Dot splitting/pulling in 1 corner of the printed sheet (KBA Rapida)

[Tomas]

Hello everyone.

Guys, I need help, who has encountered:
I have a 6-color KBA Rapida. On the third section (Magenta), in one upper right corner of the sheet, the dot crushes or stretches (the spread increases more than in other areas of the sheet)
It looks like this:

At the same time, taking into account the density, it is clear that exactly one upper right corner is distorted.
It does not look like paper crushing, since the upper left corner is an absolutely reference point. It is visible on all large-format works of about 1000 * 700 mm

The machine is decently and regularly serviced.
The problem does not depend on the change of the printing blanket (new or worn-in).

Any ideas?

 

[maks]

i have same encounter, hope experts will reply asap

Hello everyone.

Guys, I need help, who has encountered:
I have a 6-color KBA Rapida. On the third section (Magenta), in one upper right corner of the sheet, the dot crushes or stretches (the spread increases more than in other areas of the sheet)
It looks like this:

View attachment 293801
At the same time, taking into account the density, it is clear that exactly one upper right corner is distorted.
It does not look like paper crushing, since the upper left corner is an absolutely reference point. It is visible on all large-format works of about 1000 * 700 mm

The machine is decently and regularly serviced.
The problem does not depend on the change of the printing blanket (new or worn-in).

Any ideas?

i have same encounter. hope experts can give inputs or a detailed explanation

 

[Magnus59]

Hello everyone.

Guys, I need help, who has encountered:
I have a 6-color KBA Rapida. On the third section (Magenta), in one upper right corner of the sheet, the dot crushes or stretches (the spread increases more than in other areas of the sheet)
It looks like this:

View attachment 293801
At the same time, taking into account the density, it is clear that exactly one upper right corner is distorted.
It does not look like paper crushing, since the upper left corner is an absolutely reference point. It is visible on all large-format works of about 1000 * 700 mm

The machine is decently and regularly serviced.
The problem does not depend on the change of the printing blanket (new or worn-in).

Any ideas?

Do you have slur targets on your colour bars, if so, can you share a photo of those.

What is Slur in Offset Printing?

Slur is when a printed image is distorted due to running conditions on an offset printing press. The dot or type appears to be shifted. Slur...

www.offsetprinting.info

 

[Tomas]

Do you have slur targets on your colour bars, if so, can you share a photo of those.

What is Slur in Offset Printing?

Slur is when a printed image is distorted due to running conditions on an offset printing press. The dot or type appears to be shifted. Slur...

www.offsetprinting.info

This is great! I will investigate further. There are no such patches yet - I put it from today, collect the information and write an answer with photos.

 

[SteveSuffRIT]

Microphotos were very helpful in explaining problem.
Dot distortion looks more like a ghost double than an actual slur (elongation).
It is directional, diagonal, but from top left to bottom right.
I would guess paper distortion (wavy edge) would be from lower left to upper right) as it fans out.
I assume the plate is dot structure is good?
Next time this happens just pull a single of the effected color.
If it goes away, its a double dot.
If it's always the same unit/color, it could be a bag cylinder gripper/pad or transfer?