How an offset print press works


The Heidelberg XL 105 and XL 106 offset presses form the backbone of the printing production line at Graphic Packaging International’s headquarters in Bardon, Leicestershire, and represent the last three printing machines purchased for this plant.

The Heidelberg XL 105 and XL 106 offset presses form the backbone of the printing production line at Graphic Packaging International’s headquarters in Bardon, Leicestershire, and represent the last three printing machines purchased for this plant.

Beginning at the input feed, these machines represent state-of-the-art technology in printing presses. The logistics system used at Bardon ensures board for the next job to be produced is supplied on plastic pallets ready to run just as soon as the printing plates have been loaded onto the machine.

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The sophisticated guides on the feed board ensure exact positioning of the sheet prior to the beginning of the printing process.

Each printing unit of the press lays down one specific colour of ink. The ink train, pictured here, helps to ensure a fine but even film of ink is applied to the printing plate prior to the image being offset to a printing blanket before being further transferred to the board stock.

The transfer cylinder then moves the board on to the next printing unit to lay down the next colour element. Four basic colours, the printing primary colours, black, cyan, magenta and yellow form the basis of a typical colour picture. Special colours – often “corporate” or product specific colours – may be added to the standard four process inks.

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After the inks come the coatings. A clear varnish is often added to protect the base print, or to add a special finish – gloss or matt coatings, or maybe even matt and gloss coatings together.

Ultra Violet lamps are used to cure the UV inks and coatings used on Graphic Packaging International’s XL presses. These low migration inks provide a dry-to-the-touch finish once cured.

Infra Red, hot and cold air dryers can be used to assist drying on all presses.

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The finished stack grows swiftly! Don’t be fooled by these slow animations. At normal running speeds these presses produce up to 18,000 printed sheets per hour – 300 sheets per minute or 5 sheets per second!