You could try increasing your stl resolution when you export from blender. Or switch to a cam program like Rhinocam which may be able to import your model as surfaces rather than an stl.

You should be able to just increase the resolution until it is smooth enough to not be seen by the eye. This might cause issue with your computer and software as it makes the .stl file larger in size. You should hopefully be able to find a happy medium if you play about with the settings.