Computerized Simulation of Interference in Thread Milling of Non-Symmetric Thread Profiles

Thread milling is a machining technique which is becoming widely used in specific contexts such as large diameter threading. Furthermore, compared to tapping, it is fully adapted to produce internal threads in difficult-to-cut materials, because the tool can be easily removed if a breakage occurs. For thread milling, as well as for form milling, groove and worm machining, geometrical considerations are critical aspects to succeed surface machining with the required accuracy. Interference phenomena may appear and appropriate cutter profiles and tool trajectories have to be defined to generate the desired shape. The proposed study is focusing on the threading of non-symmetric profile. A geometrical model computing the envelope profiles and using full parametrical definitions of the tool and thread is proposed. Its exploitation allows an analysis to explain and to quantify the influencing parameters on overcut. Then, an iterative method based on a direct approach, is proposed to define the tool design allowing to machine non-symmetric threads with good accuracy.