The slicer, also called slicing software, is a computer software used in the majority of 3D printing processes for the conversion of a 3D object model to specific instructions for the printer. In particular, the conversion from a model in STL format to printer commands in g-code format in fused filament fabrication and other similar processes. The slicer first divides the object as a stack of flat layers, followed by describing these layers as linear movements of the 3D printer extruder, fixation laser or equivalent. All these movements, together with some specific printer commands like the ones to control the extruder temperature or bed temperature, are finally written in the g-code file, that can after be transferred to the printer.
Nearly all slicers have some additional features, like: File:Infill density.jpg|left|thumb|Different densities of infill, as generated by slicer, from solid to hollow.
Infill: solid objects needs a big amount of valuable material and print time. The slicer can automatically convert solid volumes to hollow ones, saving costs and time. The hollow object can be partially filled by internal structures, as internals walls, to provide additional robustness. The amount of these structures is called infill density, being this parameter one of the adjustments to be provided to the slicer.
File:Support structure in 3D printing.jpg|thumb|Support structure generated by software.
Supports: most of the 3D printing processes create the object layer by layer, down to up, with the layer under construction being deposited over the previous one. As consequence, all object parts must overlie, at least in some part, over another one. In the case of an object layer that is floating, the slicer automatically can add supports for it. The support touch the object in a way that is easily detachable from it at the finish stage of the object production.
File:Skirts, Brims, Rafts.jpg|thumb|Comparative of base layers skirt; b) brim; c) raft, generated by software
Rafts, skirts and brims: printing of the first object layer, the one in contact with the printer bed, has some peculiarities, like problems of object adherence to the bed, rugosity, smooth deposition of the first amounts of filament,... . The slicer can automatically add some detachable structures to minimize these problems. Usual types of these base structures are a skirt, a brim and rafts.
