As we know, STL geometry is composed of triangular facets. I’ve noticed that sometimes these triangles can be quite slender or elongated. I’m curious to know if the shape of these triangles, particularly their slenderness, has any impact on the mesh quality.
If triangles are too elongated, they will be considered as collapsed and will be removed from the meshing process, which could lead to holes in the geometry. By default, if the angle between two edges is less than 0.1 degrees, the triangle is considered collapsed and will be removed. You can relax or tighten this tolerance in the Mesh>Mesher pane:
It is better to build the stl file so the triangles aspect ratio is not too large. If you use the GUI to generate a cylinder, I recommend using the procedural cylinder, which allows to set the number of triangles in the longitudinal and circumferential directions: