The Design Of OCTG Threading Machine

With the increase demand of Oil Country Tubular Goods (OCTG), a situation that OCTG threading machines are imported from abroad and designed inland has been arisen. As the imported machines are expensive and the domestic machines cannot meet the production requirement currently, OCTG threading machine was designed and analyzed in this paper by the request of Tianjin Coupling Heat Treatment Co., Ltd..(1) Whole scheme of the machine was designed in this paper. The layout and the machine parameters such as overall dimensions, spindle speed and maximum strokes of X and Z axis were determined; the interference detection was done by Pro/ENGINEER; the displacement-time signature of tool nose was obtained according to motion simulation, and the simulation results show agreement with the design requirement of the company.(2) The design idea, structural features and working principle of the fixture, as one of the machine, were introduced. Driven by the electro-magnetic chuck and using the polyurethane rubber sleeve as the clamping element, the fixture has compact structure, is easy to control, clamps workpiece reliably and is less likely to scratch the surface of the workpiece. Based on the self-characters of polyurethane rubber and adopting the nonlinear contacting large deformation method, the feasibility and reliability of the fixture were analyzed by ANSYS. The results show that the static friction produced by 50 kPa clamping load between the polyurethane rubber sleeve and the workpiece is enough to fix the workpiece firmly with little deformation.(3) The first ten order natural frequencies of the fixture box were obtained by modal analysis. The comparison between working frequency and safety frequency demonstrates that low order natural frequencies of the fixture box meet the redundant requirement for safety. In addition, it is proved that the body meets rigidity requirement by static analysis.(4) The type selection and calculation of servo system were completed. The linear motors as feed mechanism were configured; the servo drives and encoders were selected according to the motor power and required precision. The cutting force was estimated by the formula of screw cutting force, and the cutting power was derived according to the computed cutting force. At last, a proper electro-spindle was determined based on the spindle speed and computed cutting power.