Jerry Henson, Michael R. Pfaff

Manager

Mark Andy Inc.

As all carton printers know, the business of folding cartons has become increasingly difficult in the past several years. Customers demand the highest quality printed products, while simultaneously hammering converters for lower and lower prices. The resulting squeeze has driven some out of business, and forced many others to consolidate to stay afloat.

Fortunately, not all the news is bleak. Many carton houses have discovered a wonderful tool to combat these forces in the form of web-fed inline flexographic presses to produce folding cartons. Modern-day flexography can produce quality that rivals offset and is quite acceptable for the great majority of carton work. The web-fed inline press design, by reducing most carton production to a onepass proposition, has given converters the economic efficiency needed to thrive even in these tough market conditions.

This article is intended to give those unfamiliar with the basics of flexographic folding carton production a general idea of what is involved, pointing out some of the differences and similarities between flexography and offset in the process.

I. Prepress

A. Graphics & Artwork

As in offset the artwork for flexo comes in digital format. The same hardware and software used to manipulate the offset files are used for the flexo files. What differs is that the method used to make a file “offset friendly” is not the same as that to make it “flexo friendly”. For example, separating colors to spot colors differ based on taking advantage of flexo’s strengths. Flexo offers more flexibility in separating colors, because the number of stations available on a flexo press typically exceeds that available on an offset press. This allows for better color matching, densities and repeatability for bold print or line work. In any case, after file manipulation is complete the artwork is sent to the next process, which is film output or digital plate making.

B. Film/Conventional Plate Making

Conventional films and plates are still widely used by many printers and prepress houses. While there are advantages in the processing and print quality of digital plates, it will take some time for conventional plates to become obsolete. Films are made form the corrected file that represents each plate/color to be used. The film is used to expose the photopolymer plate, which is washed out, dried, finished and ready to be mounted onto a plate cylinder. The plate cylinder repeat determines the repeat of the print. This is advantageous where plates are made for specific jobs and don’t have to be ganged together to fill a sheet.

C. Digital Plates

Digital plate making is the latest technology and offers many advantages over conventional. The elimination of films is an obvious advantage but, even more importantly, the improved print characteristics (due to better dot structure) have helped bring flexo quality to a much higher level and be competitive in the traditional offset markets. The digital plate is imaged with a laser, exposed, washed, finished and mounted to a plate cylinder.

D. Prepress suppliers and in-house platemaking

As in offset, flexo prepress can be performed in house or purchased through a professional prepress supplier. More and more companies are performing at least some prepress at their facility to control costs and get to press faster. One option commonly used is to have the professional prepress house manipulate the file for flexo and send the file (or film) for platemaking to the converter. It is common also to see the converter utilize in-house prepress on most jobs but send the more challenging jobs to a professional, who may have more experience with difficult work.

II. Printing

A. Waterbased and UV inks & coatings

Among the choices to be made is the decision to use water based or UV inks (or in some cases both) on the carton. There are many factors that must be considered due to the advantages and disadvantages of each system. The specific market(s) served is the biggest determining factor. The common advantage of both systems, versus offset, is the consistency and repeatability of color. With anilox and doctor blades, adjustments that are made by the operator have little effect on color. Correct color is achieved by anilox selection and ink formulations, not by operator tweaking of the equipment. This allows the color matched on a shift by an operator to be the same color on another shift by the next operator. The same holds true for job reproduction. If the same color formulation is used on the same anilox, the color reproduction should be the same.

Coating and laminating capabilities on today’s flexo folding carton presses offer more flexibility to deliver added value inline at reduced costs. UV, waterbase and EB coatings and adhesives are widely available for various functional properties and appearance. As in choosing ink systems, the UV, waterbase and EB coatings and adhesives choice has to be made based on various factors.

B. Substrate considerations

The type of substrate used will greatly affect the print quality of the finished carton. Smoother surfaces for example result in less dot gain and better color reproduction than a rough surface. How “white” the surface of the board is also can change the overall look of the printed carton. A duller, grayish “white” results in changes to the color of printed ink. Corrections to the art file prior to platemaking can reduce these effects and in some cases eliminate them. Every printer would like to have the best quality substrate at all times; however the reality of economics usually dictates the quality of board available.

C. Manipulating inks, anilox and plates to achieve a desired result

As in any flexo process, the proper combination of equipment, inks, anilox, substrate, plates and coatings/adhesives must be used to achieve the highest quality with folding cartons. Advancements in all of the above mentioned components have brought flexo to the level of competing with the quality of offset. Not every job produced in offset can be duplicated in flexo but the majority can with the gap narrowing more and more with each advance. Higher line anilox, for example, combined with the latest high strength inks, and printed with digital plates prints a cleaner, sharper dot than ever before.

It is common knowledge that banded anilox tests and fingerprinting are the best starting point when determining how to spec-out components and how to manipulate files for color reproduction. This is even more important due to the wide variety of substrates available for the folding carton market. You must gain experience and knowledge with each substrate and know its effect on the print prior to production. When the basics are complete, a determination of anilox, inks, stickyback and plate material are selected for that substrate and proper curves are applied in prepress. With testing and all of the proper components in place, set ups and waste will be greatly reduced and quality of reproduction improved.

Matching finished offset print quality does not mean matching how offset achieves this finished print. Number of colors, down order of inks and prepress techniques, for example, almost certainly will differ for flexo. This sometimes has to be conveyed to the end user who is used to receiving offset cartons. The focus by the end user should be on the quality of the finished print and not on the methods used to achieve it. This can sometimes be a challenge for the converter but it is important that the converter delivers this message to his customer and does not try to strictly apply offset methods in flexo.

III. Diecutting and Converting

A. Inline Rotary Diecutting – the Method of Choice

Despite it’s reputation as a high-cost process, rotary diecutting commands an increasing share of the folding carton converting pie. This is because more and more converters are recognizing the productivity and quality benefits of rotary diecutting. At the same time, increased demand for rotary dies has enabled die manufacturers to realize the cost savings of higher volume production, and they have passed these savings along to their customers. Rotary dies today are higher quality, less expensive and can be delivered faster than at any time in history. While a rotary die still costs considerably more than the equivalent steel rule die for a flatbed cutter, smart converters know that the savings that accrue to them by virtue of higher productivity and lower waste more than outweigh the additional die cost.

B. Methods of Cutting and Styles of Dies

Those new to rotary diecutting are often surprised to learn just how many variations of dies are available to them. One useful way to categorize and better understand the options is to differentiate between the method of cutting and the style of the die.

• Methods of cutting – Two principal methods exist. The first and most commonly used is known as crush-cutting. This is quite simply the use of a sharp cutting blade and a hardened, smooth anvil surface to knife through the paperboard. This is the same method typically used by flatbed dies. The second approach involves a matched set of dies which apply a rolling pressure to the paperboard that results in a bursting action, severing the paper fibers. This is known by several trade names, but can be generically referred to as “pressure-cutting”. To quickly summarize the cost and performance differences of the two methods, one can figure that pressure cut dies cost roughly double what crush cut dies cost and deliver as much as 10 times the number of cartons before wearing out.
• Styles of dies – Although there are at least four distinct variations of die styles available, the two most prominent are solid dies and flexible, or “wraparound” dies. Solid dies are just what their name implies-cutting and creasing dies where the image is engraved onto a solid tool steel cylinder. Flexible dies are made from thin sheets, and adhere to a magnetic mandrel cylinder. Converters typically use solid dies to produce higher volumes, and flexible dies for low volume and/or sample work.

C. Waste removal and Carton Delivery

These often-overlooked operations have a great deal of influence on the productivity of a flexographic press. Quite simply, if waste can’t be removed fast enough, the whole pressline slows down. The same applies to delivery of the finished blanks. The press must be equipped to deliver blanks in an organized fashion at high speed. Many press manufacturers, in an effort to keep the price of the press low, have neglected these two important aspects to the great chagrin of their customers.

Presses typically deal with trim waste by either pulling away a matrix or using a technique called “pinstripping”. Waste matrix removal appears simpler on the surface, but typically results in more downtime and more paper waste. Pinstripping, while not a surefire way to avoid all downtime, normally causes less of it and allows for the greatest efficiency in carton layouts, saving precious paperboard. It is not uncommon for a press equipped to pinstrip to achieve 2% - 4% paperboard savings over one without.

Most presses either contend with finished output by collecting blanks in a shingled presentation or accumulating stacks of a predetermined height or count. In either case, operators typically remove the blanks by hand and pack them in boxes or for transport to a folder/gluer. However the finished blanks are handled, good control is the paramount feature of the machine. An under-done delivery system costs a converter far more over the life of the press than what he may have saved on the initial purchase, and sharp companies know this and invest accordingly.

IV. The Business of Flexography

A. Productivity

No one can credibly argue that folding cartons are not a commodity. Despite our industry’s wish to see ourselves as something more artistic, our product has attained commodity status and one cannot be successful without following timetested business practices that apply to commodity markets. To remain competitive, a converter has to wring every possible nickel of cost out of his means of production, and increasing productivity remains the best way to do this. Increased productivity means that capital and labor are put to their highest and best uses, reducing unit costs as far as possible. By making possible carton production in the least number of passes, and reducing capital costs vis-à-vis traditional sheetfed equipment, inline web-fed flexography gives the converter the best opportunity to address these issues and make headway in today’s folding carton business.

B. Waste Reduction

Paperboard represents the single biggest component of the cost of goods sold in a carton plant, often reaching 60% or 70%. It stands to reason, then, than anything a converter can do to get more saleable product for his paperboard dollar increases profitability and makes him better able to withstand the downward price pressure that has become a fixture in today’s industry. An inline, web-fed production system offers several opportunities for waste savings. Among these opportunities, the removal of gripper waste can account for a 5% to 8% paper savings, better nesting ability can save another percent or two, and the elimination of most WIP inventory reduces the chances of spoilage, saving anywhere from 2% to 5%. Add it all up, and a total savings of 8% to 15% is achievable simply by virtue of a process change. Saving this amount year after year makes a good financial case for new press investment. Even if all a converter’s old sheetfed machinery is fully depreciated, the argument that it “costs nothing” is specious when one looks at the waste reduction and productivity gains available with flexo

C. Things to look for in a Flexo Press System

Inline flexographic presses come in all shapes, sizes and price ranges. Soliciting and evaluating competing proposals can be a confusing and frustrating exercise, particularly for the newcomer. Whatever niche of the market you serve, there are certain attributes you should look for in any press:

1. Rugged design – Robustness, in both frame construction and controls design, is a must for folding carton production. “Beefed-up” label presses simply do not cut the mustard, despite their attractive price tags and manufacturer’s claims to the contrary.
2. Features that lend the press to fast makeready – The more time the press spends producing the better. This basic truth is sometimes ignored by manufacturers trying to peddle cheap equipment. One would be surprised how expensive that cheap machinery gets in the long run, when it spends an inordinate amount of it’s life in makeready instead of production.
3. A sound converting section – Without the ability to diecut, strip waste and deliver cartons, a press’ value is greatly diminished. This is another area that many pressbuilders and converters have long ignored for the sake of an inexpensive machine, only to discover that they are not much better off for want of the ability to properly finish the carton in a single pass.
4. Training and support – Even the finest race car won’t win at Indianapolis without a competent driver. Press buyers should ask pointed questions about the levels of initial training and on-going support provided by manufacturers, and be willing to pay a premium for these services. Manufacturers, also, need to be aware of operators who exhibit any unwillingness to embrace new technology and report this to the customer’s management, before a bad attitude or two submarines the entire new press project.

Historically high levels of print quality, combined with economic efficiencies and productivity gains make inline webfed flexography the logical choice for carton converters wrestling with the demands of today’s market. While many carton companies have adopted a “hunker down” mentality in recent years, those who have made the bold choice to step away from the herd and invest in this technology have enjoyed much better operating results in spite of the harsh economic climate.