Hi Bernie,
Now please don't get me wrong on what i'm about to say... 3d printing has it's place and you can bet i'm hot on it's heels!
The problem (and without getting to techy) with the particular method of 3d printing used here is there are many layers used and in 'old pattern makers' terms there are many 'witness lines' left.. or in layman's terms it has a rough finish and still needs good old fashioned human intervention (soapy water & wet and dry)
There are better 3d printing soloutions but they cost .... I have an eye on the chinese guys
Regards
Kim
P.S. And at the risk of a self advert ... I sell 'smooth' vent tops at many different sizes.