Strange outstanding perimeters Hi! Since a few weeks I own an Ultimaker 2. After some relatively good prints I encountered some problems with Cura on negative angles. After some reading in the Internet I recently switched to Slic3r. The prints are much better but I got some new problems. In the attached image you can see the marked outstanding perimeters. I figured out, that they only appear if the printer prints some infill, before and after each hole of the die. I played with all parameters in Slic3r but didn't got it to work properly. Do you have some advices? Thanks and best regards Falk https://reprap.org/forum/read.php?263,490722,490722#msg-490722 Wed, 12 Aug 2026 13:38:16 -0400 Phorum 5.2.23 https://reprap.org/forum/read.php?263,490722,491415#msg-491415 Re: Strange outstanding perimeters https://reprap.org/forum/read.php?263,490722,491415#msg-491415
Thank you for the many suggestions, I will go on trying ;)

Best regards
Falk]]> smoothcriminal Slic3r Wed, 01 Apr 2015 11:03:41 -0400 https://reprap.org/forum/read.php?263,490722,491409#msg-491409 Re: Strange outstanding perimeters https://reprap.org/forum/read.php?263,490722,491409#msg-491409
This is mainly a effect of mechanic and trajectory generation.
At a lower speed the mechanic and the trajectory generation can move the head more accurate at the original path.

Therefore i asked about the minimum segment length in my other thread...

Frank]]> NitroXpress Slic3r Wed, 01 Apr 2015 10:54:08 -0400 https://reprap.org/forum/read.php?263,490722,491406#msg-491406 Re: Strange outstanding perimeters https://reprap.org/forum/read.php?263,490722,491406#msg-491406
Quote
NitroXpress
As you can see, 150mm/sec gives perfect surface quality.
With 60mm/sec you can see the created segments from the slicer.
Frank

What you are seeing is the effect of mechanical smoothing that effectively rounds off any corners due to inertia not allowing instant changes in direction. The surface that was printed fast is smoother which in this particular case is what you want, but it is in fact less accurate because it does not faithfully reproduce the input - which contained segments. Do the same when printing a polygon (e.g a hexagonal nut) and you will see the same effect - except in that case the segmented section is what you want (a polygon) and the smooth section (more circular) is what you do not want! Incidentally, the segments are more likely to have been created by the CAD application than the slicer - an STL contains only straight lines and so must represent circles as multiple straight segments, so even if the CAD application works with real circles (most do not), those circles will have to be converted to polygons when exporting as an STL.

Dave]]> dmould Slic3r Wed, 01 Apr 2015 10:40:24 -0400 https://reprap.org/forum/read.php?263,490722,491394#msg-491394 Re: Strange outstanding perimeters https://reprap.org/forum/read.php?263,490722,491394#msg-491394 But it's not the "cure"...

It's important to have the perfect interaction between printhead moves and extruder flow.

For example look at the attached picture.
I made a thinwalled tube 25mm diameter, 100mm high.
Wall thickness is 0,2mm.
Every 10mm of Z-high i increased the velocity about 10mm/sec.
Starting with the "standard velocity" of 60mm/sec at the left side, and ending with 150mm/sec at the right side.

As you can see, 150mm/sec gives perfect surface quality.
With 60mm/sec you can see the created segments from the slicer.

Frank]]> NitroXpress Slic3r Wed, 01 Apr 2015 09:45:30 -0400 https://reprap.org/forum/read.php?263,490722,491372#msg-491372 Re: Strange outstanding perimeters https://reprap.org/forum/read.php?263,490722,491372#msg-491372 - reduce the infill speed - the best (at least from this perspective) would be to maintain the same speed over the entire print
- make sure the external perimeters are not printed first
- increase the number o perimeters (to let the overextrusion inside the object, though the extra amount of plastic will anyway push the external perimeter out)]]> 3Dmaker4U Slic3r Wed, 01 Apr 2015 07:52:50 -0400 https://reprap.org/forum/read.php?263,490722,491369#msg-491369 Re: Strange outstanding perimeters https://reprap.org/forum/read.php?263,490722,491369#msg-491369
Quote
NitroXpress
Hi Falk,

indeed it is a interaction of many slicing and firmware settings.

For this model CURA is the better choice, because the higher slicing resolution and more precise extrusion calculation, also depending on model resolution.

A worse model/slicing resolution causes acceleration/deceleration peaks.
For a smooth surface it is important to have a steady trajectory generation.

You can counteract with lowering your acceleration settings.
This causes less pressure peaks in the extruder.
Of course this extends printing time, but gives much "softer" moves.

Frank.

From my experience, Cura has a lower slicing resolution. Which is what you need if your printer cannot handle lots of direction changes, because the lower resolution slices (e.g.) a curved perimeter into fewer segments and so the printer has fewer direction changes. It won't however help when the perimeter is a straight line that changes in length from one layer to the next.

Decreasing the acceleration is the preferred method, but the easiest cure-all for such printing artefacts when they are only problematic on a small percentage of prints is to print more slowly. You can usually get away with slowing down just the outer perimeter, but may need to slow all the perimeters.

Dave]]> dmould Slic3r Wed, 01 Apr 2015 07:33:50 -0400 https://reprap.org/forum/read.php?263,490722,491354#msg-491354 Re: Strange outstanding perimeters https://reprap.org/forum/read.php?263,490722,491354#msg-491354
indeed it is a interaction of many slicing and firmware settings.

For this model CURA is the better choice, because the higher slicing resolution and more precise extrusion calculation, also depending on model resolution.

A worse model/slicing resolution causes acceleration/deceleration peaks.
For a smooth surface it is important to have a steady trajectory generation.

You can counteract with lowering your acceleration settings.
This causes less pressure peaks in the extruder.
Of course this extends printing time, but gives much "softer" moves.

Frank.]]> NitroXpress Slic3r Wed, 01 Apr 2015 06:23:05 -0400 https://reprap.org/forum/read.php?263,490722,491134#msg-491134 Re: Strange outstanding perimeters https://reprap.org/forum/read.php?263,490722,491134#msg-491134
The solid infill will be done after the perimeters (unless you have set infill to print first), so it is difficult to see how it could affect the perimeter. The area of solid infill may look excessive, but when it is building up to a horizontal hole, the infill must ensure that there are the correct number of solid bottom layers for the hole channel as it will be in a few layers time (when it is wider), plus extra distance to cover the perimeters of the hole sidewall.

Dave]]> dmould Slic3r Tue, 31 Mar 2015 14:56:29 -0400 https://reprap.org/forum/read.php?263,490722,491029#msg-491029 Re: Strange outstanding perimeters https://reprap.org/forum/read.php?263,490722,491029#msg-491029
thank you for your explanation, but I can confirm, that the outstanding layer is not depending on the direction.
It comes after each fast solid infill.
But what speed I ever set for the different options, the result stays the same.

Falk

Edit:

See attachment.
Slic3r makes huge "solid" areas (2) for printing only little "caves" (1) in the perimeters.
Which setting affects this areas?
After each of this areas the perimeters are a little bigger.

Falk]]> smoothcriminal Slic3r Tue, 31 Mar 2015 10:33:46 -0400 https://reprap.org/forum/read.php?263,490722,490984#msg-490984 Re: Strange outstanding perimeters https://reprap.org/forum/read.php?263,490722,490984#msg-490984
Dave]]> dmould Slic3r Tue, 31 Mar 2015 09:19:48 -0400 https://reprap.org/forum/read.php?263,490722,490868#msg-490868 Re: Strange outstanding perimeters https://reprap.org/forum/read.php?263,490722,490868#msg-490868
Here it is.

Falk]]> smoothcriminal Slic3r Tue, 31 Mar 2015 03:59:56 -0400 https://reprap.org/forum/read.php?263,490722,490859#msg-490859 Re: Strange outstanding perimeters https://reprap.org/forum/read.php?263,490722,490859#msg-490859
can you attach the original .stl model ?

Frank]]> NitroXpress Slic3r Tue, 31 Mar 2015 03:37:40 -0400 https://reprap.org/forum/read.php?263,490722,490722#msg-490722 Strange outstanding perimeters https://reprap.org/forum/read.php?263,490722,490722#msg-490722
Since a few weeks I own an Ultimaker 2.
After some relatively good prints I encountered some problems with Cura on negative angles.
After some reading in the Internet I recently switched to Slic3r.
The prints are much better but I got some new problems.
In the attached image you can see the marked outstanding perimeters.
I figured out, that they only appear if the printer prints some infill, before and after each hole of the die.
I played with all parameters in Slic3r but didn't got it to work properly.

Do you have some advices?

Thanks and best regards
Falk]]> smoothcriminal Slic3r Mon, 30 Mar 2015 17:07:49 -0400