Preventing Intermittent Lines and Streaks - Poor Leveling?

[mitchfx]

I've been having problems with prints taller than around 2" exhibiting very noticeable lines and layer shifting at irregular intervals. This occurs more frequently and prominently on the left side of the print which is the first in the direction of extrusion of each layer. The effect diminishes on the right side as the nozzle makes it around towards the second half of each perimeter.

Another thing I've noticed which may very well be related is what appears to be poor leveling of the build platform even when calibrated via the suggested guidelines for my printer (Dremel Idea Builder). The process is to use a sheet of paper or a notecard for each of 3 adjustment points. When I do the leveling very carefully and then once more to confirm all points are spaced the same the first layer of my print always exhibits tight spacing between the extrusion lines at the right-rear corner that transition to wider gaps towards the front-left corner. I can only guess this is due to the fact that the right-rear is BETWEEN two adjustment springs and the front-left is on TOP of a single spring...thus having more "give".

I have done a quick test of using a notecard to calibrate the space of the back and front-right points and a sheet of paper for the front-left point. This seems to have made the first layer MUCH more even and perfectly filled. I will run a full size print tonight to see if this indeed reduces my lines issue.

Here are some images that show what I'm talking about. Keep in mind that many of my earlier prints never had these line issues. It's only in the last few weeks they have started to become more problematic.

uneven line width on first layers after leveling

lines!

more lines!

[JoeJ]

Yes, the bed either isn't level or it isn't flat.

[mitchfx]

Ok, I was able to get my leveling pretty much perfect and the bottom surface is extremely even and smooth. However I am still getting horrible lines in all my prints compared to just a few weeks ago. What is interesting is that almost all of my early prints exhibited the uneven gap width on bottom surface but the outer parameters were extremely nice.

There must be either some kind of partial blockage of my nozzle or a problem with the motors/belts, etc. Here is a comparison to a print I did a while back to one from yesterday using the same settings and PLA. I had even printed the same model as the one showing heavy lines about a month ago and it was extremely clean (I've since given it away so no photos).

[jimc]

looks like one of the pulleys is loose on the shaft of the stepper on the x,y or both axis.

[mitchfx]

Just received a replacement extruder assembly from Dremel and it's printing as good as new now. Must have either been a chronic partial nozzle blockage, bad stepper motor or degraded PTFE liner.

[mitchfx]

Ok, after a good run for a while my lines are back. What is interesting is on the latest part I have prominent lines in the EXACT SAME HEIGHT for two runs in a row. This to me indicates a possible issue with the Z rod threads or motor, but would love to know what others think. I guess there could be something in the slicing as the culprit so I'm running two tests for comparison tonight: One of the same print on my other printer (Same type of unit, Dremel) and another of the unit that created the lines but this time at a slightly different scale. If the lines appear in same relative spot on the model at a different scale then that to me says slicer issue. If the are at same height in MM then that indicates a Z rod issue...or so I'm theorizing

[Joules]

I have noticed that the slicers sometimes have rounding errors, so your 0.1mm per layer may have a 0.1x layer to compensate and this seems to show up as a non continuos line in a build (visible). The other issue that I battle with for quality is machine rigidity. Does you machine dance about much, make a lot of noise during printing. Make sure it sits on a level surface, as any warp in the surface it sits on can translate into the machine when its running.


Joules