I need to import an assembly from CATIA into SimMechanics but in CATIA, the .stl file format is available only for part files and not for assembly files. How can I do this? Is it possible to convert between the .CATProduct and .stl file formats?
Short answer: you can't directly import CATIA assemblies in SimMechanics.
Long answer: SimMechanics supports import of CAD models (assemblies or parts) from Pro/Engineer, SolidWorks or Autodesk Inventor via SimMechanics Link (see Importing CAD Models on the MathWorks website). The SimMechanics Import XML Schema should allow import from any CAD system, but you need to be able to export to XML from your CAD system, and the XML must follow the SimMechanics Import XML Schema. For you, that probably means having to write a custom interface layer in CATIA to export to the correct XML file schema.