| At present, most radiators are produced with manual welding in China. It has shortcomings of instable welding quality, low welding efficiency, intensive labor, poor working conditions and a large body radiation. In order to improve the situation, appropriate automatic CNC welding machines need to be urgently developed to make enterprises more competitive. According to market needs, an automatic CNC welding machine adapting to steel-aluminum radiators is designed.Steel-aluminum radiators with aluminum fin have the characteristics of small welding space and continuous risers. It is difficult to realize welding automation. Through analysis of welding process and comparison of welding methods, metal active gas arc welding (MAG) is adopted.The trajectory and mode of torch's motion and posture of torch are the main basis for the mechanical structure. Interpolation of X, Y and Z axis is desired to weld the welding seam of intersecting space curve.To improve the efficiency, reduce welding distortion and complete the continuous welding of risers, symmetrical synchronous welding with dual-torch is used and each torch completes half-curve. The relative position precision of dual-torch is ensured by the special test equipment and test methods.Through analysis of torch's structure and motion, triangle torch configuration is used. To ensure the best point of welding, a fourth axis R is to ensure torch to be adjusted in real time when welding. All axes are servo-driven. With synchronous belt and silent chain driving, synchronous motion of dual-torch is achieved on Y and Z axis, and synchronous rotation of R-axis is achieved with the sync signal.To achieve continuous automatic welding, multi-V-wheel friction drive and floating clamp of work piece is adopted to make the pre-installed framework of radiator move along the X axis continuously. Z axis bears the Y-axis device installed on the beam. Synchronization of Z-axis beam is achieved with coaxial drive and dual damping weight balance.The device to avoid obstacles of aluminum fins is designed. The angle between torch and riser in the plane perpendicular to the direction of motion can be adjusted by adjusting the rotation angle of the triangular configuration to avoid obstacles of aluminum fins.Equations of motion and motion curves of each axis can be solved based on the intersecting space curve, attitude model of torch and the welding speed.The load of servo motor can be obtained by the return calculations of the load torque and inertia torque of each axis. It is the reliable basis for selection of servo motor. Because of the real-time adjustment of torch's posture, axis R frequently starts and stops. Load inertia, load torque start, start frequency and operating frequency of step motor of axis R need to be calculated.Stiffness, damping and inertia of each servo axis and servo drive parameters such as gain on the whole servo feed device have a great impact on stability, precision and response of whole system. Under simplified assumptions, through establishment of modes of the axis AC servo drive unit model, the servo motor model and the dynamics model mechanical transmission, the model of servo feed system is established. Dynamic performance is simulated with Matlab, and the step response curve shows that the welding machine has good dynamic performance.Prototype manufacturing is completed, the debugging and a number of welding tests are conducted and the optimal welding parameters are obtained. And quality inspection is done in accordance with the design requirements. It proves the results meet the design requirements.
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