Laser Coding for PET Bottles – Which Wavelength?

CO2 lasers are often used for adding variable information, such as date and lot codes to packaging materials. Most CO2 lasers that are sold for these applications produce a beam of light with a wavelength 10.6 µm, which works well on a wide range of materials.

When dealing with products made of Polyethylene Terephthalate (PET), such as bottles for bottled water, there are some special issues that need to be taken into account. The mark that is produced by the standard 10.6-µm lasers is quite low in contrast, which can be difficult to read. Some producers, looking for a discreet mark, are fine with this. The codes printed with 10.6 µm lasers can meet this need perfectly. Others look more a mark that is easier to see and to read, however.

Another factor that has to be considered is the fact that the walls of the bottles have gotten to be much thinner in recent years, as bottled water producers strive to reduce the amount of plastic in their packaging. This can make the bottles difficult to handle on the packaging line and also if the laser coder engraves to deeply, there is a chance of producing a leak in the bottle. Not a good situation.

Our line of Macsa laser coders has a solution for these problems.

The K-Series and SPA lasers can be supplied with a special light output, specifically for PET applications. Rather than emit light with a wavelength of 10.6-µm have a wavelength of 9.3.µm. While this doesn’t seem to be a huge difference, the results on PET substrates are very noticeable.

The 10.6-µm laser creates the mark by malting the surface of the material, creating a narrow transparent image. On the other hand, the 9.3-µm laser “foams” the surface of the PET, leaving a mark with a frosted white (higher contrast) image, that is easier to see and read. The beam from the laser does not have to cut deeply into the PET for this reaction to take place – reducing the possibility of causing leaking or weakened bottles.

Further, the 9.3-µm laser requires less energy to create the mark, allowing the laser to work faster. This is particularly important when printing codes on bottles on very high seed bottling lines.

Is it Essential to Use a 9.3µm Laser for PET?

While 9.3µm lasers often have advantages when coding PET bottles, there are often applications where 10.6µm. This can be where the bottler wants a more descrete mark, on lower volume lines and also when cost is an issue. Because 9.3µm lasers are made in lower quantities and use a specialized laser source,  they do cost a little more than the 10.6µm lasers.

Which is the Best Laser to Use?

For many laser coding jobs, there is no question that the best laser to use is the SPA (Scaleable Product Architecture) laser from Macsa. This is the latest generation of laser coding system that brings some unique benefits.

• Speed – SPA has a dual processor setup that has one core talking care f the laser control and the second managing the data. This ensures that the system is always running at peak efficiency.
• Reverse Airflow (RAF) – dirt and dust are the enemies of lasers. Most laser use ambient air for cooling, but RAF ensures that cooling air never comes into contact with the electronc or scan head of the laser. This reduces the need for maintenance and keeps the print quality at high levels for longer than convention lasers.

How to Get Started?

There are many technologies for printing date/lot codes onto your packaging.  We can help you every step of the way with deciding which is best for your particular application. To get started, contact us today at 888-438-3242 Option#3. You can also email me at David.Holliday@ProMachBuilt.com. We’ll be sure to get you in touch with an expert, right in your area!