crooked master or crooked paper feed?

[gillje]

Hi, I've been having a problem with my gr3770 skewing my prints.

I've tried adjusting and re-adjusting the parallelism of the timing and guide rollers but that hasn't really improved things consistently... and now after a closer look the masters appear to be sitting under the drums clamps at an angle. I put a grid stencil onto my drum and measured the distance between the edges of the screen and the lines in the stencil across the drum and it is sitting at an angle.

What could be causing this? Could it be the pressure roller? I recently tried installing a new roller, but ran into some difficulties getting it to fit (I think it was the wrong size) so I put the older roller back... Since then my prints have been offset from the lead edge by a 1/4-1/2 inch.

Another possibly related problem are that my masters become wrinkled on the trailing edge when they are being loaded.

Ok any help would be appreciated.

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[gillje]

Thanks, I already have the parts & service manuals. I've also asked riso directly about servicing the machine but they pretty much said no. Any techs in the Greater Toronto Area with exp with GR machines?


Ok, any advice or insight into my problem would be appreciated!

[mikadonovan]

Sounds like you have a problem with the write roller, like a bearing is out of position or something. If it started AFTER you removed and reinstalled the roller you had better backtrack your steps. If the master is crooked on the drum, it has nothing to do with the pressure roller.

[gillje]

ah, the offsetting of my prints from the lead edge began after I tried to switch the pressure roller, but the skewed masters have been a persisting problem for awhile, I only just realized the masters were being loaded onto the drums crooked. Up until today I thought it was an issue with the paper feed... How do I check out the bearings of the write roller? The manual describes the removal procedure for the roller, I'll take a closer look tomorrow and check back in.

J

[gillje]

So I took off the front side cover, the write rollers bearings seem to be sitting all right on both sides, I removed the belt around the pulleys that rotate the write roller and was able to rotate it freely and it seemed to be moving pretty smoothly / evenly on both sides, but to be clear I'm not exactly sure what I was looking for in the first place.

I tightened the tension along the belt / pully G for the write roller, this seems to have improved the situation somewhat... However I don't think I can tighten it anymore and it's still a slight amount off. The pics are kinda blurry, the red drum is pre adjustment and the blue drum is what it's like afterwards. It improved about 1/8 of an inch, but is still approx 1/8 off.

Any one have any ideas about what's going on here?

riso_drum1.jpgriso_drum2.jpg

[gillje]

Things have taken a turn for the worse,

I'm trying to reset the vertical positioning of my prints (this became offset by about a half inch when I tried replacing my pressure roller)

So I'm following the steps in the service manual, trying to get the alignment holes of the shaft plate to match the one in the cam pully, but each time I try to loosen the tension on the main belt I'm unable to move the cam pully in any direction - and then when I screw everything back together, the print becomes further out of position. It went to a whole inch and a half off from the lead edge, and now its currently so far off that it's printing about 2.5 inches of the back edge at the front of the sheet - so that's like 14 inches of the image being printed before the paper is even making contact with the drum.

oh man what do i do !

I don't want to throw things any further out of whack ! Any help would be so appreciated !

[gillje]

Ok, I got the cam & main pulleys back into alignment, however every time i try to print they become misaligned by about 1/4 - 1/2 inch and it fails to feed any paper through. The error "Paper Misfeed Check Paper Feed area" comes up and it asks me to reset. I'm able to get pulley's aligned manually, but it just misaligns and misfeeds everytime I try to print.

[mikadonovan]

Might be time to call a trained Riso tech.

[gillje]

Ok I got a tech to come in, he got the gr running again. It turned out that the pickup roller shaft had come was not sitting in place properly and was kind of wedged into the machine - so it wasn't turning when the paper feed clutch would start spinning. SO paper feed problem is solved

Tech also got the timing back to where it should be, we made a master off the glass and a few copies and everything looked good. He's left and I send an image to print through my rip and it's gone out of time again! The prints are offset, which maybe isn't a huge deal

The biggest problem I'm encountering now, and perhaps this is unrelated, is that when I try to print a second colour the image skews. I print one colour and it's printing straight & fine, when I take the second colour and print it onto plain paper it's straight - it's just when trying to line them up with each other, there's a vertical skewing of the prints taking place.