Riso GR image banding/noise at intervals on side of prints (in master)

[directanglepress]

Hi all,

I’m troubleshooting a partial image banding “noise” issue occurring at regular intervals across one side of all prints. This is visible in the burgundy print on the left side of the impression. This was printed on my GR3750, and the problem is consistent across all drums — and this noise is in the master itself. It’s also still present when printing a checkerboard in Test Mode, so doesn’t seem to be related to the scanning process.

The teal print was made on my second machine, a GR3770. You can see a slightly different version of this problem happening on the left edge here as well.

Has anyone encountered this, and is there a cause or fix?
It’s interfering big time with a large project I’m working, so desperately looking for a remedy.

Things I’ve checked:
- Pressure roller: Perfectly clean, fairly new, and even when flipped, the noise is still on the same side of the print. If I switch drums between machines, the banding stays with that drum (since it’s in the master).
- Write Roller: I cleaned this well and it looks like it’s in decent shape without visible signs of wear.
- Gear & Pulley for write roller: The screw mounting the gear to the write roller seems secure.
- Drum screens are clean and clear.

Thoughts? Many thanks in advance!

Best,
Josh


IMG_6661.jpg IMG_6662.jpg

[jermyth]

It looks like the print pressure is uneven. If the impression roller is new, then the actual pressure applied is uneven. If you have a GR manual it's in there somewhere on how to check and adjust. I just don't have mine handy at the moment.

Good luck.

[itchyfinger@att.net]

I would think impression roller or pressure. you say if switch drums it follows because its the master..I would try making a new master on each machine and see if it is the same on both machines. if it is then it is in your ink cylinder.

[NeoMatrix]

Cut a blank master, stop the machine, remove the drum and see if the master is cut with the problem pattern.

[directanglepress]

Thanks for your input everyone! I looked over the machines with a tech yesterday and we ruled out the drums and pressure rollers, as the printing issue occurred the same way between both machines, but when a new master was made on the second machine the printing issue would go away.

We've concluded that the Write Roller on my GR3750 is worn, and were actually able to feel a bit of unevenness. This also is consistent with what the tech manual says about 60mm intervals of blurring/banding being symptomatic of a write roller issue.

These parts are no longer available, so I gave a call to a roller company I work with for recovering letterpress rollers in my studio. It sounds like they'll be able to match the specs of the write roller and make a new one for me. We'll see if that addresses the issue.

Thanks again!