Holes in between walls.....  

RE: Holes in between walls.....

I just checked in 2.0 and its the same.. And now I realise its got something to do with 'scale'. I am actually taking this model up to 106% and thats where the problem starts.

If I look at the layer at 100-104% its fine.. As is 107%

But at 105% the line between the internal and external wall becomes a mix of white and yellow... And then when I move to 106% the white disappears and just see yellow "infill" and thats where I get the holes

I think this is a bug and think I need do to some more testing and will create a Github report if it is.

RE: Holes in between walls.....

If you look at the key you will key what the colours mean.  The yellow are perimeter walls and depending on the wall thickness of the model and the print width settings for your perimeters the slicer will try to fit however many it can into the wall thickness.  The white areas are gap fill, thats where little bits are extruded to fill in the gaps between the walls as theres not enough room for another perimeter or for normal infill structures.

When you change the models scale you are changing the wall thickness and so the calculation on how many perimeters and if there needs to be gap fill changes naturally.  So I'd say its working as designed.  You can disable gap fill by setting it to 0 in your slicer settings.

RE: Holes in between walls.....

I probably didn't really explain this very well as I struggled to find the words.

Its not really that Gapfill is the problem here.. But as I scale the model, the gap fill (white) turns into something else which is light yellow, and thats not even shown in the key.

But worse still, where as the Gapfill (white) is a 100% fill from normal size upto 104%.. WHen I scale to 105% it becomes a mix of gap (white) And yellow (What ever that is)..

But at 106% the gap (white) disappears and just leaves the yellow fill which is full of holes

At 107% the yellow is now 100% and I don't get the holes

So this issue only occurs at 106% (on this model), but also, it leaves the question about what is this "yellow" fill which takes the place of the gap fill (White).. But is not shown in the key?

RE: Holes in between walls.....

It is in the key, its the first entry, perimeter, your holes 2.1 image shows the external perimeters and a single perimeter. 

The question is why isnt it a solid perimeter like it is with 1.4.1 ?  The only thing I can think of is that the model while it looks like a circle is actually made up of multiple straight sections to form the arc.  Where 2 lines meet there will be a corner and at the corner the thickness will be very very slightly smaller potentially.  The different slicer versions may be treating these intersections differently, the newer version may be parsing it out as not thick enough to fit the perimeter in there .  That's all speculation on my part though.

Post your issue with the project 3mf file and the images on how the 2 different versions are handling it over on github so the devs can take a look.

RE: Holes in between walls.....

Problem with this one, its a thingiverse project, so I only have the STL.. I have tried my own tests making a similar wall thickness at the same radius and its fine.

I also scaled the STL to the same 106% outside of Slic3r and when I loaded it, its the same.

So I don't think it has anything to do with scale, just some weird co-incidence that I have hit on a specific model and size that causes this issue.

I am now printing at 107% which does not have this problem.. I think I can live with it being a fraction bigger.. But I am still intreagued..

If anyone fancies a look, I have put a link to the model below.. At 100% scale it seems fine.. But at 105 and then 106% this odd 'fill' starts happening.

https://www.thingiverse.com/download:5476707

RE: Holes in between walls.....

When I say project I mean once you have the model loaded into slicer and have it all to your satisfaction that shows the issue when you slice you then go to file and Save Project as.  This exports your entire project as a 3mf.  This contains the model file(s) , all your settings for print, filament and printer as well as any modifiers you may have used, part placement, rotations etc etc, which could all potentially effect the slicing.

It allows someone else to open it with exactly the same settings you used.  That way a dev can duplicate the issue exactly on their setup and have a much better chance of figuring things out.

Its also good workflow for your normal projects as it allows you to come back later and make little tweaks much more easily as you dont have to set things up again.

RE: Holes in between walls.....

If you go to 'Print Settings > Advanced' and change the external perimeter extrusion width to 0.5mm you should find that the dotty bits disappear

the  picture above has dotty infill, the picture below is with the extrusion width at 0.5mm and there is no dottyness...

regards Joan

RE: Holes in between walls.....

Thanks Both.. Noephyl.. I didn't realise thats was where .3MF files come from.. Thanks for clarifying that.

And Joan.. Thanks for the tip.. I was looking for the Extruder width and couldn't find it.. I am from a CURA background, but when I switched to Prusa/Slic3r I have dont almost no playing and stuck with the default options, do I don't really know my way around many of the options.

Its still odd that Slic3r can't handle this and changes the 'gap fill' into something else whihc isn't complete.. I still think "bug", but its not something worth pursuing.

Thanks again

Jon

RE: Holes in between walls.....

I had to fiddle with the scaling factor in order to cause the problem to occur...    🙂   and then modifying the extrusion width sorted the  issue
I suspect the problem is caused by the printer making circles with straight lines,    so you effectively have three circles, outer perimeter, inner perimeter and infill...  and this issue will probably occur at a dimension where the ends of the straight sections on the outer perimeters 'pinch' the space for the infill...

if you print outer perimeter last, then the printer will try and print the infill first and this is likely to get messy with tiny bits of infill... it's possible that switching to print perimeters first may have resolved this issue.   (but possibly caused problems with overhangs)

regards Joan

RE: Holes in between walls.....

Posted by: joan.t

I suspect the problem is caused by the printer making circles with straight lines,    so you effectively have three circles, outer perimeter, inner perimeter and infill...  and this issue will probably occur at a dimension where the ends of the straight sections on the outer perimeters 'pinch' the space for the infill...

if you prin

When I originally posted, I was convinced it had something to do with "scale" and assumed there was some kind of calculation issue.. But I then loaded the STL into Sketchup, and scaled it to 1.06.. Then I loaded this new object into Slic3r at 100% and it had exactly the same issue as the original scaled to 106%

So its not scale.. But as you said, some kind of clash between concentric circles which only happens when the wall thickness and extruder width conflict with each other.

Now I know how to change the Extruder width, this will help me work around this kind of issue again in the future if I encounter it...

Thanks again

Jon