I am having an issue with imported a dwg file into 2018 version of Sketchup pro
I have previously imported the same file in 2017 version but when imported into 2018 version the same dwg looks to have thicker lines and a more crude appearance.
Note changes at https://help.sketchup.com/en/release-notes-0#su18 for the DWG importer.
There may have been changes to the displayed edge widths. You may need to adjust style settings (Edge panel).
Take note in the release notes that Mac now has OpenGL anti-aliasing setting. Perhaps the default is set too low (crude). Try an higher setting (better anti-aliasing.)
The Style setting (Edge panel) was the problem
Thanks again for the help