Synrad CO2 Laser Welds Polyethylene Film

Synrad's sealed CO2 lasers are used in a variety of industrial processes including cutting, welding, drilling and marking. Because CO2 lasers have very consistent output power and the heating process is always non-contact, laser-formed seals will remain consistent over hours of operation. For this particular application, which required sealing 0.05mm-thick polyethylene film, a Synrad 50W laser was used in conjunction with an XY table and a cutting head outfitted with a 63.5mm focal length lens.

This lens typically provides a 0.1mm focused spot size; however, for laser sealing operations, a larger spot size is often preferred. A larger spot size yields lower overall power density and leads to increased melting and less vaporisation of thin films. It also increases the weld line width, providing better weld strength.

For these reasons, the lens was unfocused slightly by increasing the standoff distance to around 5mm between the surface of the film and the tip of the cutting head, to obtain a 0.5mm-wide weld line on the plastic film. The cutting head traversed two layers of the film at a speed of 12.7m/min to produce the final finished seal. The resulting seal is consistent in strength across its entire length.