Making a fully solid STL without any empty gaps inside it

[miozeriux]

Hello guys, I'm new to the forum, never really had problems with 3d printing before, but now I am wondering what is the best way to make this STL truly full and solid. I attached picture of my stl, as you can see it has some weird stuff going inside it, is there any way to clean that stuff inside and make it a full solid mesh? I want to print it and if I drill a hole in it, it must be solid. Any help is much much appreciated!!

[fred_dot_u]

If the surface of the STL is manifold (has no gaps or discontinuities), you can use Meshmixer to remove the internal flaws. There are two methods. One is to use the Make Solid feature, but if the settings aren't optimized/customized, the surface will change in an undesirable manner. The other method is to use the Select feature, select the entire outside of the model, then invert the selection and delete.

Consider also to post the STL file, as a tiny JPG file is challenging to interpret.

[miozeriux]

Select and Invert feature did it! Thanks champ