Inkjet Printing on PET Plastic Bottles

PET bottles are rarely the most ideal to print on, as bottles typically have narrow necks and lightweight sidewalls. These obstacles all influence where ink droplets land, and as bottles move at various speeds through the production process, the spacing between them can shift. An industrial inkjet printer for bottle coding must remain legible regardless of motion or geometry changes.

Environmental issues can also become an issue. Cold-fill operations can introduce condensation and dust from caps or corrugate that may settle on containers before printing. Vibration from guide rails can affect alignment. Their inkjet bottle coders have to take these conditions into account without compromising code clarity.

Differences in materials also introduce other challenges. Virgin PET provides a strong transparency, while rPET (recycled PET) may exhibit slight haze or a shift in color. Those differences can affect contrast when printing small characters or dense 2D codes.

Continuous inkjet printers for plastic bottles alleviate most of the challenges associated with printing on plastic bottles and containers, and they're typically most commonly used for printing text, such as expiration and packaging dates, as well as lot and date codes.

These printers are rather versatile, as they can use various types of ink, which additionally makes them suitable for printing on a wide variety of substrates. They're capable of producing clear and legible prints, ensuring readability and accuracy of the printed text or barcode.

They provide a non-contact printing method with plenty of customization and flexibility, which is great if your production line has to deliver small batches from time to time. CIJ printers are not only reliable, but they're also quite fast, with some models printing up to 500 meters of single-line text in as little as one minute. And they're quite easy and affordable to maintain.

Here are a few common applications using CIJ on plastic in the food, pharma, and cosmetics industries.

Continuous inkjet (CIJ) technology is widely adopted as an inkjet bottle coder because it prints without touching the container. A non-contact industrial inkjet printer for bottle lines can mark curved PET surfaces while products remain in motion.

The MK-G Series by KEYENCE works as an inkjet printer for plastic bottle production with integrated diagnostics that guide operators through routine maintenance and support remote monitoring to provide status checks without the operator having to return to the print location.

The MK-G Series platform also supports high-speed character output that exceeds 2,500 characters per second, which enables multiple lines of alphanumeric data and barcodes without needing to reduce production speeds. This allows an inkjet coder machine for plastic bottles to print information like manufacturing date and lot numbers in a single pass along the neck or shoulder region of the PET plastic bottle.

Ink selection plays a very central role in inkjet printing on plastic bottles. PET is smooth and non-porous, which influences how inks bleed and spread. If the ink is not formulated correctly for the surface, any printed marks can suffer from low contrast or smearing.

Dye-based inks are typically used for their rapid dry times, which benefits high-speed inkjet bottle coders. Pigment-based inks adhere to the surface and offer a strong resistance to fading, though they may require circulation to prevent pigments from settling. An inkjet coder for plastic bottles has to be able to manage viscosity and flow to maintain droplet size throughout long production runs.

On beverage lines, inkjet printing on plastic bottles often takes place immediately after filling or capping. Bottles move in close succession and, at times, the spacing between them may fluctuate. An inkjet printer for plastic bottle coding must preserve character definition at production speed. Common printed content for PET bottles includes: manufacturing dates, best-before dates, batch identifiers, and 2D barcodes. An inkjet bottle coder, like the MK-G Series, can print on the neck, shoulder, or base of the bottle, depending on the design. Since the process is non-contact, the printer doesn’t interfere with the motion or require the product to stop on the line.

Selecting an inkjet printer for plastic bottle production begins with the type of plastic and code size. PET and rPET may call for different ink characteristics to maintain contrast and durability. If barcodes are required, the industrial inkjet printer for bottle applications must maintain the utmost clarity regardless of operating speed.

An inkjet printer for plastic bottles also needs to be easily integrated with production lines, as the printer may need to synchronize with conveyor speeds rather than running through a stop-and-go labeling machine.

When these and other factors are addressed at the selection stage, inkjet printing on plastic bottle packaging remains consistent across long production runs while maintaining traceability and readability requirements.