Choosing Between CO2 and Laser Coding

By George Allen, Strategic Account Manager at Markem-Imaje

Codes on containers are often regarded as necessary evils but, in truth, they are significant components that provide product tracking and safety information.

Beverage coding is particularly challenging since the industrial environment has a variety of containers to code across many stock keeping units (SKUs), often with high speed lines, along with an ever tightening regulatory and compliance framework which demands traceability and fiscal marking.

At the consumer unit level, such as cans and bottles, continuous inkjet (CIJ) and laser are the main methods used for coding. Multiple factors are considered when determining what type of coding and marking equipment is best suited for a product. There is a balance that must be juggled to ensure that the chosen equipment addresses the following elements:

• Packaging material (paperboard, PET, HDPE, aluminum cans, glass, etc.);
• Production speeds;
• Product handling;
• Line automation (or lack thereof); and
• Line location for coding and marking equipment.

Further to the above is the battle over capital funding. How much can be spent? What is the total cost of the initial investment versus ongoing running costs?

CIJ is very popular as it can print easily and at extremely high speeds virtually anywhere onto a surface, though care must be taken to ensure the ink chosen will adhere to the packaging surface for the desired duration of the product’s life in the market. However, where conditions permit, there is a shift away from CIJ towards laser.

Although lasers are more expensive to buy compared with CIJ coders, they reduce operating expenses. Apart from occasional filter replacement, there is no maintenance and there are no ongoing consumable purchases. The installation time varies depending on the application and production line, but it is usually completed in days.

Also, laser codes tend to be crisper and their permanence aids in anti-diversion and anti-counterfeiting efforts. Indeed, this has led to laser’s considerably large coding market share in high growth markets, such as China, where there are often concerns about whether a product is genuine.

In this article we explore which laser best suits a given production requirement.

CO₂ lasers

CO₂ lasers are primarily used on PET bottles and paperboard materials. The wavelength is always tailored to meet the application. The wavelength for a laser coding onto a PET bottle at 1,000 bottles per minute is different from that used on a 12-pack of soda in a paperboard carton running at 200 bottles per minute.

There are a variety of other factors that must be tested and reviewed before deciding on a CO₂ laser application. How deep is the penetration of the laser onto a PET container? Where on a PET container should the laser code be placed (shoulder, top, etc.)? Does the material allow any contrast after the laser code is complete?

Lasers are available in different wattages. The degree of power is determined by the size of the code, code content, density of the material, and other factors. A pre-test will help determine the best application for the job.

CO₂ lasers do not require complex guarding packages. Manufacturers place a polycarbonate shield around the area where the material is lased to provide protection. The beam emitted from a CO₂ laser is generally absorbed by polycarbonate after contact, which prohibits any type of serious injury.

CO₂ lasers are usually small enough to be positioned in the following areas:

• On high-speed production lines;
• Inside blow molders;
• Inside labelers; and
• Inside high-speed cartoners.

Some of the above applications require lasers to be installed in tight confines, which often means installing a beam delivery system. This beam delivery system can be designed and customized with different tube lengths to allow the beam to be delivered in hard-to-reach areas. There are generally no speed issues as today’s galvos (mirrors) move at high speeds to match the laser delivery.

Fiber lasers on beverage cans

Fiber laser coders are a relatively new product in the beverage industry. The ability to concentrate a highly intense beam of energy and focus it onto a beverage can is a highly technical and coveted science. While multiple companies offer fiber laser technology, beverage companies require a solution that includes the following:

• Ability to code cans on extremely fast lines;
• Fume extraction;
• Cooling;
• Customized guarding; and
• High-speed cameras, lighting, and sensors to validate code integrity.

Very few companies offer fiber lasers suitable for the ultra-high production speeds required by beverage can coding. These speeds can be up to 2,000 cans per minute (CPM). Beverage codes on cans are generally two lines with approximately 16 to 24 characters per line. They are also typically 2-3 mm in height. A fiber laser has a small window to place its code at these high speeds. The amount of time needed is code specific but is generally in the 25-millisecond range.

Product handling is paramount to successfully coding cans with a fiber laser at these speeds. Cans that are bouncing, banging into each other, or not properly indexed can be coded, but those codes may have defects making them unreadable. A smooth, consistent flow of cans will help ensure a repeatable and high-quality code.

The capital costs for fiber are greater than CO₂ lasers, varying depending on wattage, guarding, and customization required. All fiber lasers require a guarding package that protects the operators so that no limb can be inserted, and to eliminate any possible beam escape. The guarding must be interlocked for safety with weep holes to allow water or line lube to escape, but also designed to let an operator clean the laser head or adjust the height to accommodate a can height change.

Fiber lasers are available in different watts, like CO₂ lasers. The wattage is determined by several factors: line speed, material, code size, etc. Testing is recommended to specify the correct laser.
Laser technology is a clean option in the beverage industry, with an excellent return on investment. However, understanding which laser and the components required is vital when trying to match this industry’s high speeds and complex lines to the correct laser.

About the Author

George Allen is the strategic account manager at Markem-Imaje, responsible for multiple beverage customers.  He has been in the packaging industry for over 30 years and specializes in creating solutions for manufacturers with high-speed production lines that need laser technology, print and apply applications, CIJ printing, or networking solutions.