wrinkles paper on press

Hi, Currently I bought large format machine heidelberg SORSZ. I wonder, if any of you fellas could help me. Why is it if i try to print thin paper somewhat like kraft paper 120gsm, it always wrinkles at the outcome? i tried everything i could but somehow it was useless because it still keep on wrinkles.. thanks before for the help

 

Probably going to need more info before anyone can help out...

What's the grain direction of the paper?
Does this happen on all 120gm or just Kraft?
Does the creasing happen if you print just one colour?
What's the condition of the paper when you unwrap it, ie basically flat, or edges lifted?
Does the crease start at the grip edge or is it confined to the tail of the sheet?

What's the condition of the press? It could be that either the grippers need resetting or blanket packings need to be checked.

If it only happens on Kraft paper try turning the sheet through 90º and see if it still creases.

 

Hi! thanks for replying..

What's the grain direction of the paper? short grain (what is the appropriate grain supposed to be?)
Does this happen on all 120gm or just Kraft? it only happen for this kraft
Does the creasing happen if you print just one colour? nope. 2 colors also
What's the condition of the paper when you unwrap it, ie basically flat, or edges lifted? the edges already lifted. actually i helped others printer. his machine is broken. so the paper already been opened for about 2 days.
Does the crease start at the grip edge or is it confined to the tail of the sheet?it is confined to the tail. and it wrinkels not only at the same place in every paper. it moves differently.

What's the condition of the press? It could be that either the grippers need resetting or blanket packings need to be checked. the grippers are fine. they have just been fixed.

help me out will yaa??

 

If it only happens on one specific stock then you've answered your own question.

Grain direction should be 'long' for multicolour work - mainly to avoid interunit misregister due to fanout, occasionally can cause creasing depending on the character of the material.

However, turning the material thru' 90º and try to print it that way would show whether it's the grain at fault or the fact that there's been exposure to excess humidity**.

**The 'lifted edges' are evidence of this. Basically there's an elongation or deformation of the stock due to ambient RH (relative humidity) being absorbed into the paper. Usually materials affected like this will print fine at the grip but as the sheet progresses thru' the impression the paper will begin to 'gather' producing fine or heavy creases depending on the severity of the lifted edges.

I doubt whether its related to the press based on the detail you have given.

Good luck!

 

I may be wrong but I think this is related to the way S line presses transfer between units?

Have you tried adding more star wheel rods and starwheels to support the sheet better between the units?

 

That might help... but the issue is confined to one material.

 

While 120 gsm is not particulary thin, about 80 Ibs in my language, it doesn't have any body.

S line presses are notorious for this kind of problem due to the way the sheet is transferred between units.



I used to hate working on the first unit as everything is bass ackwards

Edit: 120 gsm KRAFT

 

Try a speedbump.

 

speedbump is a good idea but a bit difficult to explain here on this forum. Id recommend that you use your sheet hold downs to smooth out the sheet as its going into the front lays. You might also want to turn on and adjust the vacuum ports on the register table so that they help to smooth out the infeed of the sheet. The vacuum ports are controlled by a pump thats usually under the feedbord. You turn it on with a switch attached to the pump and regulate the suction with a hand wheel attached to a large corrogated hose if i remember correctly. Ive found that most creasing issues can be resolved like this unless of course theres too much wave in the stock. Always try to print long grain on any large format press if you can help it!!!

 

How is the front lay set?

Sounds like the centre two lays are set way to forward to the outer two. Set all lays fully back and turn centre two lays half a turn forward.

Angle out feeder tape brushes/rollers to tighten sheet and apply minimum pressure, plus check minimum sidelay pressure

I take it you are running with minimum blanket pressure?

 

Try to use same paper material but different grain direction ( this time use long grain ). You can check if the problem is grain directions.

 

Is there any cure for this if it's happening on the 2nd side of a job with the fronts already printed?

 

Try trimming your stock before you run.

 

The easiest way to prevent or solve this problem is to have someone there who understands what it is that is happening and can fix it, before it happens. Does that make sense?

 

come to see the comment, and learn some....thank you