This Riso RP3700 is printing ok for the first 250 or so prints and the a couple of small dots (about the size of a period) appear on the image side of the print. These are often followed later with several small black lines about 1/4" long by 1/16 wide on the backside (or non image area, of the print). I cannot see matching marks on the master but they must be there as when I make a new master it starts out clean but the problem soon appears. I have cleaned the pressure roller etc. The machine had been sitting unused for about a month. The ink color is black but was not a oem ink. I have also removed the master from the drum and wiped the drum with a cotton pad moistened with water in case there was a speck of dirt under the master, but I still got the problem. Any ideas would be greatly appreciated.
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Re: Riso RP3700 leaving ink spots on front and back of copy
What's happening is that the corners of your paper are wearing holes through the master material, allowing ink to leak through where it isn't supposed to. Being on the very edge of the paper, these deposit ink on the roller underneath the drum, which over time will build up to make streaks appear on the front and the back of your prints.
What you might try is, after fifty or so prints, pull the drum out and look at the master. There should be an impression the size and shape of the paper you are running in the master. Put some tape over the corners of that impression (any single sided tape will do, the Riso won't care) and then run the rest of the prints.
Hope that helps. -
Re: Riso RP3700 leaving ink spots on front and back of copy
Many thanks for your accurate advice. When I thought about it, it made perfect sense but I would have to admit I would never have thought of it myself. I had not mentioned that the "paper" being run was envelopes which, of course have stiff corners. Also, probably the edges being double thickness could have been cutting into the master. When I got back to the shop today I put it to the test, and IT WORKED! The problem might have also been compounded by the fact that I am using aftermarket masters which could well be thinner than the OEM. I am surprised that no one else has not mentioned having had a similar problem as before I posted I ran a search on the topic. Hopefully this will help the next person in resolving any similar problem.
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