Defect reduction in ready rice packaging by applying Six Sigma approach

Abstract

Ready Rice product is a ready to eat rice in a sealed plastic cup. It has been increasingly accepted by customers. The studying company had launched the Ready Rice products since 2014 but the defective rate had been found increasingly. The objective of this study is to reduce the defects of the Ready Rice product in this company.

This study applied DMAIC steps of Six Sigma approach which is the systematic procedure based on statistical methods to reduce the defective rate resulted in higher cost approximately 35,342 THB per month. Six Sigma approach is applied starting from a define phase to identify a major product problems which are the out of shape, the wrinkle of seal and the illegible date code of plastic cup. Then, in measure phase, the high defective percentage of 5.14% of the Ready Rice production is measured. Various quality improvement tools such as Cause & Effect diagram, Failure Modes and Effect Analysis (FMEA) and Pareto diagram are applied in analyze phase to determine the causes of each defect type. It is also proved by the hypothesis testing that there is one, three and two significant factors related to the defective rate of the out of shape, the wrinkle of seal and the illegible date code of plastic cup, respectively. All factors are the process parameters of the retort and sealing machines such as the pressure and temperature of the retort machine and temperature, time and vacuum of the sealing machine. The design of experiment based on the analysis of variance (ANOVA) are deployed at improve phase to determine the suggested machine setting with respect to the minimum overall defective rate. The p chart are deployed to monitor the process at control phase by setting the process parameters at 1,700 mbar of retort machine’s pressure, 160 °C of retort’s machine temperature, 150 °C of sealing machine’s temperature, 4 second of sealing time and 10 bars of sealing vacuum.

After process improvement implementation, the overall defective rate is reduced by 56.42% from 5.14% to 2.24%. As the results, the cost of defects is also reduced by 53.17% from 35,342 to 16,549 THB per month. Moreover, the process capability and process performance are increased from 1.04 to 1.17 and 0.54 to 0.67, respectively.