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Effective reliability testing to drive design improvement
This document presents a comprehensive overview of effective reliability testing methodologies aimed at driving design improvement in engineering, particularly within the HVAC industry. It outlines the importance of reliability testing, qualification processes, accelerated life testing methods, and the roles of various engineering teams in developing effective test plans. Case studies demonstrate the application of these methods in real-world scenarios to enhance product reliability and address failure modes.
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Effective reliability testing to drive design improvement
- 1. Effective Reliability Effective Reliability Testing to Drive Testing to Drive g p Design Improvement Keyanna Qi ©2011 ASQ & Presentation Qi Presented live on Dec 08th, 2011 http://reliabilitycalendar.org/The_Re liability_Calendar/Webinars_ liability Calendar/Webinars ‐ _English/Webinars_‐_English.html
- 2. ASQ Reliability Division ASQ Reliability Division English Webinar Series English Webinar Series One of the monthly webinars One of the monthly webinars on topics of interest to reliability engineers. To view recorded webinar (available to ASQ Reliability Division members only) visit asq.org/reliability ) / To sign up for the free and available to anyone live webinars visit reliabilitycalendar.org and select English Webinars to find links to register for upcoming events http://reliabilitycalendar.org/The_Re liability_Calendar/Webinars_ liability Calendar/Webinars ‐ _English/Webinars_‐_English.html
- 3. Keyanna Qi Sr. Reliabilityand Test Engineer Research Products Corporation
- 4. Agenda Introduction What and Why Reliability Testing Effective Test Plan Development Process Map Case Studies Summary Questions? 8/24/2011 2
- 5. Introduction My background Expertise in warranty analysis, reliability modeling and testing Work experience with home appliances (Whirlpool), commercial and residential HVAC products ( Trane, Research Products Corp.) Research Products Corporation: since 1938, is a leading manufacturer of products for HVAC industry, business includes: Aprilaire: Indoor air quality systems for temperature control, humidity control, ventilation and filtration. GeoSystems: Geothermal Heat Pump (ECONAR, HydroHeat) DRI-STEEM: Humidification systems for health care, industrial, process- critical, commercial and residential humidification applications worldwide. Technical Services: Authorized Qualmark testing facility: HALT, HASS, Environmental Testing IEC 6100 testing: Electromagnetic compatibility (EMC), Electrostatic Discharge Air Flow testing, ASHRAE 52.2: Air Filter testing 8/24/2011 3
- 6. Introduction Reliability is probability that a device will perform it’s intended function during a specified period of time under stated condition Design for Reliability Reliability Modeling Identify high risk components Allocate reliability growth plan for higher reliability target Perform root cause analysis for corrective actions Reliability Testing Qualification, ALT, HALT DFMEA, FRACAS, others 8/24/2011 4
- 7. Reliability Test –Qualification Qualification Test Verify if new design/components meet design specification – function and operation condition, agency specification – UL or others Functional test under expected operating conditions specified in company engineering standard or design specification Comply with industry standard / regulation Not intended to fail, not test to failure (TTF) 8/24/2011 5
- 8. Reliability Test –ALT Accelerated Life Testing Verify if the new design/components meet design life expectation Operational Cycling: on/off Continuous operating under specified conditions Elevated environmental stress Thermal cycling / thermal shock Corrosion resistance test Vibration Test to failure Simulate field failure Compare different designs/suppliers Allow life prediction 8/24/2011 6
- 9. Reliability Test –ALT Smaller sample size (4 – 16) depend on stress level Pair test: test with baseline part Current production samples Different suppliers Different Design Stress Levels to simulate real failure mode Understand failure mechanisms Operating condition and material limit Worse case scenarios What “Test to Failure” Results Reveal Same failure modes as seen in field Operation margin Root cause of failures Optimize design parameters 8/24/2011 7
- 10. Reliability Test –HALT HALT (Highly Accelerated Life Testing) Identify weak links for new design or comparison test Temperature limits Vibration limits Thermal Shock Combined Thermal Shock and Vibration Compare different design or supplier quality Design margin Operating limit 8/24/2011 8
- 11. Testing Standards Industry Standards ANSI/AMCA (American National Standards Institute / The Air Movement & Control Association International Inc) ANSI/AMCA-204: Operation Vibration (fan motor) ASTM (American Society for Testing and Materials) B117: Salt Spray NEMA (National Electrical Manufacturing) NEMA MG-1: Motor NEMA 4: enclosures UL 1995: Heating and Cooling Equipment Company Engineering Standards or Specifications ES (Engineering Standard) Design Specification 8/24/2011 9
- 12. Reliability Testing No industry standards available No specifications in design documents No testing procedures to follow Varied from part to part, from application to application Each test requires unique method Difficulties to simulate field failure in lab Even harder if complete new design or application 8/24/2011 10
- 13. Test Plan DevelopmentProcess Identify (I) failure modes and failure mechanisms Understand history – warranty performance and field feedback Evaluate/verify under conditions for seeable misuse, not just anticipated use condition Failure modes: list all well known and unknown Design (D) test method and test matrix Develop test methods for critical failure modes Determine failure detection, failure criteria, DOE Optimize (O) test method and testing parameter Run pilot tests to find out most reasonable setup Time and cost effective Validate (V) test method and failure modes Validate test method Verify testing part meet design specification – functionality and life 8/24/2011 11
- 14. Six Sigma Methodology:IDOV Road Map Success: replicate field failure and eliminate it 8/24/2011 12
- 15. Test Plan Contents Functions of part Design limit: max. temperature, pressure, current, torque Operational load – mechanical, electrical, thermal Input / output signals – wiring diagram Operating condition Normal use condition Customer misuse Material properties Failure modes What, Where and How Root Cause Analysis (RCA) – true reason of failures 8/24/2011 13
- 16. Test Plan Contents Testing Methods Follow industrial standard if possible: UL, ASTM, ASHRAE Apply correct load (stress) – thermal, mechanical, cycling, etc Set appropriate stress level to simulate real application condition ALT, HALT, functional check under certain conditions Failure criteria Define “Failure” for lab test setup and monitoring Testing Duration – how long going to test Failure detection 8/24/2011 14
- 17. Subject Matter ExpertsInput Design Engineers have best knowledge of design functions (design specs) Product Engineers know customer requirement and operating conditions (operation mapping) Quality / Manufacturing Engineers know how it fails during production (failure mode, weak links, installation issue) Service Engineers know more customer complaints (failure mode) Material Engineers to help on failure mechanisms Agency Experts: like UL and material test Reliability Engineers to complete the puzzle: collect all inputs from different teams, develop test plan for reliability testing Lab Test Engineers and Technicians to make it happen Teamwork is Essential! 8/24/2011 15
- 18. Case Study (1)Door Handle Improvement Functions Provide service access into / Identify out of unit for service Unit size from 3ftx3ft to 10ftx12ft Keep door closed while unit operating Design Background Information Failure mode: broken handle High failure rate but low warranty cost Optimize Possible Causes Impact load from shipping and handling Validate Misuse – use as ladder or grasp as moving handle Others 8/24/2011 16
- 19. Case Study (1)Door Handle Improvement Handle Broken by Impact Load Moving unit by fork truck or crane, collision Identify happens, hit handle: Split Unit Weight Range: 2500 ~ 8000lb Moving Velocity: 1.6 ft/s (1 mile/h, 0.5 m/s) Impact Force range will be from 2000lb to 6400lb Design Handles, guarding, and any protrusion may fail when encounter such huge impact force Optimize Force = (W*V)/time Assume: Collision in 2s Validate Impact Test 8/24/2011 17
- 20. Case Study (1)Door Handle Improvement Impact Test Identify Drop part to concrete floor Swing a ball to hit Design Shoot a solid block Free drop solid block to hit handle How to measure impact load? Optimize Weight Hit velocity Validate Hit time Height 8/24/2011 18
- 21. Case Study (1)Door Handle Improvement Optimize Free drop cylinder start from 1 food Identify Measure drop height Validate Design Run pilot test to confirm it will produce same failure mode Optimize Other Tests Shear test: use handle as ladder Pull test: use handle as moving tool Validate Operating rotation test not conducted because no prototype unit available 8/24/2011 19
- 22. Door Handle QualificationTest Impact Test New HDL: 2 feet, Apply impact load to center point of no failure Old: HDL: broken at 1 handle foot drop Drop throw a 10lbs cylinder, drop distance from 1 ft, increase drop distance until handle breaks New HDL: base crew Shear Test bend or pull out Old: HDL: passed 250lb Apply 250 lb load on top of handle for 3 minutes, repeat loading 3 times at 10 minutes interval Inspect any damages in handle assembly Strap Test New HDL: Not broke until 500lb, but base Apply shipping strap load to end of crew bend or pull out handle for 1 minutes, increase load from Old: HDL: Broke @ 200lb 300lbs until break handle 8/24/2011 20
- 23. Design Change onNew Handle Increase base screw size and add hardened washer Re-test Success to fix old failure mode Approval for new product application Reliability model was updated, claimed to have 70% improvement However, 3 months later in prototype units….. 8/24/2011 21
- 24. New Failure Mode Cam Roller Loosens Identify Noticed loosening handle at production floor Partially lost function, would not close door properly Design Cam Roller Potential Causes loosening gap Torque specification between cam roller and striker Optimize Insert material hardness Bolt material Validate 22 8/24/2011
- 25. Actions to FixNew Failure Mode (IDOV) P-Diagram to identify desired functions, Identify noise factors, design control factors, error modes Design Boundary Diagram to evaluate interferences FMEA Optimize Put any potential failure modes into consideration Validate Potential causes Design, material, assembly process Recommendations on Detection and Control 8/24/2011 23
- 26. Test Plan forImprovement Identify failure modes Insert Type Washer Cam Torque Identify Cam Roller loosening Current 1 Low Current 2 High Difficult to rotate Current 1 Low Base screw loosening Current 2 High Design Testing parameters Harder 1 High Harder 2 High Add 1 or 2 washers to Harder 1 Low cam bolt Harder 2 Low Increase hardness of No Insert 2 Low Optimize insert plate No Insert 1 Low Find proper bolt Torque No Insert 1 High No Insert 2 High Validate 8/24/2011 24
- 27. Test Setup Mount door handles on Identify door panel How to Rotate Handles? Manual operation? Design PLC control operation? Electrical drill? Other automaton? Optimize Rotate handle 360 degree through striker by a Validate electrical drill 8/24/2011 25
- 28. Test Result Old handle exhibited same failure mode Identify at about 50 cycles operation Samples with one washer added meet Design life cycle requirement Harder insert samples showed best result in terms of tightness and insert Optimize plate damage No insert sample also demonstrated improvement on the tightness Validate Cost benefit Easy to assembly 8/24/2011 26
- 29. Whole Plastic Handle • Impact Test Identify Apply impact load to the center point of the handle (drop throw a metal ball or other objects), using a 10lbs object, drop distance from 1 ft, increase the drop Design distance until the handle breaks: Optimize Validate Current HDL after 4 ft drops Whole Plastic HDL after 1 ft drop 8/24/2011 27
- 30. Corrective Actions basedon Test Results Generic Corrective actions for improvement: Material change: material used did not meet design specification Manufacturing assembly change: part variation or manufacturing defect cause infant failures Design change: design concept change Door Handle Use harder insert material and torque tolerance limit was specified Apply hardened washers on both sides of insert plate Handle without insert material showed similar performance in terms of rotation cycling, but failed impact test and pull test, it is not recommended 8/24/2011 28
- 31. Handles in HVACUnit This door handle becomes one of new features that our customers enjoy most High perceived quality Easy to rotate Very robust 8/24/2011 29
- 32. Lessons Learned Focus well known failure modes, but never overlook unknown failure modes New design may introduce new failure modes while removing well known failure modes Use reliability engineering tools to identify potential failure modes before start test planning Do not skip steps, if not possible to do it, find alternative way 8/24/2011 30
- 33. Case Study (2)– Anti Spin Rod Anti-Spin Rod field failures Identify Fatigue at inner groove Design life: 30,000 cycles Broken Design Mount plate Optimize Screw Actuator Validate Bracket Fracture Surface 8/24/2011 31
- 34. Case Study (2)– Anti Spin Rod Current Design and Machining Quality Very rough groove surface Identify Sharp groove edge - no radius Some samples had less 90 degree bend angle Design Optimize ALT Samples Baseline: current production samples (bend, Validate rough surface) Improved surface with radius 8/24/2011 32
- 35. Case Study (2)– Anti-Spin Rod Test Fixture Design Identify How to apply stress – air cylinder, weight blocks, actual damper? How to measure load? Design Optimize Not apply torque load to actuator, achieve Optimize desired load by using fixed Jackshaft Simple but effective Validate 8/24/2011 33
- 36. Case Study (2)– Anti-Spin Rod Validate Identify Measure actuator torque which is same as part specified Be able to duplicate field failure – Design fatigue at inner groove Optimize Validate 8/24/2011 34
- 37. Case Study (2)– Anti Spin Rod Test Results ReliaSoft W eibull++ 7 - www.ReliaSoft.com Unreliability vs Time Plot 1.000 U nreliability 20 – 40 K cycles Design Margin Design Margin Baseline: Rod Baseline Lognormal-2P RRX SRM MED FM 82% FR F=4/ S=5 Data Points 40 K cycles U nreliability Line 0.800 Rod Rounded W eibull-2P RRX RRM MED FM F=3/ S=0 Data Points I ntervals U nreliability Line 0.600 Improved: Unreliability, F(t)=1-R(t ) 40% FR 0.400 0.200 100K Cycles Keyanna Qi Trane 11/ 22/ 2010 0.000 12:39:15 PM 0 4.E+4 8.E+4 1.E+5 2.E+5 2.E+5 Time (Cycles) Rod Baseline: µ=10.9874, σ=0.7704, ρ=0.9594 Rod Rounded: β=6.2192, η=1.3496Ε+5, ρ=0.9557 8/24/2011 35
- 38. Case Study (2)–Anti Spin Rod Observe a lot from just watching Failure rate of the improved samples were 50% less than the baseline @ 100,000 cycles Rounded sample show no failures within design margin, failed part still works Good to go……but, can be better? Broke rod still functional 8/24/2011 36
- 39. Case Study (2)–Anti Spin Rod Worst stress load on weakest point Is one groove better than two grooves Inner groove is always subjected to shear stress when actuator moves If only one groove (cut outer groove) then shear (bending) stress will transfer to angle corner – much stronger Confirm with design team: no special reason to have end groove 8/24/2011 37
- 40. Case Study (2)–Anti Spin Rod Test one groove and Validate One groove with worst surface quality Test to 120,000 cycles, no failures Estimated to be better than rounded sample Less material Lower machining requirement More robust 8/24/2011 38
- 41. From Good toGreat Test suspended at 120,000 cycles without any failure ReliaSoft W eibull++ 7 - www.ReliaSoft.com Unreliabilit y vs Time Plot 1.00 U nreliability 20 – 40 K cycles Design Margin Design Margin Baseline: R odBas el i ne 0.82 Lognorm al -2P R R X SR M MED FM F=4/S=5 40 K cycles D ata Poi nts 0.80 U nrel i abi l i ty Li ne R odR ounded Wei bul l -2P R R X R R M MED FM F=3/S=0 Unreliability, F(t)=1-R(t) D ata Poi nts 0.60 Interval s U nrel i abi l i ty Li ne Rounded: R odOne Groove Wei bul l -1P 0.40 0.40 MLE SR M MED FM F=0/S=6 U nrel i abi l i ty Li ne One Groove: 0.20 0.15 100K Cycles Keyanna Qi Trane 11/ 23/ 2010 3:38:34 PM 0.00 0 4.E+4 8.E+4 1.E+5 2.E+5 2.E+5 Time (Cycle s) RodO ne Groove : β = 6 . 0 0 0 0 , η = 1 . 6 2 1 1 Ε + 5 RodBase line : µ = 1 0 . 9 8 7 4 , σ = 0 . 7 7 0 4 , ρ = 0 . 9 5 9 4 RodRounde d: β = 6 . 2 1 9 2 , η = 1 . 3 4 9 6 Ε + 5 , ρ = 0 . 9 5 5 7 8/24/2011 39
- 42. Lessons Learned Make it from Good to Great Understand functions of components and design requirement Understand limit of manufacturing process Take one more step to make design more robust and cost effective Lower machining tolerance requirement Reduce material use As reliability and testing engineer, we are able to help more than what others thought New perspective to ask more questions 8/24/2011 40
- 43. Never Skip SystemValidation Component passed qualification test alone, does not mean it works in the subsystem or system Validation tests to verify if the new component meets design specification and life expectation at system level System Validation Tests System / Subsystem Integration Follow normal installation process Subject to operating condition or accelerated stress level of operating conditions Meet life exception or confirm the old failure modes were removed 8/24/2011 41
- 44. Summary Reliability Engineer is not particular component expert (valve, sensor, electrical controls, or system design), but be able to collect information and collaborate with various engineering groups to develop comprehensive reliability test plans Reliability test plan development follows process of Identify – Design – Optimize – Validate Do not overlook any potential failure modes, especially unknown failure modes Apply DOE for design change optimization Always run validation test for final approval Put enthusiasm into your work to drive it from Good to Great 8/24/2011 42
- 45. Where to GetMore Information Annual Book of ASTM Standards Materials, instrumentation evaluation or testing ASHRAE Handbook HVAC equipments and components MG 1-2006 by National Electrical Manufactures Association Motor testing Military Handbook: Reliability Prediction of Electronic Equipment (MIL-HDBD-217F) Consult with subject experts in your organization They know more than you thought 8/24/2011 43
- 46. Questions Thank you for your attention. Do you have any questions? 8/24/2011 44