1. Life Cycle Design Reliability FMEA DFA/DFM End-of-Life MAE 156A

2. 2 Reliability Reliability is defined as the probability that a will perform satisfactorily for a specified period of time. Warrantees and guarantees that can be offered by a manufacturer must be closely tied to product reliability predictions. Assume T is a random variable that represents time-to-fail, and also assume that a probability density function is known for T.

3. MAE 156A 3 Exponential Distribution Many reliability studies assume the time-to-failure random variable has an exponential probability distribution.

4. MAE 156A 4 Mean Time Between Failures The reliability of a multi-component system is found assuming a series connection. If each component has an exponential time-to-failure distribution: 12n...

5. MAE 156A 5 Maintenance and Availability The F-22 Raptor fighter requires 34 hours of maintenance for every hour in the sky. “Air Force response to F-22 Washington Post Article by Jeff Smith” (hatch.senate.gov/public/_files/USAFResponse.pdf) Metrics can be defined to measure how maintenance and repair requirements affect the system's availability to perform as needed.

6. MAE 156A 6 Failure Mode and Effects Analysis Failure Mode and Effects Analysis (FMEA) considers each potential failure mode in the overall system design. FMEA generally includes the following steps: Step 1: Define system and its associated requirements. Step 2: Establish appropriate ground rules. Step 3: List all system components and subsystems. Step 4: List all failure modes; the description and identification of the components involved. Step 5: Assign failure rate or probability to each component failure mode. Step 6: Determine how each failure mode affects system or subsystem performance. Step 7: Enter remarks for each failure mode. Step 8: Identify and review critical failure modes and implement necessary actions.

7. MAE 156A 7 Design for Assembly Design For Assembly (DFA) requires revisiting the design to identify which elements can be combined or eliminated. Essential parts (for a theoretical minimum) meet any one of the following criteria: During the normal operating mode of the product, the part moves relative to other parts already assembled. The part must be of a different material than, or must be isolated from, all other parts assembled. Examples: thermal or electrical insulation, vibration damping The part must be separate from all other assembled parts. Examples: pre-built or out-sourced components

8. MAE 156A 8 Before DFA Boothroyd, G., Dewhurst, P., and Knight, W., Product Design for Manufacture and Assembly, M Dekker, 2002. Theoretical Min Part Count = 4 Actual Part Count = 19

9. MAE 156A 9 After DFA Theoretical Min Part Count = 4 Actual Part Count = 7 Does the new cover design cost more to manufacture than the savings gained by reducing the part count?

10. MAE 156A 10 Design For Manufacture Design For Manufacture (DFM) attempts to reduce cost by simplifying parts manufacturing and reducing waste. MAE156A Machine Shop experience is a good introduction to the various operations that may be needed to manufacture a part. In general, you want to design parts that: Avoid impossible machining operations Do not require unusually tight tolerances Produce little waste material Boothroyd, G., Dewhurst, P., and Knight, W., Product Design for Manufacture and Assembly, M Dekker, 2002.

11. MAE 156A 11 Life Cycle Assessment A new product design must consider its entire “cradle-to-grave” life cycle existence. BOL = Beginning of Life MOL = Middle of Life EOL = End of Life Niemann, J., Tichkiewitch, S., Westkamper, E., Design for Sustainable Product Life Cycles, Springer-Verlag, 2009. Product EOL will become a more important design consideration as efforts are made to promote recycling and reuse.

12. MAE 156A 12 EOL Reuse and Recycling Product recycling and reuse should be considered as early as possible in design. Design guidelines include: Integrate as many functions in one part as possible. Minimize the types of materials used in the whole product. Use recyclable materials. Avoid use of polluting elements. Mark parts made of synthetic materials with a standardized material code. Economic considerations include: Try to recover and use recyclable materials for which a market already exists. Concentrate toxic materials in adjacent areas so that they can be easily detached. Ensure that components can be easily separated into groups of materials that are compatible for recycling.

13. MAE 156A 13 Design for Disassembly Design for Disassembly (DFD) might consider adding special separation features, that allow the product to be easily disassembled for recycling. DFD features may help to: Assist in material recycling Facilitate component re-use Facilitate maintenance and repair Assist in product testing and failure mode or EOL analysis Facilitate product take-back or producer responsibility

14. MAE 156A 14 Excuses to Avoid EOL Analysis Your roommate will work for a company that is only interested in short-term profit. Your company, on the other hand, will be environmentally-conscious and awesome. Here are some of the excuses that your roommate will use to avoid EOL analysis: There is no time. The techniques were not invented here. EOL considerations make the product unattractive. Why bother with DFA when assembly costs are low? Low volume production Reliability data does not apply to our products. We have been ignoring EOL for years, why change now? DFMA leads to products that are more difficult to service. There is no incentive for me to do this analysis.

15. MAE 156A 15 Further Reading Fisher, F.E. And Fisher, J.R., Probability Applications in Mechanical Design, Marcel Dekker, 2000. http://roger.ucsd.edu:80/record=b6335442~S9 Kutz, M. (ed), Environmentally Conscious Mechanical Design, Wiley, 2007. http://roger.ucsd.edu:80/record=b6684932~S9 Boothroyd, G., Dewhurst, P., and Knight, W., Product Design for Manufacture and Assemby, Marcel Dekker, 2002. http://roger.ucsd.edu:80/record=b6601111~S9