Goss Community colore registration/pull in problems

[moundcitynews]

We are running an 8 unit Goss Community with a Goss SC folder.

Config. =
4 mono units on the left side of the folder and a Goss UOP three color unit with 3 other mono units on the right side. All units are on the ground.

We have 2 web tensioners - one for the UOP and one at the very end of the "left" (Units 1-4) side of the press that we run through before hitting the cyan (unit 1)

The paper roll starts under unit 2 and then travels under unit 1, then through the tensioner, then through the 4 mono units to the folder.

No pull in problems at all with any of the other webs, just when we add the bottom web color from the "left side" of the press.

The color registration on the UOP is nearly perfect, but when we add the "left" side of the press printing 4-color through the 4 mono units (which is the very bottom web) we get color registration/pull in/paper stretch problems with the bottom web.

Normally print 3 to 4 webs total.

Pull-in problem worsens when running more webs, but paper stretch/registration problems always occur when printing from the "left side" of the press which is always 4-color. (even when running only one web through that end)

Any thoughts?

 

[jshawy]

Get your iron to iron settings(cylinder pressure)checked on all 4 mono units. Make sure blanket and packing are correct specs.
John

 

[Robert L.]

I'm assuming that your "bottom" web from the left side is baggy due to paper stretch in the four mono units. Printing 4 color unit to unit like that is never easy! If you often print 4 color from the left, you might want to experiment with blanket packing and iron to iron pressures. I've seen where some users have under packed the units progressively to keep the web tension between units and reduce the overfeed due to paper stretch. For example, unit 1 -.004, unit 2 -.003, unit 3 -.002 and unit 1 -.001. However by doing so, you will probably have to adjust the iron to iron to maintain proper pressure for print quality. This will not work out well if you also use the left side units for mono printing as you will then get under feeding! The under-packing/paper stretch can cause image fit problems, but, if relatively constant, they can be addressed in the CtP system. Hope this helps!

 

[BeauchampT]

I am with Robert L on his last comment - see if you can use a web growth profile in the CTP workflow to correct. Messing with the pressures in your units can have too many other undesirable results - especially if there is an easier way to correct upstream.

 

[Rickyo]

I would check blankets and packing ,brakes on units nippers on folder ? ,do you hit eng idler rollers underneath units to take bit of web movement out