Integrating Delphi Method into Design of Experiments for Improving Quality Control: A Case Study of Mechanical Company  
Author Anh-Van Nguyen

 
Co-Author(s) Khac-Hieu Nguyen;  My-Hanh Nguyen

 
Abstract The forging industry plays a crucial role in various manufacturing sectors, where process optimization is essential for improving product quality and efficiency. This study applies the Design of Experiments (DOE) method to optimize the Ratchet forging process, addressing the limitations of the traditional One Variable at a Time (OVAT) approach. Using the Delphi method, key influencing factors were identified, including billet heating temperature, heating time, and forging force. A randomized experimental design with 32 trials was conducted using Minitab (Version 20), followed by statistical analysis through ANOVA. The optimal process parameters were determined as a billet heating temperature of 1131.92°C, a heating time of 112.015 seconds, an upsetting force of 441.45 kN, a rough and finish forging force of 1226.25 kN, and a flash trimming force of 441.4 kN. Validation tests showed that these conditions consistently got a 30/30 quality score for the product while cutting processing time by 20%, costs by 22.22%, and the number of trials by 38.82%. The quality also got better by 6.67%. Based on these results, DOE is a very useful tool for optimization, providing better quality and efficiency gains than traditional trial-and-error methods.

 
Keywords Forging process, Design of Experiments (DOE), ANOVA, optimization, quality improvement, Delphi method
   
    Article #:  RQD2025-135
 

Proceedings of 30th ISSAT International Conference on Reliability & Quality in Design
August 6-8, 2025