can someone make the file a solid part please ? i tried many times but i just dont know how to do this
This is one of the Holy Grail goals for CAD systems. How to convert a triangulated mesh model into a smooth solid or surface model.
One of the issues with the helicopter model is that there are a large number of errors in it. These inverted surfaces, duplicate faces, holes and other defects need to first be repaired. Files created in programs like 3D Studio often have these types of errors.
It is then possible to stretch a skin over the model so it will import into SolidWorks as a solid or surface body, but before taking the time to do this, the question of "Why?" should be asked.
The imported results into SolidWorks are not usually able to be modified in any useful way, and the results are often lacking many of the fine details that may have existed in the STL file.
Depending on how the "Why?" question is answered, it may be better to recreate the model. But, there are times when an STL to SolidWorks conversion can make sense.