Engineering Design: Process, Principles & Best Practices
Turning an idea into a product, machine, structure, or system requires more than imagination. Engineers need expertise, analysis, and judgment to navigate the process of defining requirements, considering constraints, developing concepts, performing analysis, testing, managing risks, and documenting the results. Engineering design applies to a vast range of projects.
Whether you’re designing a mechanical component, a consumer product, an industrial machine, an electrical system, or a complex infrastructure project, the underlying objective is the same: to turn a need or desire into a solution that serves a particular function.
Modern engineering design also makes extensive use of computers and related technologies to enhance the design process. From computer-aided design and engineering tools to digital prototyping, additive manufacturing, and data management systems, there are many powerful technologies available to engineers. With that said, engineering design is ultimately a matter of process, requirements, analysis, and judgment.
A well-defined process can help engineers navigate the design process, anticipate potential failures, ensure that the product can be manufactured, and make decisions with confidence.
This guide covers the essentials of the engineering design process, including requirements and constraints, concept development and selection, analysis and modeling, CAD and digital engineering tools, prototyping and testing, verification and validation, standards and documentation, design for manufacturing and assembly, and risk, reliability, and safety considerations.
Table of Contents
1. What Is Engineering Design?
2. Why Engineering Design Matters
3. The Engineering Design Process
4. Understanding Requirements and Constraints
5. Concept Development and Selection
6. Engineering Analysis and Modeling
7. CAD and Digital Engineering Tools
8. Prototyping and Testing
9. Design Verification and Validation
10. Standards, Drawings, and Documentation
11. Design for Manufacturing and Assembly
12. Risk, Reliability, and Safety
13. Sustainable and Cost-Conscious Design
14. Common Engineering Design Mistakes
15. Best Practices for Successful Projects
16. The Future of Engineering Design
17. Frequently Asked Questions
18. Conclusion
19. Key Takeaway
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What Is Engineering Design?
Engineering design is the process of using science, math, engineering fundamentals, imagination, and constraints to arrive at a solution to a defined problem.
Engineering design can be applied to virtually every branch of engineering, including mechanical, civil, electrical, aerospace, automotive, chemical, industrial, biomedical, manufacturing, and systems engineering.
The design process typically involves identifying a need or set of requirements, investigating the problem and possible solutions, developing alternatives, and converging on a particular solution that can be turned into a physical product or system.
The output of the engineering design process can take many forms, from a simple machine to a complex machine and control system.
An important characteristic of professionally engineered systems is that the design decisions should be justified by analysis, whenever possible.
Calculations, tests, demonstrations, standards, material properties, previous design data, and other forms of analysis can support design decisions.
Engineering design is an iterative process, which means that it often involves going back and reworking previous design decisions.
For example, NASA’s systems engineering guide refers to technical requirements as “quantitative and/or qualitative statements of what the system must do or be to meet user needs and expectations.” The agency’s guide further indicates that requirements should be clear, fully defined, consistent, verifiable, and traceable.
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Why Engineering Design Matters
A strong engineering design process enables designers and engineers to go from an abstract idea to a concrete solution that can be manufactured, tested, operated, maintained, and upgraded.
Without a strong design process, projects can suffer from poor definition, excessive redesign, and uncontrolled costs.
Projects can suffer from poor definition, excessive redesign, and uncontrolled costs. In addition, poor design decisions can lead to products that are challenging to manufacture, operate, maintain, calibrate, or upgrade.
Design problems tend to get more expensive to fix as a project progresses.
It’s much easier to make changes and decisions at the beginning of a project than after detailed design, tooling, or manufacturing has occurred.
Standards play an important role in ensuring that design decisions are consistent and that designs can be manufactured and verified.
For example, ASME’s Y14 standards cover general engineering drawing practices and product definition, including presentation, dimensions, tolerancing, and other specifications and requirements.
ASME states that standards “address the need for communication and precision throughout the product lifecycle.”
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The Engineering Design Process
While every organization has its own process, most share certain similarities in the design process.
1. Define the Problem
Before jumping into solutions, the design team must understand the problem.
Some typical questions include:
O What problem are we to solve?
O Who will use the product?
O What will it do?
O Where will it be located?
O What are the existing limitations?
O How will we measure success?
2. Establish Requirements
Requirements take the general needs and desires stated in the problem definition and turn them into specific, measurable items.
For example, a designer might turn a general requirement, such as “the component must be strong,” into a specific requirement, such as a maximum load or stress value.
3. Generate Concepts
Next, the design team brainstorms alternative solutions to the problem.
Designers can use sketches, calculations, CAD models, simulations, prototypes, comparative studies, and even raw imagination to develop concepts.
4. Evaluate Alternatives
At this point, the design team can score and compare various alternatives based on criteria such as performance, cost, safety, manufacturability, reliability, and environmental impact.
5. Develop the Selected Design
With the best concept selected, the design team works to expand on the idea and turn it into something that can be manufactured or built.
Activities in this phase might include CAD modeling, design drawings, materials selection, tolerance analysis, engineering analysis, supplier meetings, and prototype development.
6. Verify and Validate
At this stage, the design is analyzed and tested to ensure that it will work as intended.
7. Release and Improve
The design is finalized and released, incorporating lessons learned from testing and manufacturing.
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Understanding Requirements and Constraints
One of the most vital activities in the design process is developing requirements that the design or product must meet.
Requirements define what must be achieved, and constraints define limitations within which the design must be developed.
Constraints can include budgets, materials, manufacturing capabilities, physical size and weight, energy consumption, safety, operating environments, regulations, schedules, interfaces with other components or systems, and many other factors.
Make Requirements Measurable
A requirement such as “the product must be lightweight” is too vague and subjective.
Instead, think about ways to make the requirement objective and measurable.
A good example might be a maximum mass for a given component.
A similar example would be to replace “the machine must be fast” with a specific cycle time.
In either case, requirements must be specific enough that it is possible to assess whether they have been met.
NASA’s systems engineering requirements guide indicates that requirements should be “clear and unambiguous,” “complete and consistent,” and “individually verifiable and traceable.”
Identify Conflicting Requirements
Sometimes, requirements are conflicting.
For example, one requirement might dictate that a product should be as light as possible, while another requires it to be as strong as possible.
Other examples could include reducing cost while increasing performance, or reducing production time while increasing precision.
By identifying these conflicts early in the design process, engineers can make informed decisions about which requirements are more important than others.
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Concept Development and Selection
At this point in the design process, creativity becomes an important part of the task.
The goal is not to develop a detailed solution, but rather to think of many possible approaches.
Generate Multiple Solutions
Designers and engineers can use a variety of methods to develop concepts, including hand sketches, CAD concepts, design reviews, mathematical models, existing products, engineering calculations, simulations, and even prototype experiments.
By generating multiple solutions, the design team can separate the best ideas from the rest.
Compare Concepts Objectively
One way to do this is to build a decision matrix that objectively compares options based on a variety of criteria.
Some common criteria include performance, cost, reliability, manufacturability, safety, and maintainability.
The weights assigned to each criterion should be based on the needs of the project, rather than arbitrary preferences.
Consider the Whole Lifecycle
A good designer considers the entire lifecycle of a product, from its creation to its disposal.
Concepts that look great on paper can be extremely expensive to manufacture or extremely difficult to maintain once they reach the field.
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Engineering Analysis and Modeling
Engineering analysis provides the justification for nearly every design decision.
Depending on the type of project, a designer or engineer might perform structural, thermal, fluid-flow, electrical, fatigue, vibration, tolerance, reliability, finite element, or computational fluid dynamics analysis.
The type of analysis performed will vary depending on the situation and the question being investigated.
For example, a designer might perform a stress analysis to ensure that a component will not deflect or fail when subjected to a specific load.
Understand Your Assumptions
Any engineering calculation or simulation involves assumptions.
Assumptions can include simplifications made to create a mathematical model, the properties of materials, the expected loading and boundary conditions, and many other factors.
It is critically important that everyone understands the assumptions that have been made and the implications of those assumptions.
Use the Right Level of Analysis
Many times, projects require no more analysis than a simple spreadsheet calculation.
Other times, particularly for high-consequence or high-complexity projects, analysis might involve finite element modeling and a variety of other tools.
The appropriate methods and level of analysis will vary depending on the project and its requirements.
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CAD and Digital Engineering Tools
Computer-aided design, or CAD, tools have revolutionized the field of engineering design.
These tools enable designers and engineers to create highly detailed geometry, assemblies, and product drawings.
Depending on the industry, engineers might also use finite element analysis software, computational fluid dynamics tools, electrical design simulation software, product lifecycle management systems, requirements management software, digital manufacturing tools, 3D scanning, generative design, or additive manufacturing tools.
Benefits of CAD
When used properly, CAD can greatly improve accuracy, visualization, collaboration, drawing creation, design iteration, assembly development, and manufacturing communications.
Designers and engineers can make quick edits, experiment with alternate concepts, and create drawings and other documentation with relative ease.
Digital Models Are Not Automatically Correct
No matter how beautiful a digital model might be, it is not automatically a correct design.
Designers and engineers who use CAD tools must still apply sound judgment and understand the limitations of their models.
These tools simply create a digital representation of whatever information is input into them.
As such, if incorrect or unrealistic information is input into a CAD tool, the output will also be incorrect or unrealistic.
ASME’s Y14 standards explicitly cover digital product definition, in addition to traditional engineering documentation.
This indicates that engineering drawings and documentation are becoming increasingly digital.
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Prototyping and Testing
A prototype can be anything from a 3D-printed component to a machined part, a fabricated assembly, a scale model, an electronic circuit, a software simulation, or a full-scale test article.
Prototypes support the design team in evaluating potential design solutions and identifying unforeseen challenges.
Depending on the situation, a prototype might be needed at a variety of different scales.
A designer must determine which aspects of a prototype are important and which details can be simplified.
Some examples of items that might be investigated using a prototype include ergonomics, fit, movement, assembly, thermal performance, stress levels, load capacity, fluid flow, and user interface.
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Design Verification and Validation
Verification and validation (V&V) are critical elements of the design process, ensuring that the final design meets requirements and is fit for its intended purpose.
V&V covers many of the same topics, but at slightly different stages of the design process.
Verification
Verification assesses whether the design or product meets stated requirements.
Common methods of verification include inspection, analysis, testing, demonstration, calculation, and document review.
The National Aeronautics and Space Administration (NASA) defines product verification as “evidence that a product meets specified requirements or specifications.” In turn, NASA states that verification “can be accomplished by test, analysis, demonstration, and/or inspection…”
Validation
Validation assesses whether the product will fulfill its intended purpose.
A machine, for example, might meet all of the dimensional tolerances specified in the design, but it might not meet the broader needs of the operator, supporting equipment, or process.
In short, validation looks at whether the product will actually work, given the intended application and environment.
NASA’s guide refers to validation as determining “whether a product meets the intended purpose based on the needs of the stakeholders and the concept of operations…”
Create a Traceability Structure
A traceability matrix can help to organize relationships between requirements, design elements, verification methods, and test results.
The matrix can help to ensure that all of the requirements have been addressed in the design and that all of the design elements have been properly verified.
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Standards, Drawings, and Documentation
Engineering design requires a great deal more than a working prototype.
The design must be able to be accurately recreated, which often means producing engineering drawings, using specification sheets, and applying other forms of documentation.
Technical documentation can include engineering drawings, CAD models, specifications, bills of materials, assembly drawings, test reports, inspection plans, material specifications, calculation packages, revision records, and other items.
Engineering Drawing Standards
Engineering drawing standards ensure that drawings are created and interpreted consistently.
ASME Y14.100 specifies requirements for preparing and revising engineering drawings and associated lists, unless otherwise noted in a specialty standard.
ASME Y14.24 covers types and uses of engineering drawings, and Y14.3 specifies the use of orthographic and pictorial views.
Dimensioning and Tolerancing
Dimensions indicate the size and location of features on a part or assembly.
Tolerancing specifies how much variation is allowed.
Geometric Dimensioning and Tolerancing (GD&T) provides a set of symbols and definitions that relate tolerances to the function of the features of parts and assemblies.
ASME specifies Y14.5 as its standard for dimensioning and tolerancing, including symbols, rules, definitions, and requirements.
Revision Management
Designs rarely remain the same, which means that drawings and specifications must also change.
Applying a controlled revision process ensures that everyone has the correct documents and that older versions of drawings are not used.
ASMEY14.35 covers the revision of engineering drawings and associated documents and provides methods of identification and record keeping.
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Design for Manufacturing and Assembly
One of the most important lessons in engineering design is that a design cannot be separated from its manufacturing and assembly processes.
In other words, no matter how good a theoretical design might be, it has to actually be manufactured in the real world.
Design for manufacturing, or DFM, refers to the practice of considering manufacturing requirements during the design process.
Some questions to ask include:
O What manufacturing process will be used?
O Can the required tolerances be achieved?
O Will the necessary materials be available?
O Can specialized tooling be avoided?
O Can production be automated?
O Can the design be inspected?
Design for assembly (DFA) takes a similar approach to automation and assembly operations.
Design for Assembly refers to design practices that make a product easier or more reliable to assemble.
Some good design for assembly practices that may be considered include:
• Minimizing part count
• Promoting simplification of fasteners
• Improving access
• Preventing misorientation
• Designing for sequence of assembly
• Providing clearance
Manufacturing and assembly considerations should ideally be considered during concept selection rather than left for later in the design process.
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Risk, Reliability, and Safety
Risk management is an important element of engineering design as well.
This involves identifying what can go wrong, the effect it would have, and then taking actions to minimize that risk.
Some common risk management techniques that apply to engineering design include:
• FMEA (Failure Mode and Effects Analysis)
• Fault-tree analysis
• Hazard analysis
• Reliability calculations
• Design reviews
• Safety testing
Design for Reliability
Reliability is the probability that a product or system will perform its intended function for a specified period of time, under stated conditions.
When designing products, engineers may want to consider factors such as:
• Fatigue
• Wear
• Corrosion
• Temperature
• Vibration
• Moisture
• Contamination
• Material degradation
• Maintenance
Build Safety into the Design
Safety is something that should be considered in the early stages of design.
Some examples of this include:
• Guarding moving parts
• Preventing excessive loads
• Fail-safe mechanisms
• Managing temperatures
• Incorrect assembly prevention
• Appropriate emergency controls
Determining specific requirements depends on the industry, product, jurisdiction, and applicable standards involved in the project.
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Sustainable and Cost-Conscious Design
Modern engineering design can increasingly factor in environmental and lifecycle concerns along with traditional technical considerations.
Concerns related to sustainability in engineering design may include:
• Materials
• Energy
• Manufacturing waste
• Lifecycle
• Repairability
• Recyclability
• Transportation
• End-of-life processing
Avoid Optimizing Only for Initial Cost
A lower purchase price for parts and materials does not always create a lower lifecycle cost.
For example, buying a higher-quality part that lasts longer may actually be less costly overall.
Lifecycle cost analysis can be valuable in these situations.
Reduce Material and Energy Waste
Engineers should consider options for minimizing material and energy waste such as:
• Lightweight structures
• Bulk material optimization
• Energy-efficient features and operation
• Minimization of manufacturing waste
• Minimization of service costs through longer service intervals
• More reusability
Which sustainability goals are most appropriate for a particular product depends on its intended purpose and environment.
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Common Engineering Design Mistakes
Inexperienced engineers are not the only ones who make mistakes in the design process.
Even experienced teams can run into issues if key aspects of the design process are not followed.
Starting With the Solution
Jumping right into CAD software can cause engineers to miss the opportunity to define the actual problem first.
The solution needs to actually address the underlying problem.
Poorly-Defined Requirements
Vague requirements make it very challenging to design or verify a solution.
Ignoring Manufacturing
If the solution cannot be manufactured cost-effectively, it may need to be completely redesigned.
Relying Entirely on Simulation
Simulation is a valuable tool, but simulation does not replace actual testing.
Neglecting Documentation
Incomplete documentation such as drawings, specifications, or revision records can create major downstream problems.
Making Changes Without Reviewing Their Impact
Making a seemingly minor change to a design can have a major secondary impact on strength, tolerances, assembly, safety, cost, and other concerns.
Failing To Learn from Testing
Testing only has value if the team takes the time to actually analyze the results from their tests.
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Best Practices for Successful Projects
An effective engineering design workflow can be enhanced through certain best practices.
Define Success Before Designing
Define requirements before starting to develop a solution.
Explore Alternatives
Engineering design students should consider alternatives before settling on a particular solution.
Involve Relevant Teams Early
Discussions with manufacturing, quality, procurement, maintenance, safety, operations, and other support teams can help reveal important constraints that you did not know about.
Manufacturing and other teams can identify important requirements and limitations.
Document Important Decisions
Engineers often need to provide justifications for major design decisions they make.
Documentation should state the basis and supporting information for decisions made during the design process.
Review At Key Milestones
Design reviews help uncover problems early, before you spend too much time and money on a particular approach.
Verify Critical Requirements
Requirements that address safety, performance, cost, and other critical areas should receive special attention.
Maintain Configuration Control
Make sure that drawings, models, specifications, and other design elements are properly synchronized and available.
Treat Feedback as Engineering Intelligence
Prototype failures, manufacturing and supplier problems, customer input, failures in the field, and feedback from service engineers all represent valuable engineering data that can be used to update or refine a design.
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The Future of Engineering Design
The future of engineering design will involve increasingly sophisticated combinations of traditional techniques and emerging technology.
Artificial intelligence, generative design, digital twins, additive manufacturing, advanced simulation, automated inspection, and integrated product data are transforming the profession.
Generative and AI-assisted tools may allow engineers to explore more options more rapidly.
Digital twins can link product models with operational information.
Additive manufacturing might make some traditionally challenging designs significantly more straightforward to develop and test.
That said, the basic engineering principles will remain largely the same.
Even as these advanced methods become widely used, engineers will still need to understand physics, materials, manufacturing, and safety, and consider requirements, test, validate, and make decisions based on analysis and experience.
NASA's current systems engineering tools continue to emphasize disciplined design, requirements, verification, validation, and technical management in addition to emerging advanced engineering methods.
The best possible future workflow will integrate computational capabilities with human technical expertise and engineering judgment.
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Frequently Asked Questions
What is engineering design?
Engineering design refers to the process of developing solutions to well-defined problems through the application of technical knowledge, analysis, creativity, requirements, constraints, testing, and practicality.
What Are the Major Steps in the Engineering Design Process?
Common steps include defining the problem, defining requirements, creating concepts, evaluating concepts, developing a chosen concept into the proposed solution, analyzing the solution, building prototypes, testing, verifying the solution, validating the solution, documenting the solution, and refining it.
Why Are Engineering Requirements Important?
Requirements define what a product or system must do; requirements provide a clear picture against which a proposed solution can be evaluated.
What Is the Difference Between Verification and Validation?
Verification ensures that a specific design actually meets given requirements.
Validation ensures that the final solution does what it was intended to do.
How Does CAD Aid Engineers?
Engineering design software can assist engineers in creating, modifying, visualizing, analyzing, and documenting a design; it is not a magic tool that makes everything easy.
Why Are Standards Important in Engineering Design?
Standards establish conventions that facilitate communication, inspection, documentation, and other activities in manufacturing.
Engineers, manufacturers, inspectors, fabricators, designers, and others need to share drawings, dimensions, tolerancing, and other technical information with various stakeholders, and that is easier and more accurate when standards provide shared definitions for those terms.
What Is Design for Manufacturing?
Design for manufacturing is an approach to product design that takes into consideration how the product may actually be manufactured.
This helps ensure that designs can actually be built, tested, and used reliably and economically.
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Conclusion
Engineering design is much more than creating a drawing, CAD model, or prototype of some kind. It is a comprehensive process for developing a solution to a defined need by integrating requirements, analysis, creativity, manufacturing, testing, and other considerations.
The most effective engineering design projects clearly define the problem to be solved, establish requirements, explore multiple concept options, analyze the impact of key technical trade-offs, test critical aspects and assumptions, recognize that it is often necessary to go back and change an earlier design choice based on new information - or even reject a favored solution in favor of one that is now clearly better.
Standards establish conventions that let designers, manufacturers, inspectors, and others share and interpret technical drawings, documentation, and other requirements.
Likewise, while CAD, simulation, prototyping, and other tools make the engineering design process more powerful, more efficient, and more sophisticated, they are still most effective when used in combination with sound technical reasoning and judgment.
Whether you are designing and analyzing a simple mechanical component or a complex engineered system, one thing remains fundamentally true: to get a product from concept to completion involves defining its intended purpose and then developing an appropriate solution that you verify, validate, document, and refine.
Finally, good engineering design considers how a product can be made more sustainable, safer, more reliable, or designed with consideration for its overall lifecycle. When you balance performance, safety, cost, manufacturability, and lifecycle needs, engineers create truly successful products, both on paper and in the real world.
Key Takeaway
Creating value through innovation and engineering design solutions requires a comprehensive process of solution development based on requirements, concept development, technical analysis, CAD design, prototyping, verification, validation, standards, risk management, manufacturability, and continuous improvement.
References
ASME Y14 Standards: cover engineering drawings, product definition, dimensioning and tolerancing, as well as related documentation.
ASME Y14.100 — Engineering Drawing Practices: Regulations concerning engineering drawing practices for the preparation and revision of manual or computer-generated engineering drawings and the associated lists.
ASME Y14.24 — Types and Applications of Engineering Drawings: Guidance on the types and applications of engineering drawings: relating to the types and applications of engineering drawings.
ASME Y14.3 — Orthographic and Pictorial Views: Requirements relating to orthographic and pictorial views in engineering drawings and models.
ASME Y14.35 — Revision of Engineering Drawings and Associated Documents: Practices for identifying and recording revisions to engineering drawings and associated documents.
NASA Systems Engineering Processes and Requirements: Guidance is provided by NASA regarding systems engineering processes and requirements, covering technical requirements, verification, validation, traceability, and systems engineering processes.
NASA Systems Engineering Handbook: Guides validation planning, testing, analysis, modelling, and lifecycle engineering.
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