GTOV-52 Banding...

[kdw75]

We have an '85 GTOV-52 4-color with 30MM impressions on it. It has Crestlines and a Royce refrigeration unit. Whenever you run anything with a large solid or near solid you always see a single faint band, only seem to notice it on the magenta unit, that is horizontal across the sheet and about 1/3 of the way down from the gripper. The distance down the sheet seems to about match a roller diameter. Again it has always done this and it isn't real noticeable but when you run a flooded sheet it can be seen. Anyone have any idea what this might be? Rollers are all set properly.

Thanks,
Keith

 

[jetscreamer]

have you tried changing the oscillation timing and speed?

 

[kdw75]

No I haven not. The ink form oscillation on all units is set to its maximum.

 

[exheidmech]

Roller streaks will typically occur more than once on the sheet. If you measure the distance from streak to streak (if you have more than one) and it matches the roller diameter than you might have something. Measuring form the lead edge to the steak with only one streak almost eliminates rollers. I would think its more of a bump streak caused from either the plate cylinder or impression cylinder coming on contact with the blanket. I would make sure you are packing the blanket correctly, to bearer height and no more. You can also try shingling the packing under the blanket. Cut the packing on a bias from OS to DS this will lessen the impact on the blanket from either the plate or impression. If you see any improvement in the streak you know its a bump streak. Also try rolling the plate cylinder coarse adjustment a good amout maybe 40mm or so, see if your streak moves, if so you know its coming from contact with plate to blanket. Usually these kind of streaks can be "helped" with high quality blankets with a quicker release.

 

[Bruiser]

I assume you have checked the damper and form roller settings to the plate. If one is to heavy, it can bounce causing a bar mark. We had a similar problem on a press. We were trying to get a 4 mm stripe, but the form was so old that the middle of the roller was closer to 8mm, which caused a bar. Once replaced, no problems.