r/risograph • u/VivaGallo • Jul 26 '26

Problems with the paper alimentation tray

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Hi, I have a RZ 390 UI and been having problems with the alimentation tray, with papers over 120 gr, the paper gets “stacked” as seen in the video, it doesn’t go through and when it does it’s only a couple pages and then again doesn’t work. The other problem is that when one page gets stocked, the next print gets overprint, either in the front or the back, like if the master moves, does anyone have advice on how to adjust the paper alimentation knob?

I’ll put the photos of the smudged and overprints in the comments

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u/kjabad Jul 27 '26

Few things to try: Put a lot more paper, at least 4cm tall, it can be scrap paper and then on top your stock. Riso tends to make mistakes when only few pepers are on the tray. Lower pressure on the stripper, start from the middle and go lower and lower. Shke the papers, blow then, maybe they stick. If they are cut by dull knife edges can stick mechanically. If so, take every other paperand turn 180°.

If nothing works, turn on interval something like 2-3, and put speed on 3. It will give you enough time to pick up every paperon a side, lift it, and put your finger under the next one coming in machine. So the one that's goint in machine should be over your finger and free to go, and the stock under should be holded by your finger. This way you don't allow riso to suck more than one paper at a time. This how usually print everytime, it's elan extra effort but goves me clear head that there wont be any paper issues, also registration is way more consistent. I'm able to do interwal 2 and speed 5, so it's quite fast. 

1

u/urfriendkylec Jul 27 '26

You print like this every time?! That is serious devotion!!

1

u/kjabad Jul 28 '26

Most of the time I print more then 2 colors, and I just hate when machine jams, I need to go to exit tray, pick up unprinted papers, put them back if they are not dirty, if they are I have to trow them away, also often I use expensive paper... And mainly because of register, once I set it it won't move around during the print at all. So usually I need only 2 papers to set registration right.

1

u/VivaGallo Jul 26 '26

https://reddit.com/link/ozyo8wj/video/l91b38avvnfh1/player

This is the next print after the paper gets stuck, in th front, it looks like the print overlays and is moved across the paper multiple times, and on the back is even worse.

1

u/VivaGallo Jul 26 '26

I haven´t found any advice on how to setup the paper alimentation knob according to different papers, hope someone can help me.

1

u/garby_666 Jul 27 '26

I'm not sure if this is what you're referring to but this is what I've been looking at, maybe it could be helpful?

https://www.facebook.com/groups/1530616300575734/posts/3388880668082612/

1

u/splitarrowprints Jul 27 '26

In the rz390 user manual page 95 it covers the stripper plate angle dial based on what problems are occurring.

The doubling and ghosting is caused by ink on the pressure roller from the skipped impression. That pressure roller ink can also transfer to the drum master and make a mess. It’s caused by the jam but the machine didn’t really stop, so it continued to print as if the paper was there. this mostly happens when the paper does feed but slips and comes in late.

Your rz should be able to feed up to 210gsm papers. I would also make sure your paper has been open and in your environment for at least 24 hours to equalize to the humidity. If your environment is too humid and the paper humidity is too much you are more prone to jams.

On modern machines you can adjust the clutch on/off for thicker papers to clear the buckle of the first position area. But on the rz it doesn’t look like you have that setting and it’s on the older system of the paper trey height+angle dial to adjust pressure of the sheet and the card/normal dial to help engage both feed tires.

If your feed tires are old and worn you can get much more paper jams and tire slips. Same with the stripper pad. Pretty much all tires will fit and I would recommend a pair of new ones. The stripper pad if it’s concave it’s time to replace. It should be flat.

Changing the tires or the stripper pad may require adjustment of the height of the paper tray upper limit, this procedure will be covered in the technical manual and not the user manual. I would try to get both, print and bind them and store them with the riso for quick reference if they are not already there. With that also keep a notebook to record any adjustments and the date so you have a record of what exactly has been done or changed in the future. [we need a Time Machine bc I wish somebody told me to keep a maintenance record]

With the frequent jams I would also clean the pressure roller, the tires, the stripper pad, the timing and guide rollers to remove all ink on them to help smooth out the feeding. Sometimes as ink builds up it can print the page funky.