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Vertical Line problem appear (UM original kit)

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There is a big vertical line appear on cylinder object while printing the object vertically.

Is anyone might know what could caused the problem and how to fix? Much appreciated.

P.S. I wanted to post picture, but it told me that "You are not allowed to use that image extension on this community.", as such, I post link below:




Many Thanks.


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I don't think it's possible to completely avoid this effect. But material has a big impact on it. As said, it's the position where the nozzle goes from the outer skin to the inside of the object.

Increasing the travel speed might help, if I see those settings, I would say your travel speed can be way higher, 150 or even 200mm/s. Also, 100% infill might not help you in this case. You could reduce that to 80%.

(Final thing I wanted to add. These potentially look like adult toys :wink: . No problem with that. But PLA absorbs moister, and thus bacteria, so I wouldn't recommend using PLA directly as adult toys, instead print molds and cast silicon from that, or coat them)


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A couple of points. Your shell thickness should be a multiple of your nozzle width, which I assume is 0.4mm. Now if you cannot resolve this and it is important for you - you will probably find that the slicer Slic3r will give you a better result on this point as it lets you start the new layers at random points which stops the pronounced line being formed. I prefer Cura these days but Slic3r is not bad and I do normally use it for cylindrical objects to avoid artefacts on the external surface


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PLA is very strong. 80% infill is strong enough for people to stand on this. Vertically or horizontally. Do you really need it that strong? You can save lots of time by printing it hollow or only 10% infill. I wouldn't go over 24%.

The simplest way to remove that Z scar is to slow it down. I don't recommend slowing it below 30mm/sec but if you go to 20mm/sec that Z scar will be very hard to see.

If this is for a mold you can use wet sandpaper and Bondo to hide that seam.

What is your "infill speed"? It's best to use the same speed everywhere. Every time you switch speeds you get small bumps like this due to brief overextrusion or underextrusion caused at the speed change. That's why 20mm/sec works so well - speed changes are smaller.


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George's last point I think is very important. When I first started I used Slic3r because it has loads of settings options and different speeds for everything and naively I thought that was cool. I then moved to Cura because I found the Slic3r extraction process to be poor compared with Cura and I certainly found a better quality. Over time I have now moved to having no changes in the settings at all - i.e. level 1 bed temp and extruder temp are the same as the rest of the model; no changes in speed for anything.

Two caveats to the above, if the geometry tests the bed adhesion, eg a large flat bottom covering most of the build plate then I will start with a higher bed and extruder temp. If the geometry ends with a point, as well as probably printing two up I will slow the print speed as I get near to the end.

Funnily enough I am using Slic3r right now; I have some smallish pieces running at 100 microns and 20mm/s print speed and I was getting a z scar on one of the vertical edges, so hoping that redoing it with Slic3r will remove this.

If it works I will post the pics.

Also and this may well differ with geometry but with the pieces I am working on at the moment I am finding that 100% infill gives a faster time than using 40% or 20% infill.


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update from printing: Picture below. Same problem with different settings(30mm/s & 20 mm/s print time). Now I have no clue...any setting need to be adjust?


I have tried 2 different speeds for one print object, but one is bigger size. Here is the setting:

Date 2014/9/27 2014/9/28

Name Bigger One Smaller One

Layer height 0.1 0.1

Shell thickness 3.6 3.6

Fill Density 20 20

Print Speed 30 20

Temperature 190 190

Retraction 60 60

Scale 0.7/0.7/0.7 0.5/0.5/0.5

size 60.51/60.51/131.11 43.22/93.65/43.22

print time 11h 6h40

weight 61 22

Travel Speed 50 50

bottom layer speed 0 20

Infill speed 0 20

outer Shell speed 30 20

Inner shell speed 0 20


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So, in most pictures the scar is "negative" (some missing plastic), but I saw at least one that is "positive" (some more plastic than necessary).

The factors that influence the scar are:

- retraction speed/acceleration: at the end of the outer line of the shell (exterior or interior) retraction takes place before moving to infill; if the retraction is too fast, a bit of the already extruded plastic will be sucked back, leaving kind of a hole - the negative scar; if the retraction is too slow, the nozzle could ooze, leaving kind of a bump - the positive scar

- printing speed/acceleration: if it is too fast, too much plastic will come out during deceleration, due to the pressure inside the nozzle that could not be reduced at the same pace, resulting in positive scar

- travel speed: if retraction is too short/slow, fast travel may pull a bit of extruded plastic -> negative scar, while slow travel will let more plastic to ooze -> positive scar

- temperature/cooling: this will influence viscosity of the extruded plastic hence will boost or dim the above effects.

And we can list more factors that contribute. So, there is no simple setting solving the issue. However, thinking og negative scar, you may want to:

- reduce retraction speed and/or acceleration

- increase (!) printing speed and/or acceleration

To complement/compensate the produced effect, you may also try to adjust travel speed and/or temperature.

But first, try adjusting retraction. Since you are printing one object at a time (I may assume that from the printing time you mentioned), there is little need for 60 mm/s retraction speed at the quite low printing/travel speeds.


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Hi Erwin

Select the print settings tab and then the Layers and Perimeters menu option. Scroll down and you will see Seam Position, under Advanced. Set this to random to avoid the Z scar.

Please note thatSlic3r was incredibly slow at generating the gcode compared with Cura which is almost instantaneous. IE for a complex model Slicr 3r could take 10minutes. It may be that vs 2.n variants are much faster.


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Hmn, I have just been able to access your pics. On the first ones the green gherkin has a negative indent which starts say half way up. Personally I never experienced a z scar like this, the line has always been positive. I am wondering whether this this is a fault in the mesh rather than a z scar? The white/clear round thing looks a pretty good print to me!!


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there are some gaps between layer walls of my object


Ah! Important clue! UM Original? One thing can explain both issues!

I think your belts are too loose. Loose belts means that when it draws the circle it might not quite finish the circle before going to the interior. Also loose belts cause the outer shells not to connect and not to connect to the infill sometimes also.


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@Daid (is that even suppose to notify him in anyway?) Do you think adding random position layer start can be added to Cura without too much work? I'm asking to see if it could be done by someone else since your busy saving the world :D


That would only work against the "material buildup" type of Z scar. Which I rarely see these days and is usually solved with proper temperature settings. This scar is actually a sort of gap, and randomizing the start point will only make it visible on the whole skin.


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