Form, fit and function

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The assessment of impact on form, fit, and function is commonly used to determine if a proposed change to a part will be "minor", that is, it has no impact on the form, fit, and function, or "major", that is, it does impact the form, fit, function. The F3 rule is at the basis of enterprise material management systems, ERP, Product Data Management (PDM) or Product Lifecycle Management (PLM) systems.

Definition

Physical, functional, and performance characteristics are specifications that uniquely identify a component or device and determine its interchangeability in a system.

Specifications

Form

• the shape, size, dimensions, mass and/or other visual parameters which uniquely characterize an item. This defines the "look" of the part or item. Sometimes weight, balance and center of mass are considerations in 'form'. Color is not generally considered in 'form', except when it has a specific functional meaning.

Fit

• the ability of an item to physically interface or interconnect with or become an integral part of another item or assembly. This relates to the associativity of the part in relation to the assembly, or to other parts, and includes tolerances.

Function

• the action[s] that an item is designed to perform. This is the reason for the item's existence, which also includes secondary applications.

References

Federal Acquisition Regulation Section 52.227-14 "Rights in Data - General" (Dec 2007) [1]