<h2><strong>NEW UPDATE BELOW</strong></h2>
<hr />
<p>I am having trouble finding the cause for this under-extrusion at start/end of each layer.
Something changes halfway into the print creating a visible seam at some specific layer height.</p>
<p>This also creates dimensional inaccuracy making my parts unusable.<br />
The first layers are just fine - roundness deviation around 0.03 mm!</p>
<p><strong>Any ideas on which settings I should look into?</strong></p>
<p><strong>Settings</strong><br />
Printer:  Dremel 3D45 (newest firmware)<br />
Slicer:   Dremel DigiLab (also tried Cura Ultimaker 5.0)<br />
Filament: <a href="https://www.dasfilament.de/filament-refill/petg-1-75-mm/305/petg-filament-1-75-mm-feuerrot-refill-800-g?c=57" rel="nofollow noreferrer">PET-G</a></p>
<p>Printing Temperature: 250 °C<br />
Initial Temperature: 240 °C<br />
Final Temperature: 235 °C<br />
Flow: 105 %<br />
Retraction Distance: 1 mm (tried 3 - 1 mm)<br />
Retraction Speed: 40 mm/s (tried 60 - 20 mm/s)<br />
Prime Amount: 0.6 mm³  (tried 0 - 0.6)
Retraction Minimum Travel: 0
Retract at Layer Change: Off<br />
Maximum Retraction Count: 90 (could this be a problem?)<br />
Minimun Extrusion Distance Window: 1 mm<br />
Print Speed: 35 mm/s<br />
Wall Sprint Speed: 30 mm/s<br />
Combing Mode: All<br />
Fan Speed: 50 %<br />
Seam: Shortest</p>
<p><a href="https://i.stack.imgur.com/2oBBX.jpg" rel="nofollow noreferrer" title="Photo of the top of a 3D printed model showing printing errors"><img src="https://i.stack.imgur.com/2oBBX.jpg" alt="Photo of the top of a 3D printed model showing printing errors" title="Photo of the top of a 3D printed model showing printing errors" /></a>
<a href="https://i.stack.imgur.com/lueum.jpg" rel="nofollow noreferrer" title="Photo of the side of a 3D printed model showing printing errors"><img src="https://i.stack.imgur.com/lueum.jpg" alt="Photo of the side of a 3D printed model showing printing errors" title="Photo of the side of a 3D printed model showing printing errors" /></a></p>
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<h2><strong>Update 18/05</strong></h2>
<p>Fixed the seam by setting the alignment to random and changing retraction settings.<br />
Remaining problem is the inaccuracy right next to the Y axis (see marked area on the pictures). Besides a hardware issue I cant think about any slicer setting which would adress this deviation.</p>
<p>Diameter X: 30.02 mm<br />
Diameter Y: 30.04 mm<br />
Diameter Marked: 29.90 mm</p>
<p><a href="https://i.stack.imgur.com/ZKcvO.jpg" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/ZKcvO.jpg" alt="0.13 deviation in this area" /></a>
<a href="https://i.stack.imgur.com/VxHCQ.jpg" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/VxHCQ.jpg" alt="Fixed seam" /></a></p>

[{'answer_id': 19394, 'author': 'Trish', 'author_id': 8884, 'author_profile': 'https://3dprinting.stackexchange.com/users/8884', 'pm_score': 2, 'selected': False, 'text': "<h1>That's not under extrusion</h1>\n<p>That is the seam, and technically it is over extruding around it. You will find that if you turn the item, you have such a spot on every layer, actually with an inner and outer perimeter, you'll have two visible seams. The seam is where the extrusion line meets itself, and thus the extrusion has to stop.</p>\n"}, {'answer_id': 19395, 'author': 'R.. GitHub STOP HELPING ICE', 'author_id': 11157, 'author_profile': 'https://3dprinting.stackexchange.com/users/11157', 'pm_score': 2, 'selected': False, 'text': '<p>&quot;Prime Amount&quot; sounds like &quot;extra prime on unretract&quot;, which <em>necessarily</em> deposits a blob of extra material at the location of unretract, including the Z seam. Setting this to zero should help reduce the problem. This setting is a hack to compensate for material loss to oozing during travel, but if you have oozing you should just fix that instead rather than chucking out a blob to make up for it.</p>\n'}]
['https://3dprinting.stackexchange.com/questions/19393', 'https://3dprinting.stackexchange.com', 'https://3dprinting.stackexchange.com/users/34178/']