I created an addon to import STEP directly into Blender. https://gum.co/stepper
Information on the old & free version
Depending on what operating system you are using, you can delete the modules (.dll = Windows, .so = Linux, .dylib = Mac)
So far tested only on Windows 64-bit. You can also download the SDK from http://gmsh.info/ for your OS if it’s not working, and copy the Python module from that into the addon folder.
Addon creates UV based on CAD surfaces, also creates automatic smooth/sharp in an attempt to make the model look good. There’s also an option how high polycount you want to make the model better approximate the base CAD model.
The location is in the import menu.
I rewrote the entire thing from scratch again with OpenCASCADE. It should now work much better. As it’s quite a bit of work, I also set a price and created a new version on Gumroad. The old one is still free. If you got the free version before this update let me know if you didn’t also get the OCC, so I can send you a free copy as a thanks for the interest. Note: it currently supports only STEP, no IGES.
If you have any comments, let me know.
How to report issue
Copy & paste the following:
import platform as p; import bpy; "|".join([p.machine(), p.platform(), p.python_version(), p.python_compiler(), bpy.app.version_string,bpy.app.binary_path_python]) into Blender Python Console and tell me what it prints out, in addition what your issue ie. Use the email address you got from your receipt from Gumroad and send the message there, using the email address you used to buy the addon.