me/meca 238a - mechanical/mechatronic design project i
DESCRIPTION
ME/MECA 238A - Mechanical/Mechatronic Design Project I. Course notes prepared by G.A. Kallio, based on The Mechanical Design Process, by D.G. Ullman. Project Planning (Ch. 5). Step 1: Identify the tasks Use WBS (work breakdown structure) or flowchart network - PowerPoint PPT PresentationTRANSCRIPT
ME/MECA 238A 1
ME/MECA 238A - Mechanical/Mechatronic
Design Project ICourse notes prepared by G.A. Kallio, based on
The Mechanical Design Process, by D.G. Ullman
ME/MECA 238A 2
Project Planning (Ch. 5)
• Step 1: Identify the tasks– Use WBS (work breakdown structure) or
flowchart network– Be as specific and detailed as possible– Include course-related presentations & reports
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Project Planning, cont.
• Step 2: State objective of each task– What will be the result (deliverable) of each
task?– May be information, a completed drawing,
calculation results, test data, a report, a generated concept, manufactured component, etc.
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Project Planning, cont.
• Step 3: Estimate the personnel, time, and other resources needed to meet objectives– Specify who– Specify work rate (e.g., hours/week)– Specify period of time– Specify total time for each task
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Project Planning, cont.
• Step 4: Develop a sequence for the tasks– Identify precessors and successors for each task– Sequential (series) vs. parallel tasks– Coupled vs. uncoupled parallel tasks– Design structure matrix (DSM)– Identify critical path(s)
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Project Planning, cont.
• Step 5: Estimate the product development costs– Design costs de-emphasized– Material costs are real– Manufacturing costs may be real– Testing costs de-emphasized
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ISO-9000
• International Standards Organization’s quality management system
• Standardized documentation of the product development process
• ISO-9000 certification – similar to University accreditation – indicates to the world that product quality is managed, controlled, and assured by the ISO
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Concept Generation (Ch. 7)
• A concept is an idea or “structure” that is sufficiently developed to – evaluate the physical principles that govern its
behavior – evaluate technologies needed to realize them– allow a rough sketch
• Concepts follow function• Products follow concepts
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Functional Decomposition
• Technique used to define and refine product functions at all levels
• Function can be described in terms of– energy flow (mechanical, electrical, fluid,
thermal)– material flow (through-, diverging, converging)– information flow (mechanical & electrical
signals, software)
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Step 1: Find Overall Function
• Single, most important, statement of function based upon customer requirements
• Verb-noun-modifier form• Model using control volume approach
– system boundary– inflows, outflows– conservation of material, energy
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Step 2: Describe Subfunctions
• Decompose overall function using verb-noun-modifier description– Consider what, not how– List all alternative functions– Consider all operational sequences– Include all input and output energy, materials,
and information– “Post-it” note exercise
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Step 3: Order the Subfunctions
• Ordering may be chronological, spatial, disciplinary, or some other logic
• remove redundancy• finalize functional choices• eliminate functions not within system
boundary
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Step 4: Refine the Subfunctions
• Examine each subfunction to see if it can be further divided
• Decomposition ends when function becomes “atomic”, i.e., can be satisfied with an existing object or the invention of a new object
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Generating Concepts from Functions
• Recall: “concepts follow function”• Concepts can be represented by sketches,
block diagrams, verbal description, or models (paper, clay, etc.)
• Two-step process
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Step 1: Develop Concepts for Each Function
• Develop as many as possible• Should be able to generate at least three (3)
concepts for each refined function; if not– Re-examine function: “what” vs. “how”– Have ridiculous options been eliminated?– Is knowledge of function limited?
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Step 2: Combine Concepts
• Combine each possible concept from each function into “n” overall conceptual designs
• This generates (too) many possible designs• Some combinations will be mutually
incompatible, obviously inefficient, or ridiculous – eliminate these
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Sources for Concept Ideas
• Use existing information and designs!– Patents– Reference books– Trade journals– Research journals– Group brainstorming– Faculty, industry contacts
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Example: Tortilla Maker
• Primary Specifications:– Tortilla diameter: 101/2 (251.3 cm)– Tortilla thickness: 1/16 – 1/4 (1.6 – 6.4 mm)– Speed: 60 sec per tortilla (1/16)– Footprint size: 2 2 (60 cm 60 cm)– Weight: 10 lbs. (4.5 kg)
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Example: Tortilla Maker
• Features:– Auto start/stop with cancel function– Adjustable thickness– Adjustable cooking time– Easy cleaning: food handling parts removable
and dishwasher-safe
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Concept Evaluation (Ch. 8)
• Choose best concepts for development into a product (with limited information)
• Evaluation consists of comparison, followed by decision making
• Comparison can be absolute or relative• Two or more concepts may be developed in
parallel until relative merits become clear
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Evaluation Techniques
• Text suggests a sequence of steps for evaluating concepts and two different decision-making paths (Figure 8.1)
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Feasibility Judgment
• Gross judgement based upon intuition or “gut feel”
• Do not eliminate concepts for reasons such as “it’s too different” or “it’s already been done”
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Go - No Go Screening
• Customer requirements/engineering specifications – can they be satisfied with a given concept?
• Readiness of technology – is the technology (engineering & manufacturing) mature?
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Decision Matrix Method
• Semi-quantitative method for evaluating concepts (Tables 8.2, 8.3)
• Most effective when done by each team member
• Often requires iteration (repetition) as more is learned about the problem and concepts
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Robust Decision Making
• Robust – insensitive to uncertainty, incompleteness, and evolution of design
• Decisions based upon:– Satisfaction = belief that a concept meets the
criteria– Belief = knowledge + confidence– Figures 8.4-8.9, Tables 8.4, 8.5