This translucent polycarbonate sample exhibits a nicely contrasting mark using 10 watts at a speed of 20 inches per second.

Polycarbonate is commonly used to fabricate products such as bulletproof windows, automotive headlamp covers, CDs/DVDs, and housings for appliances, cell phones, and computers. Polycarbonate, as do most plastics, processes very well with CO₂ lasers because of its high absorptivity. As a general rule, marking polycarbonate provides engraved marks with some contrast, while multiple passes at higher powers exhibit a darker contrast. When marking transparent, opaque, or colored polycarbonates using laser powers less than 10 watts, it is possible to achieve a condition where the surface boils—then rapidly cools—leaving a white, raised mark that contrasts with the surrounding surface.

We obtained this type of contrasting mark on these polycarbonate filter cases using a Synrad 48 Series laser, FH Series marking head, and our WinMark Pro laser marking software. For this project, we created an eight-digit text object and set the Auto Text Type to Date Code Text. To generate the automatic date format, we created a custom date string using WinMark Pro’s format identifiers for a two-digit day, two-digit month, and four-digit year. Before each mark, WinMark Pro reads the system date and time, then generates the correct date (and/or time) information.

To create the mark, we specified an FH Series 125 mm lens that provides a 180-micron (0.007”) spot with a 3 mm (0.118“) depth of field. The ratio of character height (3 mm or 0.108”) to spot size (0.18 mm) is over twice the recommended ratio of 7:1, which allows the formation of sharp, crisp alphanumeric text. With mark power set to 10 watts and a mark Velocity of 508 mm/second (20 in/sec), we obtained cycle times of 0.09 seconds per part.