Form, fit and function: Difference between revisions

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{{Short description|Concept in design processes}}

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'''Form, Fit, and Function''' (also '''F3''' or '''FFF''') is a concept used in various industries, including manufacturing, engineering, and architecture, to describe aspects of a product's design, performance, and compliance to a specification. F3 originated in [[military logistics]] to describe interchangeable parts: if F3 for two components have the same set of characteristics, i.e. they have the same shape or ''form'', same connections or ''fit'', and perform the same ''function'', they can be substituted one for another.<ref>{{cite journal |last1=Moore |first1=James W. |title=Structure for a Defense Software Reuse Marketplace |journal= ACM Ada Letters|date=May–Jun 1994 |volume=XIV |issue=3 |page=88 |doi=10.1145/181468.181473 |url=https://dl.acm.org/doi/pdf/10.1145/181468.181473}}</ref> The idea behind F3 is to contractually require the original manufacturer to provide the customer (US government) with the free use of F3 data so that the customer can [[second source]] the part and thus enable [[competition]] between multiple suppliers. In practice, F3 is usually used not for final products (like entire [[weapon systems]]), but for the procurement of components and

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'''Form, Fit, and Function (F3)'''  is the identification and description of characteristics of a part or assembly. Each defines a specific aspect of the part to help engineers match parts to needs. The F3 framework increases design change flexibility by allowing changes to the part with minimal documentation and design cost as long as the fit, form and function of the product is maintained constant.

FFF refers to a set of characteristics or requirements that are essential for the design and compatibility of products, components, or systems, and can have legal considerations in regulated industries like aviation and defense (e.g., for technical data rights and configuration management).<ref name="ECFR252">{{cite web |url=https://www.ecfr.gov/current/title-48/chapter-2/subchapter-H/part-252/subpart-252.2/section-252.227-7015 |title=Title 48, Chapter 2, Subchapter H, Part 252, Subpart 252.2, Section 252.227-7015 |publisher=Electronic Code of Federal Regulations |accessdate=2023-10-14}}</ref><ref name="GlobalSpec">{{cite web |url=https://www.globalspec.com/reference/60484/203279/chapter-11-configuration-management |title=Chapter 11: Configuration Management |publisher=GlobalSpec |accessdate=2023-10-14}}</ref><ref name="NASA">{{cite web |url=https://www.nasa.gov/reference/6-5-configuration-management/ |title=NASA Procedural Requirements: Configuration Management |publisher=NASA |accessdate=2023-10-14}}</ref>

== Definitions ==

'''Fit:''' refers to the ability for the part or feature to connect to, mate with, or join to another feature or part within an assembly. If a part requires “fit” it usually implies that there are relatively tight assembly tolerances that must be met in order for the part to be useful.

The concept originates in the 1960s, and in some cases called "form-fit-function".<ref name="DTIC">{{cite web |url=https://apps.dtic.mil/sti/tr/pdf/AD0700066.pdf |title=Form-Fit-Function |publisher=Defense Technical Information Center |accessdate=2023-10-14}}</ref> The United States (US) Government formally recognized it in the legal incorporation of Public Law 98-525 regarding technical data and design changes.<ref name="USCode">{{cite web |url=https://www.govinfo.gov/content/pkg/STATUTE-98/pdf/STATUTE-98-Pg2492.pdf |title=Public Law 98-525 |publisher=U.S. Government |accessdate=2023-10-14}}</ref> F3 can also refer to the ability of a replacement unit or technology upgrade to be compatible with existing systems, or be compatible with change control procedures (e.g., NASA's use in reliability via military standards).<ref name="NASA2">{{cite web |url=https://nepp.nasa.gov/docuploads/6000C904-3093-44CA-96A78169BC195A26/Commercial%20Plastic%20Microcircuits%20A%20Total%20Solution%20For%20Military%20Applications.pdf |title=Commercial Plastic Microcircuits: A Total Solution For Military Applications |publisher=NASA |accessdate=2023-10-14}}</ref><ref name="DLA1">{{cite web |url=https://quicksearch.dla.mil/qsDocDetails.aspx?ident_number=69354 |title=Quick Search Document: 69354 |publisher=Defense Logistics Agency |accessdate=2023-10-14}}</ref><ref name="DLA2">{{cite web |url=https://quicksearch.dla.mil/qsDocDetails.aspx?ident_number=67840 |title=Quick Search Document: 67840 |publisher=Defense Logistics Agency |accessdate=2023-10-14}}</ref>

'''Form:''' refers to such characteristics as external dimensions, weight, size, and visual appearance of a part or assembly. This is the element of F3 that is most affected by an engineers choice of enclosure, chassis, control panel, etc. that becomes the outward "face" of the product.

== Alternate Uses ==

'''Function:''' is a criteria that is met when the part performs its stated purpose effectively and reliably. In an electronics application, Function can depend on the solid-state components used, the software/firmware, and quite often on the features of the electronics enclosure selected. Poorly placed or dimensioned ports and misleading/missing labeling are just two of the most common ways in which an enclosure can fail the Function criteria of F3.

Some organizations have supplemental considerations for F3. The United States Navy has been using Form, Fit, Function, and Interface (F3I) since the 1970s, and NASA has published references to Form, Fit, Function, and Reliability to facilitate reliable designs.<ref name="NASA3">{{cite web |url=https://www.nasa.gov/wp-content/uploads/2018/09/nasa_systems_engineering_handbook_0.pdf |title=NASA Systems Engineering Handbook |publisher=NASA |accessdate=2023-10-14}}</ref><ref name="DTIC2">{{cite web |url=https://apps.dtic.mil/sti/tr/pdf/ADA322079.pdf |title=Configuration Management |publisher=Defense Technical Information Center |accessdate=2023-10-14}}</ref><ref name="NAVAIR">{{cite web |url=https://acqnotes.com/wp-content/uploads/2014/09/NAVAIR-Configuration-Management-Policy-Manual-21-Dec-2016.pdf |title=NAVAIR Configuration Management Policy Manual |publisher=AcqNotes |accessdate=2023-10-14}}</ref>

== External linksDefinitions ==

=== In the Code of Federal Regulations - US Government ===

* [https://www.clickfoldplastics.com/form-fit-function.html Understanding the Role of Form, Fit, and Function]

* [http://www.intrinsys.com/blog/2016/evaluating-the-change-form-fit-and-function Evaluating the Change: Form, Fit and Function (FFF)]

Source:<ref name="ECFR120">{{cite web |url=https://www.ecfr.gov/current/title-22/chapter-I/subchapter-M/part-120/subpart-C/section-120.42 |title=Title 22, Chapter I, Subchapter M, Part 120, Subpart C, Section 120.42 |publisher=Electronic Code of Federal Regulations |accessdate=2023-10-14}}</ref>

[[Category:Product design]]

'''Form''' The form of a commodity is defined by its configuration (including the geometrically measured configuration), material, and material properties that uniquely characterize it. For software, the form means the design, logic flow, and algorithms.

'''Fit''' The fit of a commodity is defined by its ability to physically interface or connect with or become an integral part of another commodity. For software, the fit is defined by its ability to interface or connect with a defense article.

'''Function''' The function of a commodity is the action or actions it is designed to perform. For software, the function means the action or actions the software performs directly related to a defense article or as a standalone application.

==References==

{{Reflist}}

== Sources ==

* {{cite book |last=Morris |first=R. |title=The fundamentals of product design |year=2009 |publisher=AVA Publishing |isbn=978-2-940373-17-8 }}

* {{cite book |last=Norman |first=D. |title=The design of everyday things |year=2002|publisher=Basic Books |___location=New York |isbn=0-465-06710-7 }}

* {{cite thesis | last1=Deets |first1=Douglas M. |title=The use of form, fit, and function in the acquisition of major weapon systems |date=1985 |publisher=Naval Postgraduate School |___location=Monterey, California |degree=Master's |url=https://core.ac.uk/download/pdf/36714841.pdf}}

[[Category:Product design]]

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