1. EPT 221 ENGINEERING DESIGN FORMULATING A DESIGN PROBLEM

2. Objectives of this lecture Describe the overall process of formulating a design problem Describe and use sources of product and customer information Prepare an engineering design specification Understand and implement various design methods: objective trees, pairwise comparison chart, quality function deployment (house of quality)

3. Defining the Problem: Problem Statement Need - an expression of dissatisfaction with the current situation. Goal - a brief, general, and ideal response to the need statement. Need: There is too much damage to automobiles in low-speed frontal collisions. Goal: Design an improved front bumper.

4. Need vs Goal Need: Childproof pill bottles are too difficult for people with arthritis to open. 4 possible goals: Design a childproof pill bottle that is easier to open Design a childproof pill container that is easier to open Design a childproof system for dispensing pills Design a childproof system for dispensing medication More general

5. Objectives - quantifiable expectations of performance  measurable - E.g.: Objectives for design of automobile front bumper i.The bumper should be inexpensive. ii.The bumper should not be significantly damaged in the collision. iii.Other parts of the car should not be significantly damaged in the collision. iv.The bumper should be easily recyclable. v.The car should still be operative after collision Specify the performance measures for each objective and identify the units of measurement. Include all relevant performance characteristics ( behaviour, performance) without referring to any design parameters.

6. Objectives, their Bases for Measurement, and their Units of Measures ObjectivesBasis for MeasurementUnits 1. InexpensiveUnit manufacturing cost for a production run of 50,000 Dollars 2. No significant damage to bumper Distance bumper is pushed into body Inches 3. No significant damage to other parts Repair costDollars 4. Easily recyclableAmount of aluminumlb. 5. Retain maneuverabilityTurning radiusft. 6. Retain braking capabilityBraking distanceft.

7. Constraints - define the permissible condition of design features and the permissible range of the design and performance parameters. - three general forms: –Yes-no constraints: represent conditions that either exist or do not exist. E.g.: the doors must open and shut. –Equality constraints: specifies that some characteristics of the design must take on a specified value, with no leeway for variations from that value. E.g.: in order to prevent over-riding bumpers in collisions between automobiles, the bumpers should be installed 18” up from the ground. –Inequality constraints: requires some characteristics of the design to be greater than, or less than, some specified values. One-sided inequality constraints: requires some characteristics of the design to be greater than, or less than, some specified value. E.g.: the weight of the bumper cannot exceed 50 lb. Two-sided inequality constraints: requires that a design/ performance characteristics be greater than one specified value and less than another specified value. E.g. the mounting brackets on the bumper must be between 8.0” and 12.5” from the centre so they match with the brackets attached to the automobile frame

8. Example

9. Assignment Describe a reasonable set of objectives (including performance measures and units) and constraints (please identify each type of constraints) for the design of either (i) an electric pencil sharpener or (ii) a flashlight Due on the 1 st August 2008. Pass up during class hours.

10. The Process of Problem Formulation

11. 4 primary activities in the process of formulating a design problem: 1.Seeking information surveys, studies. objective - to get detailed understanding of the customer, his or her specific needs, and the competition. 2.Interpreting detailing the specific requirements of the part, assembly, or product, desired performance targets, necessary constraints, evaluation criteria. 3.Gaining consensus team members discuss data interpretations, revising this conclusions, reporting data source, resolve conflicts. prepare preliminary engineering design specification. 4.Obtaining management approval  design review meeting, memorandum, technical report

12. Seeking Information Gather, examine, evaluate information regarding –customer requirements –company requirements –engineering characteristics –constraints –customer satisfaction

13. Customer and Company Requirements What product functions are desired How well the functions are performed The operating environment that the product is subjected to Marketing Manufacturing Financial concerns Company requirements Customer requirements

14. Customer Requirements Product functions desired How well functions are performed Operating environment Value = benefits/ costs So, if benefits, so value, customer satisfaction

15. Customer Requirements….continued Function and Performance  Functions / Importance  Engineering characteristics  (units, limits)  Performance Targets  Satisfactions Operating environment  Air temp., humidity, pressure  Contaminants  Shock, vibration Safety Economics Geometric Limitations Maintenance Repair Retirement Reliability Robustness Pollution Ease of use Human factors Appearance

16. Example Motorcycle design: Customer requirements –Function / performance: start engine quickly, support rider(s) comfortably, … –Operating  road shock  wet, cold, high altitude –Other maintenance intervals fuel economy

17. Company Requirements Marketing  knowing who are the customers and consumers  individual, group, business, government agency  Purchasing procedures, evaluation criteria of different customers  Time to market  understanding what the competition is and what it will be doing during the time it takes to get the product to the market  Advertising resources, annual volume that is to be produced and sold. Manufacturing  Purchasing, fabrication, assembly, warehousing, distribution.  Expected annual production volume (number of units to be made). Financing concerns  Estimate of the capital expenditures necessary to purchase and install manufacturing equipment or modify existing facilities.  Projection of sale revenues, expenses, profits, return on investment.  To determine whether to continue or terminate the project Others  Patents, legal & voluntary regulations, standards, codes.

18. Example Motorcycle design: Company requirements –Marketing: need product in 24 months, sale price competitive –Manufacturing  5,000 units per year  use existing manufacturing plant –Financial $300,000 R&D budget

19. Engineering Characteristics measures that quantify how well a product performs each requirement. Can be used to impartially assess how well an existing product satisfies its customer requirements. Assess how well a new product might perform engineering requirements  to measure these characteristics Characteristics  a means to establish requirement Requirement  a desirable or necessary target value for an engineering characteristics Has appropriate units and limits

20. Engineering Characteristics, Units and Limits

21. Constraints Restrictions on function or form. Maximum or minimum performance limits relating to the desired functions or sub-functions. Specific limitations regarding shape, size, configuration, materials, or manufacturing processes.  design parameters Explicit vs implicit (not directly expressed) constraints Feasible design – when a part (or product) satisfies all the constraints  unfeasible design

22. Customer Satisfaction Customer decide what a good or excellent design is  not the designer Try establish qualitative and quantitative levels of satisfaction Qualitative measures  not satisfied, somewhat satisfied, moderately satisfied Quantitative measures  express customer satisfaction in numerical form/values Graphing  can be used to provide satisfaction values as a function of a performance variable  Customer satisfaction curve:  3 categories: 1. more-is-better, 2. target-value-is-better (i.e., nominal-is-better), 3. less-is-better

23. Qualitative and quantitative measures

24. Graphing Less-is-better Target-value-is-better More-is-better

25. Information Sources Surveys – customer feedback system  service reports, customer support reports, warranty claims Market Studies  by trade associations/ government agencies Literature  reference handbooks, technical journals, periodicals, electronic sources, internet Focus Groups  a group of customers gather in one locations to discuss a product Observation Studies  done by company representatives/ consultants Benchmark Studies  assessments of competitive products

26. Engineering Design Specification (EDS) A single document that captures the whole team’s understanding of the specific details of design problems. Includes information of:  Customer requirements  Company requirements  Engineering characteristics  Constraints  Customer satisfaction Equivalent to preparing a ‘statement of the problem’ that we find in general problem solving methods Also known as Product Design Specification Work-in-progress, dynamic in nature NOT the same as Product Specification (PS)  Printed information about the finished product usually given to the customer in the owner’s manual or ‘instructions’ sheet. The process of writing the EDS establishes a team consensus on the important customer and company requirements.

27. Engineering Design Specification Template Cover page Title Stakeholder Date Introduction Design problem description Intended/unintended uses Special features Customer requirements Functional performance Operating environment Safety Economic Geometric limitations Maintenance Repair Retirement Reliability Robustness Pollution Ease of use Human factors Appearance Company requirements Marketing Manufacturing Financial Other Appendices Site visit data Sales/ marketing data House of quality