thin walls and numbers of outlines used (gaps between 2 perimeters)

[jgeerds-zz]

https://picasaweb.google.com/lh/photo/W0brohD6QMSl3oDEXfNgQTIYJXjTqlQYmaNWFtjfw8o

I was getting random, and hard to explain thicknesses for thin walls, so I made a quick rake (ranging from 0.5mm to 3.0mm in 0.1mm steps), so see what each slicer is actually doing.

results are in the chart/link above. long story short, neither slic3r nor cura are doing a particular good job slicing thin walled objects, but it this chart may help to pick a certain wall thickness that will produce no gap in between.

Either slicer was set to 1.6mm walls or 10 perimeters, to ensure it's all walls.

in the long run, it would be great if the slicers would have some form of "gap avoidance" and/or at least to use infill or an extra line+combed jump.

[jgeerds-zz]

you can download the STL at http://nypano.com/clients/UM/rake.stl

[buserror]

I've been scratching my head over this problem for a while, no amount of "logic" appeared to remove the gap. Thanks for the idea of making a rake...

[alranel]

@jgeerds, thank you for your chart, that's useful work. Actually, I wrote an algorithm for filling gaps, but I left it disabled because it needed a bit of more work. Sadly I haven't had a chance to review it so far, but as soon as I put my hands on it Slic3r will fill those gaps.

[jgeerds-zz]

@alexrj that is fantastic, I am looking forward seeing the result of your algorithm!

[tgfuellner]

I'm also looking forward. This is the one cause for using skeinforge sometimes.

[jgeerds-zz]

One way around this could be using fractional line widths:
the "outliner" (however you call this part of the code) would calculate the outline based on the standard line width, and once it encounters a feature that is narrower than the line width (instead of dropping it), it would use a half line width (i.e. a 0.2mm instead of a 0.4mm extrusion) to make that segment. this (in theory should get rid of any gaps, and this would also help with very small features for outside walls as well, where less small things would we "rounded away". the outliner could also go a step further, and maybe use 1/4 line width (0.1mm for a 0.4mm nozzle), but the practical results for this would need to be tested to see if it actually works.

[jgeerds-zz]

btw, I just sliced something last lats night with the new 0.82 version, and it left some gigantic gaps between 1.5mm wide walls, turning the part completely unusable.

[alranel]

Done! The gaps filling algorithm is enabled. Your rake.stl chart was very very useful.

[alranel]

[alranel]

One more example of filled gap:

[jgeerds-zz]

awesome. can you push an updated and compiled build to the download section, please? (the compile instructions work only for 10.7, and I am still running 10.6)

[alranel]

Release will happen in a few days. Btw, just install Developer Tools/XCode for 10.6 and those instructions will work fine regardless of the version.