Mechanical Design Foundations and Systems Thinking

Introduction

Mechanical systems design is the disciplined activity of transforming a need into a safe, useful, manufacturable, economical, and maintainable product or process. It combines mechanics, materials, manufacturing, control, economics, human factors, and project management. A mechanical designer therefore does more than calculate dimensions. The designer interprets ambiguous needs, identifies interactions among components, evaluates alternatives, manages risk, and makes decisions that remain defensible throughout the product life cycle.

A gearbox, robot joint, agricultural machine, pump, medical device, or automated production cell is a system. Its performance depends not only on individual parts but also on interfaces, operating conditions, users, suppliers, software, maintenance practices, and disposal. Systems thinking provides the broader perspective needed to avoid local improvements that create global problems.

This chapter establishes the foundation for later study of mechanisms, machine elements, materials, manufacturing, control, and reliability. It presents a practical design process, explains how stakeholder needs become measurable requirements, develops functional structures and concepts, and introduces standards, planning, risk management, and design reviews.

Learning Objectives

By the end of this chapter, a student should be able to:

1. Explain the engineering design process and distinguish it from routine analysis.
2. Describe the principal stages of a product life cycle.
3. Translate stakeholder statements into verifiable engineering requirements.
4. Construct a functional structure and identify system boundaries and interfaces.
5. Develop and compare mechanical design concepts using explicit criteria.
6. Explain the roles of standards, codes, regulations, and organizational procedures.
7. Prepare a basic design work plan using deliverables, dependencies, and reviews.
8. Apply systems thinking to interactions, trade-offs, risks, and life-cycle consequences.
9. Participate effectively in design reviews and communicate technical decisions.

1. Design as a Professional Engineering Activity

Design is purposeful synthesis. In analysis, the engineer begins with a defined system and predicts its behavior. In design, the engineer begins with a need and selects or creates a system that will provide the required behavior. The two activities are iterative: analysis is used to evaluate designs, while design decisions determine what must be analyzed.

A design problem is usually characterized by incomplete information, competing objectives, uncertainty, and constraints. For example, reducing the mass of a lifting arm may increase deflection, reduce fatigue life, complicate manufacture, or increase material cost. There is rarely a single mathematically optimal answer. Instead, a satisfactory design must balance technical, economic, environmental, legal, and human considerations.

A useful distinction is:

• Need: a statement of a problem or desired outcome.
• Requirement: a precise condition that the system must satisfy.
• Function: an action the system must perform.
• Concept: a proposed principle or arrangement that may realize the functions.
• Embodiment: the selected physical architecture, components, materials, and interfaces.
• Detail design: the definition required for manufacture, assembly, inspection, operation, and maintenance.

Design is also a social and organizational activity. Stakeholders include customers, operators, maintenance personnel, manufacturers, regulators, owners, suppliers, and people affected by the product. Their goals may conflict. A professional designer makes those conflicts visible rather than silently optimizing for one stakeholder.

2. The Integrated Design Process

Although organizations use different names, a robust mechanical design process commonly follows these activities:

1. Opportunity or problem identification: establish why action is needed.
2. Stakeholder and context investigation: identify users, environments, constraints, and affected parties.
3. Requirements definition: convert needs into measurable, prioritized, and verifiable statements.
4. Functional analysis: describe what the system must do without prematurely selecting components.
5. Concept generation: create several feasible operating principles and architectures.
6. Concept selection: compare alternatives against agreed criteria and risks.
7. Preliminary embodiment: establish geometry, loads, materials, interfaces, and operating logic.
8. Detailed design: produce drawings, models, calculations, specifications, bills of materials, and manufacturing information.
9. Verification and validation: determine whether the design was built correctly and whether it solves the intended problem.
10. Production, deployment, and support: manufacture, install, operate, inspect, repair, and improve the product.
11. Retirement and learning: decommission, reuse, recycle, dispose of, and record lessons for future designs.

These stages are not strictly sequential. New test results may alter requirements; a manufacturing review may require a concept change; a safety analysis may reveal an omitted function. Iteration should be controlled through documented decisions and configuration management.

Verification and validation

Verification asks, “Did we build the system right?” It uses inspection, calculation, simulation, testing, or review to demonstrate conformity to specified requirements. Validation asks, “Did we build the right system?” It evaluates whether the product satisfies the real user need in its intended context. A component can pass a strength calculation yet fail validation if it is too difficult to adjust or unsafe to operate.

3. Product Life Cycle and Life-Cycle Thinking

A product life cycle begins before manufacture and continues after operation. Typical stages are:

Life-cycle thinking prevents a narrow focus on purchase price. A low-cost component may require frequent replacement, consume more energy, or be difficult to recycle. Conversely, a higher initial cost may be justified by reduced downtime and longer service life.

A simplified total life-cycle cost can be represented as:

where C_L is total life-cycle cost, C₀ is development or acquisition cost, C_i is installation and commissioning cost, C_e is operating energy and consumable cost, C_m is maintenance and repair cost, C_d is decommissioning cost, and S_r is residual or recovery value. All terms must use the same monetary basis and time basis. If costs occur over many years, discounting may be required; the simple expression is a planning approximation, not a financial valuation model.

Life-cycle assessment extends this reasoning to environmental effects, including material extraction, manufacturing energy, transport, use-phase energy, maintenance, and end-of-life treatment. Designers should consider material reduction, repairability, modular replacement, energy efficiency, and recovery without compromising safety.

4. Stakeholders, Needs, and Requirements

Stakeholder statements are often valuable but unsuitable as direct design specifications. A customer may say, “The machine must be fast, quiet, affordable, and easy to maintain.” These terms require interpretation.

A requirement should ideally be:

• Necessary: linked to a genuine need or obligation.
• Unambiguous: open to only one reasonable interpretation.
• Measurable: expressed using a quantity, condition, or observable criterion.
• Feasible: achievable within available technology and resources.
• Traceable: linked to its source and to later verification evidence.
• Prioritized: identified as mandatory, important, or desirable.
• Stable but controlled: changes are possible through an agreed process.

A strong requirement normally includes an object, action or condition, performance measure, operating context, and acceptance criterion. For example:

The conveyor shall transport 25 kg loads at a belt speed of 0.60 ± 0.03 m/s in an ambient temperature of 5–35 °C without load slippage.

This is stronger than “The conveyor should move loads quickly.” The measurable version still requires clarification about duty cycle, load distribution, belt condition, and test method.

Needs-to-requirements example

Suppose operators report that a portable drilling unit is “too tiring to use.” Investigation identifies long periods of hand support, vibration, awkward posture, and frequent repositioning. Possible requirements include:

• total mass shall not exceed 8 kg;
• the primary handle shall permit operation with a neutral wrist posture;
• weighted hand-arm vibration exposure shall remain below the applicable occupational limit for the defined work shift;
• drill-bit changeover shall require no more than 30 s using gloved hands;
• the unit shall withstand a 1 m accidental drop without creating an exposed electrical hazard.

The specific values must come from research, regulation, benchmarking, or negotiated stakeholder decisions. A designer must not invent performance limits without justification.

Requirements hierarchy and traceability

Requirements may be organized from mission level to system, subsystem, and component levels. A high-level requirement such as “provide safe lifting” can be decomposed into load capacity, stability, guarding, emergency stopping, inspection access, and structural integrity. Each lower-level requirement should support a higher-level requirement, and each should have a planned verification method.

A traceability matrix may contain the following fields:

Traceability reduces omissions and supports change control. When a requirement changes, affected components, calculations, tests, suppliers, and documents can be identified.

5. Functional Analysis and Functional Structures

A function describes what a system must accomplish, not how it will accomplish it. A useful functional statement uses a verb and an object, such as “support load,” “convert rotation,” “transfer heat,” “contain fluid,” or “protect operator.” Avoiding solution terms at this stage encourages wider exploration.

A functional structure represents flows through the system. Common flow categories are:

• Material: solids, liquids, gases, workpieces, waste.
• Energy: mechanical, electrical, thermal, hydraulic, pneumatic.
• Signal: commands, measurements, feedback, status information.

For a powered lifting table, the top-level function might be “position load.” Subfunctions could include receive command, supply energy, convert energy, transmit motion, guide platform, support load, limit travel, detect overload, and communicate status.

Figure: An illustrative functional structure for a powered lifting table.

The diagram is not a final physical layout. It helps the team identify missing functions and interfaces before selecting a motor, screw, hydraulic cylinder, or control system.

6. Specifications, Constraints, and Trade-offs

A specification defines how performance will be judged. It should distinguish:

• Performance requirements: speed, capacity, accuracy, efficiency, noise, life.
• Physical constraints: envelope, mass, mounting points, available power.
• Environmental conditions: temperature, humidity, dust, corrosion, shock.
• Interface requirements: electrical connections, shafts, fasteners, data, human access.
• Safety requirements: guarding, fail-safe behavior, emergency stopping, containment.
• Manufacturing and service requirements: tolerances, processes, inspection, access.
• Commercial requirements: cost, delivery, supplier availability, intellectual property.

Design objectives often conflict. A concept-selection matrix makes assumptions explicit. A simple weighted score is:

where S is the total score, w_i is the normalized weight of criterion i, and r_i is the normalized rating of a concept for that criterion. Usually, weights satisfy ∑w_i = 1. Ratings must use a defined scale, such as 1–5, and higher ratings must consistently mean better performance. This method supports discussion; it does not replace engineering judgment, safety analysis, or feasibility checks. A concept that violates a mandatory safety requirement should be rejected regardless of its total score.

For example, three concepts may be rated for capacity, cost, serviceability, and risk. The team should record why each rating was assigned, identify uncertainty, and test whether the preferred concept changes when weights vary. This sensitivity analysis is important when stakeholder priorities are uncertain.

7. Concept Generation and Selection

Concept generation should precede premature detail. Techniques include functional decomposition, morphological charts, analogy, physical principles, benchmarking, sketches, and structured brainstorming. A morphological chart lists alternative principles for each subfunction. For “convert rotary input to linear motion,” alternatives might include a lead screw, rack and pinion, belt drive, cam, or hydraulic actuator. Combining alternatives creates candidate architectures.

Good concept work separates generation from evaluation. During generation, unusual alternatives should not be rejected too early. During evaluation, however, concepts must be subjected to feasibility, safety, cost, manufacturability, maintainability, and performance scrutiny.

A concept description should state:

1. the operating principle;
2. major components and energy paths;
3. critical interfaces;
4. expected advantages and disadvantages;
5. uncertain assumptions;
6. likely failure modes;
7. the tests or calculations needed next.

8. Systems Thinking in Mechanical Design

Systems thinking focuses on relationships, boundaries, feedback, and emergent behavior. A system is more than the sum of its parts because interactions can create behavior not evident in isolated components.

Important systems-thinking questions include:

• What is inside and outside the system boundary?
• Which inputs, outputs, and disturbances affect performance?
• Which components share loads, heat, vibration, or information?
• What feedback loops exist?
• What happens during abnormal or degraded operation?
• Which life-cycle stage is creating the observed problem?
• What second-order effects follow from the proposed improvement?

For example, increasing motor power may improve acceleration but increase heat, gearbox load, structural vibration, electrical demand, and braking requirements. A locally successful change can therefore reduce overall system reliability.

Interfaces deserve special attention. Mechanical interfaces include bolts, shafts, bearings, fits, seals, and guides. Non-mechanical interfaces include power supplies, control signals, software commands, operators, maintenance procedures, and supplier responsibilities. Interface control documents can define ownership, dimensions, loads, tolerances, connectors, and acceptance tests.

Safety should be treated as a system property. A guard, sensor, brake, warning label, and operator procedure may work together as a protective strategy. Removing one element can alter the risk of the entire system.

9. Standards, Codes, Regulations, and Ethics

Standards are agreed technical or procedural references. Codes may establish accepted engineering practice, while regulations are legally enforceable requirements imposed by authorities. Company procedures and customer specifications may add further obligations. Their applicability depends on product type, location, industry, and intended use.

A design team should determine early:

• which laws and regulations apply;
• which product and safety standards are mandatory or contractually required;
• which material, welding, dimensional, electrical, or testing standards are relevant;
• what evidence is required for conformity;
• who is responsible for certification and technical files.

Standards do not eliminate engineering judgment. A standard may define a test method or minimum safety provision, but the designer remains responsible for foreseeable misuse, integration effects, and conditions outside the standard’s scope.

Professional ethics require protection of public safety, honesty in reporting, competence, confidentiality, and disclosure of conflicts of interest. A designer must not conceal failed tests, misrepresent simulation accuracy, or approve work beyond their competence. Sustainability and accessibility are also ethical design considerations because costs and risks may be distributed unevenly across users and communities.

10. Project Planning and Configuration Management

Design projects require a technical plan and a management plan. The technical plan identifies work packages, analyses, prototypes, tests, and decisions. The management plan addresses people, time, cost, procurement, communication, risk, and change.

A work breakdown structure divides the project into deliverable-oriented packages. A schedule then identifies dependencies. For example, final shaft drawings depend on the selected bearing arrangement, which depends on loads and speed, which depend on the chosen architecture and operating requirements.

A practical design plan includes:

Configuration management controls versions of requirements, models, drawings, software, test procedures, and bills of materials. Without it, a test may be performed on one revision while production uses another. Changes should be identified, assessed for impact, approved at the proper authority, and recorded.

11. Risk, Uncertainty, and Design Reviews

Risk is commonly considered in terms of the likelihood of an undesired event and the consequence if it occurs. A qualitative risk matrix can prioritize attention, but numerical risk scores should not create false precision. High-severity hazards require rigorous treatment even when their probability is uncertain.

Common risk responses include:

• eliminate the hazard through inherent design;
• reduce likelihood through robust geometry, materials, or controls;
• reduce consequences through containment, guarding, or emergency systems;
• provide warnings and procedures as a later line of defense;
• monitor, inspect, and maintain the system.

Failure mode and effects analysis (FMEA) systematically considers how a component can fail, what causes the failure, what effect it has, and how the failure can be detected or controlled. Fault-tree analysis begins with an undesired top event and reasons backward through combinations of causes. These methods are complementary and should be connected to requirements and verification plans.

Design reviews are formal decision points, not ceremonial presentations. Typical reviews include:

• Requirements review: Are needs understood, measurable, and complete?
• Concept review: Are alternatives credible and risks visible?
• Preliminary design review: Is the architecture feasible and interfaces controlled?
• Critical design review: Is the design sufficiently defined for manufacture and verification?
• Readiness review: Are tests, production, installation, and safety evidence ready?

An effective review states entry criteria, provides evidence, records decisions and action owners, and defines closure conditions. Reviewers should be independent enough to challenge assumptions constructively.

12. Worked Example: Selecting a Manual Lifting Concept

Consider an illustrative design problem: a workshop needs a manually operated device to raise a 250 kg fixture through 0.8 m. The device must fit within a 1.2 m by 0.8 m floor area, be stable on a level floor, require no external electricity, and allow controlled lowering. The example is conceptual; final dimensions and safety factors require detailed engineering and applicable standards.

Step 1: Interpret the need

The need is not simply “provide a jack.” The system must raise, hold, and lower the fixture while protecting the operator and maintaining stability.

Step 2: Establish preliminary requirements

Possible requirements include:

• rated working load: 250 kg fixture mass;
• vertical travel: 0.8 m;
• manual operation with no external electrical supply;
• controlled lowering under normal operation;
• defined maximum operating effort, to be established through ergonomic assessment;
• stable operation within the specified floor envelope;
• positive load retention when the operator releases the control;
• inspection access for wear-critical components.

The gravitational force associated with the fixture is approximately:

where W is weight in newtons, m is mass in kilograms, and g is gravitational acceleration, approximately 9.81 m/s² near Earth’s surface. For m = 250 kg, W = 250 × 9.81 = 2452.5 N, or approximately 2.45 kN. This is the static load only; acceleration, impact, eccentric loading, friction, and required design factors must also be considered.

Step 3: Generate concepts

Three candidate principles are:

• a hand-operated hydraulic cylinder;
• a screw lift with a handwheel;
• a foot-operated toggle or linkage lift.

The hydraulic concept may provide compact force multiplication but can leak and may require a reliable lowering valve. The screw concept can provide positive holding and precise positioning but may require many turns and careful consideration of self-locking, wear, and buckling. The linkage may be inexpensive but could have poor mechanical advantage near parts of its stroke.

Step 4: Compare concepts

Assume the team uses criteria of safety, controllability, manufacturability, maintenance, and operator effort. Safety is a screening criterion: any concept lacking positive load retention is rejected until corrected. A weighted matrix can then compare the remaining alternatives. The result is not a final answer; it identifies which uncertainties deserve testing.

Step 5: Plan verification

The selected concept requires calculations for structural strength, stability, buckling, bearing or seal life, handle effort, and fatigue where applicable. Tests should verify rated load, overload behavior, controlled lowering, retention after release, stability, repeated cycling, and foreseeable misuse. Inspection criteria and maintenance intervals must be defined before release.

Learning from the example

The central design work occurred before detailed sizing. The team translated a vague need into requirements, recognized system-level functions, compared operating principles, identified hazards, and planned evidence. A mathematically precise component calculation would be premature if the architecture and requirements were still uncertain.

13. Contemporary Tools and AI-Assisted Design

Computer-aided design, finite-element analysis, computational fluid dynamics, digital manufacturing, additive manufacturing, and product-data management can accelerate design. However, software output is not automatically valid. Model assumptions, boundary conditions, mesh quality, material data, contact definitions, tolerances, and validation tests determine credibility.

AI tools can assist with requirements classification, alternative generation, document search, anomaly detection, scheduling, and design-space exploration. Their use requires governance:

• verify generated technical claims against authoritative sources;
• protect confidential and personal data;
• record important prompts, inputs, versions, and decisions where traceability matters;
• test for bias or omission in stakeholder analysis;
• maintain human accountability for safety-critical decisions;
• do not treat plausible language as engineering evidence.

The best use of automation is to expand disciplined engineering work, not to replace professional judgment or independent verification.

Challenges and Limitations

Mechanical design is limited by uncertainty in loads, material properties, user behavior, manufacturing variation, environment, and future maintenance. Requirements may conflict or change. Models simplify reality, and tests sample only some operating conditions. Cost and schedule pressure can encourage premature design freeze or inadequate verification.

Systems thinking also has practical limits. A system boundary cannot include everything, and excessive analysis can delay action. The appropriate response is to state assumptions, identify the most influential interactions, prioritize risks, and revise the model when evidence changes. Engineering maturity is not the absence of uncertainty; it is the explicit management of uncertainty.

Chapter Summary

Mechanical systems design transforms stakeholder needs into a verified and validated product or process. It is iterative, multidisciplinary, and constrained by safety, performance, cost, manufacturing, service, regulation, and sustainability. The design process moves through problem definition, requirements, functional analysis, concept generation, selection, embodiment, detail design, verification, validation, production, operation, and retirement.

Effective requirements are necessary, measurable, feasible, traceable, prioritized, and verifiable. Functional structures describe material, energy, and information flows without prematurely selecting components. Concept selection uses explicit criteria but must respect mandatory constraints and safety obligations. Systems thinking draws attention to boundaries, interfaces, feedback, emergent behavior, and life-cycle consequences.

Standards and regulations establish obligations and accepted practices, while ethics requires honest reporting and protection of people and the environment. Project planning, configuration management, risk analysis, and formal design reviews provide the governance needed to convert technical work into a reliable deliverable. Modern CAD, simulation, manufacturing technologies, and AI can improve productivity, but their outputs require engineering judgment and independent evidence.

Key Terms

Need: A recognized problem or desired outcome.

Requirement: A precise condition the system must satisfy.

Function: An action the system must perform, stated independently of a particular solution.

Concept: A proposed operating principle or arrangement.

Embodiment: The physical architecture and major component arrangement.

Specification: A documented, measurable definition of required performance or characteristics.

Verification: Evidence that the design conforms to specified requirements.

Validation: Evidence that the product satisfies the intended real-world need.

Stakeholder: A person or organization affected by, responsible for, or interested in the system.

Functional structure: A representation of functions and flows of material, energy, and information.

Interface: A boundary where components, subsystems, people, or organizations interact.

Life-cycle thinking: Consideration of impacts and decisions across development, use, maintenance, and retirement.

Traceability: The ability to link needs, requirements, design features, tests, and decisions.

Configuration management: Control of product definitions and changes throughout development.

Design review: A formal evaluation of design evidence against defined criteria.

Risk: The possibility and consequence of an undesired event.

FMEA: A structured analysis of failure modes, causes, effects, and controls.

Standard: An agreed technical or procedural reference.

Systems thinking: Analysis of relationships, interactions, boundaries, and emergent behavior.

Life-cycle cost: The total cost associated with acquisition, use, maintenance, and retirement.

Review Questions

Short Answer Questions

1. What is the difference between verification and validation?
2. List four characteristics of a well-written engineering requirement.
3. Why should functional analysis precede detailed component selection?
4. What types of flow are commonly represented in a functional structure?
5. What is the purpose of configuration management?

Long Answer Questions

1. Explain the integrated mechanical design process from problem identification through retirement, including the role of iteration.
2. Discuss how stakeholder needs can be transformed into measurable and traceable requirements. Use an example.
3. Explain how systems thinking changes the design of a mechanical product compared with optimizing individual components.
4. Describe the purposes of standards, regulations, ethics, risk analysis, and design reviews in professional design.
5. Explain how life-cycle cost and environmental considerations can influence concept selection.

Analytical / Application Questions

1. A production machine is made lighter by reducing frame thickness, but vibration and maintenance failures increase. Analyze the problem using systems-thinking concepts and propose an investigation plan.
2. Develop a preliminary requirements table and functional decomposition for a manually operated mobile lifting device intended for a workshop.
3. Compare a screw drive, hydraulic actuator, and belt mechanism for a positioning application. Define selection criteria, identify mandatory constraints, and explain what evidence would be needed before selecting one concept.

Multiple Choice Questions with Answers

Question 1

Which statement best distinguishes verification from validation?

A. Verification confirms that the product meets specified requirements; validation confirms that it satisfies the intended need.

B. Verification is performed only after production; validation is performed only before concept generation.

C. Verification concerns cost; validation concerns material selection.

D. Verification replaces testing; validation replaces engineering judgment.

Correct Answer: A. Verification confirms that the product meets specified requirements; validation confirms that it satisfies the intended need.

Question 2

Which is the strongest engineering requirement for a conveyor?

A. The conveyor should be reasonably fast.

B. The conveyor shall transport loads reliably.

C. The conveyor shall transport 25 kg loads at 0.60 ± 0.03 m/s under the defined operating conditions.

D. The conveyor shall use a high-quality motor.

Correct Answer: C. The conveyor shall transport 25 kg loads at 0.60 ± 0.03 m/s under the defined operating conditions.

Question 3

Which item is normally a function rather than a solution?

A. Support load

B. Use a hydraulic cylinder

C. Use a lead screw

D. Use an aluminum frame

Correct Answer: A. Support load

Question 4

For a 250 kg mass near Earth’s surface, using g = 9.81 m/s², what is its approximate static weight?

A. 25 N

B. 245 N

C. 2.45 kN

D. 24.5 kN

Correct Answer: C. 2.45 kN

Question 5

What is the primary purpose of a requirements traceability matrix?

A. To replace all design calculations

B. To link requirements to sources, design elements, and verification evidence

C. To select the cheapest material automatically

D. To eliminate the need for design reviews

Correct Answer: B. To link requirements to sources, design elements, and verification evidence

Question 6

Which statement about a weighted concept-selection matrix is correct?

A. It makes safety constraints unnecessary.

B. It provides structured comparison but does not replace engineering judgment.

C. It proves that the highest-scoring concept is physically feasible.

D. It can be used without defining rating scales.

Correct Answer: B. It provides structured comparison but does not replace engineering judgment.

Question 7

Which example best illustrates systems thinking?

A. Selecting a bearing solely by its catalog load rating

B. Increasing motor power without considering heat or braking

C. Examining how motor power affects vibration, heat, gearbox load, and safety systems

D. Ignoring interfaces until detail drawings are complete

Correct Answer: C. Examining how motor power affects vibration, heat, gearbox load, and safety systems

Question 8

Which activity is most closely associated with configuration management?

A. Controlling revisions of drawings, models, requirements, and bills of materials

B. Estimating gravitational acceleration

C. Choosing a brainstorming technique

D. Calculating only the purchase price

Correct Answer: A. Controlling revisions of drawings, models, requirements, and bills of materials

Question 9

Which risk response is generally the most preferable when practical?

A. Rely exclusively on warning labels

B. Eliminate the hazard through inherent design

C. Ignore low-probability hazards

D. Transfer every risk to the operator

Correct Answer: B. Eliminate the hazard through inherent design

Question 10

What is a principal limitation of AI-generated engineering content?

A. It can never process technical text.

B. It automatically provides certified evidence.

C. Plausible output may contain unsupported or incorrect technical claims.

D. It eliminates the need for data governance.

Correct Answer: C. Plausible output may contain unsupported or incorrect technical claims.