Laser welding of plastic film

The packaging sector has numerous applications for CO2 laser. There is nothing surprising there since the materials best suited for packaging are also the ones, due to both composition and shape, that work best with CO2 laser technology.

In previous articles, we have already seen some of the CO2 laser applications on materials such as thermoplastic film, wood and some of its by-products like MDF and paper and cardboard for innovative forms of packaging. The distinctive wavelength of CO2 laser makes cutting, perforation, incision and marking particularly efficient and cost effective.

Laser welding plastic film in a factory

CO2 laser is an efficient and versatile tool for the laser welding of thermoplastics, a popular technique used in the packaging sector. This process takes advantage of the fact that thermoplastics are easy to work with once they’ve been through a thermic treatment. In layman’s terms, the welding process consists of heating the area where the two thermoplastic pieces join with the laser beam until fusion point is reached.

This process can be applied to different types of plastics, either laminated or molded, opaque or transparent. There are many advantages to laser welding:

  • it’s a very fast process
  • like all laser processes, it’s extremely precise and easy to control
  • it doesn’t leave residue or waste
  • it doesn’t expose pieces to thermal or mechanical stress because the heated area is localised and the process isn’t mechanical
  • it’s highly automatable and easy to integrate with other systems, whether they be digital or analog

These characteristics have made it a tool of choice in sectors where precision, cleanliness and the absence of thermal or mechanical stress are determining factors. The production of biomedical devices or electronic devices, the production of parts and components for the automotive industry, the production of airtight packaging for the pharmaceutical and food industry are all examples of the applications of laser welding.

Laser welding for plastic film

In the world of packaging, laser welding is most used on laminated thermoplastics. The laser of choice for this technique is the CO2 laser.

Direct welding is the type of welding that works best with thin materials. As opposed to transmission laser welding used mainly for three-dimensional and moulded pieces, direct welding operates directly on the material. This process allows for a higher speed of productionand therefore increases productivity while lowering production costs.

The materials most used in the packaging industry are:

  • nylon
  • polyethylene
  • polypropylene
  • PMMA

The interaction between the laser beam and the material cannot be predetermined. Many factors come into play: the type of polymer, the existence of added additives to the formula, the laser beam’s speed of movement on the surface and the laser beam’s intensity itself. But as a general rule, the laser’s effect is stronger on the material’s surface and decreases the deeper it gets. Adding carbon to thermoplastics can highly increase the material’s capacity for energy absorption, thus making the laser much more efficient.

Laser welding plastic film in rolls

Laser welding is perfect for the production of original packaging that brings added value to the product because it can work in a very localised way on complex shapes.

Equipment for laser welding of plastic film

A laser system for laser welding needs different components. The fundamental ones are a laser source, a scanning head and a software system to program and control the process.

Apart from the afore-mentioned items, a laser welding system should also include devices for product management, loading and unloading, and powering the laser source.

Laser welding plastic film in a packaging plant

In conclusion, laser welding applications are numerous since laser technology is so versatile. It can be adapted to completely digital processes or be integrated with analog production lines. This technology greatly lowers production costs and not only increases productivity but also the quality of the product.