Digital printing and offset printing explained

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Digital printing, wide format bubble-jet printing and offset printing explained

This page attempts to explain some of the differences (and some of the similarities) of digital printing presses, wide format bubble-jet presses, and offset printing presses.

 

Digital printing presses use toner (dry ink), instead of the traditional wet (chemical-based) inks

Digital printing is a modern printing process that uses toner (i.e.: a dry, powdered ink). Offset printing presses are the traditional means of printing, and offset printing presses use wet inks. Wide format presses use ink that is fired out of an ink-box.

Digital printing presses are similar to the photocopiers that you might use, in that digital printing presses use heat to melt the powdered toner (dry ink), and then that heat bakes the toner onto the paper. However, any similarity with photocopiers ends with that heat-based process, as modern digital printing presses are capable of producing finished full colour products that are equal to any traditional offset printing press.

 

Full colour printing in the CMYK colour gamut

As mentioned above, digital presses are state-of-the-art machines that produce high quality products, and they are printed in full colour. Most digital printing presses use the CMYK colour gamut. This means that our digital printing presses use four colours (C—cyan, M—magenta, Y—yellow and K—black) to produce all the colours in the rainbow.

Traditional offset printing presses use either the CMYK colour gamut or the RGB colour space (R—red, G—green and B—blue). TheInternetPrinter's offset printing presses and wide format bubble-jet presses use the CMYK colour gamut. So, there is no difference in the colour of inks that TheInternetPrinter uses on our digital printing presses and our offset printing presses.

 

An image of a digital printing press and an image of an offset printing press

Below are three images. The top left-hand image is of a Fuji Xerox iGen3 digital press, and this is the type of press that TheInternetPrinter uses. The top right-hand image is of an offset printing press. The bottom centre image is of an Océ Colorwave 600 wide format press.

Modern digital printing presses are slightly taller that the height of an average-sized person, and they are quite long. Modern offset presses are about one-and-one-quarter the height of an average-sized person, and are very short when compared to digital printing presses.

 
Wide format presses are about one-and-one-half metres in height, and almost two metres long.

 

Digital presses are sheet-fed and use A3-sized stock, offset presses are sheet-fed and use A1-sized stock, and wide format presses use rolls of paper

What you will notice is that the digital printing press is completely enclosed, whilst the offset printing press is 'open'.

The digital printing press's paper is placed in the four baskets at the left of the digital printing press — you should be able to see the four draws. The digital printing press is a sheet fed press that uses A3 sheets, and this means that A3 sheets (twice the size of a standard A4 business letter) are placed in the draws, and the job is printed onto the A3 sheets. The printed sheets are then placed into the two large bins at the right of the image — you can see the printed A3 sheets in the two small windows at the right-end of the digital printing press.
Each of the four in baskets take take a different type of paper stock (e.g.: one might have 350gsm stock, and anothert might have 150gsm stock). The digital printing press's ability to accommodate up to four different paper stocks means the press can change from one printing job to another printig job quickly.

The offset printing press is a sheet-fed A1 printing press, and you can see the A1-sized paper on a tray at the left of the offset printing press. The offset printing press can take only one type of paper stock in its in tray, so it takes time to change from one printing job using one type of paper stock (e.g.: 150gsm Gloss) to another printing job that is using another paper stock (e.g.: 310gsm Satin Art Board).

 

Offset printing presses use four printing plates, and digital presses do not use any printing plates

You will notice that the offset printing press has four towers. Each tower contains a drum and each drum has a printing plate placed upon it. Each plate prints a different colour in the CMYK colour space (C—cyan, M—magenta, Y—yellow and K—black). The plates are manufactured by a computerised plate manufacturing machine, and are then manually placed upon each drum. This process takes time and it expensive, so the set up costs for an offset printed job are large.

Digital printing, however, does NOT use plates. The whole process is electronic, so it takes only a few moments to change from one printing job to another printing job. If you consider that fact that digital printing presses can hold up to four different paper stocks in their in baskets (see above), and you add to that the ease of electronic printing, then digital printing presses can change jobs extremely quickly — the set up costs on digital printing presses are minimal.

Wide format presses have no drums. They fire ink out at high speed and at high pressure onto the paper. Below is an image of the ink guns. They are quite large (i.e.: a fully-grown man can easily place in hand in the handle at the back of the ink gun). Four ink guns are used (i.e.: one for each of the CMYK colours — C—cyan, M—magenta, Y—yellow and K—black).

 

Offset printing presses are super fast, and digital printing presses are quick (but nowhere near as fast as offset printing presses), wide format presses are slow.

Digital printing presses print between fifteen and one-hundred A3 sheets per minute. Our Fuji Xerox iGen3 digital printing press has a constant speed of 100 A3 sheets per minute. In comparison, offset printing presses print about 30,000 A3 sheets per hour (or 500 sheets per minute). This simple comparison highlights the major difference between offset printing presses and digital printing presses — once an offset printing press is set up, it can press huge volumes in a very short time.

The difference in the speed of the printing presses have another influence. Specifically, both digital printing presses and offset printing presses are very expensive — a minimum of $1,250,000 each — and the cost of owning that press must be spread accros all the jobs that are printed on that printing press. So, digital presses (that print any a small number of images each minute) must spread the cost of owning that press over fewer printed sheets than does an offset printing press (that printed heaps and heaps of images each minute).

So, digital printing presses are very good for short-run jobs, as digital printing presses can change from one job to another job (and change the paper stock that is used) very quickly. And offset printing presses, whilst difficult to set up, are supurb for printing large quantities.

 

 

So, you now know a bit about offset printing and digital printing, and the differences between them.