Printers using flexography are, in the vast majority, converters of flexible substrates: films (in general), paper and foil. In order to provide their customers with value and to optimize profit, they have to cover as much of the conversion process as possible—and lamination is definitely one of the most consistent converting processes in terms of added value and, consequently, profit.
In the conversion process, lamination happens just after printing and, because of its very nature, involves multiple substrates. It is used to protect print, improve barrier and enhance mechanical characteristics of the compound. In every case, materials handled are expansive and the quality required for the end product is high.
There are a few adhesive-lamination technologies to evaluate. Some of those technologies allow for high performances of the final compound (mechanical resistance, thermal resistance, etc.), and some will feature very interesting characteristics—for instance, no emissions and very low energy consumption.
End Use of the Laminated Compound
Depending on the specific market a converter serves, customers may be interested in upgrading to laminating some products. How should a converter orient its investigation on how to approach the conversion of those products?
Focusing on the end use of the pouch (in particular) or of the laminated compound (in general) will influence a lot of the following steps, but primarily the lamination process that will best fit the specific application. There are numerous factors to be taken into consideration, such as:
- Nature of the goods to be packaged (e.g. sharp edges, fat-containing food and shelf life requirements)
- Potential thermal process involved (e.g. exposure to high temperature during product life, hot fill, retort, sterilization or pasteurization requirements)
- Chemical resistance (will the final laminated compound be exposed to specific chemicals during product life?)
- Economics or how the product will position itself in the converting market with all of the cost factors involved (general purpose lamination or specific targets?)
- Composition of the laminated compound (substrates to be laminated)
Almost every laminated compound will require such an analysis process at this level. Those factors will eventually influence the adhesive technology to be used and, consequently, the laminator design. The completion of this step will allow the proper approach to step two.
Completing step one will allow the converter to move on to selecting the appropriate adhesive-lamination technology for the specific application. It is mostly a chemical-influenced step; it is the adhesive performance that has to be taken into account and therefore the selected supplier should be the proper partner involved at the initial phase of this step.
There are a few families of adhesive technologies available, and the converter can be easily guided through this choice by professionals with the proper knowhow. A professional and knowledgeable partner will be of help and will ensure all aspects of the technology have been taken into account: dry bond processes, wet bond processes, solvent-free adhesive technology, thermoplastics, energy cured, just to name those most used currently.
Today, all of the best adhesive suppliers in North America are able to offer consultancy and test support on production scale laminators installed at their laboratories. This means the converter will not only be guided, but will also be able to see actual samples of the final compound before starting to select the laminator.
Lamination Machine Design
In step three, the key partner becomes the laminating machine manufacturer. This is the stage that will take care of the selection of the most appropriate machine design influenced by the specific adhesive technology identified in step two. The adhesive choice will definitely determine the machine setup at the coating stage. “Coating” is the phase of adhesive lamination that provides the deposition of the adhesive on the “coated” substrate.
The characteristics of the selected adhesive will influence the choice of the coating head technology. There are a few options, but adhesive selection is the main driver determining which to use. Adhesive selection will also dictate if a drying oven is required to run the process and, if it is, how much drying power, ultimately influencing performance.
Performance selection opens an important section of this chapter. Machine performance requirements are directly influenced by the adhesive of choice and the nature of the business the converter is interested in running. Whether a business is centered on short-to-medium runs or, alternatively, on long runs, will definitely have an impact on machine design. Speed and performance become more critical as the length of the run grows, while quick setup and quick job changeover are critical as the target length of the run shrinks.
The lamination machinery market offers two main families of products: one expressly designed for short and medium runs, and another for long runs. Investment is an important factor, of course, but is not the only one. When performance grows, so will the number of operators involved, the size of the equipment and the energy consumption. All of those factors will be properly analyzed and evaluated in collaboration with an OEM.
Through this point, the converter has been involved in what I will define as “high-level” decisions: decisions that are influencing all of the most important aspects of the “new” business. There are other decisions about machine design that a printer/converter is used to dealing with, sometimes entering into incredibly minute details. This may not be the case for the selection of a laminating machine.
Since the 1980s, a concept of turnkey machine design approach has been introduced, which offers converters all they need to run a specific application with few questions asked, once the key guidelines have been defined. This is particularly valuable when a machine is sold to a company with no experience in lamination. The point is to not put the decision maker into the position where he or she has to ask, “Have I ordered all of what I may need?” Lamination is a high-tech process; it can be made very easy if the proper ethics are used at the machine design and customer support levels.
If converters experienced in lamination are involved for specific high-tech applications instead, the collaboration between the converter and the OEM will definitely go into deeper levels of analysis and the final machine design, which remains the responsibility of the OEM, will experience a deeper involvement by both parties.