I want to soften the text edges but any handle value breaks the edges and adds artifacts.
How text edge softening should be done?
This is a typical problem with objects based on text - they contain both sharp edges and just off-tangent discontinuities which wreak havoc with Rhino fillets. There is no real good solution, unfortunately. If there is little text, fixing the text curves and re-extruding the letters may allow you to fillet them.
Otherwise, you can fake the fillets with ApplyEdgeSoftening - which doesn't actually change the NURBS objects, but will alter the display mesh to "round" the edges. You can extract this mesh for rendering or RP purposes with ExtractRenderMesh. ApplyEdgeSoftening has it's own set of problems, it's only currently possible to do all the edges of an object or none, and the results at certain places can still be a bit rough.
thanks for the information
but i'm not sure I understand; will ApplyEdgeSoftening is an operation that will be valid while printing the object or will be only visual - valid for rendering?
thank you so =0)
Both. Since you do 3D printing with a mesh (.stl), you can use the display mesh produced with ApplyEdgeSoftening to print. To do so, you need to extract it - that is to say convert it into a "real" mesh object - with ExtractRenderMesh. Once you have that you can export it as an .stl for 3D printing.
As I said previously, the original NURBS surfaces are not affected by edge softening, so if you export those as .stl, you will not get the rounded edges.