The Trotec RayJet 300 we have in the lab is designed to cut relatively thin materials up to around 1cm. It is commonly used for making accurate cut-outs of flat pieces of wood or plastic i.e. for making custom signage, or assembling boxes or cases. However, it can also be put to many interesting and creative use (see below).
It quite a simple machine in terms of what it does, but takes a little experience to use it safely and get good results, which is why we insist on some basic training. The great advantages of laser cutting are accuracy and speed, which allows us to cut multiple copies of the same design or quickly iterate on designs. The main limitation is that we are working in two dimensions with a fixed material thickness, meaning laser-cutting may be less suited to complex forms and shapes.
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Simply put, we place a sheet of material inside the cutter and computer-control the position of a motorised laser-head in order to specify where on the material to cut or engrave. This is done by printing a vector graphics file from software such as CorelDraw, Inkscape or Adobe Illustrator. We work with power and speed to cut at a certain depth, the exact settings of which depend on the material being cut. For most purposes you can think of the laser as having a very fine cutting line, although an advanced technique called controlled defocussing can be used to thicken it somewhat.
The main difference between cutting and engraving is that cutting provides enough power to get through the material completely, whereas engraving uses less power to etch patterns on the surface of the material. The other important difference is the path the laser takes. For example when cutting, the laser will directly follow the lines shown in your image file, whereas when engraving the laser moves from left to right across the whole image, like a printer, turning on and off at the right moments to engrave your image.
When creating image templates, we typically use red to represent cut lines and black to represent engraving lines (though the colours can be changed inside the RayJet Manager software).
To control the laser cutter we use an application called RayJet manager. Typically, to get images into RayJet Manager we simply print them from our graphics application of choice (e.g. Inkscape, Adobe Illustrator, etc). For best results, images should be created in (or converted to) a vector graphics format (i.e. .svg or .dxf).
The laser cutter is a relatively simple device and there are only a few parameters we can control. The most important two are power and speed. By controlling the ratio between them, you can make surface cuts, deep cuts or cut completely through the material. Their effects are different depending on the material chosen. For example, thicker woods may need to be cut slowly and with more power, whereas paper or cardboard typically need to be cut quickly and with low power to avoid burning.
PPI (or pulses per inch) is a way to control how many times the laser pulses over a given distance. The higher the frequency the more the pulses overlap, resulting in a smoother cut, however the downside to this more heat. Very low PPI’s can result in a perforated cutting line. For most materials apart from acrylic, you should use 30-50% of the max PPI available.