Week 9 Design for Reliability 2024 (2).pptx

DM306 Week 9 – Design for Safety & Reliability Vicky Hamilton [email protected] Programme 1-1.30 : Boeing 737 Max Case Study discussions 1.30-1.50 : FMEA & Reliability Methods Overview Break 2-2.45 : FMEA Activity 2.45-3: Summary 3-4: Group Work Objectives of todays session Objective 1:...

DM306 Week 9 – Design for Safety & Reliability Vicky Hamilton [email protected] Programme 1-1.30 : Boeing 737 Max Case Study discussions 1.30-1.50 : FMEA & Reliability Methods Overview Break 2-2.45 : FMEA Activity 2.45-3: Summary 3-4: Group Work Objectives of todays session Objective 1: Understand the importance of safety and reliability Objective 2: Develop practical skills in applying the FMEA method & understand its benefits and limitations Objective 3: Understand the role/responsibilities of the designer with regards to safety and reliability The questions you should be able to answer by the end of today: Why is safety and reliability important? How do you apply FMEA and what are its benefits and limitations? What responsibility do you have as a designer with regards to safety and reliability? Setting the scene for reliability: Boeing 737 Max Case Study What do we know about the Boeing 737 Max? https://www.youtube.com/watch?v=H2tuKiiznsY&t=5s Boeing 737-Max – Key Facts What happened? 346 people died in 2 crashes Lion Air Flight 610 on October 29, 2018 and Ethiopian Airlines Flight 302 on March 10, 2019 Grounded in March 2019 Why did it happen? In early 2010’s, Boeing was under pressure to compete with Airbus, who had just announced a new model of A320 In response they decided to focus or upgrading the existing Boeing 737, rather than design a new model One design change meant engines were lifted up from under wings The raised engines caused the nose to tilt risking engine stalls A new system was introduced to prevent engine stalls.This system was called Maneuvering Characteristics Augmentation System (MCAS), in theory this was meant to cause the front of the plane to tilt forwards if the nose raised too high. One USP of the Boeing 737-Max was that pilots did not need to undertake any additional costly flight simulator training. Instead they were given training in the form of an online course. Pilots were not aware of the new software system as the new MCAS system was not mentioned in any manuals or the online course. In both Lion Air 610 and Ethiopian Airlines 302, MCAS, which was triggered by only one sensor, took control of the plane and caused a nose dive crash. Pilots had only 5 second intervals to react in between MCAS taking over the system and were unable to regain control of the plane. In January 2020, the company estimated a loss of $18.4 billion for 2019, and it reported 183 cancelled MAX orders for the year. 15 minute discussion Using what you know from the case study video and google for further research, discuss the following: – What do you think Boeing could have done differently during the design phase? What were their biggest mistakes? – How could they have ensured DfSafety & DfReliability are considered throughout the decision making process? – What are the risks to a business of not giving DfSafety and DfReliability the attention it needs? Failure to give consideration to Safety & Reliability can be fatal - and can expand well beyond just ‘product failure’ Safety – Life at stake Reputation Why is reliability important? Lawsuits Customer retention Staff Morale Duties of the designer As designers, we are required to identify any risks to health and safety in our designs. We should: Make clients aware of their duties under the regulations Avoid or minimise risks in relation to health and safety Provide adequate information about the risks and health & safety aspects of the design Co-operate with others involved in the project. Express our concerns and speak out if something isn’t right! Failure Mode & Effect Analysis 5 Whys Poka Yoke How can we design reliable products? Finite Element Analysis Simulations Fault Tree Analysis Highly Accelerated Life Test (HALT) Cause and effect analysis A technique to graphically identify and organize the possible causes of a problem (effect). Uses a causal diagram to develop an understanding of problem. Supported by the 5 Whys method Washing Machine doesn’t work! Why 1 Why 2 Why 3 Why 4 Why 5 root cause Solve through design? Can the design be changed to eliminate the need for a seal? Can the design be changed to make it impossible to omit the seal? Poke Yoke A Lean manufacturing tool. Involves introducing low cost adaptions to designs and manufacturing process to help operator(s) avoid mistakes. Its purpose is to eliminate product defects by preventing, correcting, or drawing attention to errors as they occur. Poke Yoke example Often, parts entered the process upside-down. Sometimes, the Operator did not notice and problems would occur. © University of Strathclyde 2014 20 After Improvement A dump slot was added to the delivery chute that causes upside-down items to fall off but allows correctly oriented items to pass. © University of Strathclyde 2014 21 Poke Yoke - Error Proofing What is FMEA? A method which can be used in Design For Safety & Design For Reliability. A systematic group of activities aimed at: Recognising and evaluating the potential failure of a product/process Identifying actions that could eliminate or reduce the chance of the potential failure occurring Documenting the design process FMEA Method 1. Define the system that is to be analysed. 2. List the components/sub systems and identify functions & failure modes. 3. Identify & assessing the effect (severity & occurence), the potential cause and the current detection control (detection) for each failure on the overall product/system performance using the FMEA rating chart. 4. Calculate RPN and prioritise areas of improvement. 5. Suggest design improvements. The Risk Priority Number (RPN) RPN = Severity (S) * Occurrence (O) * Detection (D) It is calculated for each failure identified and used to prioritise areas of improvement. Score Severity Occurrence Detection Never Very high- will detect failure Very occasionally High –likely to detect failure Exceeds specification but not 1 perceived by customer Noticed by customer but does not 2 affect the line function Noticed by customer, minor effect on 3 4 product, customer accepts condition Customer dissatisfied with product & its function Medium – failure may be Occasionally detected Significant effect on customer 5 satisfaction Significant inconvenience to 6 customer Low – unlikely to detect Frequently failure Significant annoyance to customer 7 8 Customers endangered Very frequently Zero – impossible to detect failure FMEA Rating Chart 2. List the components/sub systems and identify functions & failure modes. 3. Identify & assessing the effect (severity & occurence), the potential cause and the current detection control (detection) for each failure on the overall product/system performance using the FMEA rating chart. 4. Calculate RPN and prioritise areas of improvement. 5. Suggest design improvements. Part Function Potential Failure Mode Potential Effect(s) of Failure Mode Potential Causes of Failure Current Controls Prevention Detection DETECTION Define the system that is to be analysed. OCCURRENCE 1. SEVERITY Design FMEA Process RPN Actions Design FMEA Process Ball pen example 1. Enter the part name and fora all 2. Enter function offailure each part – use verb 5. thethe severity rating table tonumber rate the most serious 4. Use Describe the effects of the failure 3. Enter the potential modes for each ofnoun Ink Function provid e writin g mediu m incorrec t viscosit y Potential Effect(s) of Failure Mode highink flow low flow Potential Causes of Failure Current Controls Prevention Detection DETECTION Part Potential Failure Mode SEVERITY inkno flow flow, viscosity OCCURRENCE parts/sub assemblies of product e.g combination e.g. provide writing medium effect due to the potential failure. 4 (customer dissatisfied) each failure mode identified e.g. high ink the functions listed in step 2the incorrect RPN Actions Score Severity Occurrence Detection Never Very high- will detect failure Very occasionally High –likely to detect failure Exceeds specification but not perceived 1 2 by operator Noticed by operator but does not affect the line function Noticed by operators, minor effect on 3 line function, operator accepts condition Operator dissatisfied with the line & its 4 function Medium – failure may be Occasionally Significant effect on operator detected 5 FMEA Rating Chart satisfaction Significant inconvenience to operator 6 Low – unlikely to detect Significant annoyance to operator Frequently failure 7 Operators endangered 8 highink flow Zero – impossible to detect Very frequently failure low flow Ink provid e writin g mediu m incorrec t viscosit y highink Potential Causes of Failure 4 too much solvent 4 Too little solvent flow no flow Current Controls Prevention Detection DETECTION Function Potential Effect(s) of Failure Mode OCCURRENCE Part Potential Failure Mode SEVERITY 7.6.Enter rating forfailure eachmode cause of the Enterthe the occurrence potential causes of the e.g. too much / little solvent failure identified in previous step: 2 (very occasionally) RPN Actions Score Severity Occurrence Detection Never Very high- will detect failure Very occasionally High –likely to detect failure Exceeds specification but not perceived 1 2 by operator Noticed by operator but does not affect the line function Noticed by operators, minor effect on 3 line function, operator accepts condition Operator dissatisfied with the line & its 4 function Medium – failure may be Occasionally Significant effect on operator detected 5 FMEA Rating Chart satisfaction Significant inconvenience to operator 6 Low – unlikely to detect Significant annoyance to operator Frequently failure 7 Operators endangered 8 highink flow Zero – impossible to detect Very frequently failure no flow Ink provid e writin g mediu m incorrec t viscosit y highink 4 Potential Causes of Failure too much 2 solvent Current Controls Prevention Detection QC on ink supply flow low flow 4 Too little solvent 2 QC on ink supply DETECTION Function Potential Effect(s) of Failure Mode OCCURRENCE Part Potential Failure Mode SEVERITY how the rating process that is currently in place can help 6.7. Consider Enter a detection that reflects the ability to detect the detect the potential failure mode. QC on ink supply cause of the failure identified in step 8: 4 (medium) RPN Actions Score Severity Occurrence Detection Never Very high- will detect failure Very occasionally High –likely to detect failure Exceeds specification but not perceived 1 2 by operator Noticed by operator but does not affect the line function Noticed by operators, minor effect on 3 line function, operator accepts condition Operator dissatisfied with the line & its 4 function Medium – failure may be Occasionally Significant effect on operator detected 5 FMEA Rating Chart satisfaction Significant inconvenience to operator 6 Low – unlikely to detect Significant annoyance to operator Frequently failure 7 Operators endangered 8 highink flow Zero – impossible to detect Very frequently failure low flow Ink provid e writin g mediu m incorrec t viscosit y highink 4 too much 2 solvent Prevention Detection QC on ink supply DETECTION Potential Causes of Failure OCCURRENCE Function Potential Effect(s) of Failure Mode SEVERITY Part Potential Failure Mode Current Controls 4 flow low flow 4 Too little solvent 2 QC on ink supply 3 RPN Actions Design FMEA Process (cont.) 10. Calculate the Risk priority Number (RPN) by calculating the product of the severity (S), occurrence (O) and detection (D) RPN = S x O x D (RPN = 4 x 2 x 4 = 32) 11. Prioritise all failure modes according to the RPN and suggest a plan for action. Ink provid e writin g mediu m incorrec t viscosit y highink 4 too much 2 solvent Prevention Detection QC on ink supply DETECTION Potential Causes of Failure OCCURRENCE Function Potential Effect(s) of Failure Mode SEVERITY Part Potential Failure Mode Current Controls RPN 4 32 3 24 flow low flow 4 Too little solvent 2 QC on ink supply Actions Outer tube Ink Ink Ball & seat Ball & seat Ball & seat Inner tube Plug Plug Provide grip for writing Provide writing medium Provide writing medium Meter ink supply Meter ink supply Meter ink supply Contain ink Close outer tube end Close outer tube end Hole gets blocked Incorrect viscosity Vacuum = no ink flow High Flow Incorrect viscosity Low flow Incorrect fit Ball detached Incorrect fit Ball loose Incorrect fit Ball tight Tube kinked Ink flow restricted Wrong size Can not be fitted Wrong size Falls out 4 Debris in hole Too much solvent 4 Too little solvent 7 8 6 7 5 2 4 Total failure Blotchy writing Intermitte nt writing Poor handling Incapable process Incapable process Current Controls for Detection 2 Check clearance QC on ink supply 2 QC on ink supply 3 2 3 4 2 2 2 Inspection checks Sampling Sampling No current checks During Assembly No current checks/test s DETECTION Function Potentia l Causes of Failure OCCURRENCE Part Potential Potential Effect(s) Failure of Failure Mode Mode SEVERITY Ball pen example RPN 5 105 4 32 3 24 2 32 6 108 6 168 8 80 1 4 Actions Make hole larger Remove/redesign cap More rigid QC No action 8 64 No action Introduce in-process checks Control ball and seat variation Introduce detection checks No action Eliminate part. Control process FMEA Tutorial In groups, you will analyse a simple product (a corkscrew) from a design for reliability perspective Identify at least 5 potential failure modes Follow the FMEA process to determine a RPN (risk priority number) for each of the Failure Modes. Select 2 key areas for improvement and make suggestions to enhance the existing product. FMEA Tutorial Examples of potential failure modes Cracked Deformed Loosened Leaking Sticking Oxidized Fractured Does not transmit torque Slips No support Inadequate support Harsh engagement Disengages too fast Inadequate signal Intermittent signal No signal FMEA Tutorial Over to you Penetrate Corkscrew cork Failure to penetrate cork Not coupling with screw Failure to retract cork Blunt screw Teeth in handle Provides linear motion of screw Handles Provides lever for removing cork Lever breaks Product fails to function … … … … Potential Causes of Failure Current detection control 4 Overuse, improper ly specified material 2 Unlikely through inspection, End user?? 4 Parts outside tolerance 2 Sampling checks 2 16 6 Material failure (crack improper use) 2 Visual inspection 5 50.. ….. ….... DETECTION Function Potential Effect(s) of Failure Mode OCCURRENCE Part Potential Failure Mode SEVERITY Corkscrew Possible Solution RPN 7 56 Actions … FMEA Conclusion FMEA encourages you to think about severity, occurrence and detection of potential failures RPNs can be useful to identify which failure modes should be addressed first, normally those with the highest RPN. This allows design or process modifications for each of these modes to be considered. Things to remember: Only works if RPN numbers have levels of variation Does not solve every risk, but helps you to identify the most catastrophic and put in place preventative measures Reliability & Your Project This week you should be thinking about how you can improve the reliability of your chosen solution and reduce the risk of product failure. You may wish to consider methods such as FMEA, Root Cause Analysis, Poke Yoke, or you may conduct your own research to identify other reliability methods that suit the needs of your project.