Design to Cost · Value
Functional Analysis
Express the product as functions — verb plus object — free of solutions: what must it do, not how.
- Time1 h 30
- FormatTeam
- StageValue
Functional Analysis: what it is and why it works
Functional analysis describes a product by what it must do rather than by how it currently does it. Each function is written as an active verb plus a measurable noun, such as isolate flow, resist abrasion or indicate position, which deliberately avoids naming parts or solutions. Functions are then classified as basic, secondary or aesthetic, ranked by their importance to the user, and assigned an estimated share of the product's cost. Comparing importance with cost shows where the product spends heavily on functions users value little.
The method is the foundation of value analysis as developed by L. D. Miles at General Electric: value is the relationship between the function delivered and its cost, so cost reduction starts by understanding functions. Separating need from solution frees the team from defending existing parts, because a part is only one way of delivering a function, and cost usually attaches to functions more clearly than to individual parts. Functional analysis provides the input for FAST diagrams, which arrange functions logically, and for the useless function hunt, which challenges functions with no clear requirement behind them. It also connects customer needs, captured in QFD, to engineering characteristics.
What you need
- A description of the product and its operating context
- Knowledge of user requirements, from specifications, customers or field service
- The product's cost breakdown by part or module
- A cross-functional team with design, manufacturing, service and sales knowledge
- Any regulatory or safety requirements the product must meet
What you get
- A list of functions in verb-noun form, classified as basic, secondary or aesthetic
- An importance ranking of functions from the user's perspective
- An estimated cost per function
- A list of functions whose cost is out of proportion to their importance
When to use it
When solutions are defended by habit and nobody remembers the need.
How to do it, step by step
- List the product’s functions in verb-noun form: conduct heat, fasten cover, signal state.
- Separate basic functions, secondary functions and aesthetic functions.
- Rank functions by importance to the user.
- Estimate the cost share of each function.
- Spot functions that cost disproportionately more than their value.
Worked example: Knife gate valve for mining slurry service
Illustrative scenario — figures are realistic but not from a real company.
A valve manufacturer supplied 12-inch knife gate valves for tailings and slurry lines at mines. Customers were pushing for lower prices, and internal cost discussions kept returning to the same few parts without progress.
- The team listed nine functions in verb-noun form, including isolate flow, cut solids, seal pressure, resist abrasion, resist corrosion, withstand pipe loads, indicate position, allow liner replacement and display brand.
- They classified isolate flow as basic; most others as secondary; display brand as aesthetic.
- Maintenance planners from two mine sites ranked the functions. Resist abrasion and allow liner replacement came out as most important; indicate position ranked low because the rising stem already shows valve position.
- Allocating part costs to functions showed resist abrasion at 31 percent of cost, indicate position at 6 percent, due to a separate indicator kit fitted to every valve, and display brand at 5 percent, due to a separate branded topcoat over the protective coating.
- The team flagged indicate position and display brand as out of proportion and noted that resist abrasion deserved more investment, not less.
Result. The indicator kit became an option, and the branded topcoat was replaced by a colored final coat of the existing corrosion protection system. Part of the savings funded a longer-lasting liner. Net cost fell by about 6 percent while liner life improved, and the team learned that users valued durability far more than the extras engineering had assumed they wanted.
Common pitfalls and how to avoid them
- Writing functions as parts or solutions, such as provide gearbox.Use an active verb and a measurable noun that describe the effect, such as transmit torque.
- Ranking importance only from the engineering team's view.Involve users, customers or field service to rank functions.
- Treating safety or regulatory functions as candidates for cost removal like any other.Mark them as required and focus on delivering them more efficiently, never on removing them.
- Spending hours debating the perfect verb-noun wording.Agree on wording quickly; refine it only where it changes the analysis.
Frequently asked questions
What is the difference between basic and secondary functions?
The basic function is the main reason the product exists; if it is lost, the product loses its purpose. Secondary functions support the basic function or result from the chosen design, such as resisting corrosion or allowing maintenance. Aesthetic functions relate to appearance or brand. Secondary functions are often where cost reduction opportunities lie, because they depend on design choices.
Why use verb-noun pairs in function analysis?
A verb-noun pair forces a short, precise description of what something does, without naming how it is done. That keeps the discussion open to alternative solutions and makes it easier to compare functions and assign costs. Good verbs are active and specific, and good nouns are measurable, such as transmit torque, contain pressure or reduce noise.
How do you allocate cost to functions?
Take the cost of each part or module and distribute it across the functions it contributes to, using engineering judgment. A pump casing might support contain pressure and guide flow, for example. The allocation is approximate, but it is usually enough to reveal functions whose cost is clearly out of proportion to their importance.
Origin
Function analysis — value analysis foundations (L. D. Miles, GE, 1947).
Used in these playbooks
Cost redesign sprint 1 week
One week to redesign the expensive parts: analyze functions, run the workshop, apply DFM rules and cost the prototype honestly.
- Functional Analysis
- Value Engineering Workshop
- DFM / DFA Review
- Prototype Costing
Related methods
- FAST DiagramOrder functions logically: how, why, when — to expose functions that exist only by tradition.
- Useless Function HuntChallenge every function: who needs it, what breaks without it, what does it cost? Kill the orphans.
- QFD LiteTranslate customer requirements into technical characteristics with weights — the light house of quality, one…
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