Figure 1. This clear polyester film was cut using 50W of laser power.

Figure 2. An FH Marking Head and 60W laser was used to cut small parts from the polyester film.

Whether produced in the form of a fiber, film or plastic, polyester or polyethylene terephthalate (PET) is increasingly found in various products including clothing, beverage bottles, photographic-quality printing film, and food grade packaging, to name just a few examples.

In particular, PETF – a semi-crystalline polyester film – has a variety of uses depending on its thickness, which is measured in mils (1 mil = 0.001 inch). Thin gauge, 1.5 mil material, is flexible enough to serve as a protective coating when laminated over products while thicker gauge films are specified depending on a product’s desired rigidity. In some cases, a polyethylene layer is added to create a polyester/polyethylene laminate.

In our first application (Figure 1), large sheets of 7-mil clear polyester film were cut on an XY table. Our cutting setup consisted of a 50 W Synrad sealed CO₂ laser with the beam delivered through a 2.5” focusing optic, which provided a 0.004” (100 micron) beam diameter with a 0.07” (1.8 mm) depth of focus. We used air, at a pressure of 5 PSI, as an assist gas. This setup allowed us to cut the polyester film at line speeds of 2000 inches per minute (IPM). The cut edge was clean and burr-free; however, because PETF exhibits exceptional clarity, cut edges sometimes appear “cloudy” due to the deposition of vaporized residue. If this occurs, careful adjustment of fume extraction or the use of secondary cleaning procedures easily eliminates this issue.

The second application (Figure 2) shown here involves cutting small parts from sheets of 7-mil PETF using an FH Series marking head. The marking head was fitted with a 125 mm focusing lens (0.007” / 180 micron spot) and aligned to a 60 W Synrad CO₂ laser. Although the part shape could have been imported into WinMark Pro as a CAD drawing, this object was created entirely in WinMark using WinMark Pro’s new capability to draw elliptical objects. At a power level of 60 W and a velocity of 30 inches per second (1800 IPM), parts were cut out at the rate of one every 0.17 seconds.