Epson r1800 Post script?
Postscript is "page description" language made by adobe. Your r1800 does not have postscript. Most inkjet printers do not come with postscript. The epson 3800 pro does come with RIP software that runs on your computer that emulates postscript.
I do not know of a RIP for the r1800. What kind of document are you trying to print?
hope this helps