Advanced Techniques


Rastering is a process whereby the laser cutter traverses back and forward to gradually impart an image or hatched area onto a piece of material.

Basic raster outcomes are affected by how you adjust your speed, power, black & white threshold, and Dots Per Inch (DPI). This is particularly true with images that have high DPI.

Conditions of Rastering

Image Quality

Raster image quality is measured by pixel density. The more pixels per inch, the sharper an image will appear. Pixelation occurs when the number of pixels per inch in an image is low, causing each pixel to have visible edges. This distortion becomes worse as the image is enlarged.

Tracing bitmaps and converting them into vectors allows you to scale an image while avoiding pixelisation from occurring. Because vector images can be engraved as well, they typically work better for a custom basic raster. Vector images are the native format for Illustrator and vectorising images with those programs is an easy process using the Live Trace functions to create your design.

Once an image is vectored, it can be easily scaled and edited without pixelation.

Adjusting Black & White Threshold

The Black & White Threshold application replaces each individual colour pixel in an image, with a black or white pixel image.

In our laser software, colours other than black and white (including vector lines in the same design) will register as an engraving if the black and white threshold is not adjusted.

You can adjust the intensity toward black or white, but it is best to find a good contrast. If vector lines are present in your raster job, best practice is to make them a lighter colour, so they don’t register as a raster.

Adjusting Rasters with Vector Lines

If they are still registering as an engraving, simply adjust the b/w threshold to remove the unwanted rastered sections.

Rastering at the FabLab

When you submit a file to be rastered on the laser cutter, make sure the area to be rastered is a fill and is on the raster layer which is CYAN, this should be a blue colour.

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