Hi Paul, so it looks like the main thing with a real degeneracy problem is a little thin sliver along the back. On the back side I noticed this anomaly here:



Then deleting the large back pieces I could get a little better look at it:



Often times that kind of shaded triangle "leak" can be because of degenerate trim boundaries. I zoomed in closely to that area and there are some very skinny slivery faces in there, these seem to be likely culprits:



So maybe something like the curves along the back side didn't quite exactly align with each other and are leaving that messy little fragmentary result in it.

Or maybe there is a tiny line segment in one of the curves. Something akin to that probably. If you can maybe post a simplified file that has just the curves used to create that piece that would help me to examine it more closely.

But it's likely that spot with such tiny compressed/degenerate surfaces in it are causing boolean problems.

- Michael

I appreciate your help in the forum. Besides the improvements of MOI that is definitely a reason to update my MOI license, when Version 4 is ready.

Probably my questions in this thread are also a help for other not so experienced users.
What have I done now. First of all as requested I add the underlying dxf-file from my friend.

Than I have extensively reduced the number of points in the sections with the rebuild function by setting tolerances to 0.5 or reducing points while keeping edges. Also I deleted points, which were to near or out of the line.


The result looks to me much more "clean", as far as I can see from visual inspection (an professional inspection command would be in deed very valuable in the future). Are that still to many points or is this an order, MOI can handle? I found some small faces left at the bottom, but there are not many points left there. The network function worked very quick and after gluing the separately build planar front section, I got a solid with no edges.

I also reduced the point of the cutting sections a lot (green parts with style cut, the circle is only for testing purposes).



But unfortunately the boolean operations still do not work or lead to unexpected results, for example the difference of the solid and the circle leads to outer tubes glued to the solid.


Regarding the shell: In deed, I see that is mathematically a complex problem. On the other hand that things will be more and more interesting in combination with 3d printing, as in many cases it is valuable for the slicer to have a solid shell (exported to stl) then a full solid which is printed without infill. In my case I see 3 choices, as the outer shell (laminating form) does not have any accuracy demand:
- construction the shell and not the original solid -> not ideal
- scaling the solid and extract the original part, if that works
- extracting the solid model form a cube and forming the outer part with a simple surface, an ellipsoid or a simply loft (to much material in the shell extends the printing time extensively).

Best regard,
Paul

Hi Paul, yes so the problem with the DXF file is that everything in it is made up of polylines. So the areas that look like smooth curves are not actually smooth curves, they're actually hundreds of little line segments.

So that DXF data is not suitable to be used directly for constructing surfaces from, you'll need to create smooth curves from those, either by using the Rebuild command or possibly by drawing completely new curves and using the DXF data as a guide. For the Rebuild command if you join together a sequence of lines that should be smooth you could use the "Endpoints" mode of the rebuild command which will be the same as doing a "Through points" type curve through the polyline vertices.

It would be better if the DXF file contained higher level data in it like at least arcs for circular areas. It would be good to ask your friend if he has the data in that form and could send that rather than only linearized data.

re:
> But unfortunately the boolean operations still do not work or lead to unexpected results, for
> example the difference of the solid and the circle leads to outer tubes glued to the solid.

The "outer tubes glued to the solid" happening in a boolean is a result of the outside direction of the solid being oriented incorrectly. That is one of the things that can happen with degenerate geometry like I was describing earlier and the degenerate faces that I showed in the previous post here http://moi3d.com/forum/index.php?webtag=MOI&msg=9219.6 are still present in this model as well so those still need to be cleaned up before booleans will work properly.

I also noticed an additional thin slivery surface along the front side here:







That might be a remnant of one of the little tiny lines in the original polyline data. It won't be possible to do a proper boolean on a model with these degenerate faces in it.

It looks like I can figure out now what things to select to make the Network so in a bit here I'll examine those curves more closely to see what needs to be trued up to avoid the malformed faces.

- Michael

Best in general is to redraw with curves above the existant "polylines" ! ;)
Maybe one minute in your case for this little piece!

Hi Paul, I found one problem area in the curves, there is a little tiny line segment in this area here:







I think that's not the only problem though.

- Michael

I rebuilt all the dxf-polylines with curves through points. For me it took me a little more time than for Pilou :).

But the more time consuming part was to snap all sections together and keeping all lines flat.

- Is there an advise, how you snap the perpendicular Curves efficient and keep them snapped?
- Is there an easier way to look for the intersection points? I always used ->curve->insect and constructed points.

I also found that the closed crossections introduced problems at the backside. It was no longer flat. So I build it afterwards from the edges.

The outer shell took some additional time, but I was much faster, because I knew the problematic area already.

At the end the result looks quite promising.



The slicer gives an estimated printing time of 9 hours per half. We will see.



I will add some photos of the printed form, when we are ready.

Thank you again for your help. It showed me the my problem could be solved with MOI.

Best Regards,
Paul

Hi Paul, it looks like you're making great progress now!

re:
> - Is there an advise, how you snap the perpendicular Curves efficient and keep them snapped?

There isn't really any built in tool for doing that. Depending on the particular situation some kinds of strategies could be helpful like have some extended flat reference lines to target.


> - Is there an easier way to look for the intersection points? I always used ->curve->insect and constructed points.

The Construct > Curve > Isect command is the main way to check for intersection points. The Network command can actually tolerate curves that do not exactly intersect. That can be messy at a major nexus point but out in the middle somewhere it can be ok.

Sometimes it can be good to overbuild something and plan to hack excess areas off with a cutting line rather than trying to do the initial surfacing directly to a target shape...

- Michael