1 Introduction to Engineering Spring 2007 Lecture 4: Engineering Design II

2 Review Design Steps Requirements Preliminary Design Class Project

3 Presentation & Delivery Test & Evaluation Preliminary Design Review - Design Steps Design is an iterative process: Word Description Detailed Design

4 Cost of Changes Costs increase exponentially as the project lifetime increases Cost Time

5 Outline Detailed Design Test & Evaluation Presentation Project

6 Detailed Design

7 Detailed Design Goals Starting with your selected preliminary design, develop it into a producible form that provides the desired function… in other words, develop a complete engineering description to include determination of the arrangement form dimensions materials method of fabrication for all the parts, and how exactly all the parts will be joined together in the final product.

8 Detailed Design Activities The “Five D’s” Doodling Digging Doing Documenting Design Reviewing

9 Activities I Doodling Understand the problem Figure out what needs to be done Sketch some ideas Digging Research Talk to experts Look at what’s out there Check out catalogs, vendor websites, hardware store

10 Activities II Doing Calculations Layouts Selections Components Materials  “When in doubt make it stout out of things you know about” Costs Make sure your design will do what it’s supposed to do!

11 Activities III Documenting Sketches Drawings Layout drawings Part drawings Assembly drawings Bill of Materials/ Parts List Technical reports and memos

12 Activities IV Design Reviewing Is it done? Will it all fit together? Will it work? Do you have enough information to build it?

13 Iteration Considerations You will go through various detail design steps several times Designs will be evaluated by referring to the customer requirements and your specifications You may need to go back to another concept/preliminary design again if your detail design can’t be made to work Depending on how your design works out, your specifications (and requirements) may need to be modified

14 Communications Considerations Your well-documented customer requirements and product specifications will be used to evaluate your design Your design should be well-documented with Sketches and drawings BOM Other information that supports your design decisions Think about who needs to use this information A well-documented design is essential to minimize hassles during fabrication of your product! You’ll need this for your final report and final presentation

15 Detailed Design Summary Be thorough – don’t leave details to the last minute Be diligent in documenting and checking your work Put enough effort into the design – before you build it – to convince yourselves that it will work A thoroughly documented design is a necessary prerequisite for building a successful product

16 Test & Evaluation

17 Testing Testing may be more expensive than development For example, testing adds 20 to 30% to the cost of a IC chip Hence it is cost-effective to Design for Test (DFT) Test plan/Test team/Test engineering

18 Testing Motivation People are not perfect We make errors in design and assembly Important and expensive activity Not unusual to spend 30-40% of total project effort on testing For critical systems (e.g. flight control): cost can be several times the cost of all other activities combined

19 Goals of Testing To reveal failures Most important goal of testing To measure quality Difficult to quantify, but still important To clarify the specification Always test with respect to a spec Testing shows inconsistency Either spec or the design could be wrong To verify contract Includes customer, legal, standards

20 Types of Testing Validation testing To demonstrate to the developer and the system customer that the software meets its requirements; A successful test shows that the system operates as intended. Defect testing To discover faults or defects in the software where its behavior is incorrect or not in conformance with its specification; A successful test is a test that makes the system perform incorrectly and so exposes a defect in the system.

21 Presentation

22 Presentations Presentations and technical writing are important: “….many practicing engineers credited the majority of their success in the field to their ability to communicate their findings and ideas efficiently…” There are many opportunities for presentations during a design task Preliminary Design Review Detailed Design Review Final Presentation

23 Class Project

24 Project Assignment You will work in groups to complete a design It will be a system of your choice: software, hardware, mechanical, other... You will select your own group members: 2 to 3 per group Your first task will be to come up with a word description: Due Feb 27