Research On The Cutting Process Stability Of The Threading Machine

With the domestic demand for the oil pipe increasing,the market demand for the pipe thread lathe becomes huger and huger.Heading for higher precision and efficiency,processing performance of machine tools is faced more expects.But the chatter is appeared if the machine tool system is in the unstable state,which affects the processing efficiency and the quality of products.The cutting stability is the key to high efficiency machining.Therefore,SCK230 CNC thread repairing turning machine is taken as the study object to analyze its cutting stability and provide the basis for improving its machining performance.Firstly,the three-dimensional model of pipe thread lathe is established in order to find out the chattering parts,and modal analysis is carried out to get low order natural frequency and mode diagram.The analysis results indicate that the source of the chattering is not caused by the vibration of the whole machine.Then the finite element modal analysis and hammering modal test of the cutting tool system are carried out,and the frequency response curve of the tool system is obtained,which is compared with the finite element modal analysis results of the tool system.The natural frequency of the cutting tool system is similar to the chatter frequency,so the main body of the chatter is the cutter system.Secondly,the mechanism of the most frequent regenerative chatter is analyzed,and the chatter dynamic model of the cutting process is set up,and the ultimate cutting depth of the thread lathe is obtained.The dynamic parameters of the tool system are determined,and the cutting stability limit diagram of the thread lathe is simulated.On this basis,the influence of dynamic parameters on the threading machine is analyzed by using single factor method.The cutting stability limit diagram is analyzed in detail,and the optimum spindle speed and the corresponding optimum cutting depth are determined under the specific cutting conditions.Finally,according to the fact that the cutting stability is related to the rigidity and direction coefficient of the system,optimal schemes are selected for the structure design of the bed inner ribs.The thickness of the ribs and the size of the opening hole in the optimal scheme are optimized.Then the feasibility of vibration damping is proven out by the result of modal analysis which contrasts the original and optimized machine beds using computer simulation software.The angle of the bed is changed to improve the stability of the lathe.The analysis results indicate that the natural frequency of the optimized machine beds is improved,which can offer a higher cutting stability.