I have the 1626uh, the model prior to the 1638. After two years of trying different brands of corro, and different brands of prep solutions (nastiest chemicals in the shop) we send our coroplast printing out source. Approx 30 days outdoor is all we can get. And even if used indoors, the ink will flake off when trimmed. Very disappointed in the printer on this point and I even cut ties with the dealer that set me up with this machine. Mutoh themselves has never been able to answer the question as to why it fails. They just go on to say that all UV printed ink has a lower life expectancy. Not true! Would have considered the 1638 or the new Performance Jet as my upgrade path, but if the ink is the same (all accounts it is) then the conversation is a non-starter.