Need help with MOV bump streak

Anybody know how to eliminate or lessen the severity of the Heidelberg bump?
We are trying to run a 4 color screen folder on a 88' MOV and we're getting the bump about 6" from the gripper.
We have been plagued with this since this dinosaur was new. Any help is much appreciated.

 

Hi I would reduce the ink. It used to help on my mo. It was usually more prominent on the magenta. When I switched to lower tac ink seemed to help. Make sure your density is good to light the bump is more apparent good luck. Spike

 

I'll give it a shot today and see if it improves any.
I have been told it happens because of the lack of a double diameter back cylinder. To say I hate this old turd is an understatement.

 

Have you tried moving the oscillation, that is located on the drive side panel?

 

Yes Sir, I've tried every number on that. Thought it would move it, but it did squat. Tried different blankets, packing, roller stripe settings, it's been a source of headaches for years.

 

I think you have to inch the press while the bolts are loose, it's not enough to just change the numbers, apologies if you did that anyway?

 

My fault, I should have worded it a little different. I meant to say I have tried every possible position on the oscillator adjustment. I do know how to use it.

 

Does this occur even with no water? -full tone on plate-
Another thought, if your rollers tend to move along with oscillators, you could try shimming them, that worked for me. -especially 4th roller-

 

Have you checked the stability of the roller bearings in the 3 point holding pins? The sliding pin is not usually culprit, as it's a hardened pin, but the adjustable eccentric pin and the small stationary pin are soft to the point that if you don't shim the bearing to fit, the pins wear, causing the rollers to bounce excessively. Pay particular attention to the first inking form, as the z-roller (assuming you have Alcolor) tends to exert more pressure on the inking form, causing the issue you may be seeing.

 

As mantman mentioned, try isolating the issue to inkers or dampening, run a dry solid to see if it's present in inking train.

 

You could try to isolate the problem by lifting the form rollers up off the plate one at a time. Id start as Steve has mentioned, with the first form roller because of the Z rollers pressure on it. If that doesn't help work your way forward to the last form roller. Unless the form has a lot of ink coverage, 3 form rollers will suffice.

 

Sorry for taking so long to get back. We ended up running the folder with a double hit of a PMS 5th color just to get the job done. I still want to figure this out if possible.
1. The press is conventional dampening
2. It's a 4 color - not that it makes a difference
3. Reduced my ink and it made no difference
4. Ran a dry solid and the streak was barely noticeable, but still there. Much worse with water form roller engaged.
5. Tried multiple adjustments to the water form to plate with no luck.
6. All ink forms are shimmed with no lateral movement.
7. While it is in all units, it's most noticeable in Magenta.

 

Haven't had a chance to make some plates and try this job again. When I do I will try lifting the form rollers one by one to see if it makes any impact.
Just to put as much info out as I can - the press has 2 water forms per unit, I have been running with just 1 for about 6 years. Tried both in, one in the top position alone, one in the bottom position alone, makes absolutely zero difference.

 

Ahhh conventional dampening. Id bet some on this forum are too young to even remember anything but Alcolor. My experience with conventional dampening on a Heidelberg is that a single water form in the top position is all thats needed on the plate. You didn't mention if you were running it bareback or with a paper sleeve on the roller. The reason this is important is because if your running it bareback its best to have a water form with tires on the ends to ride on the plate cylinder bearers. These "tires" allow the roller to always turn at plate cylinder speed as opposed to it skidding across the plate cylinder gap. This slight skidding under certain conditions, will cause a buildup of excess fountain solution on the water form that gets deposited on the plate and causing a dampening streak. I always preferred running a shrink to fit paper sleeve on the water form. Not sure if they are even made anymore but 3M was the original manufacturer. If they no longer make the paper sleeves perhaps you can find the material to do a spiral wrap. Wrapping a water form was almost considered an art form, and as a result the preferred method was the shrink to fit sleeve. If your not into the additional hassle of another consumable I would suggest the bareback water form of the correct durometer, with the tires on the ends. This method, as im remembering, required running a small percentage of isopropyl alcohol. You could also try running both water forms in the dampening unit but with only the top roller making contact with the plate. The bottom form would be set to the water vibrator but the back off of the plate and used as a means to smooth out the fountain solution a bit.

 

Haha, I'm not even 40 yet. This is my third conventional dampening press I've run at this place. I much prefer my Alcolor sm52. We are running bareback with alcohol, but without the trucks or "tires". I'll talk to my roller guy and see about getting a couple to try. Makes total sense what you said about the skidding across the plate gap. We used to run the 3m sleeves until they quit making them, then ran with Red Runner sleeves, both without alcohol. We had the same bump with them. Have also tried running the second water form roller without contacting the plate with no change.

 

Thanks for all the suggestions, I'll see if I can't get some new form rollers with the tires to try.

 

Do check the stability of the forms, both inking and dampening, not for lateral play but up down/forward back. The worn pins, as I'd mentioned.

 

You used to be able to get MOs retrofitted with Dahlgren or Kompac dampening systems that would make life a lot easier, and are definitely worth the cost. Probably under $5k for each unit but that was years ago. Not sure how much it would cost today or if they’re still available or not. Regardless, you should already know that this isn’t the problem so I’m not sure why you’d still be pursuing it.

 

Hello, there is scheme colorful apparatus? Roller. Their diameter.

 

And it wouldn’t. I operated various conventional K-Line presses for years that all had similar dampening setups, and I only ever used one form roller. Printed some absolutely beautiful jobs with those presses, too. Also ran a Miehle Favorite with a bareback dampening system and never had any form roll skidding in the gap, because the oscillator is what should be driving the form roller, not the plate. I’m pretty sure that basically applies to all dampening systems, excluding the Delta type.