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Cabiri-Prusa
(@cabiri-prusa)
Active Member
Weird Line on Print

Hi all,

I recently printed a box with Prusa Pearl Red. Mostly solid with cut-outs.

At the end of the print, one of the edges had this ridge on it. The rest of it was perfect. This was printed at 0.2mm Quality and behind the ridge was some infill (15% grid). Nothing weird, and I haven't seen this before.

Any ideas what could be causing it?

Posted : 07/01/2020 1:44 pm
Neophyl
(@neophyl)
Illustrious Member
RE: Weird Line on Print

Looks like the seam to me.  Its where all the start/end of layers join.  Depending on your settings the seam gets moved around and usually hidden in a corner but with certain shapes (like what the box looks like) there are no corners so they can be more noticeable.  Theres various options like back (which puts them in a line at the rear of the model), random, nearest etc.  The default is nearest and when it has a corner to work with its quite good at putting them there.  It  just so happens that nearest in this case is acting alot like aligned as the nearest position is right on top of the lower layers start/stop position.

For curved shapes random **might** be better, but it might not be either.  When you slice a model make sure you carefully look at the preview and turn on the option to show retract/un-retract points.  That usually coincides with the seam placement and you can make a judgement call on if its what you want.  You cant ever get rid of them as its unavoidable with fdm printers but carefull tuning and seam placement can minimise them or hide them to a large extent. 

Depending on the model and its intended purpose its sometime better to have them aligned as it makes post processing (ie sanding) easier if they are all in one area.

Posted : 07/01/2020 4:39 pm
Dave Avery
(@dave-avery)
Honorable Member
RE: Weird Line on Print

that's the seam line. an inherent part of 3d printing 

Posted : 07/01/2020 8:37 pm
Sembazuru
(@sembazuru)
Prominent Member
RE: Weird Line on Print

Some filaments (like the silky ones) really showcase the warts inherent in FFF plastic printing. To get really good prints with silky filaments you really need to fine tune the printing process for each and every filament.

One tuning that often helps reduce the appearance of seams is to tune the linear advance for the filament you are using. See these links for tuning linear advance any one of which should be sufficient. (I use the Matt's Hub method and determine a new one for each filament type&brand that I use.) Unfortunately, if you determine a linear advance "K" value that matches the filament profile you are using then a different tuning will be required to reduce the effects of seams.

https://mattshub.com/blog/2017/10/02/linear-advance

http://projects.ttlexceeded.com/3dprinting_techniques_filament_calibration.html#linear-advance

http://marlinfw.org/tools/lin_advance/k-factor.html

https://help.prusa3d.com/article/t5w9VsdVai-linear-advanced

See my (limited) designs on:
Printables - https://www.printables.com/@Sembazuru
Thingiverse - https://www.thingiverse.com/Sembazuru/designs

Posted : 07/01/2020 8:38 pm
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