Winter, D., Ashton-Rickardt, P., Ward, C., Gibbons, P. et al., "An Enhanced Risk Reduction Methodology for Complex Problem Resolution in High Value, Low Volume Manufacturing Scenarios," SAE Int. J. Mater. Manf. 9(1):49-64, 2016, doi:10.4271/2015-01-2595.
This paper reports on a methodology for risk reduction, developed and tested at a brand new aerospace manufacturing facility, producing high value aero-structures. The facility was formed as part of a ‘Risk Sharing Partnership’ between Airbus and GKN for production of the Airbus A350 ‘Fixed Trailing Edge’ (FTE). Whilst operating in New Product Introduction (NPI), the challenge for GKN was to increase production volume for each successive year of operations. At the time of writing, the facility was producing FTE structures at a rate of 4 per month i.e. Rate 4, and attempting to transition to Rate 6. The ultimate aim was to produce FTE structures at Rate 13 within an 8 year period whilst concurrently engineering the product and improving its processes. For schedule adherence, elimination of process failures was critical and often manifested at the final stage of assembly (integration cell). The ‘integration cell’ comprised of turnkey solutions where, on attempting to increase to scheduled rate, failures increased impacting on cycle times. Most failure types encountered were considered complex, since their permutations were often unknown i.e. caused through varying interactions between hardware, software and staff. To explore the problem further, a conventional Failure Mode and Effects Analysis (FMEA) was conducted but proved subjective, since the standard template was restricted to ordinal and qualitative outputs. A process FMEA (PFMEA) was then developed to account for the risks posed through safety, quality, cost, delivery and people (SQCDP). Utilising SQCDP criteria enabled a means of quantitative analysis for capturing optimal RPN values. Further, whilst the enhanced PFMEA proved effective, the method was limited for in-depth determination of root cause, apparent from the permutations of failure observed. The literature provided options, where the properties of Fault Tree Analysis (FTA) were deemed most suitable for identifying critical path, common cause and probability of failure on demand. Combining enhanced PFMEA with FTA provided a holistic means for quantitative risk prioritisation, plus in-depth determination of root cause when faced with complexity. From the root cause analysis, a set of functional requirements were derived that detailed how the solution would perform in practice. The methodology was then effectively completed once the solution had been implemented, validated and verified delivering improved Value Stream performance over the life cycle of the aircraft programme. Two cases are provided where the outputs have delivered marked reductions in process cycle time and predictability.