Investigations on the Impact of Mold Age on Green Sand Properties and Casting Defects: A Comparative Study of FIFF and LIFF Methods

Green sand molding remains a cornerstone of ferrous casting, yet the time-dependent deterioration of mold properties, referred to as mold age, has not been quantitatively explored. This study introduces a novel method to define and calculate mold age based on molding and holding times. It examines its influence on critical green sand properties: Green compressive strength (GCS), moisture content, permeability, and hardness. Using a Taguchi L[Formula: see text] design of experiments (DoE) approach, two mold scheduling strategies were experimentally evaluated: First-In, First-Fill (FIFF), and Last-In, First-Fill (LIFF). Under FIFF, molds aged 30-24 min significantly deteriorated, with moisture content dropping to 2.0–2.2%, GCS falling to 1126–1173 g/cm 2 , and permeability rising to 158. These molds also exhibited the highest defect rates. In contrast, LIFF scheduling preserved mold integrity more effectively; molds aged 12–26 min retained higher moisture (3.9–2.5%) and GCS (1350–1203 g/cm 2 ), with defects only appearing beyond a critical threshold of 26–28 min of mold age. Regression models demonstrated excellent predictive accuracy ([Formula: see text] 2 up to 1.00; RRMSE as low as 0.02%), validating the link between mold age and property degradation. This research is the first to quantify aging thresholds, offering a practical, data-driven framework for scheduling optimization. The findings highlight the value of LIFF scheduling in enhancing casting consistency, especially in small- and medium-scale foundries, and provide a foundation for integrating real-time mold age monitoring into digital foundry workflows.