[Jamming] Ink marks

[Guest]

Hi,

I have a Riso RP3700 recently it has started to play up and I can't find the cause. The machine works fine on standard 80gsm paper, but when I use 140gsm or thicker a strange ink pattern appears when I am printing solid colours. When the pattern happens the paper also kicks to the right when it is being fed out of the machine. At first I thought this is what might have been causing the problem with the ink, but having looked into this I think this is because of the problem not the problem itself. (I thought the kick was causing the ink to smudge, but it seems it is just laying down more ink.)


It is not with the drum either because I have tried multiple drums and it still happens.

Here is an example of what the ink looks like.

riso_page.jpg

Also when this problem happens I get a large amount of offset on the backside of the page which corresponds to the denser ink pattern on the front.

I am really at a loss with this problem and it only happens sporadicly so any help would be greatly appreciated.

Thanks
Charlie

[jermyth]

Re: Ink marks

It sounds like the impression roller needs replaced. How many prints are on the machine and has the impression been replaced before? It also could be parallelism of the timing roller or of the impression roller. If you got a service manual you look on how to check them.

[Iowatech]

Re: Ink marks

I don't know if this will help, but I've seen where running heavier stock through the machine sometimes will wear out the surface of the master on the drum, which will cause random looking marks on both sides of the prints. If that is the case, after running about 10 or so prints, pull the drum out and you will see a clear impression on the master, and put whatever tape is handy on the corners of that impression on the master.
That works with envelopes, anyway.