Laser Coding on Printed Metallic Foil Labels
In many packaging applications, the combination of a preprinted label and laser marking is a perfect fit. In addition to the base label color, the images on a label can include several spot colors or even a four-color process print for realistic full-color graphics. Laser marking adds the ability to add customized information including date codes or lot numbers on-the-fly at the time of actual product packaging.
A case in point is this packaging for processed meats, which consists of a self-adhesive gold foil label that is overprinted with both spot and process color. At the time the product is packaged and sealed, the manufacturer is required to mark a date code on the package. The CO2 laser makes a perfect non-contact marking tool and ablates the ink away from the gold foil, leaving an impressive gold-colored mark that matches the packaging perfectly.
To create the mark, we set up a Synrad 48-2 (25 W) laser with an FH Flyer marking head with a 370 mm lens that provides a 540-micron (0.021") spot with a 20 mm (0.788") depth of focus over the extents of a 241 mm x 297 mm (9.5" x 11.7") mark field. In our WinMark Pro laser marking software, we created an eight-character date code using the European Standard (DD.MM.YY) format. Using WinMark Pro's automated Date Code Text property forces WinMark Pro to read the computer's internal date/time clock prior to each mark so the date is always accurate. When FH Flyer is operated in stand-alone mode, Flyer's real-time clock accurately keeps track of date and time parameters, even when power to the head is cycled off.
The date code text measures 3.18 mm (0.125") tall with 0.46 mm (0.018") of Extra Character Spacing and was created using European, one of WinMark Pro's twelve built-in stroke fonts. We then set a Power, duty cycle percentage, equivalent to 25 watts and set a marking Velocity of 635 millimeters per second (25 inches/second). At these parameters, we cleanly ablated the ink away from the gold label in a cycle time of 0.13 seconds per label.
Using 25 watts of power, we ablated the ink on this printed label to reveal the gold under-layer.