Thermal transfer technology: Ideal coding solution for film packaging

Product coding is a common process that is now generally accepted and was initially applied at food factories and pharmaceutical plants to mark expiration dates. Today, as part of the manufacturing process, products from all industries need to be coded. In addition to the expiration date, the product is usually marked with a lot number, real-time date, bar code, and various other information. This allows manufacturers to track product as needed, and provide protection when the product is recalled on a large scale. It also enables consumers to sell. Get some protection. Coding is an important part of all quality systems, whether it be "6 Sigma" or another Total Quality Management (TQM) system.

Traditionally, the most commonly used technique for film packaging coding is to mechanically apply ink or to digitally print code. Such technologies include: First, letterpress technology uses fonts on script holders to create images. The image is mechanically embossed or rolled onto the film surface. Common letterpress printing techniques include hot stamping, wet ink, and one-touch ink marking machines. Second, the continuous inkjet printing system (CIJ) through the print head inkjet, print a variety of data in the primary packaging and paper box, including a simple date code, logo, bar code and serial number. Third, thermal transfer coder uses a digital print head to print a variety of information on the film packaging, such as the date, batch number, production line information, bar code and real-time data.

Although each of these methods has advantages, thermal transfer technology is the world's preferred thin-film printing technology, which is based on its consistent coding effect, ability to print real-time data, and the cleanliness and reliability of operation. .

Thermal transfer printing technology

The main components of thermal transfer printers are print heads, print ribbons and controllers. Printheads typically contain 8-12 dots per millimeter or 200-300 dots per inch (DPI). These dots can be quickly and continuously switched to transfer ink from ribbon to film to print images. Thanks to digital means, the coder can print in real time and change batch number and date information very quickly for batch and continuous packaging.

On an intermittent packaging line, the print head carriage moves on the packaging film while the film is at rest. The stepping rate of the printhead carriage motor is directly related to the linear motion of the carriage, and the length of time that the dots are energized is determined based on the linear velocity.

On continuous packaging lines, images are printed as the packaging film moves. The length of time the dots are energized is determined based on the ribbon speed, which is controlled by the data provided by the high speed synchronizer. The control box determines which points will be energized and when. The printed characters can then be part of the design text or graphics or logo. The entire process takes less than a fraction of a second, allowing the printer to print up to 250 letters (or 500 mm) per second.

Technical Overview

When considering the coding equipment for the packaging line, the user must fully consider the maintenance issues, reliability, and the downtime required for converting products, ribbons, shifts, and print content. Shown are the cost and quality comparisons of several coding technologies that are currently popular on the market. Quality operating costs include downtime due to maintenance, coding, and ribbon replacement.

The purchase prices for hot-coded, wet-ink, and one-touch ink-jet printers are low, but such machines can be expensive to run. Some of the disadvantages of this type of technology are: increased cost of metal particles due to loss and wear; letterpress printing technology fails to achieve real-time coding; characters fall into the packaging or fall to the ground; easy to occur when replacing coded content Human errors and hot characters are more difficult to manipulate; character particles may be subject to uneven wear, resulting in poor coding quality and breakdown of the packaging film; the format of the printed content is limited by the font holder; the thermal printing ribbon may be expensive, and the ink Dirty, not easy to clean; requires warm-up at startup.

A continuous inkjet printer (CIJ) determines the pattern by a computer and forms an image by spattering or guiding ink droplets. Although CIJ can print at high speeds on plastics and other packaging materials, it is generally not suitable for use on film packaging: CIJ uses liquid inks. The inks often contain solvents that are volatile and toxic; the inks need to be blended with solvents during operation and used more. Many solvents are used for cleaning, resulting in dirt, machine downtime, and production loss; liquid inks can seep into the substrate, and at the line speed, they may not dry quickly, resulting in smearing, smudging, and other problems; CIJ needs reinforcement Supervise and maintain to ensure consistent print quality and prevent ink blockage; CIJ print content format can only be in the same direction as the film; traditionally the equipment costs more.

Advantages of thermal transfer printing on film products

Thermal transfer printing has many practical benefits. With digital printing technology such as thermal transfer, it is possible to automatically change the code without downtime or human error, thereby maintaining a high level of production capacity. From the first code to the last code, thermal transfer maintains consistent print quality and prints letters, numbers, graphics, and bar codes with a high degree of clarity. Thermal transfer also eliminates the risk of punch-through. Compared with traditional letterpress printing and CIJ technology, the operator needs fewer interventions, which will help increase productivity and reduce waste. (peter)

Source: United States Marken Shanghai Representative Office