Principles of Support and Location

Referencing refers to the use of fixed points or known dimensions to establish the position of a part. Repeatability refers to the ability to consistently achieve the same position or result in multiple attempts. Interchangeability refers to the ability to replace one part with another that is functionally equivalent.

The basic rules for locating include positioning the locators, considering part tolerance, implementing foolproofing measures, and using duplicate or redundant location methods.

The planes of movement refer to the degrees of freedom (DOF) and the 3-2-1 principles. 12-DOF represents the different ways a part can move in three-dimensional space, while the 3-2-1 principles refer to the three primary directions of movement (x, y, and z axes) and the two secondary directions (rotation about the x and y axes) that can be controlled during the assembly process.

The types of locating for flat surfaces include using pins or dowel holes. For internal diameters, locating methods can include using mandrels or expanding collets. External profiles can be located using features like slots, tabs, or protrusions.

The types of ejector devices include mechanical-level ejectors and spring-type ejectors. Mechanical-level ejectors help remove parts from molds or fixtures using mechanical force, while spring-type ejectors utilize the force of a spring to push the part out of the mold or fixture.