Recent casting production is impossible without the implementation of new strategies and concepts. In the foundry industry a few concepts has been stand out: "Near net shape castings" - castings with almost finite dimensions, where machining is minimal or is not required and "Right for the first time" – correct production for the first time. These are conceptions of qualitative management in terms of prevention which is superior in front of detection and elimination of errors. The main objectives of these procedures are highly material utilization, with minimal number of forming operations. In this paper, the focus has been centred on following technologies: CAE - Computer Aided Engineering, development of casting and solidification process, and errors prediction. CAE technology enabled optimization of gate system and casting technology of cast product with the surface roughness defect. Numerical simulations of casting were performed in order to determine mathematical, physical and chemical phenomena during casting process, with respect to material, mold and applied casting technology parameters. The obtained highly accurate results visually qualitative and quantitative indicate the casting flow and solidification process. The optimization of the gate system using numerical simulation of pouring and solidification processes of the solid fuel furnace set part has been performed. Casting were performed in foundry Plamen Ltd. Considering the parameters and results of the numerical simulation original casting process, and taking into account the results of CALPHAD methods of modeling the phase diagram and solidification sequence, thermal analysis obatined by DSC method and metallographic investigations, modification of the gate system through numerical simulation of pouring and solidification process with the origin casting parameters. According to the modification and optimization of the gate system construction, obtained through this work, casting process was repeated. Repeated casting with modified gate system construction resulted with cast product with significantly lower expressed surface roughness defect. Results of numerical simulation of pouring and solidification enabled significant improvement of melt flow and thermal load of the casting and mold. Simulation results and casting performance indicate that the casting surface roughness error is not directly related to the construction of the gate system. In order to eliminate the appearance of these errors, further detailed investigations of casting technology, besides adjustment of the chemical composition and metallurgical treatment of the melt, and the study of composition and properties of mold mixture should be performed.