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Hi

Quick Look uses thumbnail preview stored inside DWG file to show quick view in Finder.
To get better Quick Look resolution you can adjust two System variables in AutoCAD:
THUMBSIZE2D and THUMBSIZE.
Try to set them as follows:
THUMBSIZE2D=1
THUMBSIZE=5 (or even more, maximum is 8)
Now save drawing and use Quick Look.

https://knowledge.autodesk.com/support/autocad/learn-explore/caas/CloudHelp/cloudhelp/2019/ENU/AutoC...

https://knowledge.autodesk.com/support/autocad/learn-explore/caas/CloudHelp/cloudhelp/2016/ENU/AutoC...