Chapter 2. Design Concept Generation and Creativity After the first design stage, the designer should have good understanding of the background and needs of the design project, and should be able to propose a mission statement to clearly describe the goal and important specifications of the design project. The designer now faces the following questions: Is there any existing solution or new design concept that can satisfy the needs? How to search or generate these design concepts? Which design concept is the best? The second stage of the design process is called conceptual design. A design concept is an approximate description of the technology, working principles, and form of the design. A design concept is usually expressed as a sketch and is often accompanied by a brief textual description. Conceptual design is the most creative activity in mechanical design process. 1
Can We Learn to Be Creative? Ulman has the following description of a creative designer [1992]: The creative designer is generally a person of average intelligence, a visualizer, a hard worker, and a constructive nonconformist with knowledge about the domain and the ability to dissect things in his or her head. The Ah-Ha Experience We may consciously imitate these creative characteristics or thinking processes. 2
Creative Methods Analogy The principle of making analogies is to transfer an unfamiliar problem into a familiar one. Direct Analogy: Experienced designers always ask themselves, What other devices solve a related problem? What devices do something similar in other applications? Example: to design the steering system for an electrical wheel chair. Self Analogy: Pretend you are the user and experience the design. Use a story, a scenario, to describe how to use this design, or even act out your design. Try to find problems or more creative ideas during the process. video 3
Creative Methods Brainstorming(I) Brainstorming is a classic technique for a group to generate ideas to solve a problem. The purpose of brainstorming is to generate as many ideas as possible. There should be 4-8 participants in a brainstorming group, which should include a few people who are neither experts of the field nor member of the design team. There should not be boss-subordinate or teacher-student relation during brainstorming. 4
Creative Methods Brainstorming(II) Rules for brain storming: There should be a facilitator for the brain storming. To start, all participants think a few minutes on the topic then write down their ideas. All participants present their ideas in turns. During brainstorming, all participants should suspend judgment. When presenting ideas, try to build on other people s idea. Be concise when presenting ideas. Keep a humorous atmosphere. The brainstorming meeting may last for 20~30 minutes, or ends when there is no new ideas. After the brain storming meeting, designers can collect all ideas generated and evaluate them. Keep an open mind when evaluating ideas. 5
A Top-Down Design Process Mission statement: A simple sentence to state the goals of the design. Understand your design problem The 6 steps of QFD. Conceptual design for the whole system Application Scenario: From user s point of view, describe how the design is used. Technical event sequence: From technical point of view, describe how the design works. Schematic and system decomposition Conceptual design for subsystems Detail design 6
Conceptual Design for the Whole System Use an event sequence (more than just a scenario ) to describe the design concept of the whole system. Example: A transfer device is needed to transfer goods up to 400N from the warehouse to the automatic guided vehicle (AGV). One design concept is described as follows: The goods to be transferred are on a board. There is a board of the same size on the AGV. the board in the warehouse lifting arm rotation and lifting mechanism the board on the AGV As shown in the figure, initially the lifting arm is on a horizontal position. When the position sensor sensing that both boards from the warehouse and AGV are at the waiting positions, a rotation mechanism rotates the lifting arm to the vertical position. Then a lifting mechanism drives the lifting arm to lift both boards. 7
Conceptual Design for the Whole System (II) the board in the warehouse The rotation mechanism rotates the lifting arm 180 degrees again, and the lifting mechanism lowers down the boards. Now the two boards have changed positions. The goods have been transferred to the AGV. Finally the rotation mechanism rotates the lifting arm back to the horizontal waiting position. The whole sequence, including power supply and the transmission of the sensing and control signals, are controlled by a control box. lifting arm rotation and lifting mechanism the board on the AGV 8
Conceptual Design for the Whole System (III) Use the event sequence to describe the design concept of the whole system should achieve 3 purposes: The designer can confirm the concepts, methods, and techniques used in the design. The designer can go through the event sequence iteratively to see if the design concept is reasonable. The designer can confirm all the components to be designed, and the interactions between the components. In the example above, there are 6 components to be designed: board, lifting arm, position sensor, rotation mechanism, lifting mechanism, and control box. 9
Schematic and System Decomposition The input and output of each component, and the interactions between components can be expressed in the following schematic. force board signal energy lifting arm position sensor rotation mechanism lifting mechanism control box The whole system is decomposed into smaller subsystems. A critical subsystem is selected to be designed first. 10
Evaluate the Design Concept The Decision Matrix Method Feasibility evaluation and comparison evaluation. 列出設計概念 列出比較項目 權重 概念 A 概念 B 概念 C 概念 D 需求 1 基 0-1 +1 需求 3 準 +1 +1 0 需求 2 +1-1 +1 需求 2 概 0 0-1 需求 1 念 -1 +1 +1 正總和 0 2 2 3 負總和 0 1 2 1 原始總分 0 1 0 2 加權總分 0 4 1 2 加總分數 評定分數 11
Evaluating the Lifting Mechanism (I) (a) A cam mechanism (b) A power screw mechanism 12
Evaluating the Lifting Mechanism (II) (c) A pneumatic mechanism (d) A linkage mechanism 13
Design Prototype Design prototype is an effective tool for designers to evaluate the design concept and communicate with each other. A general comprehension of the word prototype is a physical approximation of the product that is usually in full scale and fully functional, such as an a- prototype or a b-prototype. Ulrich and Eppinger[1995] defined prototype as an approximation of the product along one or more dimensions of interest. This definition includes prototypes ranging from concept sketches, system equations, computer simulation, to fully functional artifacts. They further classified prototypes along two dimensions: physical as opposed to analytical, comprehensive as opposed to focused. 14
Tools for Design Prototype Tangible artifacts created to approximate the product. Implement one or a few attributes of a product. Implement most attributes of a product. Represent the product in a non-tangible manner. 15
Select Tools of Prototyping Design is a dynamic problem solving process, and can be viewed as dynamically generating design prototypes to answer or evaluate the current design sub-problem. A designer or a design organization s ability directly reflect on the ability of using prototyping tools. 4 factors to be considered when selecting a prototyping tool: Design flexibility Data to be generated Amount to be made Level of approximation Data to be generated amount to be made level of approximation 16
Documenting and Presentation of Design Concept At the end of conceptual design stage, there should be enough information, concept sketches and textual description to start detailed engineering drawings. Wheelwright and Clark[1992] suggested a contract book to document the project plan and the results of the conceptual design stage. The contract book represents an agreement between the design team and the senior management about project goals, direction, and resource requirements. Item No. of pages Item No. of pages Mission Statement Customer Needs List Competitive Analysis Product specifications Sketch of Product Concept 1 1-2 1-2 1-3 1-3 Project Plan Task List Team Organization Schedule (Gantt or PERT) Budget 1-5 1 1-2 1 Sales Forecast 1-3 Risk Areas 1 Economic Analysis 1-3 Performance tests 1 Manufacturing Plan 1-5 Motivation 1 17