Chapter 1 Introduction To Mechanical Design Process 496848
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MECHANICAL ENGINEERING DESIGN 1 MEC 531
PART A MECHANICAL DESIGN PROCESS
By: NURZAKI IKHSAN
CHAPTER 1 INTRODUCTION TO MECHANICAL DESIGN PROCESS Chapter Outline 1. The Phases of Design 2. Problem identification and definition 3. Product design specifications 4. Concept development, evaluation and selection
The Phase Of Design What is Design? •
Design is an innovative and highly iterative process. It is also a decision-making process.
Why do we design ? •To survive! •As an engineer as technical provider, we provide solutions to particular problems •However -if clients are not completely satisfied with provider then they will dismiss •They will go somewhere else and tell everyone about the unsatisfactory
The Phase Of Design 7 Phases Design Process
Define Problem
Gather Information
Concept Generation
Evaluation of Concepts
Product Architecture
Phase I. Conceptual Design
Configuration Design
Phase II. Embodiment Design Phase III. Detail Design
Phase VII. Planning for Retirement
Phase VI. Planning for Use
Phase V. Planning for Distribution
Phase IV. Planning for Manufacture
Parametric Design
The Phase Of Design 7 Phases Design Process
Define Problem
Gather Information
Concept Generation
Phase I. Conceptual Design
Evaluation of Concepts
•Feasibility Study. •Requires greatest creativity, involves the most uncertainty and requires coordination among many functions in the business organization. •Discrete activities to be considered: − Identification of customer needs − Problem definition − Gathering information − Conceptualization − Concept selection − Design review
The Phase Of Design 7 Phases Design Process
Define Problem
Gather Information
Concept Generation
Phase I. Conceptual Design
Evaluation of Concepts
• Most important steps in the engineering design process is identifying customer needs. • The customer needs can be gained from: – Interviewing customers – Focus group – Customer survey – Customer complaints • Tools to achieve this: – Benchmarking – QFD – PDS
The Phase Of Design 7 Phases Design Process
Define Problem
Gather Information
Concept Generation
Phase I. Conceptual Design
Evaluation of Concepts
• Information from Internet – Engineering URLs • Patent Literature – Intellectual Property – Patents • Handbook
The Phase Of Design 7 Phases Design Process
Define Problem
Gather Information
Concept Generation
Phase I. Conceptual Design
Evaluation of Concepts
• Brainstorming • Functional decomposition • Morphological chart
The Phase Of Design 7 Phases Design Process
Define Problem
Gather Information
Concept Generation
Phase I. Conceptual Design
Evaluation of Concepts
• Comparison Based on Absolute Criteria • Pugh’s Concept Selection Method • Weighted Decision Matrix
The Phase Of Design 7 Phases Design Process • Preliminary Design.
• Decisions are made in this design phase: strength, material selection, size, shape, and spatial compatibility. • Any major changes beyond this design phase become very expensive.
Product Architecture
Configuration Design
Phase II. Embodiment Design
Parametric Design
The Phase Of Design 7 Phases Design Process • Arrangement of the physical elements to carry out its required function.
Product Architecture
Configuration Design
• i.e. defining the building blocks of the product in of what they do and their interfaces • Design for Human Factor • Creating -friendly Design
Phase II. Embodiment Design
Parametric Design
The Phase Of Design 7 Phases Design Process • Establishing the shape and general dimensions of the components.
Product Architecture
Configuration Design
• Components include special purpose parts, standard parts, standard assemblies or modules. • Develop from function. • Configuration depending on: 1. Available materials and production methods 2. Spatial constraints 3. Product architecture
Phase II. Embodiment Design
Parametric Design
The Phase Of Design 7 Phases Design Process • Set the dimensions and tolerances in order to maximize quality and performance and minimize cost. • Objective : to set values for the design variables that will produce the best possible design considering both performance and manufacturability. • A few established method in deg to maximise performance and quality : – FMEA – Design for reliability – Robust design – Design for Assembly (DFA) – Design for Manufacture (DFM)
Product Architecture
Configuration Design
Phase II. Embodiment Design
Parametric Design
The Phase Of Design 7 Phases Design Process
• Any missing or incomplete information are added → arrangement, form, dimensions, tolerances, surface properties, materials and manufacturing of each part
• Activities to be completed in the detail design phase (documentation): – Detail engineering drawing. – Verification testing of prototype. – Assembly drawings and instruction, BOM. – A detailed product specification. – Decisions either to fabricate each part or to buy it – A detailed cost estimation. – A design review as a conclusion of the detail design phase before beinged to manufacturing.
• Final Phase- Detail design • Waiting for final decision to be manufacture • The design is brought to the stage of a complete engineering description of a tested and producible product.
Phase III. Detail Design
The Phase Of Design
Product Design Specifications (PDS)
•
A document that contains all of the facts related to the outcome of the product development (document listing the problem in detail).
•
It should avoid forcing the design direction toward a particular concept and predicting the outcome.
•
Should be understood that the PDS is evolutionary and will change as the design process proceeds.
•
It is important to work with the customer and analyse the marketplace to produce a list of requirements necessary to produce a successful product.
•
The designer should constantly refer back to this document to ensure designs are appropriate.
Product Design Specifications (PDS) Example: PDS 1. What is the product going to be? 2. What are the dimensions of the product? 3. What materials does the product require? 4. What is the estimate cost of the materials? 5. What tools/technology will be used to work on the project? 6. Are the tools/technology accessible, or will special arrangements need to be made? 7. What is the time estimate for completing the project? 8. Where will the product be worked on primarily? 9. Will an outside company be used to complete the project? 10. Will materials need to be ordered? If so, how much time should be allotted for shipping, ordering, etc? 11. Will an expert in the field need to assist with the creation of the product? If so, when will this person be ed to set up a mutually convenient time to meet? 12. Who will benefit from the benefit from the creation of the product? 13. Why is it necessary to create this product? 14. How will the product demonstrate technical knowledge?
Product Design Specifications (PDS) PRODUCT DESIGN SPECIFICATION
Product: Lightweight wheel for Formula Student car. Weight Size
Timescale Cost Quantity Safety
:Maximum 3kg :13” diameter; 15-25mm centre thickness :18 weeks from initial phase to manufacture. :Maximum RM300 per wheel :4 on initial design run :-Design for fatigue life of 250000 cycles at approximately 1.4g loading -Interface between centre and rims must be airtight -Smooth surface finish -Secure fittings
Product Design Specifications (PDS)
Competition Maintenance Customer Manufacturing Facilities
Installation Materials
:There are few competitors in niche market, but various racing wheel manufacturers. :Seals and bolts must be checked occasionally. :Lightweight motorsport / weekend racer. :Dependent upon material CNC and Casting in-house. Other manufacturing must be out-sourced. :4 inch PCD 4 stud formation. :Range of materials to be modelled: Aluminium 2024 T6 Steel Plastics
Concept Development, Evaluation and Selection Generating Design Concepts Brainstorming − Most common method used by design teams for generating ideas for design concepts in conceptual design. − Think of all the possible limitations or shortcomings of the product.
Functional decomposition (breakdown) − A logical approach for describing the transformation between the initial and final states of a system or device. − Physical decomposition → separating the product or subassembly directly into its subsidiary subassemblies and components (output = physical decomposition block diagram). − Functional decomposition → a general description of a device is refined into more specific arrangements of functions and subfunctions.
Concept Development, Evaluation and Selection Physical decomposition Urban Car
Suspension system
Steering system
Chassis
Braking system
Power train
Functional decomposition Power train
Variable valve timing
Direct injection
3.5 cc
The controller are use to varies the operational of the open-closed valve
The gasoline is highly pressurized, and injected via a common rail fuel line directly into the combustion chamber
The engine consist of 6 pistons
Concept Development, Evaluation and Selection Morphological chart − Representing and exploring all the relationships in multidimensional problems regarding shape and form
Concept Development, Evaluation and Selection
Concept Evaluation & Selection
Evaluation methods: 1. Pugh concept selection method. 2. Weighted decision matrix.
Concept Development, Evaluation and Selection
Pugh Concept Selection Method
• This method compares each concept relative to a reference or datum concept. • Each criterion determines whether the concept is better than, poorer than or about the same as the reference concept. • Steps in this Pugh concept selection method: 1. Choose the criteria by which the concepts will be evaluated - Can refer to QFD (House of Quality). 2. Formulate the decision matrix - Concepts on the row headings and criteria on the column headings.
3. Clarify the design concepts - Make sure every team member understand every concept developed.
Concept Development, Evaluation and Selection
4. Choose the datum concept
- Reference concept with which all other concepts are compared. 5. Run the matrix - Use a three-level scale, better (+), worse (-) or same (S). 6. Evaluate the ratings
- Sum up the +, - and S ratings. 7. Establish a new datum and rerun the matrix - To gain added insight regarding the highest rated concept. 8. Examine the selected concept for improvement opportunities - Is there any improvement that can be done considering the worse ratings gained for the selected concept.
Concept Development, Evaluation and Selection
Concept Development, Evaluation and Selection
Weighted Decision Matrix •
Evaluating competing concepts by ranking the design criteria with weighting factors and scoring the degree to which each design concept meets the criterion.
•
Weighting factors: - A 5-point scale (0-4) → knowledge of the criteria is not very detailed. - An 11-point scale (0-10) → the information is more detail.
•
The evaluation steps are quite similar to Pugh concept selection method but without any datum.
Concept Development, Evaluation and Selection
PART A MECHANICAL DESIGN PROCESS
By: NURZAKI IKHSAN
CHAPTER 1 INTRODUCTION TO MECHANICAL DESIGN PROCESS Chapter Outline 1. The Phases of Design 2. Problem identification and definition 3. Product design specifications 4. Concept development, evaluation and selection
The Phase Of Design What is Design? •
Design is an innovative and highly iterative process. It is also a decision-making process.
Why do we design ? •To survive! •As an engineer as technical provider, we provide solutions to particular problems •However -if clients are not completely satisfied with provider then they will dismiss •They will go somewhere else and tell everyone about the unsatisfactory
The Phase Of Design 7 Phases Design Process
Define Problem
Gather Information
Concept Generation
Evaluation of Concepts
Product Architecture
Phase I. Conceptual Design
Configuration Design
Phase II. Embodiment Design Phase III. Detail Design
Phase VII. Planning for Retirement
Phase VI. Planning for Use
Phase V. Planning for Distribution
Phase IV. Planning for Manufacture
Parametric Design
The Phase Of Design 7 Phases Design Process
Define Problem
Gather Information
Concept Generation
Phase I. Conceptual Design
Evaluation of Concepts
•Feasibility Study. •Requires greatest creativity, involves the most uncertainty and requires coordination among many functions in the business organization. •Discrete activities to be considered: − Identification of customer needs − Problem definition − Gathering information − Conceptualization − Concept selection − Design review
The Phase Of Design 7 Phases Design Process
Define Problem
Gather Information
Concept Generation
Phase I. Conceptual Design
Evaluation of Concepts
• Most important steps in the engineering design process is identifying customer needs. • The customer needs can be gained from: – Interviewing customers – Focus group – Customer survey – Customer complaints • Tools to achieve this: – Benchmarking – QFD – PDS
The Phase Of Design 7 Phases Design Process
Define Problem
Gather Information
Concept Generation
Phase I. Conceptual Design
Evaluation of Concepts
• Information from Internet – Engineering URLs • Patent Literature – Intellectual Property – Patents • Handbook
The Phase Of Design 7 Phases Design Process
Define Problem
Gather Information
Concept Generation
Phase I. Conceptual Design
Evaluation of Concepts
• Brainstorming • Functional decomposition • Morphological chart
The Phase Of Design 7 Phases Design Process
Define Problem
Gather Information
Concept Generation
Phase I. Conceptual Design
Evaluation of Concepts
• Comparison Based on Absolute Criteria • Pugh’s Concept Selection Method • Weighted Decision Matrix
The Phase Of Design 7 Phases Design Process • Preliminary Design.
• Decisions are made in this design phase: strength, material selection, size, shape, and spatial compatibility. • Any major changes beyond this design phase become very expensive.
Product Architecture
Configuration Design
Phase II. Embodiment Design
Parametric Design
The Phase Of Design 7 Phases Design Process • Arrangement of the physical elements to carry out its required function.
Product Architecture
Configuration Design
• i.e. defining the building blocks of the product in of what they do and their interfaces • Design for Human Factor • Creating -friendly Design
Phase II. Embodiment Design
Parametric Design
The Phase Of Design 7 Phases Design Process • Establishing the shape and general dimensions of the components.
Product Architecture
Configuration Design
• Components include special purpose parts, standard parts, standard assemblies or modules. • Develop from function. • Configuration depending on: 1. Available materials and production methods 2. Spatial constraints 3. Product architecture
Phase II. Embodiment Design
Parametric Design
The Phase Of Design 7 Phases Design Process • Set the dimensions and tolerances in order to maximize quality and performance and minimize cost. • Objective : to set values for the design variables that will produce the best possible design considering both performance and manufacturability. • A few established method in deg to maximise performance and quality : – FMEA – Design for reliability – Robust design – Design for Assembly (DFA) – Design for Manufacture (DFM)
Product Architecture
Configuration Design
Phase II. Embodiment Design
Parametric Design
The Phase Of Design 7 Phases Design Process
• Any missing or incomplete information are added → arrangement, form, dimensions, tolerances, surface properties, materials and manufacturing of each part
• Activities to be completed in the detail design phase (documentation): – Detail engineering drawing. – Verification testing of prototype. – Assembly drawings and instruction, BOM. – A detailed product specification. – Decisions either to fabricate each part or to buy it – A detailed cost estimation. – A design review as a conclusion of the detail design phase before beinged to manufacturing.
• Final Phase- Detail design • Waiting for final decision to be manufacture • The design is brought to the stage of a complete engineering description of a tested and producible product.
Phase III. Detail Design
The Phase Of Design
Product Design Specifications (PDS)
•
A document that contains all of the facts related to the outcome of the product development (document listing the problem in detail).
•
It should avoid forcing the design direction toward a particular concept and predicting the outcome.
•
Should be understood that the PDS is evolutionary and will change as the design process proceeds.
•
It is important to work with the customer and analyse the marketplace to produce a list of requirements necessary to produce a successful product.
•
The designer should constantly refer back to this document to ensure designs are appropriate.
Product Design Specifications (PDS) Example: PDS 1. What is the product going to be? 2. What are the dimensions of the product? 3. What materials does the product require? 4. What is the estimate cost of the materials? 5. What tools/technology will be used to work on the project? 6. Are the tools/technology accessible, or will special arrangements need to be made? 7. What is the time estimate for completing the project? 8. Where will the product be worked on primarily? 9. Will an outside company be used to complete the project? 10. Will materials need to be ordered? If so, how much time should be allotted for shipping, ordering, etc? 11. Will an expert in the field need to assist with the creation of the product? If so, when will this person be ed to set up a mutually convenient time to meet? 12. Who will benefit from the benefit from the creation of the product? 13. Why is it necessary to create this product? 14. How will the product demonstrate technical knowledge?
Product Design Specifications (PDS) PRODUCT DESIGN SPECIFICATION
Product: Lightweight wheel for Formula Student car. Weight Size
Timescale Cost Quantity Safety
:Maximum 3kg :13” diameter; 15-25mm centre thickness :18 weeks from initial phase to manufacture. :Maximum RM300 per wheel :4 on initial design run :-Design for fatigue life of 250000 cycles at approximately 1.4g loading -Interface between centre and rims must be airtight -Smooth surface finish -Secure fittings
Product Design Specifications (PDS)
Competition Maintenance Customer Manufacturing Facilities
Installation Materials
:There are few competitors in niche market, but various racing wheel manufacturers. :Seals and bolts must be checked occasionally. :Lightweight motorsport / weekend racer. :Dependent upon material CNC and Casting in-house. Other manufacturing must be out-sourced. :4 inch PCD 4 stud formation. :Range of materials to be modelled: Aluminium 2024 T6 Steel Plastics
Concept Development, Evaluation and Selection Generating Design Concepts Brainstorming − Most common method used by design teams for generating ideas for design concepts in conceptual design. − Think of all the possible limitations or shortcomings of the product.
Functional decomposition (breakdown) − A logical approach for describing the transformation between the initial and final states of a system or device. − Physical decomposition → separating the product or subassembly directly into its subsidiary subassemblies and components (output = physical decomposition block diagram). − Functional decomposition → a general description of a device is refined into more specific arrangements of functions and subfunctions.
Concept Development, Evaluation and Selection Physical decomposition Urban Car
Suspension system
Steering system
Chassis
Braking system
Power train
Functional decomposition Power train
Variable valve timing
Direct injection
3.5 cc
The controller are use to varies the operational of the open-closed valve
The gasoline is highly pressurized, and injected via a common rail fuel line directly into the combustion chamber
The engine consist of 6 pistons
Concept Development, Evaluation and Selection Morphological chart − Representing and exploring all the relationships in multidimensional problems regarding shape and form
Concept Development, Evaluation and Selection
Concept Evaluation & Selection
Evaluation methods: 1. Pugh concept selection method. 2. Weighted decision matrix.
Concept Development, Evaluation and Selection
Pugh Concept Selection Method
• This method compares each concept relative to a reference or datum concept. • Each criterion determines whether the concept is better than, poorer than or about the same as the reference concept. • Steps in this Pugh concept selection method: 1. Choose the criteria by which the concepts will be evaluated - Can refer to QFD (House of Quality). 2. Formulate the decision matrix - Concepts on the row headings and criteria on the column headings.
3. Clarify the design concepts - Make sure every team member understand every concept developed.
Concept Development, Evaluation and Selection
4. Choose the datum concept
- Reference concept with which all other concepts are compared. 5. Run the matrix - Use a three-level scale, better (+), worse (-) or same (S). 6. Evaluate the ratings
- Sum up the +, - and S ratings. 7. Establish a new datum and rerun the matrix - To gain added insight regarding the highest rated concept. 8. Examine the selected concept for improvement opportunities - Is there any improvement that can be done considering the worse ratings gained for the selected concept.
Concept Development, Evaluation and Selection
Concept Development, Evaluation and Selection
Weighted Decision Matrix •
Evaluating competing concepts by ranking the design criteria with weighting factors and scoring the degree to which each design concept meets the criterion.
•
Weighting factors: - A 5-point scale (0-4) → knowledge of the criteria is not very detailed. - An 11-point scale (0-10) → the information is more detail.
•
The evaluation steps are quite similar to Pugh concept selection method but without any datum.
Concept Development, Evaluation and Selection
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