Big Red lines even if "force NURBS surface to triangle mesh" and export stl

[fredOnGitHub]

System information

• SolveSpace version: 3.1 70bde63
• Operating system: win11

Hello,

from this it is ok

but from this arc version

i get

and it is ok when i do "force NURBS surface to triangle mesh" => no red lines
but when i export triangle maillage
i get

I am furious and disappointed (LOL).

Thanks

[ruevs]

It is a known problem #1291.

Make the straight parts (corner) of the cutting ark sketch stick out of the part by a bit (instead of coinciding with the corner) - it will solve your problem. In other words the 13mm line segments and the ark should not meet tangent to each other at the edge of the part. Instead there should be two short line segments perpendicular to the arc ends (and the part) sticking out.

[fredOnGitHub]

Hello,

if i understood i have done that

that

that

that

to get

1st question :
Is it the good way ? More simply ?

and finally with Windows 3d viewer

But I see polygons...
2nd question :
Are 'chord tolerance (in percent)' and all other parameter good ? I don't remember the default values.
How can I get nice shape without polygon mesh ?

Thanks

[ruevs]

You did it in a way that is more complicated than needed. Here is what I would do:

The failing case asks the software to make two "complicated" (for an algorithm) decisions:

1. Does an infinitely thin (zero thickness) "sliver" of material remain in the spots marked in yellow?
2. The material being cut approaches zero thickness when approaching the points where the line segments and the arc meet tangential to each other. this poses a numerical problem.

To avoid this I just used two construction lines to position the arc and moved the two lines forming the sketch to the outside.

Another hint - make the extrusion with the "difference" operation "two-sided" to avoid asking SolveSpace to solve a similar singularity problem where the "front" faces of the two solids coincide (it does usually handle it OK).

The test model:
FilletTests.zip

Some previous explanations on the topic:
#470 (comment)

The issue collecting all such problems:
#738

[ruevs]

Are 'chord tolerance (in percent)' and all other parameter good ? I don't remember the default values.

The export chord tolerance (in mm) and export max pieceise linear segments parameters control how fine the exported meshes are. Make the former as small as you want and the latter as big as you want to get the desired precision. After an export operation SolveSpace displays the exported mesh until you press ESC. Turn on the mesh to check if it is acceptable.

Read these two sections of the reference:
https://solvespace.com/ref.pl#Chord
https://solvespace.com/ref.pl#Known

[fredOnGitHub]

More simply !
Thanks !
I have a nice NURBS into the form now.

compared to rendering before

About the exportation, I have done that :

to get

Thank You very much !