The machine for producing plastic tubes is equipped with the principle of hot body welding, which was chosen as the cheapest and most reliable. Hot-tool welding is a widely used technique in which the joint surfaces are brought to the melting temperature by direct contact with a heated metallic tool. In this welding method, many parameters must be followed to achieve the desired results. The shapes and materials of the welding elements are also very important. A numerical model was created to study the thermal behaviour of the welding process to optimize the welding element. The main goal was to find the most efficient welding wheel shape, ensuring optimal heat transfer to the weld, resulting in a high-quality joint. The numerical model was verified on the basic shape of the welding wheel. Based on the results of the numerical simulations, the welding wheel shapes were designed in detail. Subsequently, numerical simulations were created to design an optimized welding wheel shape. Simulations were performed for film materials such as PVC and PET and recycled materials such as rPET. Various foil thicknesses from 0.2 to 0.6 mm were also simulated. The result was the design of optimized welding wheel shapes. Optimum temperatures for different thicknesses and materials of the welded films were also proposed. A suitable welding element shape with good thermal properties was selected and tested in the welding process. This modified shape of the welding element has resulted in an improved weld.