What is Web Press Printing?

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A web printing press is a type of printing press that uses a roll of paper to feed it.  Much like the picture above, the paper runs through it like a web. The best comparison would be a sheetfed printing press which simply uses stacks of sheets. Web presses use a similar method of printing, except that they can run at much higher speeds.

What does a web press look like?
Web presses are much longer than your typical printing press. They are long.  Typically, web printing presses consist of the following:


  1. A rollstand. Often referred to as a splicer.  It is either a zero-speed or a flying paster. The difference between the two is shown when a roll runs out.  With a zero-speed splicer, the printing press will remain at full speed, but the running roll will stop.  The press will draw on paper built up in festoons while the new roll is automatically spliced to the next one and accelerates.  A flying paster is a little different. When the roll is about to run out, the new roll accelerates to the same speed as the press and splices at just the right moment.  The video below shows a flying paster. 
  2. An infeed tension control unit This device controls the tension of the paper as it enters the web press. With all the processes taking place on the paper - inking, drying, cooling etc - it is necessary to keep the paper taut or tight.  The infeed tension control unit will provide consistent paper tension to the rest of the printing press. 
  3. Printing units. They print individual colors such as black, cyan, magenta and yellow. They are usually referred to as the 1st, 2nd, 3rd, and 4th unit.  Each lays down a layer of ink.
  4. An oven.  This is only on heatset web presses. This helps dry the inks. Coldset web presses rely on absorption into the paper to partially dry, whereas heatset will "set" the ink.  
  5. A chill unit. To cool the paper down as it leaves the oven.  This "sets" the ink. After the ink leaves the dryer, it sets in a similar that wax does when it is cooled down.
  6. A silicone applicator. To provide a smooth finish and prevent marking.  This prevents what is referred to as setoff or ink buildup and readies the paper to enter the web press folder.
  7. A ribbon deck. To configure the paper for different product layouts before entering the folder.  Any slits to the paper occur here before entering the folder.
  8. The folder. Usually folders have many configurations to fold newspapers, magazines or flyers.  Most often, these folders can only fold in multiples of 8 pages.
Below is a video of a heatset web printing press.  



What is a coldset web press?
A coldset web press doesn't have a dryer.  Newspapers are typically printed this way.  The result is that the ink will rub off on your hands.  The inks are solvent based and so will produce a smell... like ink.  Absorption into the paper is how most of the "drying" takes place.

Coldset web press without dryer.


What is a heatset web press?

A heatset web press has a dryer.  The inks are also solvent based.  When the web of paper enters the oven after the printing units, the solvents evaporate from the heat. They reach a "flash point" and are exhausted outside the oven.  What is left on the paper are pigments, resin, wax and other trace chemicals. The ink then "sets" when going over some chilled rollers.  This chilling process solidifies the ink much like wax does when chilled.

Heatset web press with dryer.

 
What is the difference between a web press and a sheetfed press?

  • Quality.  Sheetfed presses produce better image quality than web presses can. The difference can be negligible, but the mechanical design does not allow it.
  • Speed. Web presses typically print 3 to 5 times faster than sheet fed presses.
  • Size. Web presses are much larger.
  • Raw materials. Web presses require rolls of paper. 
  • Energy. Web presses also require gas for ovens and typically have internal cooling systems because of their speed.

What type of publications do web presses print?

Publishers choose web press printing because of the high volume that can be produced in a short period of time.  For example, a print run of 20,000 or more will typically be printed by a web press.  The reason is that a digital printing press, or a sheet fed press could take days, even weeks to complete longer runs.

Pricing is another reason.  Since slower printing methods take so much longer, the cost will run much higher.  Materials also cost more for non-web press printing methods, especially ink.

Web printing presses can print on glossy paper, while sheetfed presses do not unless they have a dryer. 


Conclusion
In simplest terms, a web printing press differs from other presses in that it uses a roll of paper.  It's advantages are speed and economics and very large print runs. 










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