I RECENTLY PURCHASED THE EPSOM 870 PRINTER , AS I NEEDED GOOD PHOTO QUALITY ON GLOSSY PAPER . THE TINY COGS THAT FEED THE PAPER THROUGH ARE LEAVING MARKS ON THE PAPER THAT CAN BE SEEN ON CLOSE EXAMINATION . I EXCHANGED THE PRINTER FOR ANOTHER ONE AND THIS DID THE SAME. HAS ANYBODY NOTICED THE SAME . I HAVE AND OLDER EPSOM 600 , SO I CHECKED IT AND NOTICED A SLIGHT MARK BUT NOT ON THE SAME SCALE . I WILL HAVE TO GO FOR ANOTHER PRINTER OF A DIFFERENT MAKE , MAYBE THE CANON 8200 BUT THE REVIEWS ON QUALITY ARE NOT AS GOOD , ANY ONE CAN HELP?

Are you using the proper paper for your chosen resolution? If you use paper that can't handle the resolution, some of the ink ends up on the rollers and cogs, and then gets transferred onto the page. Or is it actually the indentation of the cogs that's visible?

I noticed this too when I recently looked at this printer. It's not ink on the cogs but the cogs themselves (or, I suspect, rollers) impacting on the page, causing slight but noticeable tracks on the borders of the printed page. It wasn't a problem with regular paper but on glossy photo paper you could see it quite clearly.
I've also seen other printers in Epson's lower-end range and was fairly disappointed with the printing quality. IMHO Hewlett Packard and Lexmark now lead the home market inkjet brigade and Epson really should pull their socks up. Consider a Lexmark Z52 (or Z42). I forget the Hewlett Packard model numbers but even their budget £100 model was very good indeed - great photo printing and text quality.

I've just seen what you mean, this time on a Stylus Color 900. As you say, it's fine on standard paper, but on glossy paper you can see tracks. Since the cogs are in front of the print heads, they must be denting the paper so that the ink doesn't stick. It's not hugely obvious, but it's definitely there.

I remember doing an inkjet group test for a certain magazine three years ago. When I started, EVERYBODY in the office said something along the lines of, "Epson will probably win."
Not to be biased, I did all my print tests and then did a blind jury test of my colleagues (ie not saying which print out came from which printer and asked them to judge the quality). Which printers do you think won? The Lexmark printers came top followed (I think) by HP. It was a long time ago although I remember it was a close run contest (inkjets weren't that great back then).
I did another inkjet group test a few months ago. Again, my (different) colleagues said, "Epson will probably win." Again, testing proved otherwise. This time it was Hewlett Packard who provided stunning and impecable prints. Lexmark came second. Epson came third with some of their printers (the 900 was good but the 1270 was very questionable IMHO).
Like any industry, computer magazines can be very biased. Sadly in many cases people enter a group test having already decided the winner, even before testing has taken place. In certain comp magazines I've seem the printers that I thought were rubbish being given awards. I've then gone back over my extensive test prints with disbelief - how could they have thought this was a good printer? The skin tones make people looked like they've been boiled in beetroot, landscapes are washed out patches of cyan and almost nuclear green, and there are stacks of other print faults like dithering and even corruption caused by bad paper handling mechanisms (this last comment isn't completely directed at the Epson printers, btw -- another manufacturer also suffered from the problem).
Let the buyer beware.