This is a detailed article about popular inexpensive semiconductor lasers and about what you can engrave and cut using a 5.6 W semiconductor laser, installed on a 3D printer or CNC machine. The laser diode is a solid-state source of coherent radiation. In this case it is a solid crystal of aluminate gallium, a source of the laser beam with the wavelength of about 445 nm. The basic components of the laser are a laser diode, a cooling system and a power driver of the laser diode. The main trick in their production is how to make the driver as compact as possible and at the same time fail-proof, how to ensure sufficient cooling of the laser diode without the crystal degradation. That is, a laser, ready for operation, has not just an energy source but also a power driver and a cooling system. We are lucky in this, as diode lasers are rather small and light unlike huge CO2 and fiber lasers. It is easy to install a conventional diode laser on any 3D printer or CNC machine. Besides, the market offers a variety of DIY kits of the makeblock plotter XY 2.0 type, which are also suitable for laser installation.   Standard installation hardware is used for most of lasers, though sometimes on...