Flexible packaging is one of the most common and useful packaging materials on the market today. Commonly used to hold food items like cookies, chips, nuts, etc., flexible packaging protects products in a lightweight, cost-effective manner. When used as primary packaging, flexible materials also offer companies a way to appeal to shoppers, as the entire surface can be covered with eye-catching designs. These clear benefits have caused flexible packaging to become the second-largest segment in the U.S. packaging market, generating $31.8 billion in 2018 alone.
Despite the widespread use of flexible packaging, the material is not free from challenges, particularly when it comes to placing distributor-required markings and codes. Expiration dates, lot codes, and barcodes are all frequently required by distribution channels to ensure traceability, inform customers, and facilitate the vending process. Failure to place these markings in a legible, machine-scannable manner can result in wasted product and hefty fines from distributors.
Here’s are three key tips manufacturers can use to avoid printing defects in flexible packaging:
1. Use a Printer That Fits Your Line
Until recently, thermal transfer overprinters (TTO) were the go-to option for coding flexible packaging. The TTO printing process uses a thermal printhead and a thermal ribbon to apply a code to the substrate. Heat is applied to the ribbon, causing it to melt onto the substrate in a controlled manner, taking the form of the desired code.
Manufacturers choose TTO models as they were able to create sharp images at high speeds, on both intermittent and continuous lines. Additionally, the “ink” used by TTO can dry quickly, a valuable asset when the flexible packaging needs to be moved through rollers shortly after printing. However, there are some drawbacks to TTO that are being mitigated with other printer types.
The main issue is that if the ribbon breaks, no printing can be performed until there’s a replacement. This can cause production to come to an abrupt halt, costing you time and money. Another common issue is that TTO models do not perform well in the cold, as the ribbon cannot reach the optimal melting temperature.
Continuous inkjet (CIJ) printers are increasingly being used to print on flexible packaging as they do not face these same issues. CIJ printers are capable of high printing speeds similar to TTO models but can be refilled with ink while in operation and have a wider operating temperature range. Dry times vary depending on ink types used, such as food grade ink which usually has a longer dry time vs MEK based ink which has a quick dry time. On substrates being printed within a packaging machine, quick dry times are a must due to possible contact with rollers or guides after an image is placed on the substrate in use.
Thermal inkjet (TIJ) printers are another printer type whose use on flexible packaging has risen in recent years. However, TIJ printers are not a great match for the continuous line conditions that both TTO or CIJ excel with, but their compact size can make them ideal for fitting into the tight spaces of vertical form fill seal (VSSF) packing machines. It is worth noting that modern thermal inkjet printers are quickly closing the gap on the deficits of their predecessors.
Just as the printer you use is important, so is the ink you pair with that printer.
2. Use an Ink Formula That Matches Your Substrate
To print clear codes, you need an ink that will work well with the substrate you are using. Using an incompatible ink may lead to streaks, uneven transfers, and drying issues. Flexible packaging is a large category made up of various papers, plastics films, and foils. Consequently, some flexible packagings are porous while others are non-porous, and these two types will require different inks to be used.
Broadly speaking, water-based inks work well with porous substrates, while solvent-based inks work well with non-porous substrates. However, each ink formula also has certain characteristics that must be considered with the broader line setup (e.g., ink dry time, material surface temperature, environmental factors, etc.). Accordingly, it’s best to consult with an expert to find an ink type that will work best for your production line.
After getting the proper printer and ink for your operation, there are still a couple of things you need to keep in mind.
3. Achieve Proper Tension with Tension Control Technology
Flexible packaging film provides a great printing surface only if tension is properly held. However, if tension varies, codes will become distorted, eliminating scannability and greatly reducing legibility. Fortunately, companies can ensure that the film is at a proper tension level with a tension control system.
Tension control equipment is generally installed where the film unwinds. The system senses the tension in the web being unwound from the roll. Based on the tension level, the device controls the unwinding roll to maintain an ideal tension level. By maintaining ideal tension, operators can prevent printing defects in flexible packaging, thus prolonging uptime while printing perfect codes.
Tension control systems have few moving parts, so high-quality, well-installed equipment should work successfully for years with minimal maintenance.
Avoid Printing Defects in Flexible Packaging with the Proper Hardware and the Right Information
Printing on flexible packaging can be simple when you use the right products and have the right guidance. Most printing issues arise from using an incorrect combination of hardware and ink, which can be easily avoided when you consult with an expert.
The expert team here at InkJet, Inc. has been developing inks and offering printers for over 30 years. We have seen the evolution of production line technology and understand the unique challenges of modern manufacturing. When you work with us, we can help you find a printer and ink combination that will perfectly meet your needs and your production line’s specifications.
To learn more about how to avoid printing defects in flexible packaging, or for any other questions related to printers and ink, contact InkJet, Inc. today by dialing (800) 280-3245.