Generally, CO2 lasers can directly mark stainless steel parts and create dark, high-contrast marks. These marks typically require power levels between 80–100 watts with scan speeds ranging from 25.4–63.5 millimeters per second (1–2.5 in/sec) depending on the focal length of the lens. In manufacturing situations where high production rates demand faster mark speeds, the use of powder coating, painting, or other proprietary coatings on stainless steel provides a double bonus. Coated parts can be marked at much higher scan speeds (resulting in lower cycle times) and laser power requirements can drop as low as 25 watts.

A recent application illustrates how coating selection affects laser requirements, mark quality, and customer satisfaction. We received two sets of stainless steel (S.S.) samples for evaluation. One set of components was powder-coated while the other set of S.S. parts were nickel-plated.

To process the powder-coated parts, our marking setup included a 25-watt laser, an FH Flyer marking head, and a version of our WinMark Pro laser marking software. The Flyer head was fitted with a 125 mm lens that provides a 180-micron (0.007”) focused spot with a 3 mm (0.118”) depth of focus. Using WinMark Pro, we created a 2D code object measuring 7.6 mm by 7.6 mm (0.30” x 0.30”) square that contains a 10-character part number. Larger codes are best marked with a raster-scanning technique, so we set WinMark’s 2D Barcode Bitmap property to Yes. On the Marking tab, we entered a Power level corresponding to 25 watts, a Velocity of 635 millimeters per second (25 in/sec), and a Resolution value of 300. Using these settings, we marked the powder-coated stainless steel parts in a cycle time of 0.8 seconds per part. The 2D code is easily scanned by a 2D reader and is as durable as the powder coating.

The polyethylene marking application shown here requires a three-line, 21-character product and expiration code. Using our WinMark Pro software, we created a text object using the European stroke font, set a Text Height of 4.8 mm (0.19"), and then added 0.2 mm (0.008") of Extra Character Spacing to enhance readability.

Our marking setup consisted of a Synrad sealed CO2 laser and FH Series marking head fitted with a 125 mm focusing lens. This lens provides a 180-micron (0.007") spot with a 3 mm (0.118") depth of focus. At a Power, duty cycle percentage, corresponding to 10 watts and a Velocity of 381 millimeters per second (15 inches/sec), we created this 21-character contrasting mark in a cycle time of 0.62 seconds per container.