Defect Reduction in Thermoforming Process of Tray Side 2.5 inches by Applying Design of Experiment (DOE) Technique

Abstract

The objective of this research was to reduce rumple defects problem from thermoforming process by applying the theory of the thermoforming and design of experiment (DOE) technique to analyze a major cause and factors affected on the quality of product. The research methodology included the determination of possible causes of defects with a fish bone diagram and the use of FMEA to select the major affected factors with RPN over 100 score.  From FMEA, it illustrated that there were three major factors. Then the experiment was designed to test the level of significance of these three factors by 2³ full factorial designs with 2 repeats, number of block 1 at 95% confidence level. The levels of three factors were set by temperature at 190°C and 210°C, heating time at 22 sec. and 37 sec. and vacuum time at 17 sec. and 27 sec. The result showed the optimal level was set the temperature at 190°C, the heating time at 22 sec. and the vacuum time at 17 sec. Then the defect rate can be reduced from 3.53% to 0.93%. This improvement result is able to achieve the company’s goal which defect target should be less than or equal 1%