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I have a Prusa i3 that I am mostly happy with. However, I am seeing these strange artifacts when the extruder moves along one axis in one direction - in particular from the back of the printer towards the front. The extruded lines look uneven and the surface is quite rough, but only in that area and only while the extruder moves in that direction.

Here is a recent print that shows this happen. The pieces were printed side by side, and both of them show this on the left hand side, while the right is okay.

Left hand side of the print shows uneven and rough lines

I am thinking maybe the extruder tip is slanted (not perpendicular to the bed), which causes some sort of scraping while extruding? What do you think?

Catsunami
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  • What material are you using? Is there a possibility that it's warping/delamination? – tbm0115 May 09 '16 at 03:29
  • Does the printer *sound* the same when moving along both sides? Could this be some kind of self-resonance? – Tormod Haugene May 09 '16 at 05:23
  • @tbm0115, this is PLA. There is some warping going on, but it's very minor and I don't believe this is it (it is mostly evident on lower layers). – Catsunami May 09 '16 at 06:02
  • @TormodHaugene, it sounds the same to me, but I won't pretend that I am musically gifted or anything. I don't hear anything anyways, I just see this poor result on one side. – Catsunami May 09 '16 at 06:03
  • I noticed that your question has not had much activity lately, are you still looking for an answer to this question? How might we be able to close some gaps? – tbm0115 Jul 03 '16 at 20:23

2 Answers2

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In case of such difference in printing in different directions you can check if;

  1. for x and partially z axis
    • filament is blocked and cannot be pulled as it should
    • spool is blocked
  2. for x and y axis
    • rods on which caret/HB is sliding are parallel
    • timing belt idlers are parallel and they are in a line

Shape of the nozzle or its perpendicularity should not be the case as it's hot and it wipes layer itself.

You can also check if it's not an issue of cooling fan. It can vibrate as such.

Eventually it could be an issue of cooling itself. Let's assume you have cooling fan at the back and it pushes air to the front then when caret moves from the front to the back then cooling time is longer than when the fan goes in opposite direction.

darth pixel
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  • Those are some very good ideas. I recently had problems with the pneumatic connector on the extruder, so I will check (and probably replace) that, maybe it is affecting the filament feed. My x & y rods are fine though, so are the timing belts. Cooling fan might be it, as well. I will try it tomorrow and report back. – Catsunami May 09 '16 at 06:05
  • @Catsunami double check your timing belt idlers. Look closer if they don't twist your timing belt not at all. Such little twist can cause that teeth touch flange and cause "jumping". Everything almost not recognized visually. – darth pixel May 09 '16 at 07:23
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    @Catsunami: If you have a "wind shade" on the left side of your prints from a cooling fan on the right side of the prints, then that is most likely be the source of your issues! – Tormod Haugene May 09 '16 at 10:55
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In my case, there were some artifacts only on the right side, and the problem was that the screw was partly out of the pulley under the bed. I would suggest moving the bed to the back and checking the pulley. You might also consider cleaning and lubricating the rods, which is what I was doing when I discovered it.

Here is an example of the bumps when the pulley was loose (using TPU):

3d print showing bumps on one side

Brian Slesinsky
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