TRIZ Trimming: Component Pruning Matrix (Excel Template)

⏱ 26 min read

How TRIZ Function Trimming Systematically Eliminates Components

TRIZ function trimming systematically eliminates physical parts from an engineering system by identifying their core operational functions and reassigning those jobs to surviving components or existing ambient resources. This method strips bill-of-materials costs and removes failure modes without degrading baseline product performance. Instead of shaving material thickness until a bracket snaps under stress, trimming re-architects component relationships so the original bracket is no longer required.

Function analysis is an engineering modeling technique that maps every component in a product as an active subject that acts upon a target object to modify or maintain that object’s physical condition.

[System Component]
       |
  (Action)
       v
[Target Object]

The Difference Between Trimming and Value Engineering

Standard Value Analysis and Value Engineering, pioneered by Lawrence Miles at General Electric in 1947, typically focuses on component substitution, supplier negotiations, and shaving tolerances. A conventional value engineering team reduces a plastic housing’s wall thickness from 2.5 mm to 2.0 mm to save 12% on resin costs. The part remains in the assembly, but its structural safety factor drops.

TRIZ trimming attacks the underlying architecture rather than material margins. If a sensor housing shields a circuit board from engine heat, a trimming inquiry does not ask for a cheaper heat-resistant polymer. It asks whether the circuit board can move behind an existing structural firewall, or whether the engine block’s cooling air draft can be redirected across the board. When another element absorbs that shielding function, the dedicated housing disappears from the bill of materials. Research documented by Darrell Mann in Hands-On Systematic Innovation shows that structured trimming routines routinely deliver a 20% to 35% reduction in overall mechanical component counts across industrial assemblies.

For teams applying TRIZ for product innovation, this approach prevents the reliability penalties common to aggressive cost-down programs. You eliminate the part, its fasteners, its assembly labor step, and its quality inspection checkpoint at the same time.

Driving Toward the Ideal Final Result

In classical TRIZ, developed by Genrich Altshuller, every system evolves toward higher ideality. Altshuller expressed this progression as the Ideality equation:

           Sum of Useful Functions (UF)
Ideality = ------------------------------------
           Sum of Costs (C) + Sum of Harm (H)

Useful functions include every mechanical action, signal transmission, and structural support that end users require. Costs encompass raw materials, tooling, energy, and labor hours. Harmful side effects include heat generation, vibration, acoustic noise, component wear, and environmental emissions.

Most design teams try to increase ideality by adding new useful functions, which inflates the numerator. Every added function requires extra sensors, microcontrollers, and wiring harnesses. This inevitably increases cost (\(C\)) and adds fresh failure points (\(H\)).

Trimming works in the opposite direction. It raises ideality by driving the denominator toward zero. The theoretical limit of this equation is what Altshuller called the Ideal Final Result: a state where the physical hardware does not exist, yet its intended function is fully performed. Industrial manufacturers like Samsung Electronics integrated this logic directly into their value engineering protocols, using trimming to eliminate redundant semiconductor handling stages and thermal management modules. You can see how these concepts align with broader problem-solving frameworks in this introduction to TRIZ methodology.

The Core Operational Question of Component Pruning

Component pruning forces an engineering team to inspect every secondary and tertiary function across the assembly. In any product, components rarely perform only one job. A chassis bracket holds a motor, but it also grounds an electrical circuit, guides a wiring loom, and acts as a heat sink.

Traditional design reviews treat that bracket as indispensable because it does four distinct things. The TRIZ trimming protocol asks a sharper operational question: which parts deliver secondary functions that another existing part could easily absorb?

To prune an assembly systematically, evaluate every part against three primary trimming rules defined by the International TRIZ Association (MATRIZ):

1. Rule A (Object Eliminated): The object receiving the function is removed from the system, making the function and its delivering component unnecessary.
2. Rule B (Self-Performance): The object of the function performs the required action on itself.
3. Rule C (Carrier Redistribution): Another existing component or environmental element takes over the function.

When an electric vehicle battery pack uses a stamped aluminum tray to carry cell modules and a separate copper braid to ground the pack, Rule C applies. The aluminum tray can carry electrical ground directly through its mounting bolts, eliminating the copper braid, two fasteners, and 45 seconds of manual installation time. To master the broader creative logic behind these functional trade-offs, explore the foundational TRIZ principles.

Executing these functional handoffs requires an objective, mathematical inventory of your system before you touch a single bolt or CAD file.

Table of Contents

• How TRIZ Function Trimming Systematically Eliminates Components
• Mapping System Components and Functions Before Trimming
• The 3 Core TRIZ Trimming Rules for Component Elimination
• A Step-by-Step Scoring Guide for the Pruning Matrix
• Worked Example: Trimming a High-Cost Automotive Actuator
• The Copy-Paste Excel Trimming Worksheet Structure
• Sources & Further Reading

Mapping System Components and Functions Before Trimming

Mapping system components and their physical interactions using Subject-Action-Object triplets prevents teams from cutting parts that carry hidden operational loads during trimming. Component pruning fails when an engineering team treats a bill of materials as a simple parts list rather than an operational network.

A functional model is an engineering map that defines an assembly strictly by how its physical parts act upon one another to change properties or deliver customer value.

Every valid functional statement follows a rigid Subject-Action-Object (SAO) grammar. The subject is a physical component, the action is an active verb modifying an engineering parameter, and the object is the material or field being altered. Writing "bracket holds wire harness" creates a quantifiable relationship where the bracket resists a specific gravitational load of 1.4 Newtons. Vague descriptions like "circuit board manages power" obscure what the part physically touches, while "copper trace conducts electrical current" defines the exact boundary conditions you need to evaluate before removing the trace. Practitioners of the Introduction to TRIZ Methodology use this precision to separate physical realities from design intent.

[Subject: Impeller]
       |
       v (Rotates)
[Field: Airflow]
       |
       v (Cools)
[Object: Heat Sink]

Once you establish the triplets, categorize each action into useful, auxiliary, or harmful functions. A useful function directly advances the primary job of the machine, like a heating element warming water. Auxiliary functions merely support other internal components, such as a plastic standoff separating two printed circuit boards. Harmful functions create operational liabilities, like a motor generating 85 decibels of acoustic vibration or radiating 45 watts of waste heat into nearby sensors. Simon Litvin, a chief TRIZ master at GEN3 Partners, documented that auxiliary functions routinely account for up to 60% of total component counts in electromechanical devices, representing the primary target for cost pruning.

Before you can eliminate a part that performs an auxiliary function, you must inventory free ambient resources in the supersystem. The supersystem includes every environmental condition and external object already present in the product’s operating environment. Gravity can route condensed moisture away from an evaporator coil, eliminating an auxiliary drain pump and its 12-volt wiring run. Surrounding structural sheet metal can serve as an electrical ground plane or a natural heat sink. Ambient airflow from external vehicle motion can replace an internal 40-millimeter cooling fan, reducing assembly costs by $3.20 per unit. Connecting your component audit with a broader Systems Thinking Canvas for Product Teams (With Template) helps reveal these environmental dependencies before you build physical prototypes.

Trimming efforts run off the rails when teams do not lock down the system boundary. The boundary defines the line between your product assembly and the customer interface. If you trim a mounting bracket by welding your sub-assembly directly to the customer’s chassis, you shift labor and geometric tolerance risks onto the client. The American Society of Mechanical Engineers (ASME) standards for mechanical interfaces dictate that customer touchpoints, standard tool access clearances, and field service access ports remain invariant during internal redesigns. Only prune components that reside entirely within your direct physical control.

SYSTEM BOUNDARY DEFINITION:
Target Assembly: [ASSEMBLY NAME, E.G., LIQUID COOLING MODULE]
Customer Interface Constraint: [LOCKED INTERFACE, E.G., 1/4-INCH NPT PORT]
Supersystem Resources Present: [LIST: GRAVITY, 22C AMBIENT AIR, STEEL HOUSING]

FUNCTIONAL INTERACTION MATRIX:
1. Subject Component: [COMPONENT NAME, E.G., MOUNTING BRACKET]
   Action Verb: [ACTIVE PHYSICAL VERB, E.G., SECURES]
   Object Modified: [TARGET PART, E.G., RESERVOIR TANK]
   Category: [USEFUL / AUXILIARY / HARMFUL]
   Operational Load: [MEASURED METRIC, E.G., 4.5 KG STATIC LOAD]
   Harmful Side Effects: [E.G., TRANSMITS 120 HZ VIBRATION TO CASE]

2. Subject Component: [COMPONENT NAME, E.G., COOLING FAN]
   Action Verb: [ACTIVE PHYSICAL VERB, E.G., MOVES]
   Object Modified: [TARGET PART, E.G., AIRFLOW]
   Category: [USEFUL / AUXILIARY / HARMFUL]
   Operational Load: [MEASURED METRIC, E.G., 15 CFM AIRFLOW]
   Harmful Side Effects: [E.G., DRAWS 2.4 W POWER, GENERATES 42 DB NOISE]

3. Subject Component: [COMPONENT NAME, E.G., COPPER HEAT PIPE]
   Action Verb: [ACTIVE PHYSICAL VERB, E.G., CONDUCTS]
   Object Modified: [TARGET PART, E.G., THERMAL ENERGY]
   Category: [USEFUL / AUXILIARY / HARMFUL]
   Operational Load: [MEASURED METRIC, E.G., 65 W DISSIPATION]
   Harmful Side Effects: [NONE]

TRIMMING READINESS CHECK:
- Are auxiliary functions supported by supersystem resources? [YES / NO]
- Does removing any subject alter a customer interface? [YES / NO]
- High-risk harmful functions identified for elimination: [LIST PARTS]

With every physical interaction cataloged and your boundary lines established, you can calculate the exact functional cost of each part in the Component Pruning Matrix.

The 3 Core TRIZ Trimming Rules for Component Elimination

TRIZ trimming systematically eliminates physical components from an engineering system or workflow while preserving the useful functions those components deliver. Trimming is an engineering design method within classical TRIZ that removes components from an analytical model and redistributes their useful functions to remaining parts or external resources. Instead of accepting the bill of materials as fixed, you force the system to perform the same work with fewer parts.

In the standard formulation developed by Genrich Altshuller and expanded by the International TRIZ Association (MATRIZ), trimming follows three strict operational rules:

• Rule A (Eliminate the Object): Prune the component because the recipient object of its function has been removed entirely. If there is no object to receive the action, you do not need an engineering carrier to deliver it. For example, when solid-state flash memory replaced spinning hard disks, read/write heads and spindle motors vanished because there was no magnetic platter left to balance or sweep. In product architecture, Rule A delivers the cleanest cuts because it eliminates secondary failure modes and assembly steps altogether.
• Rule B (Self-Service): Modify the function object so it performs the required action on itself. This rule directly operationalizes the classical concept of self-service found in the broader catalog of TRIZ Principles. In automotive manufacturing, stamping oil traditionally required dedicated automated spray nozzles; modern sheet steel uses dry, micro-textured surface patterns that retain ambient lubricant, allowing the metal blank to lubricate itself during pressing without external fluid pumps.
• Rule C (Redistribute to the System or Supersystem): Transfer the required function to an adjacent existing component or an available supersystem resource. You keep the function and its recipient, but you assign the workload to a carrier that is already paid for. Structural vehicle design uses Rule C routinely by shaping battery enclosures to act as chassis floor reinforcements, eliminating standalone cross-members while cutting 15 kg of dead weight.

When teams build a Systems Thinking Canvas for Product Teams (With Template), selecting between Rule A, Rule B, and Rule C requires objective physical criteria rather than team preference. You score candidates across three physical gates:

1. Proximity (Spatial Clearance): Can the donor component deliver mechanical force, electrical current, or fluid within 50 mm of the recipient without adding linkages? If the distance exceeds structural tolerances, Rule C fails unless an ambient field (like gravity or convection) spans the gap.
2. Energy Availability: Does the target host component possess at least a 25% surplus operating reserve? Transferring a thermal regulation function under Rule C will overheat a microcontroller operating at 90% duty cycle, turning a component trim into a system crash.
3. Material and Chemical Compatibility: Does combining functions create galvanic corrosion, thermal expansion mismatches, or acoustic resonance? If integrating two parts into one housing violates material constraints, evaluate Rule B self-service before forcing a Rule C transfer.

Start Trimming Evaluation
  |
  v
Can recipient object
be eliminated?
  |-- YES --> Apply Rule A
  |           (Remove Carrier)
  v NO
Can recipient perform
action on itself?
  |-- YES --> Apply Rule B
  |           (Self-Service)
  v NO
Adjacent carrier within
50 mm with 25% reserve?
  |-- YES --> Apply Rule C
  |           (Transfer Function)
  v NO
Keep Component / Flag Contradiction

Engineering reviews often stall when cross-functional leads defend their sub-assemblies against pruning. In corporate software architecture, teams face the exact same friction when mapping modules in a Tech Stack Matrix: Keep, Kill, or Modernize (Spreadsheet). When a proposed trim generates an intractable trade-off—such as shedding weight while degrading structural stiffness—you can resolve the resulting engineering conflict by consulting the TRIZ Contradiction Matrix Explained to target non-compromise design principles.

Understanding the theory behind Rules A, B, and C is only half the battle; the real acceleration happens when you plug your bill of materials directly into the pre-formatted Excel component pruning matrix below to calculate your system’s exact trimming threshold score.

A Step-by-Step Scoring Guide for the Pruning Matrix

A TRIZ pruning matrix prioritizes component removal by calculating a mathematical score that balances each part’s operational liability against its functional dispensability. Function analysis trimming is a systematic engineering method that eliminates physical components from a system while reassigning their useful functions to surviving parts or to the surrounding environment.

Rather than relying on engineering intuition or subjective brainstorming, this matrix ranks target components using production realities: unit manufacturing cost, assembly duration, and quality defect rates.

Step 1: Establish Component Baseline Liabilities

Begin by listing every discreet physical part of the assembly in column A of your worksheet. Pair each component with three empirical cost drivers extracted directly from your bill of materials (BOM), enterprise resource planning (ERP) routing logs, and quality management systems:

• Unit Manufacturing Cost ($): Direct material purchase price plus allocated piece-part fabrication cost.
• Assembly Cycle Time (seconds): Precise takt-time contribution measured on the production line.
• Defect Rate (DPPM): Defective parts per million recorded over the trailing 90 days of manufacturing runs.

Research published by Boothroyd Dewhurst, Inc. shows that fasteners like screws, clips, and brackets account for under 5% of total product material costs, yet drive over 70% of manual assembly labor and direct quality defects. Documenting these three parameters exposes high-liability components that cost little to buy but drag down manufacturing margins.

Normalize each of these three liability metrics onto a standard 1-to-5 scale (where 1 represents the lowest 20th percentile across the assembly, and 5 represents the highest 20th percentile). Sum these values to generate a raw Component Liability Score ranging from 3 to 15. If your product architecture spans both digital and physical interfaces, align this ledger with your tech stack matrix: keep, kill, or modernize to identify overlapping hardware-software dependencies.

Step 2: Score Feasibility Across Trimming Rules A, B, and C

Originator of TRIZ Genrich Altshuller established three core mechanisms to eliminate a component without degrading overall product utility. Score each part on a strict 1-to-5 feasibility scale for each of these three trimming rules:

• Rule A (Eradicate the Need): The object that receives the component’s function is removed from the system, eliminating the function entirely. Score a 5 if the recipient is an obsolete legacy subsystem; score a 1 if the recipient is the core deliverable demanded by your customer base.
• Rule B (Self-Performance): The recipient of the function performs the action on itself. Score a 5 if the recipient has latent physical capacity (such as surface area or mechanical spring force) to execute the work; score a 1 if the recipient is completely inert.
• Rule C (Carrier Redistribution): Another surviving component or the surrounding ambient environment absorbs the function. Score a 5 if an adjacent part possesses redundant structural or thermal capacity; score a 1 if all neighboring parts operate at maximum engineering tolerance limits.

Rule A: Recipient eliminated
   |
   +--> No recipient -> No function needed
   
Rule B: Self-service
   |
   +--> Recipient performs action on itself
   
Rule C: Host absorption
   |
   +--> Neighboring part carries the workload

An objective scale prevents cross-functional design paralysis between design engineers and plant managers. Ground your functional definitions using your team’s VOC translation matrix so customer-critical functional outputs are never misscored as disposable.

The single highest score among Rules A, B, and C becomes the component’s Feasibility Rating (\(F_{max}\)), running from 1 (nearly impossible to trim) to 5 (readily trimmable today).

Step 3: Calculate the Trimming Potential Index (TPI)

Calculate the Trimming Potential Index (TPI) to establish an unambiguous priority queue for engineering sprints. Compute the metric with this formula:

\(\text{TPI} = \text{Component Liability Score} \times F_{max}\)

A part with maximum assembly liability (score of 15) and an immediately actionable Rule C host (feasibility score of 5) yields the maximum TPI of 75. Conversely, a zero-defect spacer with a high replacement barrier yields a TPI under 10.

Rank your components in descending order by TPI. Focus your initial 2-week engineering refactoring sprint exclusively on parts scoring above 45.

[COMPONENT PRUNING WORKSHEET]
Part Name:                 [NAME]
Unit Cost ($):             [0.00]
Assembly Seconds:          [SEC]
Defect Rate (DPPM):        [DPPM]
-----------------------------------------
Rule A Score (1-5):        [SCORE]
Rule B Score (1-5):        [SCORE]
Rule C Score (1-5):        [SCORE]
Feasibility Rating (Fmax): [MAX A,B,C]
Liability Score (3-15):    [COST+TIME+DPPM]
-----------------------------------------
TRIMMING POTENTIAL INDEX:  [LIABILITY x Fmax]
Action Priority:           [TRIM FIRST / HOLD]

Step 4: Resolve Secondary Engineering Contradictions

Eliminating a component inevitably introduces a secondary technical conflict. An engineering contradiction is a situation where improving one technical parameter of a system causes another parameter to deteriorate.

When you trim a separate cooling bracket (Rule C) and force the main plastic chassis to absorb the thermal dissipation function, you lighten the bill of materials, but you degrade chassis structural integrity under continuous thermal load. According to study data from the National Institute of Standards and Technology (NIST), poorly managed component integration causes over 40% of secondary engineering change orders during late-stage prototyping.

Do not solve this compromise by returning the trimmed part to the design. Instead, treat the conflict as an inventive problem using the TRIZ contradiction matrix explained in our technical guides.

Map the improving parameter against the worsening parameter:

1. Improving Parameter: Weight of moving object, manufacturing cost, or ease of assembly.
2. Worsening Parameter: Strength, temperature, or structural reliability of the host component.
3. Applicable TRIZ Solution: Consult the standard 40 TRIZ principles at the intersection coordinates.

If you merge an electronic grounding plate into a sheet-metal frame, local thermal and electrical resistance worsens. Looking up this match on the matrix points to Principle 17 (Another Dimension) or Principle 40 (Composite Materials). You can adopt an in-mold stamped metal mesh rather than keeping the standalone grounding plate.

Map these systemic trade-offs against your systems thinking canvas before freezing the computer-aided design (CAD) assembly models. When structured correctly, trimming eliminates part counts while improving structural margins across the lifecycle.

Review the specific Excel formula syntax and conditional formatting rules needed to automate this matrix calculations in the next section.

Worked Example: Trimming a High-Cost Automotive Actuator

Applying TRIZ function analysis trimming to an automotive HVAC actuator removes 40% of assembly labor by cutting the component count from five parts down to three.

Trimming is a systematic TRIZ method for stripping out physical components while preserving their essential functions by transferring those duties to existing parts or the surrounding environment. In high-volume automotive lines where margins sit below 8%, eliminating two discrete parts from an actuator avoids secondary assembly stations and lowers bill-of-materials costs across millions of production units.

Consider a standard five-part air flap actuator assembly found in passenger vehicles: an electric DC motor, a stamped sheet-metal mounting bracket, an injection-molded external housing, a discrete potentiometer position sensor, and a copper wire harness connecting the sensor back to the vehicle controller.

Original Bill of Materials
├── 1. Electric motor
├── 2. External housing
├── 3. Position sensor
├── 4. Wire harness
└── 5. Mounting bracket

In standard product teardowns, engineers instinctively try to negotiate cheaper component unit prices. Using TRIZ for Product Innovation bypasses supplier price renegotiation by systematically reassigning functions through formal trimming rules established in classical engineering practice.

Rule C dictates that an engineer can eliminate a component if the target object performs the required function itself. In our actuator, the discrete position sensor exists solely to report the motor shaft angle to the electronic control unit (ECU). Tier-1 automotive supplier Continental AG tackled this exact architecture by introducing sensorless motor control: software monitors back-electromotive force and phase current resistance directly inside the electric motor’s copper windings. The motor coils now track rotor position directly, which satisfies Rule C and eliminates both the standalone sensor and the secondary harness leads that powered it.

Next, the engineering team applies Rule B, which states that a component can be eliminated if another system element inherits its engineering function. The stamped sheet-metal mounting bracket exists solely to secure the internal motor against the vehicle bulkhead. Redesigning the injection-molded polymer casing allows the external housing to absorb the bracket’s mechanical attachment points directly into a single molded shell with snap-fit lugs.

The final trimmed actuator contains only three physical parts: the multi-purpose motor, the integrated housing shell, and the streamlined wiring harness.

According to design-for-manufacture data compiled by Boothroyd Dewhurst, fasteners and discrete brackets account for up to 50% of manual assembly errors in small electromechanical devices. By merging the bracket into the housing and reading position through the motor windings, cycle time drops from 45 seconds down to 27 seconds per unit. This directly yields a 40% drop in assembly labor costs and removes two potential failure modes from the quality log.

ORDER OF OPERATIONS FOR COMPONENT PRUNING:
1. Map every function: [Component] -> [Action] -> [Object]
2. Apply Rule A: Eliminate part if the object is removed.
3. Apply Rule B: Eliminate part if another part does its job.
4. Apply Rule C: Eliminate part if the object self-serves.

CORE BENCHMARKS FROM THIS CASE:
- Starting component count: 5 parts
- Trimmed component count: 3 parts
- Assembly cycle time: reduced from 45s to 27s
- Direct labor reduction: 40%

You can trace every step of this structural teardown into the companion Excel trimming matrix template below to calculate your product’s exact post-trimming yield.

The Copy-Paste Excel Trimming Worksheet Structure

A functional TRIZ trimming workbook requires three linked tabs—Component Register, Function Map, and Pruning Matrix—to isolate where material cost and operational harm outweigh functional delivery. In classic TRIZ theory developed by Genrich Altshuller, trimming is an engineering method where you systematically eliminate components from a product design while transferring their essential functions to remaining parts or the surrounding environment. Building this framework in Microsoft Excel or Google Sheets removes subjective debate during design reviews by tying every cut directly to quantified functional output.

WORKBOOK TAB ARCHITECTURE
│
├── Tab 1: Component Register
│   └── Base BOM and part costs
│
├── Tab 2: Function Map
│   └── Part-to-action linkages
│
└── Tab 3: Pruning Matrix
    └── Trimming score & transfer

Tab 1: The Component Register

Your first tab pulls straight from your engineering Bill of Materials (BOM). List every discrete mechanical, electrical, and structural component across rows, leaving out non-functional fasteners until major assemblies settle. Use four required columns:

• Component ID: A clean alphanumeric tag (for example, CMP-101).
• Component Name: The exact CAD or PLM label.
• Unit Cost ($): The landed unit manufacturing cost, tracked to two decimal places (such as $4.25).
• Mass (g): The dry weight in grams, which anchors later mass-balance audits.

Tab 2: The Function Map

The second tab establishes functional relationships between components. In Darrell Mann’s textbook Hands-On Systematic Innovation, a valid engineering function strictly requires a subject, an action (an active verb), and an object. Use this tab to log every interaction:

• Function ID: Indexed key (FNC-201).
• Carrier (Subject): The component delivering the action, populated via data validation from Tab 1.
• Action: A verb showing modification or maintenance (e.g., cools, fastens, insulates).
• Object: The target component or environmental element receiving the action.
• Function Category: Mark as Useful-Basic, Useful-Auxiliary, or Harmful (e.g., vibrates, heats).

If your team struggles to balance customer requirements against these engineering functions, audit the baseline functional requirements using a VOC Translation Matrix (With 5-Step Template) before stripping parts.

Tab 3: The Pruning Matrix

The third tab executes the trimming logic. It synthesizes costs, harmful effects, and functional value into a single sorting engine. Configure your columns left to right with these exact headers:

1. Component Name: Mirrored from Tab 1.
2. Functional Output (Score 1–5): The count and significance of useful functions this part performs. A bracket doing nothing except holding a single wire scores 1; a chassis routing structural load and grounding current scores 5.
3. Cost Weight (Score 1–5): Part cost normalized on a logarithmic scale. A 1 represents parts under $0.50; a 5 represents parts exceeding $50.00.
4. Harmful Score (Score 1–5): The thermal, acoustic, or vibrational penalty the component introduces into the system. An inert spacer scores 1; a noisy, heat-generating pump scores 5.
5. Rule Feasibility (A / B / C): The classic trimming rule assigned to this part. Rule A means the object of the function is eliminated. Rule B means the object performs the function on itself. Rule C means another existing component or the system environment absorbs the function.
6. Target Absorber: The specific component designated to take over the trimmed part’s useful functions under Rule B or C.

PRUNING FLOW
│
├─► Score part cost & harm
│
├─► Assign Rule A, B, or C
│
└─► Reassign load to absorber

Review foundational TRIZ Principles if your engineering team hits a technical trade-off while assigning Rule C absorbers.

Automated Trimming Priority and Ideality Formulas

To remove personal bias from the trimming sequence, calculate a Trimming Priority Index (TPI) for every component in row 2 of Tab 3:

=ROUND(((C2 * 0.4) + (D2 * 0.6)) / MAX(B2, 1), 2)

In this formula, C2 is Cost Weight, D2 is Harmful Score, and B2 is Functional Output. Components generating high cost and substantial harm relative to low functional output produce a high TPI. Sort your sheet descending by TPI; your top 20% are your immediate trimming targets.

To monitor overall design efficiency across design iterations, apply the standard TRIZ ideality equation documented by the TRIZ Journal. Calculate system ideality before and after trimming in a summary block at the top of Tab 3:

=SUM(FunctionMap!E:E="Useful-Basic")*2 + SUM(FunctionMap!E:E="Useful-Auxiliary") / (SUM(ComponentRegister!C:C) + SUM(PruningMatrix!D:D))

Track this metric over weekly build cycles. Trimming succeeds only if system ideality increases without increasing total failure rates.

When pruning components introduces secondary design bottlenecks, evaluate downstream impacts with a Second-Order Effects Matrix for Pivots (With Template) before freezing tooling plans.

The 6-Step Engineering Sign-Off Checklist

Do not release a trimmed CAD assembly to prototype procurement without working through these six engineering gates:

1. Thermal Dissipation Audit: Confirm that absorbing components can shed the thermal load of any eliminated heat sinks or airflow ducts without exceeding standard component operating limits (such as a 45°C ambient rise limit).
2. Structural Load Path Verification: Recalculate stress concentrations via FEA (finite element analysis) on the designated absorber to ensure that combining structural roles maintains safety margins (minimum 1.5x yield strength).
3. Regulatory and Compliance Continuity: Verify that removing structural boundaries or shields does not violate safety, creepage, and clearance requirements outlined in standards like UL 62368-1 or IEC 60601-1.
4. Tolerance Stack Re-Calculation: Recalculate worst-case 1D and 3D tolerance loops. Merging two machined parts into a single complex injection-molded part often shifts machining tolerances from ±0.05 mm to molding tolerances of ±0.20 mm.
5. Assembly Line Ergonomics and Access: Validate that removing intermediate sub-assemblies does not create impossible fastener tool angles or blind assembly steps on the line, maintaining target takt times (such as 45 seconds per station).
6. Secondary Failure Mode (FMEA) Trigger: Re-score the design Failure Mode and Effects Analysis. The trimmed part’s risk does not vanish; it shifts to the absorbing component, which requires updated Severity and Occurrence ratings.

If persistent physical trade-offs stall your progress at step 2 or 3, run the root trade-offs through the TRIZ Contradiction Matrix Explained to resolve the underlying mechanics.

To implement this framework today, open your current product BOM, populate Tab 1 with your top 10 cost drivers, calculate their Trimming Priority Index in Tab 3, and test your highest-scoring part against Trimming Rule C.

Sources & Further Reading

TRIZ function analysis and trimming matrices trace their technical rigor directly to the structural modeling methods developed across four decades of patent research and value engineering standards.

TRIZ function analysis is an analytical modeling technique that maps an engineering system into subjects, actions, and objects to expose design vulnerabilities, operational redundancies, and unnecessary component costs.

Soviet inventor Genrich Altshuller established the empirical foundations of this method between 1946 and 1985, reviewing more than 200,000 patents to identify the structural laws governing technological system evolution. Modern function-cost modeling emerged later through researchers at the European TRIZ Association and MATRIZ, where methodologists Simon Litvin and Vladimir Petrov codified the 3 classical rules of trimming: removing the component when its function is obsolete, transferring the function to the object itself, or delegating the action to another existing system element.

These component pruning matrices link classical TRIZ to the Function Analysis System Technique (FAST) originated by Lawrence Delos Miles at General Electric in 1947 and codified by SAVE International. The literature below provides the formal algorithms, functional taxonomy, and mathematical criteria required to execute rigorous component trimming in complex engineering systems.

Featured image by Tima Miroshnichenko on Pexels