Paper in the web heatset press.

[ronson]

Hi to all,

i was trying to ask a question here a while ago, and it came out badly, that even I could not understand what exactly was i asking for, sorry for that and no more coming from late night partys and typing questions here on PrintPlanet


But Id really like to understand what kinda forces are influencing paper as it enters first printing unit after infeed and comes out from the fourth, before dryer and chillrolls?

Best Regards,
Ron

 

[Alois Senefelder]

Forces, mmmmmm let me see

Forces, mmmmmm let me see

Hello Ronson,


Well I'll start with two of them, Expansion, Contraction and Expansion

I suggest you read some of the PDFs I have posted on this forum.


Regards, Alois

 

[gordo]

But Id really like to understand what kinda forces are influencing paper as it enters first printing unit after infeed and comes out from the fourth, before dryer and chillrolls?

Well I'll start with two of them, Expansion, Contraction and Expansion

Forces: Water, ink, pressure.
Result: Expansion, Contraction and Expansion

best, gordon p

 

[Bloodsaler]

And take care of the paper tension,this also influence the dot shape,you must ensure the tension in the paper roller same as in the press~Or it will cause some problem~

 

[ronson]

but what happens to the tension, when blanket gaps are aligned, is there a brief moment when paper can freely move thru?

 

[ronson]

And take care of the paper tension,this also influence the dot shape,you must ensure the tension in the paper roller same as in the press~Or it will cause some problem~

tension in the paper roller, how can I find out what it is?

 

[Bloodsaler]

You can judge by the printing samples~If the tension varies a lot,the star strips will show the change~Especially in black unit~

 

[Alois Senefelder]

Web Offset Fundamentals

Web Offset Fundamentals

Ronson,

Some fundamental answers.

1) Tension is maintained at the Cyl. Gap by means of Web Wrap

2) Tension level for the substrate, is set at the Infeed

3) Paper does not flow, but is drawn through a web offset press. This creates a force in the web known as Web Tension

4) Web control involves three major factors -- Tension, Flow Rate and the Modulus of Elasticity of the web All three are fundamentally interrelated.

Regards, Alois , I enclose PDFs

 

[ronson]

so what about increasing infeed tension during printing? I have noticed that when running press on very slow speed and increasing tension I can hear paper slipping through blanket gaps.

 

[printer in heart]

Hello All, Does anyone know where can I get in Canada cust sheets of 35lb offset paper or 23x35 sheets of 35lb paper which can be converted to smaller size, i.e. 11x17, 12x18, 8.5x11, etc. Thanks

 

[Alois Senefelder]

Tension

Tension

Hello fellow Lithographers - Web Offset,

1) Infeed tension should be set at a suitable load for the Substrate.

2) Properly tensioned, the press should be able to Crawl/Run,
if needed just disengage Infeed Nip Roller, when on crawl -- lower tension.

3) Slip??? The Blanket to Blanket printing nips are the most stable on the press.

PDFs

"From knowledge to competence is a great step --- from ignorance to competence an
even greater one"

Regards, Alois

 

[ronson]

Thank you for your answers, I really appreciated your help!

 

[ronson]

what about maintaining tension between units, for example, when all the blankets have run 10 million copies and are still OK, but pressman has to change blanket on second or third unit?