By far the best way to avoid entry and exit marks is to plunge to depth OFF the part, then do an arced or tangential entry to the part for the finish pass. If you're careful about *where* the tool contacts and leaves the part, you can eliminate the mark altogether. Plunging and retracting on the cut line will pretty much always leave a mark. To do otherwise would require a machine with absolutely *perfect* tram, a tool with zero runout, etc. etc. IOW, not the real world....
Regards,
Ray L.