Ink Dams

[walterz]

Sometimes we use ink dams on our litho presses to reduce the amount of ink needed when printing just a small portion of the sheet. Can the same be done on a flexo press? (Reduce the width of the ink pan to about 4 or 5 inches so we require less ink to print a small logo on only a small portion of the web.)

Walter

 

[Cornishpastythighs]

As you say ink dams are used in offset to reduce the amount of ink buildup going to the rollers, plate and blankets where there is no image to take ink away. Litho being a Planographic process will take ink water over all the plate whether or not it has image. In Flexo being a raised image process I would have thought that no matter how much ink is supplied through the doctor blade chamber only the raised part of the plate will become inked and ink dams would serve no purpose or be practical
Just my opinion

 

[walterz]

@cornishpastythighs
I'm not talking about ink consumption throughout the run. I'm talking about the amount of ink to fill the fountain/pan in the first place. If we have a short run with a minimal print area, why should we mix/purchase a large amount of ink just to fill the tray and dump it afterwards. If we could reduce the pan size we might only need to mix a batch that is a quarter the amount.

 

[D Ink Man]

This dam idea for flexo is not a very good one.

In offset, it can be done with dividers to run as many as 3-4 spot colors in a fountain. But in between the colors, dividers, lubrication has to introduced to prevent the burning up of the non printing area of the ink train. this is usually accomplised by the use of an open pocket compound which serves as the lubricant. An open pocket compound can either be a grease, vaseline type substance or a very stable medium to high body varnish.

Back to flexo, trying to spilt an ink reservoir would be futile, as the low water like viscosity of the ink would spread through the unit. The risk you would run with the dam, is that the anilox roller would likely become damaged because on no lubricating fluid to sustain the non image area of the print unit. These reservoirs are also more like troughs rather than a more shallowed offset ink fountain.

D Ink Man

 

[Cornishpastythighs]

Oh sorry so you have one of those open pan flexo ink systems that an Arpeco press uses and runs ink viscosity much like litho and not a chambered doctor blade system. you just got to try it and see.

 

[aqazi81]

As D INK Man mentioned, there will definitely be a chance of wear on anilox roller and duct blade.

 

[dkelley]

You can purchase a low volume ink pan form many Flexo supply houes, We use a company call DIP.

 

[euman]

Just put something else in the tray to take up space. Could be anything that sinks and displaces ink, as long as it doesn't react with the ink or run up against the anilox. I've done that in a pinch when I was close to the end of a run and running out of ink.

 

[rking]

Our company had tubes made that were filled with sand and capped on either end. This displaced the ink in the fountains enough that they only had to make half the ink needed.

 

[D Ink Man]

Our company had tubes made that were filled with sand and capped on either end. This displaced the ink in the fountains enough that they only had to make half the ink needed.

I must say, that's using your noggin.