Nowadays, due to the growing need for lightweight high strength structures, many attentions have been paid to tubes and hollow profiles. Among applicant industries are aerospace, automotive, chemical industries and household appliances. Following the increasing demand, new methods for tube bending were proposed. One of the most widely used methods is free tube bending method. Using this method forming potential of complex shape geometries is provided without any need to change dies and re-clamp the tube. This method is practically easy and leads to bending with a ratio of 3 (R/Dout = 3 ). In this study, the free tube bending is investigated. A variety of bending methods are introduced, the free tube bending method, which is one of the approaches of the cold tube bending, is explained, and the components of the bent machine are explained. The available bending machine did not have sufficient accuracy and various factors cause errors during the bending process. In this study, sources of error and factors that cause inaccuracies are detected and implemented in order to overcome and reduce these errors. These errors include static and movable die clearance, lack of proper movement of ball bearings of ball screw, and the eccentricity between static die and moveable die in the absolute zero mode of the machine. With rebuilding and modification of some parts of the machine, identified sources of error were removed and the device was brought to a good reproducibility. After modifying the hardware problems of the free tube bending machine, the bending correction coefficients were extracted for various radii. For this purpose, two dimensional bendings with different radii were produced and measured. Then, a function for the correction factors were proposed in terms of the radii of curvature and new coefficients were given in the form of an equation to the G-code curve. In order to create various spatial bendings, the bending process should be properly understood and because this process is performed by a CNC system, then a comprehensive program is needed to transform spatial curves into the machine in a readable format. This program was prepared to produce G-codes for spatial bends. Finally the program was tested and three - dimensional bendings were formed accurately. Key word: free tube bending machine, improvement of accuracy, three - dimensional bend production program, correction coefficient