3-2-1 principle

Every part has 6 degree of freedom (3 linear + 3 rotary) which need to be arrested to ensure proper location of the part in space.The location principle used to to achieve this is called 3-2-1 principle.

1)       3 stands For - Minimum 3 Rests with clamps to establish a part plane thus restricting 1 up-down motion plus 2 Rotary motion

2)       2 stands For – Two locating pin in a round hole that restrict motion in the two directions in the established plane.

3)       1 stands For – A Round locating Pin in a slot that restricts the rotary motion in in the established plane about the round pin.