Horizontal streaking

[John Arneson]

Kaoticor,
A couple of suggestions here.
One- change your plate to an 8mil. and put a .004 packing in. It will not fix your streaking problem but you will print a much better dot. Metal to metal prints like crap.

Two- Have your two "G" rollers and your "I" roller recovered with a rough grind, you may see your banding go away.
John

 

[Alois Senefelder]

Really !!!!

Really !!!!

Well I never knew that !!!!!!!!!!!!!!!!!!



Regards, Alois

 

[Alois Senefelder]

Blanket Height

Blanket Height

Hello fellow Lithographers,


I suggest you read the PDFs on page 2 from the following thread -


http://printplanet.com/forums/sheetfed-web-offset-discussion/27640-dot-gain-problem-man-roland-505-need-help


Regards, Alois

 

[Dan Roll]

Alois,

Interesting as always, but Willer's experiments were done with one cylinder surface driving the other, assuring identical speeds, unlike a press where the cylinder surface speed is determined not only by the rotational speed the shaft is driven at, but by the circumference of the cylinder itself.

This is all reminiscent of the old feud between Miehle and Roland over the 'true rolling cylinder' concept (Miehle in support, Roland against. I am sure Miehle had it right). I have been involved in many situations where a printer had attempted to eliminate packing under the plate by increasing the packing under the blanket, leading inevitably to streaking, plate wear, and plate cracking. The introduction of the Goss C700 was accompanied by all of these issues (with the added bonus of the plates sometimes being flung from the units, sometimes into the inker with expensive results).

The higher the speed of the press the more important it is for the plate and blanket surfaces to be moving at about the same speed. Inevitably, the higher one of these surfaces is packed, the faster it will be moving and the lower the surface is packed, the slower it will be moving. If one surface is moving faster than the other, a variety of factors will influence how this will manifest as a printing problem, with parallel streaks across the press being the mildest indicator.

Miehle

 

[D Ink Man]

Ah loom ah noom.

Ungawa. D

 

[REYES1377]

Dear printplanneters,

We have a job that we only print once a year, a 4 color cover that is a solid brown. It is close to a 7504 brown if you had to put it in pantone... We get horizontal streaking (parallel to cylinders) consistently in the same place every time we print this job. I pulled individual color samples, and it seems you can see the streaking on all colors. We have other Lithrone 28's as well in different print shops who also print this same job, and the same problem appears on their samples. So we believe it is entirely mechanical, perhaps a design flaw or something of the sort.


Do you all have any other things you would try to better this problem? I think we have tried everything we can, but wanted to see if anyone had any comments before we close this. Thanks for your time,

-K

Well it seems you have it nailed down, if every press you have is doing it.