Printing With High Humidity And Heat

I'm not fortunate enough to work at one of those printers that has perfect climate control in the building, so I deal with all the fun variables that come with it.  Our summers are hot and humid while our winters are cold and dry (above is an example of our current running temperature in the pressroom).  I would like to share a few tips on how we deal particularly with hot and humid environments.  I beleive that this is most felt on a heatset web press, but it applies all the same to coldset or sheetfed.

Hot and Sticky
Offset printing works best by operating within a specific temperature window to work properly.  If the printing unit heats up to hot, expect problems with a narrow ink and water balance window.  Controlling scumming will be hard.  Being on the cold side however isn't as bad.  Too cold however may result in condensation.  That in turn will result in drips that ultimately fall on the plate or paper, and that is no fun either.

With a humid and hot environment, what it boils down to is your delta.  If the rollers, lets say chill rollers in this example, are too far below the ambient temperature of the factory, then condensation will occur.  The problem is that you cannot raise the temperature of your chill rollers as you need to set the ink properly.  The same can be said for the printing units.  You cannot heat them up for the sake of reducing condensation.

The Problems
Especially on a web press, all it takes is one water drop on the paper and your done - web break.  This can make web breaks difficult to troubleshoot and control.  It can drip from a guard or spray off the edge of a vibrator roller.  Additionally, drips can fall on the plate causing image and even ink and water balance problems.  

Case In Point
On our heatset press, the edges of our cooling rollers were building up with condensation.  When a splice would go through, the web would wander slightly onto the wet part of the roller.  Kaboom!  There goes the web.  The answer:  Just before the splice we would wipe the edges (very carefully of course) to get the edges dry.

The real solution for most printers unfortunately is far too expensive - climate control.  Many printers, especially in Europe, put an enclosure around the press and run the perfect temperature.  Is it really worth it?  Over the 20 years or so lifetime of the press, how many web breaks and quality issues were missed because of such forethought?  Europeans seem to think its worth it.  Its an investment that is hard to quantify unless careful record keeping could tally up all the lost minutes from those web breaks or quality issues.

Our Solution
For us, it was decided to invest in a press enclosure which we did a year ago.  Though it is hard to keep cool in the summer, there is definitely a difference.  Besides, on those hot days it's nice to go inside and cool off.

No comments:

Post a Comment