UV Laser Marking for Plastic Parts

From airplane cockpits to ID cards, laser marking and engraving can be applied to a variety of products for a range of uses. Plastics Decorating sat down with Faycal Benayad-Cherif, business manager for FOBA Laser, to discuss how laser marking/engraving works, as well as issues such as the best application for use and selecting the best laser for a given application.

Explain the laser marking/engraving process on plastic parts.

Plastic parts are laser marked through a process called foaming. As the plastic is exposed to the laser beam, it creates a molten area that turns into a foam of microcavities that either capture or reflect light. Unfortunately, not all polymer materials react with a color contrast when laser marked. Depending on the characteristics of the material, the resulting effect can be lighter, darker or no mark at all. A common technique to overcome this limitation is the addition of additives or dies to the material. Additives act as a catalyst to create a contrasted reaction of the laser on the plastic.

How are lasers best used for marking 3D plastic parts or products?

Since their conception, laser markers have been designed to provide the best mark on flat surfaces. The reality is that most marked surfaces are not flat. Luckily, lasers have a “depth of focus” or range of focus that allows them to mark on curved surfaces, for as much as the curvature does not exceed a few millimeters. The range is limited but covers many marking applications. Take the example of the steering wheel control module with its multi-shape buttons. Even though the surfaces are angled and curved, lasers have enough depth of focus to create a good mark.

If the mark area is significantly curved (more than a few mm), the use of an optical focus shifter or third axis is required. A focus shifter is an opto-mechanical device that displaces the focus of the laser, allowing it to follow the object’s shape. A third option consists of mounting the part on a multiaxial gantry that reorients the part as the laser is engraving. This