A Modified Risk Prioritization Approach Using Best–Worst Method

Abstract

Manufacturing plants often face many defects during manufacturing processes. It is not possible to eliminate all failures in the process. Therefore, there is a need for a risk assessment methodology, such as Failure Mode and Effect Analysis (FMEA). The risk priority number (RPN) calculation has been criticized in many aspects in the classical FMEA analysis. Some of these criticisms include the inadequacy of the number of risk factors, uncertainties in determining risk factors, and reaching the same RPN number with different risk combinations. To eliminate the disadvantages of the classic RPN calculation of FMEA, a modified approach was proposed in this study. A case study was carried out in a company that makes plastic production by injection molding in Germany. RPN elements of severity (S), occurrence (O), and detection (D) were evaluated by an occupational health and safety expert from the observed company. The weights of these parameters were calculated using Best and Worst method (BWM). Then, six failure modes were evaluated with respect to S, D, and O elements, and their preference values were also calculated via BWM. Modified RPN values of each failure mode were calculated by multiplying the evaluation matrices and weight matrix. Preventive measures were taken in operation for three failure modes with the highest RPN value.