All About SLS Printers
The SLS type printers are industrial grade printers that work on a fine powder that gets melted by a high power, high precision laser, before the next thin layer of dust is swiped over the top.
The roller is a very important part in these printers, its purpose is to roll an extremely thin, and ultimately even layer of powder from the supply tub to the work tub for the laser to sinter.
There are two tubs, one that starts filled and goes up to allow more powder to be spread onto the other tub, and the other tub starts empy with the piston level with the top and slowly goes down as it fills up.
The laser is one of the most important bits, because without it, you would have no way of melting the particles together. The laser is a high power beam that is focused and passed onto a mirror that rapidly jumps around to melt very specific lines and points on the work piece, and does so at extreme speeds.
The powder is formed by grinding up plastic at cryogenic temperatures, causing the plastic to shatter and turn into pieces smaller than the eye can see. The powder is usually nylon, but it can be other materials such as metal and other plastics.
Wikipedia – Selective Laser Sintering