The engraving form known as 3D laser engraving is a special type of engraving that involves either engraving on a three-dimensional surface on more than one edge at a time, or creating a 3D image with different levels of depth. Laser engraving, which uses a laser instead of a cutting bit, is better at this 3D process, because it can easily dig into the surface without a bit accidentally getting in the way or hitting previous engraving marks. The image to be used with 3D laser engraving is typically taken from a grayscale image, and the operator must know how to calibrate the grayscale to achieve the right depth and effect. There also are special laser engravers that are able to engrave beneath the surface of glass or crystal to create 3D images inside the material.
The simplest version of 3D laser engraving is when more than one side of a 3D object is engraved into at the same time. For example, if someone wants a cube engraved, it will take less time to engrave several sides at once than to do each side individually. This type of engraving equipment uses two or more lasers simultaneously, and the user must have all the sides loaded into the program correctly or the engraving will come out wrong.
More commonly, 3D laser engraving is used to create a 3D image with depth. For example, with a regular engraver, a flat image with lines suggesting depth will be placed into the material. Carving is similar to 3D engraving in that both actually dig away at the material to create a visually distinct foreground and background. With engraving, this is done via differing laser intensities.
Sub-surface laser engraving (SSLE) is a 3D laser engraving method that does not engrave on the surface of the material, but under it. This is usually done to crystal or glass, because other, nontransparent materials would be unable to display the image. SSLE is used for promotional items and often leaves people scratching or rubbing the surface of the crystal or glass, wondering how the engraver got an image inside the material without leaving marks on the surface.
Most 3D laser engraving machines have the 3D image set up with a grayscale image. Between black and white, there are 256 shades of gray. The closer to white, less is cut away; the closer to black, the more material will be cut away. By knowing how to properly color an image, the engraver operator will be able to get the right cut into the material.