Reduction of Non-Conforming Products in the Titanium Jewelry Manufacturing Process

Abstract

The purpose of this research is to reduce the number of non-conforming products in the titanium jewelry manufacturing process of Tita 0.5×1.2×08×4. The production process has encountered a problem in which the depth of earring holes deviates from the standard value of 6 millimeters. This issue arises from inappropriate machine parameter settings, including speed, feed rate, and depth rate. To address this problem, this research employed the 2^k factorial design to determine the optimal manufacturing conditions. The findings revealed that all the parameters had significant main and interaction effects on the depth of the earring holes. The settings should be as follows: speed of 3,750 revolutions per minute, feed rate of 0.0175 millimeters per minute, and depth rate of 0.0628 millimeters per revolution. The findings were implemented, and it was found that the optimal manufacturing conditions resulted in earring hole depths that were not significantly different from 6 millimeters. The adjustments of the machine parameters reduced the average quantity of the non-conforming earrings to 1,050 pieces per month, representing 56.03% decrease compared to the period before process improvement. As a result, the average manufacturing cost of the company case was reduced to only 43,013 baht per month. The benefits of this research can be utilized to reduce non-conforming products in other types of jewelry and serve as a guideline for continuous improvement of manufacturing processes.