Mirror image

The main purpose of a CNC program development is to create a cutter tool path in a specific location of the part or machine. If the tool path requires both the right and left hand orientation, the programming time can be shortened by using a feature called the Mirror Image.
Any sequence of machining operations can be repeated symmetrically by using the mirror image feature of the control system. Them is no need for new calculations, so this technique of programming reduces the programming time as well as the possibility of errors. Mirror image is sometimes called the Axis Inversion function. This description is accurate up to a point. Those who are familiar with a CAD system will find that the mirror image function in CNC is based on the same principles.

Mirror image is based on the principle of symmetrical parts, sometimes known as the Right Hand (R/H) and the Left Hand (L/H) parts 

BASIC RULES OF MIRROR IMAGE 
The basic rule of a mirror image is based on the fact that machining a given tool path in one quadrant is not much different than machining the same tool path in another quadrant. The main difference is the reversal of certain motion directions. That means a given part machined in one quadrant can be repeated in another quadrant using the same program with the mirror image function in effect. 

EXAMPLE

Profile

NOTE
M70 X MIRROR ON AND M71 Y MIRROR ON
M80 X MIRROR OFF AND M81 Y MIRROR OFF