Printing on PET Film: Lot Codes, Barcodes, and Other Product Information

Polyethylene terephthalate film (PET film) is one of the most popular plastic packaging materials on the market today. Valued for its durability, strength, and lightweight properties, PET film, bags, and pouches are ideal for numerous packaging applications, including:

Thanks to PET’s resistance against tears, punctures, chemicals, and moisture, PET packaging keeps products fresh and safe for significant periods of time. 

In addition to its strong packaging qualities, PET film provides a great surface for high-quality codes and images. Markings such as lot codes, date codes, and barcodes are frequently required to appear on product packaging due to distributor policies, internal best practices, and regulatory policies. To create these markings, most operations utilize inkjet printers due to their substrate-compatible inks, reliable results, and fast coding speeds.

In this blog, we explore the topic of printing on PET film by focusing on three key elements:

  1. Choosing the right printer for your needs
  2. Selecting the ideal ink formula
  3. Implementing the appropriate line accommodations

By successfully considering these factors, you can create an efficient PET printing workflow that delivers consistently excellent results. 

Choosing the Right Printer for Your Needs

Most PET film printing applications are performed with either thermal inkjet (TIJ) printers or thermal transfer overprinters (TTO). 

TIJ printers like the Anser X1 and Anser A1 are compact machines that can create high-quality markings at moderate-to-high speeds. The Anser X1, for example, can create codes at resolutions as high as 600 DPI and print lower-resolution markings (60 DPI) at speeds up to 300m/min. Most TIJ printers also weigh around 5-10 pounds, which simplifies production line installation and enables users to mount units in different positions. 

TTO systems are larger than TIJ printers and operate much differently. While TIJ printers propel liquid ink droplets to create codes, TTO models apply heat to ink-covered ribbons to transfer a marking onto the substrate. TTO models excel at printing on flexible films, delivering stark codes, offering large-character marking options, and printing at very high speeds (750-1400 mm/s, depending on the model). At the same time, TTO models have higher operating costs than TIJ printers, require more maintenance, and offer less versatility regarding line orientation.

Some operations also use continuous inkjet (CIJ) printers to complete their PET film printing applications. CIJ printers like the DuraCode Touchscreen and DuraCode Pigment Printer offer marking speeds above 300 m/min, high environmental resistance, and the ability to operate 24/7 without interruption. These qualities make CIJ systems ideal for high-volume operations. 

CIJ printers are also capable of printing on the bottom of substrates due to their substantial ink throw distances. Neither TIJ printers nor TTO systems can mark film from a bottom-up orientation. Therefore, if you need to mark the bottom of the film, a CIJ printer is automatically your best choice. 

However, CIJ printers also pose certain challenges when printing on PET film. Compared to TIJ and TTO systems, CIJ printers are:

  • Larger and more difficult to position on PET packaging lines
  • More likely to spray ink across the film
  • Incapable of creating higher-quality codes and images

Due to these factors and others, a TIJ or TTO system will likely suit your operation better than a CIJ printer unless you need to print at an upward angle.

 

Thermal Inkjet

Thermal Transfer

Continuous Inkjet

Pros
  • Compact unit
  • Zero maintenance
  • Simple mounting
  • High-quality markings
  • Easy maintenance
  • Excellent code quality
  • High printing speeds
  • Larger codes
  • Fast coding speeds
  • Environmental fortifications
  • Uninterrupted operation
  • Capable of printing on PET film from a bottom-up angle

Cons
  • Code size restrictions
  • Significant maintenance requirements
  • Larger unit size
  • Larger unit size
  • Likely to spray ink 
  • Code quality restrictions

Selecting the Ideal Ink Formula

Proper ink selection is essential to the success of any printing application, including PET film coding. To ensure coding success, you must use an ink formula that is well-suited for your line setup and application requirements. Naturally, the first consideration is PET compatibility. 

TIJ and CIJ printers are often compatible with many different types of ink, so it is important to use a formula that can reliably adhere to PET film. Most PET packaging lines also move at fast speeds and process film through rollers and other equipment. To prevent codes from smearing as they filter through these components, use a quick-drying ink so that codes are set by the time they come in contact with potentially disruptive line modules. 

In addition to these qualities, you should consider any additional elements that you require for codes to appear clean and legible throughout the product life cycle. Examples include:

  • Preferred color for better visibility
  • Moisture resistance
  • Heat resistance
  • Chemical resistance

If you are using a TTO system, both wax/resin ribbons and resin-only ribbons are viable PET printing options. Generally speaking, wax/resin ribbons are more affordable than resin-only ribbons and deliver high-quality, smudge- and smear-resistant results. Resin-only ribbons create better-quality markings that are more durable than markings made with wax/resin ribbons. However, resin-only ribbons are designed for slower-speed applications and are more expensive than wax/resin ribbons. 

Implementing the Appropriate Line Accommodations

For reliable printing results, you need more than just the right combination of hardware and ink; you must also outfit your line with the necessary accommodations to ensure that codes are placed in the correct location and have a high-quality appearance. 

Production lines can be built in a variety of ways, so necessary accommodations change from one operation to the next. The most common accommodations include:

  • Photoelectric sensors that can reliably detect the registration mark
  • PLC measures that trigger the printer to mark the film at the correct time
  • Encoders to track any speed changes and boost print consistency
  • Custom brackets to neutralize vibrations and place the printhead at the optimal location

If you are unsure of which accommodations are right for your line, call InkJet, Inc. today to discuss which measures are appropriate for your needs. 

Printing on PET Film is Simple When You Work With an Expert

Because of its strength, flexibility, and versatility, PET film is used across industries to create reliable product packaging that catches the eye of consumers. A great choice to hold food, drugs, electronics, and other products, PET packaging can keep your goods safe and fresh for years on end.

No matter what type of industry you are involved in, if you use PET film to package products, InkJet, Inc. can help you outfit your packaging with required codes and other essential information. Offering a wide range of inkjet printers, laser coding systems, and ink formulas, the InkJet, Inc. team can develop a PET coding solution that is perfect for your unique applications. Call us today to discuss which approach will work best for you.

For more information about printing on PET film, contact InkJet, Inc. online or call 1(800) 280-3245.

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