<p>This study investigates the influence of lost-foam casting process parameters on the A356 alloy, focusing on foam density, pouring temperature, and coating viscosity. The Taguchi method with an L9 orthogonal array was employed to analyze their effects on porosity, hardness, and surface defects. Optimal results were obtained with a foam density of 20 kg/m³, pouring temperature of 680 °C, and coating viscosity of 20 seconds, yielding the lowest porosity (2.6 %), minimal defects, and highest hardness. Foam density and pouring temperature were identified as the most influential factors, with impact contributions of 64.6 % and 56.4 %, respectively. Microstructure and coating permeability were analyzed using scanning electron microscopy (SEM), while optical microscopy revealed the influence of process parameters on grain size. These findings highlight the importance of parameter optimization in enhancing the mechanical and surface properties of A356 alloy castings.</p>