Performance investigation of punching operation to optimize the over cut of circular hole using Design of Experiment Technique “Taguchi Method”

Abstract

Current research investigates the optimization of over-cut in circular hole punching operations using a CNC turret punching machine. The study employs the Design of Experiment (DOE) technique, specifically the Taguchi method, to systematically analyze the influence of three critical factors: cutting load, hit rate, and material type. The factors were varied across three levels: cutting load (10, 12, and 14 kN), hit rate (100, 150, and 200 punches per minute), and materials (EN-8, EN-24, and EN-31). An L9 orthogonal array was used to design the experimental runs, resulting in nine unique combinations to explore the effects on over-cut (OC). Over-Cut (OC) was the key response parameter, measured using a microscopic testing machine to capture high-resolution images of the punched holes. ImageJ software was employed for image processing to accurately assess the deviations. The data were analyzed using Minitab software, focusing on signal-to-noise (S/N) ratio analysis with the criterion "smaller is better." The S/N ratio results indicated that the cutting load had the most significant impact on minimizing dimensional deviation, followed by material type and hit rate. The study revealed that the lowest dimensional deviation was achieved at a cutting load of 10 kN, hit rate of 200 punches per minute, and using EN-8 material. The mean effect and S/N ratio plots further confirmed that increasing the cutting load generally led to higher over-cut values, while higher hit rates improved precision. Interaction plots indicated that EN-31 material performed robustly across varying conditions, making it a suitable choice for diverse operational settings. ANOVA analysis supported these findings, with cutting load contributing the most to the variability in OC, followed by material type and hit rate. Current study provides valuable insights into the optimization of punching parameters to achieve minimal over-cut and enhance machining accuracy. The findings underscore the importance of selecting appropriate levels of cutting load, hit rate, and material type to optimize the performance of CNC punching operations.