2103-314 mechanical system design ii

1. 2103-314Mechanical System Design II By Asst. Prof. Dr. Kaukeart Boonchukosol

3. Design Process; the basic module

5. Some kind of Information Manufacturer�s catalogue Handbook data National standard Technical paper Experience

6. Problem Solving Methodology Definition of the problem Gathering of information Generation of alternative solutions Evaluation of alternatives Communication of the result

7. Definition of the Problem

8. Gathering Information What do I need to find out? Where can I find it and how can I get it? How credible and accurate is the information? How should the information be interpreted for my specific need? When do I have enough information? What decision result from the information?

9. Detailed Description of Design Process

10. Morphology of Design Phase I: Conceptual Design Phase II: Embodiment Design Phase III: Detail Design Phase IV: Planning for Manufacture Phase V: Planning for Distribution Phase VI: Planning for Use Phase VII: Planning for Retirement of the Product

11. Phase I: Conceptual Design Identification of customer needs Problem definition Gathering information Conceptualization Concept selection Refinement of the PDS Design review

12. Phase II: Embodiment Design Product architecture Configuration design of parts and components Parametric design of parts and components

14. Phase IV: Planning for Manufacture Designing specialized tools and fixtures Specifying the production plant that will be used Planning the work schedules and inventory control Planning the quality assurance system Establishing the standard time and labor costs for each operation Establishing the system of information flow necessary to control the manufacturing operation

15. Need Identification

16. Types of Design Project Variation of an existing product Improvement of an existing product Development of a new product for a low-volume production run Development of a new product for mass production One-of-a-kind design

17. How to Gathering Information from Customer Interview with customer Focus group Customer surveys Customer complaints

18. Levels of Customer Requirements Expecters: the basic attribute that one would expect to see in the product Spokens: the specific features that the customers say they want in the product Unspokens: the product attributes the customer does not generally talk about, but are nevertheless are important to him or her Exciters or delighters: the features that make the product unique and distinguish it from the competition

19. Quality Function Deployment QFD is a planning and problem-solving tool that is finding growing acceptance for translating customer requirements into the engineering characteristics of a product. Group decision-making activity Graphical representation using a diagram called �House of Quality�

22. Concept Generation and Evaluation

24. Creativity Develop a creative attitude Unlock your imagination Be persistent Develop an open mind Suspend your judgment Set problem boundary

25. Vertical and lateral thinking

26. Invention Invention is something novel and useful, being the result of creative thought. Classified into 7 categories The simple or multiple combination Labor-saving concept Direct solution to a problem Adaptation of an old principle to an old problem to achieve a new result Application of a new principle to an old problem Application of a new principle to a new use Serendipity

27. Psychological View of Problem Solving Four-stage model Preparation: The element of the problem are examined and their relations are studied. Incubation: You �sleep on the problem.� Inspiration: A solution or a path toward the solution suddenly emerges. Verification: The inspired solution is checked against the desired result.

28. Creativity Methods

29. Mental Block Perceptual blocks Stereotyping Information overload Limiting the problem unnecessarily Cultural blocks Environmental blocks Emotional blocks Fear of risk taking Unease with chaos Adopting a judgmental attitude Unable or unwilling to incubate Intellectual blocks

30. Brainstorming Four fundamental brainstorming principles Criticism is not allowed. Ideas brought forth should be picked up by other people present. Participants should divulge all ideas entering their minds without any constraint. A key objective is to provide as many ideas as possible within a relatively short time.

31. Stimulation of ideas Combination: What new ideas can arise from combining proposes and functions? Substitution: What else? Who else? What other place? What other time? Modification: What to add? What to subtract? Change color, material, motion, shape? Elimination: Is it necessary? Reverse: What would happen if we move it backward? Turn it upside down? Inside out? Other use: Is there a new way to use it?

32. Creative Idea Evaluation

33. Theory of Inventive Problem Solving (TRIZ) TRIZ is Russian acronym Developed by Genrich Altshuller and his coworkers in Russia, since 1946 About 1.5 million patents were studied, and discovered that only a few dozen inventive principles were used for solving the problems

34. Five levels of problem solutions Level 1: Routine design solutions arrived at methods well known in the specialty area. 30% Level 2: Minor correction to an existing system by methods know in the industry. 45% Level 3: Fundamental improvement to an existing system which resolve contradictions within the industry. 20% Level 4: Solution based on application of new scientific principle to perform the primary function of the design. 4% Level 5: Pioneering inventions based on rare scientific discovery. 1%

35. Engineering Parameters used Weight of moving object Weight of nonmoving object Length of moving object Length of nonmoving object Area of moving object Area of nonmoving object Volume of moving object Volume of nonmoving object Speed Force Tension, Pressure Shape Stability of object Strength Durability of moving object Durability of nonmoving object Temperature Brightness Energy spent by moving object Energy spent by nonmoving object

36. Engineering Parameters used Power Waste of energy Waste of substance Loss of information Waste of time Amount of substance Reliability Accuracy of measurement Accuracy of manufacturing Harmful factors acting on object Harmful side effects Manufacturability Convenience of use Repairability Adaptability Complexity of device Complexity of control Level of automation Producibility

37. The Inventive Principles Segmentation Extraction Local quality Asymmetry Combining Universality Nesting Counterweight Prior counteraction Prior action Cushion in advance Equipotentiality Inversion Spheroidality Dynamicity Partial or overdone action

38. The Inventive Principles Moving to a new dimension Mechanical vibration Periodic action Continuity of useful action Rushing through Convert harm into benefit Feedback Mediator Self-service Copying An inexpensive short-lived object instead of an expensive durable one Replacement of a mechanical system

39. The Inventive Principles Use of a pneumatic or hydraulic construction Flexible film or thin membranes Use of porous material Change the color Homogeneity Rejecting and regenerating part Transformation of physical and chemical states of an object Phase transition Thermal expansion Use strong oxidizers Inert environment Composite materials

40. Example A metal pipe was used to pneumatically transport plastic pellets. A change in the process required that metal powder now be used with the pipe instead of plastic. The harder metal powder causes erosion of the inside of the pipe at the elbow where the metal particles turn 90o. Conventional solutions to this problem might include reinforcing the inside of the elbow with an abrasion-resistant hard-facing alloy, providing for an elbow that could be easily replaced after it has corroded, or redesigning the shape of the elbow. However, all of these solutions require significantly extra costs, so a more creative solution was sought.

41. Solution What is the main function of our elbow? To change the direction of flow of metal particle What we want to improve? Increase the delivered particles� speed (parameter 9) Reduce the energy required (parameter 19)

42. Solution

43. Solution By counting the frequency of inventive principles suggested, the Principle 28 is the most cited (4 times). The others Principles cited are 13(3), 15(3), and 38(3). Then Principle 28 shall be firstly considered.

44. Solution The full description of Principle 28 is 28 Replacement of a mechanical system Replace a mechanical system by an optical, acoustical, or odor system. Use an electrical, magnetic, or electromagnetic field for interaction with the object. Replace fields. Example: (1) stationary field change to rotating field; (2) fixed fields become fields that change in time; (3) random fields change to structural one. Use a field in conjunction with ferromagnetic particles. Then possible solution may be placing a magnet at the elbow to attract and hold a thin layer of powder that will serve to absorb the energy of particles navigating the 90o bend, thereby preventing erosion of the inside wall of the elbow.

45. Algorithm of Inventive Problem Solving

46. Conceptual Decomposition It is common tactic to decompose the problem into smaller parts. Connections of elements in terms of structure and function within the blocks shall be stronger than those between the blocks. There are two main approaches Decomposition in the physical domain Functional decomposition

47. Decomposition in the Physical Domain

48. Functional Decomposition Function is in the nature of a physical behavior or action Function tells us that what the product must do. The process of functional decomposition describes the design problem in term of a flow of energy, material, and information.

51. Generating Design Concept

52. Morphological Chart Proposed by Zwicky Steps to follow Arrange the functions and subfunctions in logical order List for each subfunction �how� Combine concepts

53. Example �CD case�

57. Axiomatic Design Developed by Professor Nam Suh and his colleagues at MIT Focus around 2 design axioms Axiom 1: The independent axiom Maintain the independence of functional requirements (FRs). Axiom 2: The information axiom Minimize the information content.

58. Mapping process of Suh�s concept

59. Hierarchy of FRs for a metal cutting lathe

60. Hierarchy of lathe design in physical domain

62. Evaluation

63. Comparison Based on Absolute Criteria Evaluation based on judgment of feasibility of the design. Concept should be into one of three categories: It is not feasible? Next question is �Why is it not feasible?� It is conditional �it might work if something else happen? Looks as if it will work, then it seems worth to work further.

64. Comparison Based on Absolute Criteria Evaluation based on assessment of technology readiness. The technology used in the design must be mature enough not to need any additional research. Their indicators are Can the technology be manufactured with known processes? Are the critical parameters that control the function identified? Are the safe operating latitude and sensitivity of the parameters known? Have the failure modes been identified? Does hardware exist that demonstrates positive answers to the above four questions?

65. Comparison Based on Absolute Criteria Evaluation based on go-no-go screening of the customer requirements. After a design concept has passed filters 1 and 2, the emphasis shifts to establishing whether it meets the customer requirements framed in the QFD Each requirement must be transformed into a question to be addressed to each concept. The questions should be answerable as either yes (go), maybe (go), or no (no-go). The emphasis is not on a detail examination but on eliminating any design concepts that clearly not able to meet an important customer requirement.

66. Pugh�s Concept Selection Method Choose the criteria by which the concepts will be evaluated Formulate the decision matrix Clarify the design concept Choose the datum concept Run the matrix Evaluate the rating Establish a new datum and rerun the matrix Plan further work Second working session

68. Measurement Scales

69. Weighted Decision Matrix

72. Analytical Hierarchy Process, AHP Multicriteria decision process introduced by Saaty Suited to hierarchically structural system Can work with both numerical and intangible and subjective factors Use pairwise comparison of the alternatives