Awards & Engraving

June '18

Issue link:

Contents of this Issue


Page 21 of 84

A&E JUNE 2018 • 19 Laser Engraving details, particularly in wood. Not every model has this capability. It usually takes specialized software to enable the neces- sary changes in operation. A CNC milling machine requires specialized software that manipulates the cutter, moving it not only front to back and left to right, but up and down. Lasers capable of doing relief carving also require specialized software; however, while it moves the lens in the front-to- back and left-to-right aspects, it does not move it up or down. The lens stays focused on the surface of the material. The relief carving software changes the firing mode of the laser. Depth is achieved by varying power based on grayscale color values. The darker the grayscale color, the more power is used and the greater the depth of the carving. It does not do this one color value at a time, but continuously line by line. There are several differences in the capabilities of a CNC milling machine (essentially a computer-controlled router) and a laser, most notably the scale at which each is effective. CNC milling machines are great for large signs and decorative pieces. Relief carving with the laser is more appropriate for smaller items with intricate detail. The time it takes to do a larger piece with the laser would be prohibitive, while the CNC milling machine would have a difficult time handling smaller details. The CNC milling machine may require bit changes in order to achieve finer details. Even so, it cannot achieve the detail that a laser can. Done carefully, lasers can carve in very thin material. I frequently relief carve 1/8-inch thick stock, something that a CNC milling machine would have con- siderable trouble doing. A major convenience with the laser is that there are no wood chips to clean up — the wood is vaporized, not chipped off. The trade-off is that there is usually some residue from the vaporized wood left behind that needs to be removed. LASER REQUIREMENTS Referring strictly to lasers, having the ability to vary power based on grayscale color value is the primary difference between relief carving mode and regular raster mode. When a regular raster job is executed, power is set in the print menu and does not vary. Instead, it spreads that steady level of power over varying, dis- persed dot patterns based on color values. Great relief carving results cannot be easily achieved in the regular raster mode. If your machine does not have the varying power capability or the software (print option) to enable it, you will not easily be able to create a relief carving. For specific information about relief carving with your model, contact your dealer's representative. (I have a 60-watt Epilog Legend EXT CO 2 laser with a 3-D option in the print menu. As we proceed through this article, keep in mind that much of the information is specific to that model and its software, although other laser brands also have this capability.) GRAPHICS You cannot create relief carvings with regular grayscale graphics or photographs. You'll need a specialized drawing where the grayscale color value represents depth. To get down to the nuts and bolts of this, please refer to the image on page 21 for three exam- ples of a hex head bolt and washer to dem- onstrate the difference in graphic drawings. On the left is a simple line drawing. It will make dark raster marks on wood that are easily recognized as a hex head bolt and washer. In the center is a grayscale graphic, made using the Fountain Fill tool, that includes subtle shading indicating a light source in the upper left. When engraved on a two- color substrate, like silver over black, it will give the impression of a three-dimensional hex head bolt and washer, but it's just a flat image. On the right is a grayscale drawing of a hex head bolt for relief carving, also created with the Fountain Fill tool. Notice that the text is the lightest feature of the drawing; Fine details, like the faults in the weave and the rivets of the nameplate, are possible with the laser.

Articles in this issue

Links on this page

view archives of Awards & Engraving - June '18