Can't be done without damaging the press. Take a look at this solutions. It may help you accomplish what you need.
You also can use the offset to do that after printed from digital.
I'm using a Digital Press 800/1000 and would like to know if there is a way to print an image where the ink can be scratched off with a fingernail or coin, much like a lottery ticket. Can this be done by altering the fusing temp or is it a totally different process? Thanks in advance!