How to operate correctly harmonic drive/chill rollers?

[ronson]

Hello everyone,

I have seen many different heatset presses and pressmen who all have different settings for their chill rolls, some reduce their speed, some increase for various different reasons.

There is a tension meter after chill rollers but, it only measures web tension between chill roll pressure roller and the folder nip/pinch rollers and it doesn't really describe what is happening in the dryer.

Can chill roll speed affect web tension between magenta and yellow unit?

Please help me to understand a little bit about how the reducing/increasing speed of chill rollers affects printing?

press is 4 unit goss m600

Thank you very much for you help,

ronson

 

[Deleted member 16349]

There is a tension meter after chill rollers but, it only measures web tension between chill roll pressure roller and the folder nip/pinch rollers and it doesn't really describe what is happening in the dryer.

Can chill roll speed affect web tension between magenta and yellow unit?

ronson

Hi Ronson,

The answer is "yes" and the answer is "it depends".

I presented a technical paper on this related subject at TAGA in 1997. Changes in web tension after the last print unit can have some affect on the tension levels between some of the end units. This is due to the fact that blankets are flexable and not due to slippage.

When one applies a different tension levels on either side of a print unit, this difference in tension will affect the print repeat length of that unit. It affects the print repeat length by slightly distorting the surface of the rubber of the blanket making and therefore changes the effective circumference of the blanket cylinder.

How far back in the press the change in tension level after the last print unit affects tension level between units is related to the properties of the blanket.

Differences in tension levels between units is not such an important issue as long as they are stable. Basically there are always some differences in tension levels between units. What is critically important is that the tension level going into the first unit is controlled to provide a very constant level. This also applies to the tension level after the last print unit.

It is waves of variations in tension at the infeed that will go throught the press that result in minor and temporary changes in print repeat that affect register for all units. Fluctuations in tension after the last unit will work back a few units and also result in register fluctuations.

I hope this helps.

 

[Alois Senefelder]

Chill Rollers Speed

Chill Rollers Speed

Hello, the golden rule is --- SET Chill Rollers Speed at the same Circumferential speed as the Blkt to Blkt Cylinders of the last Unit, which is the surface speed of the WEB.

Don't forget that the "Tension" increases due to Paper Shrinkage in the Dryer !!


Overtime you will find that the best results of Tension control is if you obey the "Golden Rule" You can always check the "Web Tension " is OK by looking at a printed copy and examine the "Pin Pull"

Regards, Alois

 

[SpeedKing]

the print process then the dryer then the chill rolls all kick the crap out of the paper,so you to experiment by fine tuning.

 

[Alois Senefelder]

Some Sense

Some Sense

Speedking, Talk some sense - if you have any -

OH -- never mind the Queen - up the "Republic "

Regards, Alois

 

[SpeedKing]

Speedking, Talk some sense - if you have any -

OH -- never mind the Queen - up the "Republic "

Regards, Alois

ha,i have lots of sense mate,thankyou.

 

[ronson]

Thank you for responding

 

[Dr Who]

Hello, the golden rule is --- SET Chill Rollers Speed at the same Circumferential speed as the Blkt to Blkt Cylinders of the last Unit, which is the surface speed of the WEB.


Regards, Alois

Hi Alois, not sure I understand what you mean by same circumferential speed as the the blkt-to-blkt cyclinders of the last unit could you explain this a bit more and how you would ascertain the speed of the cylinders. thanks

 

[Alois Senefelder]

Speed of Cylinders

Speed of Cylinders

Hello Dr. Who , the speed of the Blanket Cylinders are checked using a "Tachometer"

just Google for "Surface speed tachometers" lots of info there


Regards, Alois