PFMEA Process Failure Mode and Effects Analysis. James Davis, General Dynamics

Transcription

1 PFMEA Process Failure Mode and Effects Analysis James Davis, General Dynamics

2 Purpose The purpose of this presentation is to share the benefits of a detailed Process Flow Diagram, conducted during a Process Failure Mode and Effects Analysis, that will ensure product quality in the manufacturing/assembly process. James Davis, GDLS Slide Number: 2

3 Introduction James Davis, GDLS Slide Number: 3

4 Definition of FMEA A FMEA is an analytical tool that uses a disciplined technique to identify and help eliminate product and process potential failure modes. o By ID of potential failures o Assessing the risks caused by failure modes and Identify corrective actions o Prioritizing corrective actions o Carry out corrective actions James Davis, GDLS Slide Number: 4

5 Most COMMON Types of FMEA's Design (Potential) Failure Modes and Effects Analysis-DFMEA Focus is on potential design- related failures and their causes. Process (Potential) Failures Modes and Effects Analysis-PFMEA Focuses is on potential process failures and their causes. James Davis, GDLS Slide Number: 5

6 Value of FMEA's Aids in improving designs for products and process Increased safety Enhances Customer Satisfaction o o Better Quality Higher Reliability Contributes to cost savings Decreases warranty costs Decreases waste, non-value added operations James Davis, GDLS Slide Number: 6

7 PFMEA's Focus is on potential process related failures and their causes. Main drive is to understand the process through the identification of as many potential failures as possible. o e.g. Incorrect material used PFMEA typically assumes that the design is sound. Development of Recommended Actions is targeted at eliminating the Root Cause of the potential failures. James Davis, GDLS Slide Number: 7

8 PFMEA Three Parts: Process Flow Diagram (PFD) Process Failure Mode and Effects Analysis (PFMEA) Process Control Plan (PCP) James Davis, GDLS Slide Number: 8

9 Information Flow Customer Requirements: SOR, Vehicle Tech Specs, System Technical Specs Product Definition: Key Product Characteristics, DFMEA Process Definition: Process Flow Diagram (PFD), Product and Process Characteristics Failure Mode Analysis: PFMEA Control Strategy: Control Plan, Error proofing Manufacturing: Work Instructions & Process Monitoring James Davis, GDLS Slide Number: 9

10 DFMEA/PFMEA Information Interrelationships Boundary (Block) Diagram, P- Diagram, Etc. Process Flow Diagram DFMEA Design FMEA PFMEA Process FMEA Design Verification Plan & Report (DVP&R) Process Control Plan James Davis, GDLS Slide Number: 10

11 Process Flow Diagrams The Process Flow Diagram provides a logical (visual) depiction of the process that is being analyzed. James Davis, GDLS Slide Number: 11

12 Process Function / Requirement The SAE/AIAG PFMEA guidelines describe two methods of defining process functions. Either or both may be used. Process Functions may be described in terms of: The product features/characteristics that are created or The process actions that are performed Process functions should be identified in detail as necessary to provide information for the PFMEA to develop effective Process Controls James Davis, GDLS Slide Number: 12 12

13 Process Function / Requirement Consider a simple operation to drill a hole in a metal part The product characteristics & requirements are: Hole size: 4.00 mm +/ Y Hole Location: X = 28.0 mm +/- 0.2 Y = 15.0 mm +/- 0.2 X 4.00 Perpendicular to surface, no burrs, etc. The process operation must create these product characteristics and meet the requirements James Davis, GDLS Slide Number: 13 13

14 Process Function / Requirement To drill the correct hole size in the specified location, the process must: Position and hold the part Align the part fixturing with the drill position Assure the correct drill bit size is used Set and control drill speed Anticipate tool wear and schedule preventive maintenance If the Function/Requirement is defined in the PFMEA as Drill Hole could any of these be missed? James Davis, GDLS Slide Number: 14

15 Process Flow Diagram (PFD) Process Flow Diagram is the foundation The process must be defined step by step, including interfaces The PFD provides the structure to document what product characteristics and requirements (OUTPUTS) are affected by a given operation and how these characteristics and sources of variation are controlled (INPUTS) PFD is a graphical representation of every possible path a part can take through the anticipated manufacturing process A well defined PFD establishes the foundation for the PFMEA Helps in developing equipment specifications. How will the process control non-conforming material? How and when will inspections be performed, what is required? How and when will parts be re-introduced into the process? James Davis, GDLS Slide Number: 15

16 Process Flow Diagram (PFD) Hidden Factories: Interfacing Processes Quality Audits Rework Processes Alternative Processes Scrap Part Buffers Part Movement Product/tooling Changeovers Part Ident./Labeling Teardown Gauging Stations Reject Handling Interface process issues affect quality performance o o Rework and scrap parts bypass process controls Mixed parts in the manufacturing process at changeovers Need for common systems Part of the overall Quality Strategy must include o Common content, common format, common approach Quality strategy must extend to suppliers o Considered an extension of the Total Quality processes James Davis, GDLS Slide Number: 16

17 SAE J1739 March 2009 James Davis, GDLS Slide Number: 17

18 Micro Level PFD Example James Davis, GDLS Slide Number: 18

19 Process Characteristics James Davis, GDLS Slide Number: 19

20 PFD Feeds PFMEA Identify the Function(s) Function is a description of what the Process does to meet the requirements Related to process specification and product characteristics Comes from the PFD operation description column Functions can be described as: Do this operation To this part or material With this tooling or equipment James Davis, GDLS Slide Number: 20

21 PFD Feeds PFMEA James Davis, GDLS Slide Number: 21

22 Linkage to PFMEA James Davis, GDLS Slide Number: 22

23 PFMEA Example continued.. James Davis, GDLS Slide Number: 23

24 Sources and Types of Manufacturing Variation Source of Variation Types of Variation Typical Process Controls Operator Component / Material Equipment / Machine Environment Methods & Systems Set Up (for stable processes) Tool Maintenance Fixture / Pallet Operator Skill, Ergonomic Factors Incoming raw material, purchased parts, previous operations Machine capability, adjustment, wear over time Temperature, humidity, dust, noise Sequence, procedure, layout Initial set up or adjustment Wear over time, breakage, tool-to-tool differences Repair, replacement, reassembly, adjustment Position tolerance, adjustment, wear over time Training, instructions, visual aids, feedback layout, motion analysis, human factors Supplier management, internal controls, error proofing Equipment specifications, closed-loop machine controls, preventive maintenance Climate control, air filtration, clean room, sound insulation Industrial Engineering techniques, Lean Flow analysis Process specification, first / last piece check, automated controls Predictive maintenance, detection errorproofing, tooling specifications Instructions, error-proofing, machine qualification, production trial run Predictive maintenance, prevention and detection error-proofing James Davis, GDLS Slide Number: 24

25 Process Control Plan PCP will be based on the previous activities in PFD and PFMEA. Review the PFMEA information developed & supplied and use to identify: Specific controls that may be needed due to the information added Identify which controls are Product or Process o o o Note any Special Characteristics Identify evaluation methods, frequency and Control Methods Note Reaction Plans (particularly related to NC parts) James Davis, GDLS Slide Number: 25

26 Process Control Plan Example Form (Rev 12Apr02) CONTROL PLAN Prototype Pre-Launch Production Control Plan No: Part Number/Latest Change Level Key Contact/Phone Date (Orig.) Date (Rev.) Customer Part Number Core Customer Engineering Approval/Date (If Req'd.) Team Part Name/Description Supplier/Plant Approval/Date Customer Quality Approval/Date (If Req'd.) Supplier/Plant Supplier Code Other Approval/Date (If Req'd.) Other Approval/Date (If Req'd.) Part/ Process Number Process Name / Operation Description 300 Initiate weld sequence / Perform TIG weld of frame parts. Machine, Device, Jig, Tools for Mfg. Robotic Arm controller. TIG welders. Characteristics No. Product Process Weld beads per design specification. Good welds, no visible defects. Special Char. Class. yes Product / Process Specification / Tolerance Tube welds meet pull test with failure in parent material. Weld appearance meets visual standard. Weld voltage yes 24 Volts AC +/- 2.0 volts Weld voltage yes 24 Volts AC +/- 2.0 volts Inert gas flow rate yes 5 cubic feet / min. +/- 0.5 cfm Evaluation Measurement Technique Pull test using test fixture Operator evaluation to Visual Std TB20-VS1 Machine Control Visual Methods Size Sample Frequency Control Method 1 pc. Per shift. Hydraulic pull test instruction TI21-01 Process monitoring form PMF % Each piece. 100% Each weld cycle. Once each Shift start or changeover or maint. event. Visual inspection OWI # Closed-loop machine control. Set-up OWI #20-02 & Form PMF Periodic maintenance per PM- WI #20. Visual twice Per shift. Operator cleans gas cup twice per shift PM-WI-20. Process monitoring form PMF Reaction Plan Quarantine material since last good pull test. Remove part and send to repair. Scrap part & Re-start welder. Scrap current part. Shut down. Notify maintenance. Notify maintenance. Inert gas flow rate yes 5 cubic feet / min. +/- 0.5 cfm Visual of verification of Flow Meter James Davis, GDLS Slide Number: 26 Once each Shift start or changeover or maint. event Set-up OWI #20-02 & Form PMF Equipment Calibration Procedure #368 Quarantine material since last good pull test. Notify maintenance.

27 Process Control Plan Example Part/ Process Number Process Name / Operation Description Machine, Device, Jig, Tools for Mfg. No. Characteristics Product Process Special Char. Class. Product / Process Specification / Tolerance Evaluation Measurement Technique Methods Size Sample Frequency Control Method Reaction Plan Initiate weld sequence / Close and latch curtain Robotic Arm TIG welders Initiate weld sequence / Perform TIG weld of frame parts. Initiate weld sequence / Confirm Weld voltage Initiate weld sequence / Confirm Inert Gas flow rate Initiate weld sequence / Confirm Wire feed rate Robotic Arm TIG welders and controllers. Weld beads per design specification. Good welds, no visible defects. Weld voltage Weld voltage Inert gas flow rate Inert gas flow rate Weld wire feed rate Weld wire feed rate yes yes yes yes yes yes yes Tube welds meet pull test with failure in parent material. Weld appearance meets visual standard. 24 Volts AC +/- 2.0 volts 24 Volts AC +/- 2.0 volts 5 cubic feet / min. +/- 0.5 cfm 5 cubic feet / min. +/- 0.5 cfm 300 mm / minute +/- 10 mm / min. 300 mm / minute +/- 10 mm / min. Pull test using test fixture Operator evaluation to Visual Std TB20-VS1. Machine Control Visual Visual Visual verification of Flow Meter Machine Control Operator setup check and verification 1 pc. 100% 100% Once each twice Once each 100% 100% Per shift. Each piece. Each weld cycle. Shift start or changeover or maint. event Per shift. Shift start or changeover or maint. event Hydraulic pull test instruction TI41-01 Process monitoring form PM Visual inspection OWI # Closed-loop machine control. Set-up OWI #20-02 & Form PM Periodic maintenance per PM-WI #20. Operator cleans gas cup twice per shift PM-WI Process monitoring form PMF Set-up OWI #20-02 & Form PM Equipment Calibration Procedure #368 Each weld Closed-loop machine cycle. control. Shift start Set-up OWI # & or changeover or Predictive Form PM maint. maintenance event pinch roller 180 days. Quarantine material since last good pull test. Remove part and send to repair. Scrap part & Re-start welder Scrap current part. Shut down. Notify maintenanc Notify e. maintenan ce. Quarantine material since last good pull test. Notify Scrap part & Re-start maintenan welder ce. Scrap current part. Shut down. Notify maintenance. James Davis, GDLS Slide Number: 27

28 Case Studies Supplier A Not ISO Certified, Primarily Defense business base Sole Source - Unique Technology No Process Flow Operator work instruction for 100 piece component o o 20 process steps on a single piece of paper (included machining) Building the component relied on Tribal Knowledge Diagramming the Process Flow 20 steps turned into 951 steps to produce the component 22 manufacturing related issues (from DFMEA) were incorporated in the PFD/PFMEA Supplier A used PFD - FMEA to Develop work instructions Determine the requirement to developed training programs for assemblers / machinists, QC personnel Develop safety program / training James Davis, GDLS Slide Number: 28

29 Case Studies Supplier B ISO Certified, Primarily Defense business base Sole Source - Unique Design Fair Documented Process Flow Relied on a combination of operator knowing what should be done next with operator work instructions. o However it did allow for repeatable assembly of component with skilled employee Diagramming the Process Flow 270 step PFD became 1,170 steps o FMEA analysis determined: work instructions that needed improvement and new work instructions were required Supplier B used PFD- FMEA to Update work instructions to error proof build process James Davis, GDLS Slide Number: 29

30 Case Studies Supplier C ISO Certified, Defense/Civil business base Well Documented Process Flow Operator work instructions allowed for repeatable assembly Error Proofing allows for assembly with average employees Diagramming the Process Flow 263 step PFD became 268 steps 32 manufacturing related issues (from DFMEA) were incorporated in the PFD/PFMEA o FMEA analysis determined: work instructions that needed improvement and new work instructions were required Supplier C used PFD- FMEA to Update work instructions James Davis, GDLS Slide Number: 30

31 Case Studies Supplier D ISO Certified, Aerospace business base Very Small Company 2 Master Assemblers (1 of which was the Assembly & Test Manager) Unique Technology Fair Documented Process Flow Relied on a combination of operator knowing what should be done next with broad operator work instructions. o However it did allow for repeatable assembly of component with highly skilled employee Diagramming the Process Flow 5 page PFD became 22 pages FMEA analysis determined: work instructions needed improvement to allow for production of more than 1 component at a time Supplier D used PFD - FMEA to Develop work instructions with boundary photos Recall non-compliant parts Determine the requirement to developed training programs for assemblers, QC personnel Develop detailed ATP James Davis, GDLS Slide Number: 31

32 Recapping Process Flow Diagram What does the process do? PFMEA What could go wrong? Could we prevent or detect? Control Plan What needs to be controlled/monitored? How do we react to problems? Operator Instructions & Monitoring What am I supposed to do? How am I supposed to do it? Where am I supposed to record it? James Davis, GDLS Slide Number: 32 32

33 References AIAG FMEA Fourth Edition June 2008 SAE J1739 March 2009 James Davis, GDLS Slide Number: 33

34 Vocabulary AIAG FMEA Fourth Edition Published June 2008 SAE FMEA J1739 Published March 2009 PFD, Process Flow Diagram PFMEA, Process Failure Modes and Effects Analysis PCP, Process Control Plan James Davis, GDLS Slide Number: 34