Application of laser processing in modern flexible packaging

Frank Wagner, a director at MLT, discusses the changing market for customized applications with filmic substrates. Laser technology is predicted to become increasingly important in the packaging industry
 
The original concept for this form of laser processing was for micro perforating cigarette tipping materials to create the cool draw concept. This remains a current market, but over the past 10 years or so, technology and machine development has also focused on other industrial processes such as perforation, scribing/scoring, and marking applications that are already in use and continuous demand worldwide, particularly in the area of flexible packaging.
 
Customers require turn-key, tailor-made solutions for their packaging needs, not only in relation to the laser process and machine configuration, but also with technical and specialist advice regarding the necessary extraction and filter system, which is a very important topic in the food and hygiene market.

 
At MLT, we offer customized laser solutions based on all key components both offline, at the film producing and converting process, and online, on the packaging machines.
 
Using a unique high speed rotating polygonal mirror it is possible to deliver maximum laser power for perforating applications across a web of material using only one laser.
 
The speed of the mirror and subsequent focus of the laser is set according to web speed, so that the holes are round, not elongated. A computer program also allows the holes to be positioned in register to the printed material.
 
Micro-perforation
Web material Laser Perforation Systems can also be used to create micro holes for Modified Atmosphere Packaging (MAP). This is especially applicable for flexo or gravure printed film materials, and is a solution commonly used for the packaging of fresh and perishable goods such as vegetables, lettuce, or herbs.
 
MAP of fresh food produce requires a completely different approach by the packaging industry, which is used to developing packaging with barrier properties that are designed to exclude atmospheric oxygen, and prevent migration of any component within the package to the outer surface of the packaging material.
 
Fresh produce, such a salads, fruits and vegetables are to some extent alive for a specific shelf life of the product, and therefore technically still require oxygen for their metabolism. Conventional flexible packaging, with regular barrier properties, has proved to be unsuitable in most cases. An alternative type of packaging is required, whose gas transmission properties are precisely matched to the gas out requirements of the product.
 
As the industry for freshly supplied produce has grown larger and more sophisticated, so have the requirements from the packaging.
 
Films with holes or pores admit oxygen (O2) and carbon dioxide (CO2) at similar rates. Therefore, the ratios of gases that can occur inside these packages are limited. It is impossible to achieve low O2 (one to five percent) without accumulating high CO2 (15-20 percent). These films are therefore applicable only for those products that tolerate high CO2, without experiencing premature decay.
 
Micro-perforated films offer the possibility to tailor the Oxygen Transfer Rate (OTR) to suit the produce to be packaged. The holes are typically from 50 microns in diameter, and can be spaced at the required pitch. Perforating speeds up to 400 m/min are possible, with our own unique MLT optical multiplexing technology used in MAP applications.
 
Laser scanning
So called scanning laser systems can run at high speeds, if compared with punching/die-cutting systems, producing ‘macro holes’ as a simple package airing system, for example Flow-Wrap of trays or pop out windows.
 
This type of scanner technology enables film processing at web speeds of up to 200 m/min. MLT Laser Scribing/Scoring systems can process all established mono and multilayer film combinations, offering both an offline solution for the film slitter/rewinder process, or an online solution during the actual packaging process. This enables defined material/film weakening in a specific location of the final package.
 
Typical examples are the Easy Opening solutions for instant products, such as coffee, soups, and pet food, which increasingly prefer the package to be opened without a tool or tear strip. More complex opening functions for convenience food applications, such as the defined/timed opening of microwave packaging during heating, are still to be properly established in the market.
 
In order to achieve an Easy Opening feature, materials can be processed in Machine Direction (MD), Cross Direction (CD), or in all variations of Free-Form contour scribing.
 
Laser Scoring/Scribing can also be implemented to create paperboard container fold lines, and the selected weakening of materials can be adjusted with a high level of precision, ensuring the barrier properties are not damaged during the scribing process.
 
Laser marking/security systems
Laser marking systems are also used as solutions for product safety and anticounterfeiting. Web materials, and other substrates with smooth surfaces, can be marked either on-the-fly or in the interrupted-cycle process, which enables the application of labels, security marks, barcodes and number combinations. A classic example is the safety code marking of cigarette packets.
 
In addition to applications in the packaging and food producing industries, MLT and other manufacturers attract interest from diverse markets where the demand for quality and product safety has increased to a point where only laser technology offers a solution.
 
An integral part of the work in packaging is the constant development and customization of the systems according to the customer’s wishes and needs.
 
Our specialists have many years of experience in Micro Laser Processing and Laser Technology, and through the company’s maxim of ‘Laser Excellence’, actively gather and increase the in-depth knowledge and experience to help develop the capability of modern laser processing machinery.
 
Like most companies, we are aware that we need to follow the market trends closely.
 
Laser technology is predicted to become increasingly important in the packaging industry, integrating the higher level of efficiency of fiber lasers, as well as providing integration systems for online quality control. By building a reputation as an innovator in the flexible web converting and food packaging industry, and manufacturer of tailor-made laser processing systems, we have been able to supply customized solutions to prominent flexible packaging producers throughout the world.