Bobst has been showing off its latest wide web flexo press, the 20Seven, which is based heavily on the existing 20Six but with a number of enhanced features designed specifically to tackle the growing interest in printing with extended colour gamut inksets.
It’s a Central Impression design that can be configured for eight or ten colours and will take both solvent and water-based inks. It can handle a wide range of substrates though it’s primarily designed to print to flexible films for packaging. It can print from 1050mm up to 1450mm wide with a repeat of 370 to 1200mm. It can run at speeds of up to 600mpm.
Bobst has long been a proponent of the extended colour gamut concept – using a fixed inkset, typically CMYK plus orange, green and violet – for all jobs to avoid having to use multiple spot colours, thereby dramatically cutting the time needed to change the press over from one job to the next. However, extended colour gamut, or ECG, printing demands extremely high quality imaging, which has to be absolutely consistent from one job to the next. Bobst has worked hard to adapt the press around these demands, introducing a number of new features.
The most obvious of these is the new TriLock system that holds the print cylinders in place. Federico D’Annunzio, Bobst’s Strategic products marketing director, says that ECG printing requires higher line screens of 60 or 70 or above explaining: “The dots are very small and the higher you go on the line count the smaller the dots become so you must have a print unit that is robust and extremely vibration-free.” He adds: “So the printing unit has to be made in a different way to achieve this.” The solution is two locking bolts next to the cylinder bearing – forming a triangle – with each bolt tightened by a pre-torqued pneumatic tool that ensures the bolts are tightened to the same degree regardless of the strength of individual operators. In addition, each pair of cylinder bearings is fixed in place between steel rails that combine with the TriLocks to form a very solid chassis, eliminating any chance of the cylinders vibrating.
Bobst has also put a lot of effort into the ink management system. The new SmartFlo system includes independent temperature control for each ink delivery system. D’Annunzio points out: “Different environments have different temperatures so we control the temperature of the ink on each unit. We cool or heat the ink so that we know we have the same temperature regardless of which country you work in.” This gives much more precise control over the viscosity of the ink.
Bobt has also improved the way the ink is physically delivered to the print units as D’Annunzio expains: “We have changed the pump system. Before we had bigger strokes but now we have small strokes with much higher frequency.” This avoids peaks and troughs in the consistency of the ink
Bobst has also enhanced the drying with a large Full Surface Matrix dryer with over 600 vents to distribute hot air more evenly across the surface of the substrate. This is to ensure better performance with a wide range of substrates.
The press also makes use of the Bobst’s SmartGPS, though this has been around for a while. The Graphic Positioning System automatically generates the registration and impression settings offline at the plate mounting stage. This information is stored in an RFID chip in the print cylinder. The press can then read this information and automatically set up each cylinder with no need to run the press. It’s a neat system that makes it quick and easy to set the press up with no waste.
Bobst demonstrated this new press at the ‘We make it happen’ open day at its Bielefeld plant in Germany in front of several hundred customers and brand managers. It’s always impressive to see a large press running and the 20Seven was no exception though it struck me as remarkably quiet and fuss-free. Bobst printed a couple of jobs to prove just how quick it is to change from one job to the next. There was very little waste between jobs – at one point the printed flexible film roll was laid out on the ground in front of the press to show the changeover, with I’d guess around 3m, maybe a little less, of waste between those jobs.
The day concluded with a brief visit to the service centre to see the remote diagnostic system in action. The Service Centre also houses Bobst’s Innovation Centre. Mark McInulty, service centre director, explained: “Everything that we gather from our experience in the field we put in the machine. This is how we try to get operational know-how in our technology and innovation.” Clearly this approach is working for Bobst, given that the new 20Seven press is essentially a refined version of the already proven 20Six.
The event also included a discussion on plastics as a packaging substrate as well as the practicalities of implementing extended colour gamut printing, both of which I’ll cover in future posts.