The design for a carton is developed and owned by a brand owner who will have a specific product that needs to be packaged. Graphics for that carton are prepared on a computer and then the necessary colour separation is carried out. Once this is done, a printing plate or cylinder is prepared for each colour that will be used on the carton.
A printing machine has different printing stations for each colour or varnish to be included in the design. Cartonboard sheets are loaded onto the printing machine and printed in one pass with each colour being added in each of the printing stations. A variety of printing processes may be used including offset / lithographic, flexographic, gravure and in some cases, digital printing. Digital Printing is still an emerging technology that is expected to become more important for carton production in the future. It allows customized prints of very small order sizes.
Several cartons can be printed on one sheet of cartonboard, so a layout is created to ensure that as little cartonboard waste as possible is created from each sheet. This layout is also used to prepare the creasing and cutting forms that will be used later in the production process.
Most cartons are printed using six colours, depending on the specification that comes from the brand owner. As well as the colours that are applied to the cartonboard, a varnish that improves the gloss finish or that adds a highlight is often printed on the board on top of the printed colour. Cartonboard can also be laminated with aluminium foil, metallised polyester, greaseproof paper, glassine or coated paper.
Carton Creasing and Cutting
At the end of the print process, the cartonboard sheets are stacked up and moved to the next stage of production – creasing and cutting. The sheets of printed cartonboard are taken to a machine that puts in creasing lines to enable it to be folded later and also cuts the individual cartons out of the cartonboard sheet. This is done using a “form” into which knives and creasing rules are set. This is also the stage of the process where it is possible to add embossing to a carton. As with printing processes, accuracy at this stage is critical to ensure that cuts and creases are marked in exactly the right position.
Carton Folding and Gluing
Once cut, the individual cartons are stacked and passed through to the next stage of production which is folding and gluing. This is done on high-speed machines that form the cartons into a folding box along the folding and creasing seams. The folding cartons are then packed for shipment to the customer, who uses them for filling on his packaging line.