Hello Muhammd, Note that your file has 18 shells, 17 of which are tiny, floating pieces. Also, the main body has a large number of overlapping/intersecting triangles. What software did you use to perform this Boolean operation? The thin spikes generated will likely create issues while meshing in Ansys.

This is an interesting structure. Our university holds a patent on the minimal-triangle diamond-structure version.

Thanks for the interest. i create these structures by using the Magics software and using Catia for solid model.

OK, if you're doing the Boolean in Magics, make certain that the .stl is "clean" - no overlapping or intersecting triangles, no bad edges, etc. The newer versions of Magics have automatic repair tools for this.

Dear cook my question is how i can convert this stl format to a solid body?

Dear Aslam, Once you have a clean .stl, you can try importing it into Ansys. Many CAE software tools handle .stl files as surface meshes, with varying degrees of success. COMSOL Multiphysics, for example, can import an .stl file and mesh it. I have yet to find a software tool that can convert an .stl into a conventional "solid," since it is only a surface-geometry definition; and, that conversion is a "lossy" process (loss of information). Keep an eye on Geomagics as a potential option for that.

Thanks alot Cook i will work on your suggestions. I'm really hoping that it will work.