What is engineering design?

Engineering design is described as a method that engineers use to identify and solve a problem by taking a fixed series of steps. The engineering design process involves designing a component or machine element that satisfies certain criteria or performs a specific function. This includes designing, building, and testing the product or machine element.

The various steps involved in the engineering design process are shown as,

Define the problem

In this step, the problem is identified and defined, such as a product or machine element which is to be manufactured along with its function. It is completely based upon customer's or society's needs.

Do background research

In this step, present solutions to similar problems are identified and mistakes made in previous solutions are avoided. The major areas of background research are customer needs and the study of existing solutions.

Specify requirements

In this step, the design requirements for the solution to succeed are identified. The best way to do this is to analyze the existing solutions deeply and eliminate their drawbacks.

Brainstorm solutions

This step involves the identification of alternative solutions over existing ones based on customer needs, existing product's drawbacks, and many other factors. A good designer will generate several possible solutions for a specific problem to obtain the best results.

Choose the best solution

In this step, the best solution among all possible alternatives is identified. The selection is made taking into account all the design constraints and requirements.

Develop the solution

The development of a solution involves its refinement and improvement throughout the design process before finalizing the product.

Build a prototype

A prototype is a sample or operating version of a created solution. It is made for testing purposes and making changes before the production of the final product. It is a key step in developing the final solution, allowing the designer to test the function of the created solution.

Test and redesign

In this step, the multiple iterations and redesigns of the solution are done based on various results and feedback obtained over the prototype.

Communicate results

In this step, the final solution is generated and displayed. The manufacturing good is now ready for sale and fulfills customer needs.

Design considerations

Following are the various common design considerations:

• Functionality and reliability
• Strength, durability, and safety
• Stress
• Deflection, distortion, and stiffness
• Wear, friction, and surface finish
• Corrosion and lubricant
• Weight, shape, and size
• Cost, competition, and marketability, etc.

Design techniques

Following are the five basic design techniques:

• Computer-aided design (CAD)
• Robust design
• Design for excellence (DFX)
• Design for manufacturing (DFM)
• Design for assembly (DFA)

Computer-aided design (CAD)

Computer-aided design is the process in which a product or machine element's design is prepared with the help of computer software. CAD uses graphical representations like points, lines, planes, and shapes to create a design or drawing. The product's design gives a detailed description of the product's function in graphical form.

Use of CAD

CAD is used to produce introductory design, layouts, design details and calculations, and three-dimensional models based on the designer's requirements.

It facilitates the manufacturing process of the product by supplying detailed information and can be used to produce two-dimensional and three-dimensional designs. The CAD software allows the object to be viewed from any angle, even from inside to outside.

The software is widely used from conceptual design and layout to definition and manufacturing of the product. CAD directly reduces design time and correction time by allowing precise simulation rather than building and testing a physical prototype.

It is widely used for designing industrial products, structural products, animation visuals, and other applications.

Types of CAD software

Following are two common types of CAD software:

• Two-dimensional CAD (2D CAD)
• Three-dimensional CAD (3D CAD)

Two-dimensional CAD

2D CAD is used to design two-dimensional products. It is used in various industries, civil works, and architect applications. Products of negligible or constant thickness are designed with this software.

AutoCAD, LibreCAD, and FreeCAD are some examples of 2D CAD software.

Three-dimensional CAD

3D CAD is used to design three-dimensional products. 3D CAD is further classified as:

• Wireframe models
• Surface models
• Solid models

CATIA, Solidworks, and Creo are some examples of 3D CAD software.

Advantages of CAD software

Following are some advantages of CAD:

• It improves the productivity of the designer.
• It improves the quality of the design.
• Corrections are easily made.
• It is easy to restore the design.

Robust design

Robust design process decreases variation in a product without reducing the cause of variation. The variation in a product is classified into three common types:

• Internal variation
• External variation
• Unit-to-unit variation

Internal variation occurs due to the wear of the product, aging of material, and other factors. External variation is a form factor relating to environmental conditions such as temperature, relative humidity, and others. In contrast, unit-to-unit variation is variations between parts due to different materials, manufacturing processes, etc.

In this process, the main aim is to find the values for controllable settings that minimize the negative effects of the uncontrolled settings. The identified controllable factors are changed to find the optimal settings to minimize cost by minimizing variation.

Advantages of robust design

Following are some advantages of robust design:

• Robustness improves the quality of the product.
• Robustness reduces variation in parts by reducing the effects of uncontrollable variation.
• Lower quality parts with higher tolerances are used.
• It improves the product's requirements.
• It reduces product maintenance.

Design for excellence (DFX)

Design for excellence is described as a set of services aiming to analyze how a product is designed. It encompasses manufacturability, design of cost or procurement, design for assembly, and design for testability.

DFX methodology improves different issues that may occur in one or more phases of the product life cycle:

• Development phase
• Production phase
• Use phase
• Disposal Phase

Development phase

The development phase contains basic rules of embodiment design, clarity, simplicity, safety, testing, and validation of design. Following factors are included in the development phase:

• Design rules
• Organization process
• System design, testing, and validation

Production phase

The production phase contains manufacturing operations based on design standards, rules, and guidelines. It addresses the combination of single parts or sub-assemblies that are based on a differential design. It also covers the issues related to strategic alliances and supply chain management.

Use phase

The user or consumer of the product wants the following qualities in product design:

• User-friendliness
• Ergonomics
• Aesthetics or visuals
• Serviceability
• Repair-reuse-recyclability

Disposal phase

The product should be designed in such a manner that it can be easily reused and recycled.

Design for manufacturing (DFM)

The design for manufacturing is described as a process of designing parts, components, or products for ease of manufacturing, resulting in a better product at a lower cost. It is achieved by simplifying, optimizing, and refining the design of the product.

Following are the five principles examined during the design for manufacturing:

• Process
• Design
• Material
• Environment
• Testing

Design for assembly (DFA)

Design for assembly is described as the method of designing the product for ease of assembly. Following are the various principles of design for assembly:

• Minimize part count.
• Design parts of the self-locating feature.
• Design parts of the self-fastening feature.
• Minimize reorientation of parts during assembly.
• Design parts for retrieval, handling, and insertion.
• Emphasize top-down assemblies.
• Design for symmetric component for insertion.

The diagrammatical representation for DFA is shown as:

Common Mistakes

Following are the common mistakes made by students:

• Students may forget the concept of steps involved in the engineering design process.
• They may also forget the basic design consideration.
• A point of confusion is whether wire-frame modeling is a 2D or 3D CAD process.
• Sometimes, students may forget principles during DFM.

Context and Applications

The topic of designing techniques is significant in various courses and professional exams at undergraduate, graduate, postgraduate, and doctorate levels. For example:

• Bachelor of technology in mechanical engineering
• Bachelor of technology in instrumental engineering
• Master of technology in machine design
• Master of technology in structural design
• Doctor of philosophy in design

Related Concepts

• Engineering design process
• Design of machine elements
• Designing criteria
• Product design

Practice Problems

Q1.______ is the identification of alternative solutions over existing solutions based on customer need, existing product's drawbacks, and many others.

1. Specify requirements
2. Brainstorming solutions
3. Communicate results
4. Do background research

Correct option: (b)

Explanation: Brainstorm solutions involves the identification of alternative solutions over existing ones based on customer needs, existing product's drawbacks, and many other factors. A good designer will generate several possible solutions for a specific problem to obtain the best results.

Q2. Which of the following is an example of 2-dimensional CAD software?

1. CATIA
2. Creo
3. Solidworks
4. LibreCAD

Correct option: (d)

Explanation: 2-dimensional computer aided design software is used to design two-dimensional products. It is used in various industries, civil works, and architect applications. AutoCAD, LibreCAD, and FreeCAD are some examples of 2D CAD software.

Q3. Which of the following is not a part of 3-dimensional CAD?

1. Wireframe models
2. Surface models
3. Solid models
4. None of these

Correct option: (d)

Explanation: 3D CAD is used to design three-dimensional products. The models produced with the help of 3D CAD are classified as wireframe models, surface models, and solid models.

Q4. Which of the following is a process of designing parts, components, or products for ease of manufacturing, resulting in a better product at a lower cost?

1. CAD
2. DFX
3. DFM
4. DFA

Correct option: (c)

Explanation: The design for manufacturing (DFM) is a process of designing parts, components, or products for ease of manufacturing, resulting in a better product at a lower cost. It is achieved by simplifying, optimizing, and refining the product's design.

Q5. The process used to emphasize top-down assemblies or pattern is _____?

1. DFA
2. DFX
3. DFM
4. CAM

Correct option: (a) 

Explanation: The design for assembly (DFA) is described as the method of designing the product for ease of assembly. The designed part in the DFA process has a self-locating or self-fastening feature.