ductor roller temp control.

[cole]

Can anybody tell how the temp control on the ductor roller is used and how it relates to everything else on a XL105 please. When is the temp adjusted up or down and how would you know when it has to be adjusted up or down.

The printers all seem have their own opinions. Can anybody throw some light on this?

 

[Deleted member 16349]

Can anybody tell how the temp control on the ductor roller is used and how it relates to everything else on a XL105 please. When is the temp adjusted up or down and how would you know when it has to be adjusted up or down.

The printers all seem have their own opinions. Can anybody throw some light on this?

When you say Ductor roller do you mean Ink Fountain Roller? Ductor roller means different things in different parts of the world.

I will assume you mean Ink Fountain Roller. What ever temperature you set, you want it to be as consistent as possible. Variations in ink fountain roller temperature will result in variations in ink film splitting between the ink fountain roller and the intermittent ductor roller that feeds ink to the press. If you have a continuous ductor that shears the ink from the ink fountain, this explanation also applies.

Think of it this way. Ink's viscosity is temperature sensitive. Between the ink fountain roller and the contacting ductor roller there will be an ink film in the nip.

Where will the ink split? If the ink fountain roller has a higher temperature than the ductor then the ink film in the nip will have a lower viscosity near the ink fountain roller surface than near the ductor roller surface. That would result in the ink splitting, not in the centre of the ink film but a bit closer to the ink fountain roller surface. The opposite holds true if the ink fountain roller is colder.

If you have variations in temperature of the ink fountain roller this then affects where the ink splits in the ink film in the nip and eventually affects density control.

I hope that helps.

 

[HKafeman]

I am afraid I do not know about the XL105.
But what I do know is that the Duct Roller (or Ink Fountain Roller) Temperature is absolutely critical to consistency of the Printing Process. Erik Nikkanen has already explained why in his post.
I believe that the most important thing is to have a consitent controlled temperature and that the actual value is less important.

 

[Cornishpastythighs]

I would think that the 105 is like most temeperature controlled presses and the Ink Fountain roller temperature is controlled through the same closed loop system as the other water cooled rollers in the roller train. Ink fountain rollers are not usually independently controlled.

 

[cole]

On the XL it is.

 

[cole]

Thank you Erik this has helped. We have had instant results. If you could help. I have had a ink guy in and he was saying that if we ran our alcohol less than 4% we might as well run without it. Is this true? We are running our CD74 at 2.5% IPA and the printers find that this works for them. This morning it was changed to 5% because the printer felt that the ink guy was correct.

 

[Deleted member 16349]

Thank you Erik this has helped. We have had instant results. If you could help. I have had a ink guy in and he was saying that if we ran our alcohol less than 4% we might as well run without it. Is this true? We are running our CD74 at 2.5% IPA and the printers find that this works for them. This morning it was changed to 5% because the printer felt that the ink guy was correct.

Sorry I can't help with the alcohol issue. All my experience with offset printing was with systems that did not run alcohol. I am sure others will step in to help.

 

[CD102]

Thank you Erik this has helped. We have had instant results. If you could help. I have had a ink guy in and he was saying that if we ran our alcohol less than 4% we might as well run without it. Is this true? We are running our CD74 at 2.5% IPA and the printers find that this works for them. This morning it was changed to 5% because the printer felt that the ink guy was correct.

I'm confused. If the operators were having no problem at 2.5%, why would they increase it to 5%? I believe the ink man was telling you that you needed no alcohol, not that you needed to increase it to more than 4%. Well, maybe he was if he is selling alcohol to you.

 

[Alois Senefelder]

Temperature is Crucial

Temperature is Crucial

Hello fellow Lithographers.

Fountain roller temperature control should be independent of the inking unit, also the temperature needs to be higher (+/- approx. 32 - 35 deg C )

By temperature control of the Inking Unit, a stable ink transfer is maintained at all times. They're the prime parameters that tell us what is happening amid the ink and the paper.

re - Where will the Ink Split ?

The fluid dynamics of an ink as it passes through a nip is summarised in Fig 1. The combination of fluid build up on the ingoing side of the nip and sub atmospheric pressures generated on the outgoing side cause first an acceleration of the ink in the X direction followed quickly by cavitation and stretching of the filaments in the Y direction.


Regards, Alois

See the PDFs

 

[Deleted member 16349]

Hello fellow Lithographers.

Fountain roller temperature control should be independent of the inking unit, also the temperature needs to be higher (+/- approx. 32 - 35 deg C )

By temperature control of the Inking Unit, a stable ink transfer is maintained at all times. They're the prime parameters that tell us what is happening amid the ink and the paper.

re - Where will the Ink Split ?

The fluid dynamics of an ink as it passes through a nip is summarised in Fig 1. The combination of fluid build up on the ingoing side of the nip and sub atmospheric pressures generated on the outgoing side cause first an acceleration of the ink in the X direction followed quickly by cavitation and stretching of the filaments in the Y direction.


Regards, Alois

See the PDFs

With a press with a conventional ink feed, the description given above is a reasonably good one. Of course it is also very difficult to analyze.

When on has a positive ink feed, the general ink transfer will not be affected by changes in temperature, viscosity, roller pressure, water setting, press speed, ink split ratios, etc. The system has not choice but to transfer what it is given.

This is the great advantage of having a positive ink feed on the press. It changes things and makes it so that the process of ink transfer is, in general, mathematically analyzable.

This does not mean that there is no benefit to having temperature control or water control. Controlling these variables can improve the quality of the ink transfer and therefore the quality of the print even if they do not affect the quantity of the ink transfer when using a positive ink feed.

 

[PSchw]

Thanks Erik this is my expirience too. To Alois I do not know of any press with a split ink temperature contrl, system what runs the ink fountain roller on a diffrent temperature then the 2 vibrator rollers. I know of several press manufacuter which do NOT control the temperature of the ink fountain roller. There are some systems out there where you can control each unit induvidual but this was made to run waterless.
To the alcohol if you can run with 2.5% run it don't let anybody tell you not too I saw press going from 15% to no alcohol in about 15 years and yes I agree print quality is better with it but 2% is enough her in the US most do not use alcohol at all and still print high quality.

 

[duct maestro]

On an XL 105 you should set your T-circuit 1 to 28 and your T-circuit 2 should be set to 32. Always maintain a 4 degrees difference

 

[The Heidelberg Guy]

I always set the IT to 77 degrees, and the ZetaT (Ink fountain roller) to 87 degrees.

 

[duct maestro]

How does that work for you? I'm at 82 and 89 with the d- circuit at 45 F