Packaging continues to be a growth market, and within the packaging market, flexible packaging is arguably the fastest growing segment. According to a Smithers Pira report (Future of Global Flexible Packaging to 2020), the global market for flexible packaging is projected to grow by 18% through 2020. But this growth brings with it new challenges for flexographic printers. Chief among these is the increased diversity of printed packs – smaller lot sizes, a wider variety of products and packaging formats, and a growing desire to regionalize packs as well as vary them seasonally and to support specific events.
According to the Smithers Pira report, flexible packaging is the most economical method for packaging, preserving and distributing food and other consumables. Flexible packaging also carries a lower supply chain cost than glass and metal and can deliver more shelf appeal and product protection. So while flexible packaging is on the rise, glass and metal packaging are on the decline in many regions. The lighter weights of flexible packaging reduce material and shipping costs. They also increase consumer convenience, since pouches can be easily stored, and they give the consumer the ability to get a meal on the go, instantly and at any time. Consumer product companies (CPCs) want consumers to be able to prepare a microwavable meal from a pouch as quickly and conveniently as they can eat a breakfast bar. The diversity of packaged food products using flexible packaging solutions is endless.
Traditionally, flexible packaging using flexographic printing technologies has been manufactured in lot sizes averaging about 15,000 metres. In most plants, job change-over times can be an hour and a half or longer, depending upon the type of equipment, number of colours that must be changed, press modules required, etc. Clearly, as lot sizes decrease, the economics of conventional flexographic printing are challenged. It is for this reason that there has been an increased interest in digital printing solutions for label and flexible packaging production as well. But technologies are now available on the market that will allow flexographic printing to strengthen its competitiveness, particularly for short run small-lot jobs, to ensure that flexography remains the printing process of choice for CPCs well into the future.
Fixed colour palette printing to opens new market potential
Printing with a fixed set of inks is also gaining popularity among both offset and flexographic printers. This approach typically uses CMYK, or CMYK + Orange, Green and Violet or Blue. The latter, often referred to as Extended Colour Gamut (ECG) printing, can completely eliminate the use of spot colours and delivers better quality than CMYK alone. [images 1 and 2] ECG printing can also match a wider array of spot colours than CMYK alone. Some experts estimate that ECG can match as much as 90% or more of the 1,726 named Pantone spot colours.
In addition to elimination of the need to use multiple spot colours, fixed colour palette printing also reduces press make-ready and change-over times. In fact, in many cases, there is no need for wash-ups between jobs since there is a fixed set of inks being used. Simply change the plates and run-up to colour. This significantly improves throughput and brings down the cross-over point between flexo and digital. For label UV flexo, the cross-over point can be as low as a 400 metre job length. Using the fixed colour palette printing process, flexographic and offset printers are also able to significantly reduce ink inventories and waste. In addition, it makes it easier to include jobs from multiple clients in the same run, also known as combo printing, co-printing or ganging. All of this saves significant time and cost and better enables the faster time to market demanded by CPCs.
While certain colours will still require a spot colour ink, the number of those inks required is vastly reduced. And, as pointed out above, the press is never down for wash-up and make ready between jobs!
If your company is already using digital printing, you are likely already printing with a fixed set of inks on those presses, so why not try it in flexo as well? After all, you—or your repro house—already understand how to make multi-colour separations! For print jobs that are designed using spot colour, it is necessary to reformulate the spot colour into a fixed ink set, creating that colour with a process build rather than using a single ink. The skills of a repro house can come in handy here. The repro house must be able to build the formulation with confidence and partner with your team to enable efficient delivery. The press must also be profiled, and that profile must then be validated. The press must be checked for performance, fingerprinted and then tested for repeatability. There is no point in starting a print run, and then having the colours drift over time or across jobs. It is critical to develop a process that delivers consistency on a long-term basis when printing with a fixed set of inks.
Although digital printing is still a niche technology in flexible packaging, there are some lessons flexo can learn that will help keep flexography viable. These include the production flexibility gained by using a fixed set of inks—a standard process in digital printing.
Choosing the right plates for fixed colour palette printing
Achieving brand spot colours with ink layers, or process colour printing, as opposed to using a spot colour ink, requires perfect plate registration to be able to match the predicted spot colour target as accurately as possible the first time around.
One approach is to use a photopolymer or rubber engraved sleeve. The registration capability of today’s flexo sleeve technologies is clearly best in class. That makes it a good fit for fixed colour palette printing. However, there are downsides to this approach as well. First, the worldwide market share for sleeves is estimated at approximately five per cent. With this low demand level, the availability of the materials can be somewhat limited. The second and most significant disadvantage for fixed colour palette printing using sleeves is the way sleeves are imaged or engraved over their complete printing width, making last-minute job changes impossible. Since sleeve delivery for special sizes can take several weeks, printing with sleeves requires a well-planned supply chain with zero tolerance for changes. And changes are one thing that are an everyday part of a flexographic printer’[s life.
Stories from the front lines
Here’s a common example from a large converter in the beverage carton business that demonstrates what can drive the need for last-minute changes. This company’s CPC customer suddenly saw, on a hot summer day, an increased demand for water beverages. Since supply chains are planned very tightly, this resulted in a sudden shortfall of drinking water beverage stock. When this type of situation arises, and in order to help the CPC meet demand, the beverage carton converter must make production changes literally at the last minute in order to produce extra cartons. These last minute changes are difficult when using sleeves, since perhaps only one printing lane on a multiple lane cylinder needs to be replaced in order to accommodate the change and enable the CPC to capture the additional sales of water beverages during this unexpected peak period.
An alternate solution that is commonly used in the industry is combo printing with flexo plates. Different jobs of similar length are combined on one printing cylinder. In the case we have described here, instead of making the complete sleeve to accommodate the change and incurring the resultant delays and costs, only the plates for the drinking water beverage must
be made, replacing a less urgent job on the cylinder. In order to take full advantage of combo printing for last-minutes job changes, a fixed set of printing inks and perfect plate-to-plate registration are required. Another important requirement is the ability for the printer to make new plates on site, within minutes, to ensure rapid plate availability. Therefore, technologies with fast plate access time are the preferred choice in an environment that is increasingly dynamic and demanding, where last-minute changes are becoming the norm rather than an exception.
In addition to print registration and plate availability, printing consistency is an important requirement for fixed colour palette printing. Since colours are made up from the overprinting of four to seven colour separations, consistency of each plate colour is absolutely crucial. A minor change or defect in one colour separation or plate will have an immediate impact on the overall colour quality, causing a colour shift. Plate technologies that make it easy to transfer inks without contamination or ink drying on the plate are the preferred way to go.
The density myth
Although there are target ink density recommendations in place for flexo, some practitioners believe that the higher the density, the better the print result. Actually, this is a myth and the opposite is true. When printing with a fixed set of inks, it is important to print as cleanly as possible, using an ink film as homogeneous as possible but without excessive amount and density. The plate will otherwise accumulate ink around the solids and a so called “picture frame” void edge will appear. With a fixed set of inks, spot colours are generated from four to seven colour separations. When overprinting those colours, light printing pressure can be used to keep plates clean, and at the same time, eliminate printing voids or printing pinholes since voids are overprinted by other colour separations (see image No.3).
Printing with a fixed set of inks opens up exciting new opportunities for flexographic printers. It enables them to better address the low run length, small lot market claimed by digital printing while at the same time delivering faster time to market for customers.
Flexo can stay competitive against emerging digital printing technologies. Now is the time to adopt printing with a fixed ink set in order to eliminate excessive job make-ready times, and to accommodate last-minute changes to facilitate the printing of combo print jobs on the same printing cylinder. The best choice of plate technologies to meet these requirements is technologies that are tailor-made to ensure high printing press consistency over the production run, fast availability of plates to the printing press for last-minute job changes, and perfect dimensional stability for the best possible plate-to-plate registration.
by Dieter Niederstadt