Raster engraving is a means of translating a pixel based graphic onto the surface of a workpiece. Our laser cutters do this by turning each horizontal row of pixels in an image into a string of laser pulses where each pulse corresponds to a pixel with its power determined by how dark that pixel is. A white pixel would result in a no pulse, and a black pixel in a maximum power pulse. The maximum power can still be adjusted in settings as a percentage, which will scale the power per pixel.
Our laser cutters receive information from printing, so users can set up their jobs in different graphics and drafting programs. For example, you can use Photoshop, Rhino, or Illustrator to send raster information to the laser cutter. In the case of Rhino and Illustrator, you can also send vector information to the laser cutter. If you want to send only raster information, Photoshop will suffice, but if you want to both engrave a raster image and then cut that same workpiece, Illustrator or Rhino will be necessary.
The A studio laser cutters have a maximum resolution of 500ppi, the B studio laser cutters have a maximum resolution of 300ppi, and the sub-basement laser cutter’s maximum resolution is 1000ppi. Keep in mind that subtle gradients tend to look smoothest at resolutions between 200-400ppi, but sharp lines and hatches will still be visible at the highest resolutions on the A laser cutters or the sub-basement laser cutter.
Materials
Wood, engineered wood products, solid paper products, rubber, linoleum, and leather all engrave very well. High density woods, rubber, and linoleum show a sharp relief in depth. Low density woods and paper products can create a deep relief, but tend to flare, which softens edges. Resinous woods (like pine, fir, cypress, and mesquite) and engineered products like MDF and chipboard show a high amount of contrast. Cardboard, foamcore, and acrylic don’t lend themselves to laser engraving.
Blued steel sheets can be laser engraved to remove the protective patina. There will be minimal visible effect right away, but the engraved areas will weather and rust very quickly. Do not use this process with galvanized sheets, due to the production of highly toxic gases. Most metals, ceramics, and glass can also be coated with different sprays that will bond with the surface of the workpiece after being struck with the laser. This process will leave a ceramic (Cermark), polymer (nylon powder), or metallic (molybdenum disulfide lubricant) material permanently bonded to your workpiece.
Setup in Photoshop
Create your new artboard with the resolution you want to use for the print. Use the Grayscale color mode. The printer driver that translates your image to a laser cutter engraving will change the color information to grayscale when you send an image through it, so you’ll have a better idea of what your results will look like if you start in grayscale mode.
To ensure that you maximize the difference in your image’s contrast without losing distinction in the gradients, adjust your levels by pressing Ctrl+L then use the Auto button to clip the image’s darkest and lightest pixels to the black and white points. Adjust your brigthness and contrast if your images don’t have enough clear difference in them. Scale your image to the size of the finished object, then crop your artboard to the bounds of your image.
Setup in Illustrator
Create an artboard the size of your finished engraving and set your resolution. Drop in your raster image, and draw out your vectors and gradients. Make sure your gradients are only grayscale and that your vectors use any of the standard laser cutter colors except black. The black channel should be reserved for your engraving.
If your raster images aren’t already grayscale, select them then click on Edit -> Edit Colors -> Convert to Grayscale. To clip the levels of your raster images, click on Edit -> Edit Colors -> Saturation. Drag the slider to the left between 0 and -100% to where you feel the level of contrast is appropriate.
Setup in Rhino
Studio laser cutters
Click on File -> Print or, if in Rhino use the Print command. Choose the laser cutter attached to the PC and click on the Properties button. Change the mode on the black layer to Raster. Make sure that the PPI value on that layer matches your input and the hardware you’re using. Keep any other layers set to Vector. Set your speed to 100% and the power low. Start at 5% power for thin paper, 20% for resinous or low density woods, 50% for high density wood or leather, and 70% for rubber or linoleum. If necessary, increase power until you reach 100%, then drop the speed to further increase the effectiveness of the engraving. If you use laser marking spray, check the manufacturer’s recommendations for a 75W CO2 laser. When your initial settings are in, click on the Set button, then click OK. Print your document to the UCP.
If you need to adjust the position of your raster geometry, click on the Move button in the UCP and drag the geometery or input a specific information. You can change the the settings after sending the print to the laser cutter, in case you need to adjust power and speed after your initial attempt.