ME349 Engineering Design Projects Concept Generation This information corresponds to the material in The Mechanical Design Process Ullman sections 7 1 7 5 It is suggested that the student read these sections to supplement this handout 1 Background Once the customer needs and project specifications are identified the work of determining the potential solution begins This is where one begins to design the actual product However it is just as unwise to jump at the first potential solution as it is to start without first understanding the true customer needs With engineering design it usually pays to be patient and spend some quality time in up front planning One step that many teams omit in the design process is that of developing a body of facts before setting out to generate alternatives The design team should meet together and collect all the information that is available about the problem at hand to insure that they don t go off and try to re invent the wheel Good engineering practice builds on the basis of existing work During the collection of the body of facts it is important to differentiate between what is fact and what is an assumption Design assumptions are critical to the understanding of the design objectives Design assumptions may become facts over time The engineering teams that can best forecast the assumptions about the future that become true usually have the winning products The design assumptions built on the foundation of the body of facts become the basis for the product strategy Once the team has identified the critical parts of the design it is time then to generate alternatives for the key parts of the design Most teams stop too early in this process and don t uncover the winning concept Don t shortchange this process Take the time to generate a large number of ideas before trying to narrow down to the final concept 2 Documentation of Objectives Documentation of the Concept Generation and Selection Process is basically a record of the steps the team made in coming up with the final design concept There are several reasons for capturing this information The design team benefits from having a paper trail of their work This allows them to look back at all their work and insures ideas don t get dropped through the cracks It also provides evidence that they have taken into account all the customer constraints in coming up with alternatives This document also provides a set of specifications jointly agreed upon by the team on what will be built It documents the proposed solution to the customer need just as the Customer s Functional Specifications documents the aspects of the problem being solved This information is also important to the management of the project The data included in the document clearly shows how diligent the team was in evaluating different ideas It also highlights the critical assumptions that the team is making about future events This allows the management team to align the company objectives with those of the development team Document Requirements The actual document should include the following information Introduction and process description This section briefly describes the process that the team used in completing the document Summary of the body of facts This section should highlight the key facts and assumptions that the team has gathered upon which they are basing their design concept Block diagram of the proposed solution Alternative architectures considered by the team should also be included Selection of which parts of the design are critical to the success of the project For critical design areas include Concept definition sheets Here the team summarizes the key alternatives that were considered This should include a brief description of each concept Concept evaluation worksheet This section should include a write up of the selection method used to determine the concepts that best meet the product specifications This forces the team to articulate the selection criteria so that others can easily see the rationale behind their decision Chosen design concept This is the last section and it should summarize the design that the team will take into the actual development phase It should clearly show why this design was chosen and what information was used in the decision For the remaining non critical design areas document how those areas will be designed and what technologies will be used 3 Concept generation process Function Determination The following details a general process that may be used for concept generation This process makes use of the customer and engineering requirements list you developed in the previous step the QFD Method Generation of solution concepts requires understanding of the function s that your design must perform Function is a statement of what that is what the system accomplishes The usual form for a function is that of verb noun Examples of function statements would be transmit force or support load Remember that your functions should not attempt to tell how to accomplish something We do not want the function to state how to transmit force for example simply that it must be accomplished Your text lists common function verbs in Figure 7 1 The first step is to determine the overall function of your design This is a statement of what your design system will be used for This statement needs to be the top level for function so it should be fairly general Next you need to decompose the overall function defined into smaller sub functions There may exist multiple sublevels to this decomposition An example of a decomposition of function is given below In this decomposition the function MOVE is decomposed into the steps of GRASP LIFT TRANSLATE and RELEASE Note the nouns have been omitted from this example MOVE GRASP LIFT TRANSLATE RELEASE Make sure in your decomposition that you document only what needs to happen and not the how it should happen If you must make some assumptions regarding design geometry remember we haven t chosen a solution yet then list those assumptions Use standard notation in specifying your functions Make use of the verb list given in the text While it is not a comprehensive list it does offer a large number of examples and will help you to determine other verbs as required The nouns should be general enough that they do not presume a specific solution Consider the logical relationships between functions Function for a design can be considered to be a flow similar to that of energy flow There