Engraving or embossing visual content into machined parts provides a more permanent solution than finishing alternatives such as powder coating and silk screening. Typically, it’s text-based content, but it’s possible to include images such as logos. That said, it’s extremely rare in CNC machining. More often, designers use silk screen for images on sheet metal.
Comparing Machined Engraving and Embossing
Both engraving and embossing require subtracting material to reveal text or image. With engraving, you are milling metal or plastic to embed something below the general surface of your part. With embossing, you are cutting around a surface to create an elevated feature above the overall surface.
Adding Engraved Text to Your Parts
Essentially, CNC engraving, or part marking, is nothing more than a series of characters included in a 3D CAD file. A permanent alternative to ink stamping, it’s used to identify part numbers, revisions, assembly instructions, and other similar text-based information. To embed this content in your parts, our machinists use an engraving tool. Alternatively, they might use a small diameter end mill made exclusively for shallow depths of 0.005 in. (0.127mm) to 0.015 in. (0.381mm). Protolabs used this technique to create our BattleBots Giant Nut Replica trophy.
Recommended Engraving Practices for Machining
Of course, legibility is an important consideration when engraving. To a great extent, your part’s material determines your font size. Here’s a quick guide to help you determine font size:
Plastic and soft metals
Minimum width of 0.018 in. (0.457mm), depth of 0.0118 in. (0.3mm). Example text size: 16-point Arial Rounded MT font.
Minimum width of 0.033 in. (0.838mm) and depth of 0.0118 in. (0.3mm). Example text size: 22-point Arial Rounded MT font.
Machined Embossing: Raising the Bar
Embossed texts and logos are modeled into the part’s CAD file to get it ready for machining with end mills.
Embossments offer a striking visual effect, for example when a company logo needs to be incorporated into a design. Here’s a quick design tip: If your design’s text includes sharp or small internal corner radii, the process can easily become time consuming, and thus, costly. That’s something you’ll want to consider in your models. We suggest that corner radii on embossed features should be greater than 0.025 in. (0.635mm), with a maximum height of 0.250 (6.35mm).
Summary: Embossing and Engraving
Both engravings and embossments offer striking 3D effects in your parts. Plus, they’re a great way to include more permanent visual information. But remember that they are more costly than using powder coating or silk screening. That’s something you’ll have to consider during prototyping.