Technology options for coding on flexible film
Historically, mechanical approaches have been used to put codes onto packaging. And, while still popular, these technologies are expensive and inflexible. As a result, many manufacturers are switching to digital alternatives which are more cost-efficient and improve traceability.
Hot stamping is used in batch processes and applies the code with a metal stamp held in a heated block. The method has several drawbacks. The stamps are static and need to be changed before each new job. This is achieved by manually placing individual types into the printhead, a procedure that offers plenty of scope for human error. It cannot easily be used for printing variable information; this can only be done at a very basic level and is extremely time-consuming. Plus, as the film becomes thinner over time, there is an increasing risk that worn or broken stamps may perforate the film, potentially leading to high volumes of wastage.
Rotary coders are used in continuous processes. This technology is also highly susceptible to human error. In addition, the print fades over time. The rotary coder operates by picking up ink from a tray and transferring it to the product. As the ink in the roller runs low, the print quality is reduced, often to the point where it becomes hard to see. Additionally, it works on a fixed pitch, which means it can be difficult to apply the print accurately to the packaging.
Neither of these mechanical technologies can be used to print barcodes, ingredient lists and real-time information, as there is no flexibility in the print design. Also, substantial downtime is inevitable when changing the print. As manufacturing processes have evolved and productivity improved, these technologies have become increasingly inadequate.
Digital technologies have been developed that enable the printing of real-time data − such as dates and batch codes − onto the packaging. This makes it easier for manufacturers to fulfill their legal and retailer-defined obligations by producing clear, correct, legible codes.
The number of characters which can be handled by digital technologies is much greater than traditional methods. With digital, a full list of ingredients can be printed versus just one date and/or a batch number and new data can be uploaded at any time without stopping the production line. Thousands of codes can be kept in the memory, potentially leading to huge time savings while eliminating the risk for human error. With such detailed and easily updatable coding, manufacturers can better trace their products through the distribution chain, helping to minimize the effects of any product recall. With more complete – yet highly cost-effective – coding, the affected batches can be traced with high accuracy and the effects can be kept to an absolute minimum.
Coding technology tends to be integrated with the packaging machine and, in a digital system, codes can be printed with one of four different technologies: • Thermal Transfer Overprinting (TTO), a contact coding process which transfers ink from a ribbon to the material, using a thermal printhead • Continuous Inkjet (CIJ), which uses a nozzle to form characters on-the-fly using individual drops of ink • Thermal Inkjet (TIJ), which uses an array of nozzles that can be independently controlled to form characters using ink drops • Laser, which operates by removing a surface material to reveal the layer underneath, or by engraving the material, or by changing the color of the material by chemical reaction All these technologies have their strengths and weaknesses when it comes to speed, cost, print quality, flexibility and other factors. The challenge for manufacturers is to find the coding method and supplier partner best suited for the company’s requirements. Typically, companies seek to balance overall line efficiency, ease of use, coding error minimization and low cost of ownership.