My source models are from Creo (CAD application), and I have had fairly good success getting them into Blender as follows:
Export from Creo in STEP format.
Import into 3ds Max (30-day trial license).
Export from 3ds Max as Open Collada using the plugin.
Import into Blender.
However, my trial license for 3ds Max is ending soon, so I'm wondering if anyone knows of a good free tool that will convert STEP into something that Blender can import. Thanks!