EPT 221 CONCEPTUAL DESIGN

Lecture Objectives Define and describe concept design Describe and apply methods to clarify functional requirements of a design: activity analysis, component decomposition, functional decomposition Understand and apply various methods to analyze design concepts alternatives: Pugh’s Concept Selection Method, weighted-rating method. Generate alternative design concepts using various methods

? Info flow during formulation and concept design phases Formulation Customer Needs Customer requirements Importance weights QFD Eng. characteristics Eng. Design Spec’s Concept Design “Best” Alternative Concepts

Alternative Concept Design

Physical Principle Definition: the means by which some effect is caused, or produced.

Abstract Embodiment Embodiment: a representation of an abstract idea in concrete terms; giving concrete form to an abstract concept Abstract: Considered apart from concrete existence

Design Concept

Example: Disc Brake A disc brake is a device for slowing/ stopping the rotation of a wheel.

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Design Process during Concept Design Phase

Clarifying Functions Why do we need to clarify functions? During the problem formulation stage, we determine the customer and company requirements. But we do not provide sufficient details/ information to achieve these requirements i.e. may lack sufficient details on specific functions and subfunctions. How do you clarify functions? Using the following methods: 1.Activity analysis 2.Product decomposition diagram 3.Function decomposition diagram

Activity Analysis Method To learn how the customer will use and retire the product. Customer activities  examine the relationship between customer and product.

Component Decomposition Method Product decomposition diagram – a block diagram of the parts and subassemblies that make up the product. A hierarchical structure of component forms, not functions Why? To obtain a better overall understanding of how individual components interact with each other and ultimately contribute to the overall product function.

Function Decomposition Method Subdivides the major/ overall product functional requirement into its respective subfunctions and subsubfunctions. (Product ) Function Decomposition Diagram – –A hierarchical structure of functions, not forms. –Helps to identify whether functions are connected, and where the interface connections might be. Sample functions

Example of a Function Decomposition Diagram for a Coffee Maker Overall product function Sub-function Sub-subfunction Helps separate what functions need to be performed versus how it gets done (form)

Generating Alternative Concept Designs Synthesis  the process of generating alternatives

the process of generating alternatives may include the following activities: –Investigating archives design catalogs, reference handbooks, encyclopedias, monographs, periodicals, technical journals, trade magazines, microfilm, etc. –Talking to people Co-workers, professors, vendors, representatives from professional societies and trade organizations, consultants –Connecting to the internet Patents, vendor catalogs, professional societies, trade organizations –Using creative methods Brainstorming – an iterative group method that takes advantage of team members’ diverse skills, experience and personalities to generate innovative ideas. Method people brainstorms. Each person writes down 3 ideas on a piece of paper. The paper is circulated 5 times where each time 3 more ideas is written down. Synectics - a method that requires the problem solver to view the problem from 4 perspectives: i.Analogy ii.Fantasy iii.Empathy iv.Inversion Checklist

Developing Product Concepts i.e. generating alternative design concepts Generate many alternative concepts for each subfunction. Use morphological matrix Sketching is encouraged during this stage.

Example A design team is developing new concepts for a gasoline-powered minibike. They decompose the primary functions into transmit engine power, steer, and brake. They select three concepts for transmitting power: chain drive, belt drive, and gearbox; two concepts for braking: disc and drum; and three concepts for steering: handlebar, airplane control stick, and fly-by-wire. Prepare a morphological matrix and systematically develop alternative combinations.

Analysing Design Concepts Reason to analyse: to screen out, or eliminate design concepts that are not feasible

Methods:  Back-of-the-envelope: do rough calculations that, while not rigorous, test or support a point.  Proof-of-concept: a short and/or incomplete realization of a certain method or idea(s) to demonstrate its feasibility, or a demonstration in principle, whose purpose is to verify that some concept or theory is probably capable of exploitation in a useful a new concept or a particular device or configuration can be shown to work in the manner in which it was designed.  Bench test/ pilot : used when a real plant is expensive. Screening criteria: functionality and manufacturability  Functionality – customer requirements, operating conditions, etc  Manufacturability – existing technology (ready for production or only for RnD), materials, financial, marketing considerations.

Evaluating Alternative Concepts 2 methods commonly used: i.Pugh’s concept selection method ii.Weighted-rating method

Pugh’s Concept Selection Method 1. Select criteria, 2. Establish datum column, 3. Rate alternatives (+, -, S) against datum 4. Select best, or better alternatives Datum = a reference concept + is for better -is for worse -S is for same as datum So the weakest concept would be eliminated form further development.

Modified Pugh’s Method Includes an importance weight column. Importance weight gives different importance to different criteria. So, the calculation for the concepts will factor in the importance weight.

Weighted Rating Method (or weighted sum Pahl and Beitz method)

references cture_notes/product_design_spec.pdfhttp://homepages