This study evaluates the impact of casting defects on productivity within a South African sand casting foundry by analyzing operational data collected between January and August 2025. Common defects such as porosity, gas holes, and cross-jointing were identified as significant contributors to production inefficiencies. Using key performance metrics, including job quantity, job losses, rejected weight, and associated financial costs, monthly productivity was calculated and analyzed. The results show that productivity fluctuated within a narrow range of 90.84% to 91.89%, with defect-related rejections accounting for an average monthly loss of 22 jobs, approximately 128 kg of material, and over R5,400 in financial losses. Although the productivity levels appear stable, the persistent nature of defects highlights systemic inefficiencies with cumulative economic consequences. The findings underscore the need for targeted quality improvement strategies, such as real-time process monitoring, enhanced mold design, and workforce training, to reduce defect rates and improve operational performance. This research contributes to the broader discourse on manufacturing optimization by quantifying the tangible effects of quality issues on foundry productivity and profitability.