Making the right laser marking choice

As manufacturing grows in speed and production size and traceability requirements increase, the need for efficient, precise, and nondamaging laser marking is more pressing than ever. Although the marking methods of laser engraving and laser etching sound like similar processes, they are different in speed, design, and application.

Laser engraving uses a pointed laser beam to hit a target and heat it until its vaporization point. Vaporizing the target disintegrates the material and leaves behind a carved-out area. Depending on the laser and the target, the engraving could be deep or shallow. Some of the carved-out areas create designs like 2D codes, text, bar codes, or numbers. Other carved-out areas make room for analyzing the inner workings of a product or cleaning out contaminants.

Laser etching is similar to engraving in that it uses a pointed laser beam to hit a target. Instead of vaporizing the target, however, laser etching heats it only to the melting point. When the targeted material reaches its melting point, it becomes malleable and sits atop the original material. The malleable material is sometimes manipulated into a textured, raised design like a bar code, or it’s made for surface processing.

Whether you choose laser etching or laser engraving, you’ll be using a laser marking machine for the process. It offers varied speed, power, and pulse frequencies that you can manipulate depending on which process you choose. You also can pick which type of laser is best for your application.

A fiber laser is an infrared laser with a 1,090-nm wavelength. It uses intense heat to engrave or etch, so it’s best for use on metals and materials that are not heat-sensitive.

A UV laser has a 355-nm wavelength and an incredibly high absorption rate. This means that the laser can mark even materials that have high melting points, like glass or metal, without using high power. Additionally, since the absorption rate is so high, the laser does not damage the material.

A CO2 laser engraves products by burning. This is a good choice for shallow engraving into sensitive or heat-resistant materials like glass, wood, cardboard, paper, and synthetic rubber.

All laser markers can engrave, and some can etch, but there is more to consider than just whether a laser can achieve the task. Regardless of the type of laser marker you choose, programming it correctly for the task at hand requires an understanding of the critical differences between etching and engraving.

Speed. Etching and engraving differ in marking speed because of the heat processes they each use. When etching, a laser only has to reach the target material’s melting point. But when engraving, the laser has to get to a material's vaporization point. Since the melting point comes before the vaporization point naturally, etching is a faster process.

Because of its speed, you might select etching over engraving for a large production project that has to be completed quickly. But be careful about choosing speed over other priorities. For example, for specific medical devices, etching is prohibited because the marks can collect contaminants.

Design. Etching and engraving produce different designs because of how the laser processes the material.

When a material melts during etching, it becomes malleable and gains height—kind of like watercolor paint on a piece of paper. When the paint is dry on the paper, it lays flat, but when the paint gets wet, it spreads out and changes color. When etching, the heat makes the material like wet paint, sitting on top of the original material. With the raised mark, light refracts and displays white, black, or gray depending on the reflectivity.

Because engraving uses heat absorption instead of melting, the material is removed instead of inflated. That removal of material leaves a shallow or deep mark.

Applications. The decision to use laser etching or laser engraving can be based on style or speed, but factors like industry and processing also come into play.

Engraving completely vaporizes material, so it’s good for surface cleaning applications. Laser engraving offers a pointed way to eliminate extra material, as opposed to manually scraping out contaminants like rust, dust, or oil—a tedious process that can compromise the product.

Etching creates raised marks and melts materials. Because it doesn’t get rid of the material, using etching for cleaning is not effective. Instead, remolding products through etching is effective because it makes the material malleable.

Also, etching is a good choice for use on the thick pipes employed in the oil industry. Melting the surface will not damage the effectiveness of those pipes as a whole, so etching is the more efficient choice and involves no drawbacks.

With laser marking, there is no one-size-fits-all choice. Understanding and applying the differences between laser etching and laser engraving to your manufacturing goals can help you make the right selection.