Engineering Design Principles

• Engineering design involves creating something new by assembling different parts to achieve a unified whole.

Design vs Analysis

• Analysis involves evaluating design parameters for specific performance criteria.

• Design focuses on creating solutions that meet specific parameters.

• Creativity is a key aspect of engineering design.

• The purpose of engineering design is not explicitly stated.

Engineering Design Process Steps

Step 1: Define Problem

• Tasks include defining the problem statement, design requirements, and initial design specifications.
• Constraints are identified.
• Available tools involve developing a House of Quality.

Step 2: Gather Information

• Tasks involve researching books, the internet, technical articles, patents, and trade journals.
• Also includes reviewing relevant engineering codes.
• Methods of finding information are key tools.

Step 3: Concept Generation

• Tasks include finding ideas or concepts to satisfy design requirements through specification.
• Involves using design forms, brainstorming, functional models, and flow charts.

Step 4: Evaluate & Select Concept

• Tasks involve selecting the most efficient concept to satisfy requirements.
• Define selection criteria, focusing on design requirements.
• Available tools: Pugh Matrix, Decision Matrix

Step 5: Product Architectural & Product Form

• Tasks involve arranging different parts to create a form.
• Also includes arranging physical elements, modularity, and grid.
• More developed drawings and drawing software are available tools.

Step 6: Configuration Design

• Focuses on preliminary selection of materials and manufacturing processes.
• Also includes modeling and sizing of parts, which usually involves calculations.
• Selection of materials from catalogs is typical.

Step 7: Parametric Design

• This is an analysis step to check the designed product for limitations of optimum operation.

• Includes robust design and setting design tolerance and limitations.

• Design software is used to check or review for optimum temperature, design loads, and certain performance metrics via analysis, lab testing, and field testing.

• Detail Design involves engineering drawing and is not a step in the design process.

Conceptual Design Phase (C.D.P)

• This phase focuses on generating new ideas and is difficult.
• C.D.P. is defined as the phase where design specifications are defined based on customer requirements and elementary cost to generate feasible ideas.

Conceptual Design Phase Steps

• Define problem
  • Define problem statement
  • Design requirements, specifications, constraints
  • Benchmarking
  • Product dissection
  • House of Quality (QFD)

House of Quality (QFD) tool

• Key parts marked from Room 1 to Room 8

• Room 1: Design requirements

• Room 2: Design specifications

• Room 3: Relationship between design specifications

• Room 4: Design specifications

• Room 5: For each design specification, calculate I.R. = specification strength (e.g. 1, 3, or 9) x importance rating

• Room 6: Comparison to competitor product includes identifying competitors and how customers perceive their abilities.

• Room 7: Divide each important ranking by the sum of all important rankings.

• Room 8: Classify each design specification with respect to others; a high rating indicates most important.

• It is important to calculate Row Score, Relative weight, and Rank Order

Ethical Issues in Problem Definition Step

• Engineers may not be qualified to define a problem or determine specifications.

• Rating of design specifications and requirements (1,3,9) is subjective.

• An engineer could rate specifications to favor certain design specifications related to their company.

• It is unethical for a company specializing in plastic products to rate plastic specification highly when designing a product with metal, plastic and wood parts.

Steps to Develop a QFD (House of Quality)

• Step 1: List Customer Requirements (WHATs)
• Step 2: List Technical Descriptors or Specifications (HOWs)
• Step 3: Develop a Relationship Matrix Between WHATs and HOWS
  • The L-shape shows the intersection of related pairs of items; it is constructed by turning the list of technical descriptors perpendicular to the list of customer requirements.
  • Double circle indicates a strong relationship, a single circle indicates a medium relationship, and a triangle indicates a weak relationship; a blank box indicates no relationship exists.
• Step 4: Develop an Interrelationship Matrix Between HOWS
  • The correlation matrix identifies any interrelationships between each of the technical descriptors; it is a triangular table attached to the technical descriptors.
• Step 5: Develop Prioritized Customer Requirements
  • Absolute Weight = (Importance to Customer) x (Scale-up Factor) x (Sales Point)
  • Used as guidance for the planning phase.
• Step 6: Develop Prioritized Technical Descriptors (PTD)
  • Absolute Weight and Percent (A.W.P.) is an easy method for assigning numerical values to symbols in the relationship matrix.

Ethical Issues in the Gather Information Step

• Honesty is important when collecting information and dealing with other engineers' designs and intellectual properties.
• Honesty includes crediting other's ideas, referencing consultant work and including sources of information.
• Engineers should give credit to others involved in design.
• All references should be honestly referenced.

Concepts Generation Methods

• Generate design ideas:
  • Creativity methods
  • Brainstorming
  • Decomposition
  • Systematic Design Methods, which involves step-by-step analysis and synthesis.
    • Analysis decomposes a complex system and studies each element.
    • Synthesis incorporates elements to create a new system.
  • Mind-maps are a tool used.

Ethical Issues in the Concept Generation Step

• Engineers should be honest in developing their design ideas.
• Did they take it from someone else? Did they give credit and reference sources?
• Does the idea satisfy customer needs and design requirements?
• Does the concept really work and is it feasible for the customer?
• Is it just proposed for financial or economic reasons?

Concept Evaluation and Selection

• Different concepts can be developed.
• Following tools can be used to evaluate and select the most appropriate one:
  • Decision-making: Examine options, compare them, and choose a course of action.
  • Selection criteria: What criterial should be considered to select a design concept?
  • Pugh chart or matrix: Evaluates alternatives against a baseline (existing product/idea).
  • Decision matrix: Concept or alternative selection tool similar to a Pugh Matrix.

Ethical Issues in the Concept Evaluation and Selection Step

• Concept selection tools can be manipulated subjectively to favor certain designs.
• Certain design criteria can be removed to prevent disadvantages from being altered.

Embodiment Design Phase (E.D.)

• E.D. covers form design, arrangement of physical elements, design for manufacture and assembly, materials and manufacturing process selection, and industrial design.
• Based on transferring the concept design into functional products or physical models.
• Embodiment process is the bridge between the conceptual and detail design stages.

Product Architectures (PA)

• PA describes how physical parts are arranged and their modularity.

Ethical Issues in the Product Architectural Step

• Consider the implications of PA on design/operation outcomes.
• Making a sports car from fiberglass may reduce safety and expose passengers to additional accidents.

Configuration Design

• Sizing of Parts: Step 5 gives the overall geometry -- details sizing and dimensions.
• Selection of materials: wood, metal, plastic, paper, etc.
• Selection of manufacturing process: manual, machine or specialized.

Parametric Design

• (Basic and simplified sense) – Analysis step of design.
• “Parametric Design is a very broad term, but it usually refers to the design parameters which considered as any measurable design factors that defines a system functions or determines its performance"
• Example: A rubber-powered airplane should have a determined max flying time with light wood.
• Elevator design should have a maximum capacity (e.g. 500 kg).
• Robust Design: Is This design suitable for user? How could it be improved?
• Service issue check: what is the total deflection of beam after designing the beam?

Ethical Issues in the Parametric Design Step

• The Challenger case: engineers didn't have data to support claims that field seal would function well in cold weather.

Detailed Design

• A details design drawing and description about the intended design.

Summary of Engineering Design Process

• A. Start Conceptual Design
  • Define Problems
  • Recognize customer design needs.
  • List product development specifications.
  • Define project plan.
  • Define QFD Stage 1
• Gather Information: Internet, technical articles, market products, consultants.
• Concept Generation: Creativity Methods, Brainstorming, Functional models.
• Evaluation & Concept Selection (decision matrix, Pugh matrix,...etc)
  • Decision Matrix
  • Pugh Matrix
  • Selecting Criteria
  • Cost Estimate 1: Estimate cost of concept selected
• B- Start Embodiment Design*
• Define QFD Stage 2 (redefine or improve stage 1)
• Product Architecture
  • Arrangement of physical parts
  • Modularity
• Configuration Design
  • Engineering analysis: Form Function , Geometry , Manufacture Process , Materials
  • Cost Estimate 2: Estimate cost of embodiment design
• Parametric Design
  • set design tolerance parameters
  • Robust design Finish embodiment design.
• Start Detail Design
• Order external required part: e.g. for airplane design order plastic fan
• Finish detail design
• Manufacture of prototypes
• Testing of product
• Cost Estimate 3: estimate cost of detail design
• Cost Estimate 4: estimate cost of external required parts from outside venders
• If no modification needed, send detail design for manufacturing

Comments

• Communications between different design parties is conducted by several methods: meetings, QFD is one way of transferring of information, drawing and graphs is another way, and detail design is also communication between parties in different entities and way of expressing final design subject
• Design is a trial and error process (iteration process). Some authors refer to this process as a redesign or redefining or refining design parameters such as requirements and specifications. This implement in above table as QFD stage 1 and 2 and parametric design step and prototype sub-step in Detail Design step
• Design specifications are subjected for review and improvement during the engineering design process.

Sketches in Design Notes

• Sketches have level of details.

• Concepts Generation Step: sample Sketch, a general purpose with some illustration lines to explain some function of incomplete sketch.

• Figure 1A - A: a skethch with some illustrative lines to explain some of the design item function.

• Figure 1A-B : a skethch to possible design concept of the design products.

• Figure 1A-C : an illustrative skethch that would show the general assembly of a product using certain items. (Can not be a detailed design because it is not clear what is the size of pipes used)

• Figure 1A-D shows one phase of a desk design. This is concept generation step.

• Product Architecture Step sample sketches: Presenting the complete physical shape of the product without dimensions or other illustrative lines or dimensions.

• Detailed Design Sample Images: Detail design provide more details about the design including dimensions, assembly process and related parts.