if those are linear bearings. But it does seem like it. I did in fact put the supplied grease in the bearing prior assembly, but it looks like it didn't really help.

RE: What is causing this creaking sound?

UPDATE:

This are not linear bearing. I loosened up a pully on X axis stepper motor and this clicking stopped. I'm starting to guess that maybe this is belt teeth sound. 

RE: What is causing this creaking sound?

Look also for any loose filament strands or other debris on the belt or pullies. Tension could also be too great or pullies misaligned axially. As noted by neophyl, posts can be only be edited within several minutes of posting. Why Prusa decided on such a short period I do not know. It's the only site I visit with such a restriction.

RE: What is causing this creaking sound?

I have feeling like belt is catching on something. But I really can't see if it is idler pulley or when it is crossing extruder to go to other side.

RE: What is causing this creaking sound?

@hooch

The linear ball bearings are unusually loud. Sooner or later a change will be necessary. It is important that new bearings are cleaned and greased before installation. I would also check the linear rods for damages.

Often used and frequently bought bearings are these here: original Misumi LMU8

RE: What is causing this creaking sound?

I disassembled whole X (and Z as there was no other way) I checked everything, added more grease to bearing and rotated them a bit. I also tightened X idler and retentioned X belt (a bit less then it was).

I still wasn't able to pinpoint that sound as it didn't happen when there was no tension on belt. And once there was tension on belt there was just no way to locate the source of it.

It is much, much less now. I'll ignore it and once it totally breaks something I'll know what to replace and just fix it then.

RE: What is causing this creaking sound?

@hooch

Good.  I have found that if I loosen screws a little, it makes fewer noises sometimes.  I think I might get them too tight and interfere with the bearings.