Process Quality Assessment Model of Hand Tools: A Case Study on the Handle of Ratchet Torque Wrench

The growing popularity of do-it-yourself (DIY) projects has increased the penetration of hand tools devices into the market. This paper thus conducts a case study on ratchet torque wrenches and develops an assessment and verification model of process quality as a means of assisting hand tool manufacturers in managing the quality of ratchet torque wrench products and promoting the on-going development in the hand tool industry. We first propose the process quality index (PQI) that can directly determine a precise level of quality based on the relationship between various process capability indices and Six Sigma quality levels. Using inference, we further develop a testing model of PQI to evaluate the quality level reached of process performance. The present case study is investigated to illustrate the practical applicability of the proposed method. We believe that the proposed model will facilitate the production of high-value products and thereby enhance the competitive advantage of firms in Taiwan.