Riso suddenly printing very light

[gillje]

So I've got an RC6300,

last weekend I went through about 800 prints and everything was totally fine,

I went to print the reverse side of my prints today, and the machine was suddenly printing very lightly, regardless of what I set the density too, why would this happen? it was definitely not putting down as much ink as last week and even the contrast seemed a little skewed.... I was printing pretty dense images in photo mode. There's still ink in the drum, and I left all the settings between master making and printing the same as last week so I'm not really sure what's happened.

is this a problem that anyone else has had?? I would appreciate any advice!

[joelsa12]

hmmm do you have another drum to test with? if so put in the other drum and try printing and see if it is light. this will tell me if it is in the drum or the machine.

[ddude]

Check the pressure roller maybe it is out of position?

[gillje]

I used a different drum today and it printed fine....

When I started having this problem it was with my gold ink drum, and it got progressively lighter over 3 masters... so the copies for each master were lighter than the last .. any ideas? It work totally fine the week before.

[ddude]

Try wiping down the drum screen with citrus solvent, see if it improves the image.

[joelsa12]

i would say that either your doctor roller or your squeegee drive bearing is out in the drum. or the belt that drives all of them has broke. there should be three 3mm allen screw on the end of the drum. take those three allen screws out and the whole drum body(outer part of the drum will slide off. check the belt on the end. if the belt is good you will see the squeegee bearing that the belt drives. this bearing can get ink in the middle and cause it to slip or i have seen the one way bearing in the middle completely come away from the outter drive portion. it could always be that the inking motor in the drum is out as well. the RC inking motors were really good and did not burn out like the GR series, but it is like 16 years old now so I would not rule this out.

[gillje]

So I've started to have this problem with a second drum, when I try to print with my red the master looks partially inked on the screen but it doesn't put any ink down onto the paper... It also makes a kind of whirring sound that I haven't heard before.

I tried to open up the drum by taking those 3 allen screws off but it doesn't really come apart (I've tried this with both drums that I'm having problems with) and I didn't want to just start unscrewing things if I don't really know whats what...

Is there something else I'm supposed do to open up the drum body so I can check out the doctor roller, squeegee drive bearing and the belt you mentioned in the last post??

thanks!!

[bigste]

In order to remove the out drum there are the 3 allen screws on the end but there are also some slot or philips head screws around the circumference of the other end. It is adviseable to also remove the clamp first which is simple enough though this is not absolutely needed.

[gillje]

Photo0084.jpg

So I thought I'd compare a working drum with one that I'm having this problem with. I opened them up and they looked pretty much the same. What I've got in the picture is that the doctor roller/squeegee drive bearing you were talking about?

I put them back together, and the gold drum which was having this problem in the first place is working fine again! Though I haven't given it a good run yet, I just popped out a few prints on a fresh master...

[joelsa12]

yes the the one on the bottom can get ink in the middle of it and cause problems is the squeegee drive bearing. if you did not take it off and clean it i would believe that your issue will happen again

[Iowatech]

Also, the bearing is pressed into the pulley, and over time will work itself loose. If you take that e-clip off and slide the pulley back and forth and the bearing moves independently, sometimes you can epoxy the bearing back in or something and it will work for a while. But the only long term solution is a new pulley, and they don't make those anymore.

[gillje]

Hey, so I got one of the drums that was printing light to start working again. However I have another two drums who won't ink up anymore,

I recently put a new tube of burgundy into one drum and it has since stopped working, ink comes through in a kind of splotchy pattern across the screen... I've wiped it down with some solvent but that hasn't changed anything, I also checked the tube and it seems to be in fine condition...

My red drum doesn't ink up at all anymore, I've run the 'ink supply mode' test on both drums as well as a third working drum, I can hear the inking motor (i think?) come on in all 3 drums, the working drum stops the test after a few rotations when the sensor sees the ink like it's supposed too... however both of these other drums just continuously run the test so that means either the inking motor isn't working or ... something else?

[bigste]

I think you need to refer to the earlier posts re the screens being clogged. Have these drums been idle for a while? Have they been kept in their storage cases? If so they have dried up which is very common. With the right cleaner it's an easy job.

[gillje]

Well I've given them a good wipe with this citrus cleaner I got... I'll go at it again, but I feel like the problem is the drum isn't taking ink from the tube... would a clogged screen prevent it?

[bigste]

I think it unlikely that more than one drum would go down with a faulty pump but it is feasable that severall would dry up, especially if they were not stored in the storage cases or if they weren't used for a few weeks.