There is only one file type that uses the .MMG extension:
Model Master 3 Axis Flat File
An MMG file contains a toolpath saved in the Model Master 3 Axis Flat format. It stores computer numerical control (CNC) instructions, which include XYZ axes coordinates used to direct a machine tool, such as a drill or boring tool, during production. MMG files are similar to .NC files.
MMG files specify 2D or 3D machine toolpaths and their coordinates and translate toolpaths into a format that machine tools can understand.
Updated: November 8, 2018