File extension is used by Artcut software.
File saved by ArtCut 6, a graphic design package used for creating and printing signs; may contain raster and vector graphics, clipart, and TrueType text; can be printed and cut by compatible sign cutting plotters.
The ac6 file extension is associated with SPICE (Simulation Program with Integrated Circuit Emphasis). The ac6 files are used for AC/frequence domain output.