Riso GR3770 Ink Coverage Not Great...

Caldera · 06-13-2014

Recently bought a riso GR3770, had a few issues that I fixed while getting it up and running, but got it working. Cleaned up a bunch of different colour drums and was happily printing.

But now... its been giving me these slightly patchy and not entirely crisp prints, coming out as though they have all been slightly scuffed and the ink has not been flowing as well as it should. This has been happening on all my ink drums. I've turned the ink density up to the highest setting and it doesn't change much.

Does anyone know what I can do about this? Should I change some of the rollers inside or something? Is there anything I should be oiling? When I cleaned up the colour drums I cleaned the outsides but not inside, perhaps I should clean something inside all the drums somehow? I'm worried if I keep using the machine then I might be breaking it or something

Thank you for helping!!!

**Iowatech** · 06-14-2014

How many prints are you making per master? Twenty is the least amount of prints you should make from a master.
If you don't use the Riso that often, you should use the "Idle" feature when you first start printing. That will distribute ink on the inside of the drum, and help lessen the recovery time.
If you haven't reset the machine in the way described in many other threads in the Riso area, this would be a good time to do that.
Um, if you have the time, please define what you mean by "scuffed". I have worked on Risograph equipment since the RG line, and during that time I have never seen any printing image defects that I would describe with the word "scuff" as I understand it. Thanks.

Caldera · 06-14-2014

Thanks so much for the reply!
Ok... hopefully these images come up large enough to show what the issue is. Maybe "scuffing" is not the correct word... the artwork is not being printed clearly, and the ink density is not very good. Looks patchy on prints from all drums. I looked inside some of the ink drums with a flashlight and they looked like there was a lot of ink in the area where its supposed to be distributed through to the screen, but somehow its not geting onto the paper.

I've been doing print runs of about 400-600 copies of various artworks/flyers etc (similar to the one below), using the machine about every 3 days.

riso image 1.jpg
riso image 3.jpg
riso image 2.jpg

Thank you!

**Iowatech** · 06-15-2014

Thanks for the pictures. As I'm not being able to see you machine in action they help a lot.
I'm going to guess that in the third picture the hair on the right hand character is supposed to be an even shade rather than streaked like in the image. If that condition doesn't improve after twenty or so prints, that would seem to indicate that the pressure roller (the roller under the drum) is bad.
Over time, that roller gets a depression where the paper passes over it. It also collects small amounts of ink. While the imperfections are small, they are quite enough to cause the image defects in your pictures.
I'm not sure what to tell you to do next. It isn't that hard to replace the pressure roller if you take into account the various nearby sharp edges, but new rollers haven't been available for the Riso GR line for quite a while. A couple of times if I'd see ridges on the pressure roller from built up ink deposits I'd try scraping them off, but it is pretty easy to damage the actual roller when doing that and it never seemed to help for that long (cleaning the roller any other way is not recommended, unless you have a lot of time and don't mind washing your hands a lot as well). And I don't think replacing that pressure roller with one from a machine that currently is not obsolete will work, those machines use pressure rollers that have a significantly smaller diameter.
I guess you might try looking for a pressure roller from a GR3770 or GR3750 that has a low copy count if you don't have to pay too much for it. I think the pressure roller from a FR3950 or even a GR1750 might work, too, but it's been a while so take that with a grain of salt.
Good luck.

Caldera · 06-15-2014

Thank you! I have a spare GR1750 pressure roller (well my brother has one he can post me) so I'll try it

**ddude** · 06-18-2014

Have you tried cleaning the drum screens on your color drums? If the drums haven't been run for a while the ink can clog the screens. Lightly clean the drum screens with some solvent and see if the quality of the print improves. I have posted these instructions on this site earlier, here is a reprint:

Easy to do- place the drum on the rails, remove any master that may be on the drum, so only the screen is exposed, then soak the screen with the solvent of your choice (everything from alcohol to diesel ), let the solvent-soaked rag sit on the drum for ten-twenty minutes, then insert drum and make a master-repeat as needed until the copies look awesome.

There are citrus-based solvents available at hardware stores that do a great job of cleaning screens, just apply the solvent gently to the exposed screen and let it dissolve the ink.

Since the introduction of soy-based ink, this issue has become more prevalent. Oil ink maintained a better storage life than the soy product.

**ddude** · 06-18-2014

I have GR color drums available for sale if you are interested in many different colors- PM me or email at ddigitaldude@hotmail.com

all drums have been tested and are shipped in a storage/travel container.

ddigitaldude@hotmail.com

**bcp** · 06-23-2014

I had similar problem with my GR 3770. The black ink worked perfect all the time but any colour gave problems (image seemed starved for ink) Had a brainwave one night - the GR3770 is a HD printer that uses HD inks & masters. The black ink is HD BUT are the colored inks HD. I don't think so, so I purchased some GR 3750 masters (these are not HD masters) and used them on the colored ink and you little beauty it worked. So try your black ink and if it is ok then try GR 3750 masters.

**irrland** · 06-30-2014

We are also Riso newbies, but maybe it still helps:

We just got an 3770 and experience the same thing with only one of the color drums.
The seller of the machine said it might be that the ink is too old and therefore too "sticky". We haven't tried new ink yet, though.
Do you know how old the ink is that is in your drums?

Caldera · 06-30-2014

Hi again!
Ok. I think I resolved my issue... it was sort of a combination of issues I think. Old drums needing cleaning/end of the master roll/pressure roller/?. I re-cleaned all the drums carefully and changed to new master roll and everything was miraculously pretty much fixed. I think if I replaced the pressure roller with the new one prints would be perfect, but I've got to get a tool to unscrew it when I can find the time.

Mostly I've been buying new inks to print with, they are quite expensive though!