Bobst has built on its MasterFlex THQ press with the new FlexoCloud approach to produce much sharper images
There is growing interest in printing high quality images direct to corrugated board and flexo is an obvious print technology for this application. Nessan Cleary looks at the market.
Corrugated boxes have traditionally been used to protect goods during transportation, but there is a growing demand to print good quality graphics to corrugated largely driven by the growth of online shopping.
Another factor is that many retailers now use corrugated boxes for on-shelf displays, mainly to cut down on the amount of packaging being used. This is partly in response to consumer concern over the sustainability of packaging, as well as the ongoing desire to reduce the costs associated with packaging.
There are several options for printing to corrugated boards, but the most straightforward and cheapest option is to flexo print to the board after the different elements have been put together, known as post printing. Due to its construction, corrugated board is a challenging media to print on as it can be crushed easily so it requires a press specifically designed for this approach.
Avoiding the crush
Bobst has developed the MasterFlex series of post-print flexo presses, including the MasterFlex XL. This can take corrugated boards from 0.8 to 10mm thick, in sheet sizes up to 1540 x 2400mm and can handle most of the common types of fluting. It uses a vacuum transfer system and ‘no crush’ feeder as well as an automated stacker. It can print up to 12,000 sheets per hour and can take up to six printing units.
There is a further variant, the XL THQ (Très Haute Qualité or Very High Quality), which can be configured with up to nine printing units.
Last year Bobst introduced THQ FlexoCloud technology, which builds on the XL THQ press but promises even higher image quality. There are three elements to this approach. Firstly, there is a specific type of THQ ceramic rolls, which Bobst supplies itself. The THQ inks come from Siegwerk and include CMYK plus varnish and are only available to THQ FlexoCloud customers. Then there is a particular type of THQ printing plate developed by Graphilabel that allows for a unique colour separation algorithm. The advantage of this combination is a much more precise image, covering roughly 65% of the colour gamut with just four inks, which is suitable for anti-counterfeiting applications such as adding coded messages to the outside of the packaging. It also means using less plates and therefore lower
ink consumption.
There is also a cheaper press, the Flexo 160 Vision, which offers quick set-up times with an independent drive system and register correction technology. It takes boards up to 1200 x 1700mm and up to 9mm thick and runs at 6200 sheets per hour. It can be fitted with up to seven printing units and the printing size of each colour can be adjusted lengthwise for better colour to colour registration.
Making the cut
Koenig & Bauer has also made a determined effort to break into the corrugated market, developing two new post-print flexo presses, including one with a high board rotary die- cutter, the CorruCut. These were announced at the end of last year at a technical conference hosted by the European Federation of Corrugated Board Manufacturers (FEFCO).
Christoph Müller, an executive board member of Koenig & Bauer, explained, ‘We studied the market very carefully and also spoke directly with many of the companies. On this basis, we then sat down to design a press which mirrors the specific needs of the customers as precisely as possible.’
The CorruCut builds on the previous Corrugraph series. It is designed to handle corrugated sheets up to 2.8m wide and from 60cm to 1.5m long. It will take sheets from 1 to 9mm thick. It uses a vacuum belt feeding system and the same DriveTronic direct drive technology that is fitted to many other Koenig & Bauer presses. The feed length is controlled automatically and there is no need for infeed shafts, which eliminates the risk of crushing the sheets.
Nyloflex FTC Digital for corrugated post-print is said to offer significant fluting reduction and outstanding print quality
The printing units are easily accessible and use dedicated servo drives for the impression cylinder, the vacuum transport, the plate cylinder and the anilox roller to ensure accurate registration. The printing units are fitted with the company’s quick-clamp chamber blade system made from carbon fibre composite to optimise the ink transfer and minimise ink losses during washing. It can produce up to 12,000 sheets/hr. There is an option to add infrared and UV dryers into the transport system and an automatic washing system to reduce water consumption.
The company is also working on a second flexo corrugated press, the CorruFlex, though this will come after the CorruCut. There is also a digital machine, the Corrujet, which is an inkjet web press based on the Rotajet but developed specifically for the corrugated industry. It is a four-colour process producing up to 6000 sheets per hour.
Corrugated plates
Not surprisingly, there are a couple of new plate developments also aimed at the corrugated market. Last year Flint Group introduced a new nyloflex FTC Digital flexo plate, which produces inherent flat top dots and is said to result in significant fluting reduction on various corrugated boards from fine to rough flute. It is said to offer sharp and defined elements with precisely reproduced text and codes, and less dot gain tolerances on press. It is a photopolymer plate and requires standard processing with no need for additional equipment or processing steps. It is said to have the same robustness and storage capabilities as other plates in the nyloflex range.
Dr Eva Freudenthaler, vice president of technology for Flint’s flexographic products, explained that users want higher print quality despite a trend to use lower quality, ‘With the development of nyloflex FTC plate, we therefore had two focal points with regard to print quality – to reduce the fluting effect across many different liner qualities and to further enhance the quality of fine highlight screens in corrugated postprint – while at the same time keeping it simple for the pre-press operation by providing a plate that can be processed like any normal digital printing plate.’
Finally, it is worth noting that there is a significant threat from digital printing in the corrugated sector that anyone investing in flexo needs to be aware of. Much of the growth in printing to corrugated comes from the increasing use of online shopping, where brands want to use the protection to goods in transit that corrugated offers but still want to deliver a good retail experience to customers through the use of graphics. Many of the inkjet presses are good for short run prints, suitable for the just in time manufacturing typical of online sales. But there are several other inkjet presses in development that are capable of higher volumes and are aimed at mid-run applications such as versioned marketing campaigns.
Clearly, flexo corrugated post printing is aimed at longer print runs but the growth in this sector comes from relatively recent retail trends and so converters may well find themselves having to compete directly against digital. This is why Bobst has opted for a fixed four-colour palette for the THQ FlexoCloud and why Koenig & Bauer has built a rotary die-cutter into its CorruCut. But flexo has a major advantage over digital – it is the only game in town when you need to produce longer runs and the only technology that can consistently produce high quality images quickly in large volumes.
