i tried the stl2dxf converter and it works great , but the problem is the STL file was 7.86 M and it comes 66.1 M after DXF conversion. It takes 1:45 hour just for opening the file with inventor and about 10 second lag for every fonction in the drawing .
 
Does anyone have a solution to get this kind of file smaller or easyer to work with ?
 
Thanks !
 
Ben  

STL file is - by its nature - composed by multiple thousands or even hundreds thousands of facets. Such huge number of individual objects is rather hard to process in 3D solid modelers. Make sure you have enough RAM, and preferably a 64-bit version of Inventor.