There are a wide variety of technologies that are used to print stuff. The main industrial printing processes are:
Additional printing techniques were developed for very specific applications. These include flock printing, letterpress, intaglio, pad printing, and thermography.
Why a certain job is better printed using one of these processes mentioned can be read on this page about choosing a printing process.
In offset lithography a printing plate, which is most often made from aluminum, contains an image of the content that needs to be printed. When the plate is inked, only this image part holds ink. That inked image is subsequently transferred (or offset) from the plate to a rubber blanket and then to the printing surface. The process can be used to print on paper, cardboard, plastic or other materials, but these have to have a flat surface.
Below is a picture of a 4 color sheetfed printing press. At the far end is the intake where individual sheets of paper are automatically fed into the press. The 4 towers or printing units each print one color, typically black get printed first, followed by cyan, magenta and yellow. The stack of printed sheets is visible on the front of the machine, underneath the press console & monitor which the press operator uses to control the press.
For higher volume work offset presses use rolls of paper. The picture below shows such a much larger web press. It is so fast that the printed paper needs to be force dried. The black unit at the end of the press is an oven.
Offset is nowadays the most widely used printing technique for an extensive range of products such as books, newspapers, stationery, corrugated board, posters, etc.
There is a trend that printing promotional material is gradually migrating to digital printing while some packaging printing is moving to flexo.
You can find more information on the page dedicated to offset printing.
In flexography the content that needs to be printed is on a relief of a printing plate, which is made from rubber. This plate is inked and that inked image is subsequently transferred to the printing surface. The process can be used to print on paper as well as plastics, metals, cellophane and other materials. Flexo is mainly used for packaging and labels and to a lesser extent also for newspapers.
Some packaging printing is moving from flexo to digital.
Digital printing can be done in various ways. Two technologies dominate the industry:
- Inkjet – In an inkjet printer the image that needs to be printed is created by small droplets of ink that are propelled from the nozzles of one or more print heads. Inkjet devices can print on a wide range of substrates such as paper, plastic, canvas or even doors and floor tiles. Inkjet printing is used a lot for posters and signage. It is also economical for short run publications such as photo books or small runs of books. In-line inkjet printers are sometimes combined with other types of presses to print variable data, such as the mailing addresses on direct mail pieces. The press shown below is the HP PageWide C500, meant for printing on corrugated board.
- Xerography – In xerographic printers, such as laser printers, the image that needs to be printed is formed by selectively applying a charge to a metal cylinder called a drum. The electrical charge is used to attract toner particles. These particles are transferred to the media that is being printed on. To make sure the toner is fixed properly, the substrate passes through a fuser that melts the toner into the medium. Laser printers are not only used in offices but also for small run printing of books, brochures and other types of document. These printers are also used for transactional printing (bills, bank documents, etc) and direct mail.
In 2009 both techniques jointly accounted for around 15% of the total volume of print.
Digital printing is increasingly utilized for print jobs that were previously printing using offset, flexo or screen printing.
- In short run small format (A3 size) printing, digital is taking over from offset for both color and B&W printing. Quick printers and copy shops print digitally on presses from vendors like Xerox, HP, Canon, and Konica Minolta.
- Labels are also increasingly being printed digitally.
- Billboard and point-of-sale or point-of-purchase jobs are being done by wide-format inkjet devices.
- There is a wide range of small format printers used to print on phone cases, mugs and other products.
- In book printing publishing companies start to rely more on print-on-demand. The Espresso Book Machine pictured below is well suited for that job.
There are a number of other digital printing processes that are geared towards specific niche markets:
- Dye-sublimation is a printing process in which heat is used to transfer a dye onto the substrate. Dye-sub printers are mainly used for printing on textiles, for proofing and for producing photographic prints. Some printers can print on a variety of materials such as paper, plastic, and fabric.
- In the direct thermal printing process heat is used to change the color of a special coating that has been applied to paper. This process is used in cash registers but also to add markings, such as serial numbers, to products. For this a transparent ink is used that changes color when a laser applies heat to it.
- In the thermal ink transfer printing process heat is used to melt print off a ribbon and onto the substrate. It is used in some proofing devices but seems to be gradually disappearing off the market.
Also known as rotogravure, this is a technique in which an image is engraved into a printing cylinder. That cylinder is inked and this ink subsequently transfers to the paper. Gravure is used for high volume work such as newspapers, magazines, and packaging.
Gravure is gradually losing market share to offset for publication printing and to flexo for packaging applications.
As its name implies, this printing technique relies on a screen, which is a woven piece of fabric. Certain areas of this mesh are coated with a non-permeable material. In the remaining open spaces ink can be pushed through the mesh onto a substrate. The advantage of screen printing is that the surface of the recipient does not have to be flat and that the ink can adhere to a wide range of materials, such as paper, textiles, glass, ceramics, wood, and metal.
The image below shows a screen printing press that is used to print t-shirts.
Increasingly screen printing is being replaced by digital printing.
Additional printing processes
- Letterpress – Once a dominant printing technique, letterpress is now used for business cards, wedding invitations,…
- Flocking – used to add a (colored) velvet-like texture to paper, textiles, etc.
- Pad printing – used to print on 3-dimensional surfaces.
- Intaglio – nowadays mainly used for used stamps and paper currency.
- Thermography – This is more of a finishing process than an actual printing process. It produces raised lettering on the printed side of the paper and is used for wedding invitations, letterheads, business cards,…
3 May 2017
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For prospective print customers, the difference between offset printing and digital printing is that digital printing is better suited for short run printing (i.e. starting at 1 single copy) and offset printing is better suited for higher volume printing (i.e. starts being economical 2,000+ identical copies).
Both types of printing produce print products that are extremely high in quality and fit for professional quality printing for businesses. The key factors that make customers choose one over the other is typically the volume of the print project and niche project requirements.
There are other differences—such as color capabilities and sheet sizes that differ between offset printing versus digital printing. This article will detail those differences as it pertains to print buying.
Note for MGX Copy customers: MGX Copy utilizes both digital printing & offset printing depending on what is best for the print project.
Picture to the right is an example of an offset press. Picture to the bottom is an example of a digital press.
The differing technologies used in offset printing versus digital printing
The technological difference between offset printing versus digital printing is in the way the images get transferred onto the paper. It is this difference that affects the cost economics of running these machinery, and this difference in cost gets passed onto the printing customer.
Offset printing uses etched metal plates that apply ink onto a sheet of paper. The setup for offset printing is generally significantly more time consuming and expensive than digital printing. The metal plates—one plate per each color being used—need to be etched, and applied to the rollers that transfer the ink onto the paper. Then, the press needs to be run for a few minutes on “scrap” sheets of paper until the plates are properly inked; think of it like “warmup” sheets that are eventually thrown away.
On the other hand, digital printing uses electrostatic rollers—called “drums”—to apply toner onto the paper. The drums—again, one per each color being printed—use an electrostatic charge that attracts toner in the form of toner density. The toner is then applied onto the sheet and then fused—passed through a high-heat unit—onto the paper.
Digital printing can easily print out one sheet of paper or a copy of a booklet with minimal setup. However, offset printing requires a considerable amount more setup time and material. The ink and each sheet of paper that comes off of an offset press is actually cheaper than that of a digital press, but the savings only make sense if the print job is at a high enough volume.
Also—it’s the number of copies that counts; not the total number of sheets. Offset only makes sense if making a few thousand copies of the same sheets. So for example, if you’re printing 500 copies of a catalog that is 100 pages long, you’re printing 50,000 pages but only 500 copies. This would qualify as “short run printing”. (Offset doesn’t make sense because each sheet would require its own plate to be made.)
Most businesses today doing frequent, quick, and constantly changing print content opt for digital printing. On the other hand—businesses that print in volume and don’t change their content frequently opt for offset printing.
So again—the volume of printing is a key difference between offset printing versus digital printing.
Other differences between offset printing versus digital printing
There are a few other differences that show up when print customers are shopping around for printing services.
The first of those differences is the sheet size. Digital printing typically runs smaller sheet sizes—typically 19” sheets with some machines going up to 29”. Offset printing on the other hand typically runs presses that are 29” and 40” sheets. This increase in size occasionally allows for some kinds printing that isn’t possible on smaller sheets. Some examples include posters, books requiring large covers, and certain kinds of brochures.
When dimensional print size is important, but the print volumes don’t merit use of an offset press, customers frequently turn to digital wide-format presses for short-run printing. There are some cases of wide-format printing that cannot be done on digital wide-format presses—as in certain kinds of printing surfaces like packaging material, plastics, etc.
The second of those differences is the color representation. Every piece of printing equipment offers slightly different interpretations and controls over how colors get applied onto a page. Offset presses can provide certain color controls that are superior to digital printing. For example, printing Pantone colors (a color management system) is more precise on offset presses because they actually use Pantone ink. This is important most typically for large corporate brands for which color consistency is worth a considerable amount of money.
The third of those differences is that digital presses are significantly cheaper for fast-turnaround projects. Digital printing offers incredible turnaround times because the significantly smaller setup time. Shops doing digital printing well can offer same-day and next-day printing much more efficiently and cheaper than those with offset printing. For example, it would make sense to throw a project onto several digital presses that require minimal setup. On the other hand, throwing it onto multiple offset presses would require multiple plates and time to properly ink the plates.
To explore your printing options for offset printing or digital printing, please contact us today!
About the author
This post was written by Andrew Shu, editor for both the MGX Copy blog (about printing) and the MGX Mindshare blog (about marketing). He is hugely passionate about all things “MGX”, and is involved in all aspects of its operation and administration; this includes web/software development, print production, customer service, and internet marketing. Ask him about anything related to MGX Copy, printing, software, and business, and he’ll probably talk your ear off! You can reach Andrew directly on Twitter (@AndrewAtMGXCopy) and Google+ (+AndrewAtMGXCopy). If you have any questions, feel free to reach out to him.