Until now, flexible package manufacturing has been predominantly restricted to two processes: flexo and gravure printing.  However, new possibilities offered by infinitely variable size web offset printing technology – such as the Muller Martini Alprinta-V press – have developed into a viable alternative for manufacturers.  At drupa 2008 (exhibit 14B38), Muller Martini will be demonstrating web offset printing with flexo varnishing on OPP film on an Alprinta 52V.

Considerable numbers of machine installations in recent months have shown that for many companies, infinitely variable size web offset printing with UV or EB curing has become more than just an alternative solution in the manufacture of flexible packaging. Does this represent the rise of a serious competitor to the established flexo and gravure printing methods, which has been the case in narrow web and label printing for quite some time?

Today’s marketplace: The benefits of established processes are disappearing
The declared goal of package manufacturers is that it must be possible to produce flexible packaging in a wide range of print lengths at a reasonable cost.  Which explains why until recently flexo and gravure printing processes have dominated this area. And now, the realization of infinitely variable size lengths is a standard feature with package printing machines.

Indeed, web offset machines have been missing this cost-efficient size range. The costs for a size set in the form of conventional printing inserts have amounted rapidly to six-figure sums for an 8-color machine and have prevented the growth of offset printing in the flexible packaging segment. As a result, expensive offset solutions have only prevailed where a small number of different size dimensions has been required. For example: as early as the 1980s, Tetra Pak started to print certain packaging for liquid foodstuffs using web offset.

However, the high cost associated with printing a wide range of sizes has become a thing of the past for web offset printing. Muller Martini, for instance, offers the Alprinta-V, an infinitely variable size web offset press for the cost-efficient printing of labels and flexible packaging. The print length on the Alprinta-V is changed as required by replacing the actual size parts: the plate cylinder and the blanket cylinder. This is a quick procedure accomplished without the use of tools.

The fact is, infinitely variable size web offset printing meets the key requirements for package printing...very low cost printing methods, rapid production, a high level of standardization, the avoidance of high levels of VOCs (Volatile Organic Compounds) and short machine make-ready times.

Possibilities and limitations
The following is intended as a comparison of the possibilities and limitations offered by the traditional methods of printing packaging and web offset printing.
 
Flexo package printing
Flexo methods for printing can be categorized into:
a) Central cylinder presses: These are ideally suited for processing a wide range of materials (flexible packaging, labels, corrugated cardboard liners). Central cylinder presses are configured for medium to large runs and deliver overall excellent print quality, including registration that other production methods cannot match. The use of solvent-based inks is resulting in the steadily rising cost of complying with environmental requirements and safety regulations that are becoming increasingly more stringent. Set-up times for a central cylinder machine are medium to short. Compared to web offset, the printing method costs are high and peripherals are cost-intensive.

b) Flexo presses in-line: These are used mainly for manufacturing folding box packaging for products such as cigarettes, cereals and containers for liquids. Equipped with in-line units for die cutting and laminating, for example, and a fully automatic delivery system, in-line flexo presses are configured for large to very large runs. Both solvent-free inks and UV inks are used.

c) Narrow web presses in-line: Typically, these have a working width from 10” (250 mm) to approximately 20” (510 mm) and deliver production speeds of 200 to 500 fpm (60 to 150 m/min). They are hybrid machines which in some cases combine up to four printing processes and have a wide range of in-line stations for finishing. UV inks are used on these machines to print self-adhesive labels, shrink sleeves and many specialized products in small to medium runs.