Does anyone know how to get solidworks to print at true 1:1?

When I print it comes out 1-2mm smaller on most dimensions, but when I scale it up to say 102%, it throws everything out of proportion dimensionally. This is because 102% of 20mm is 20.4mm but 102% of 200mm is 204mm. See the problem here? I can never get a true 1:1 representation of a part.

I need true 1:1 for a pattern maker, because the part has splined curves which are hard to dimension.

It's probably a printer problem, but any help/advice would be appreciated anyway.

Cheers.