Search

Multi-axis electrical discharging machining (EDM) is the most commonly used manufacturing method for shrouded blisks. The discharge points and discharge gap distance are time-varying in a multi-axis EDM process. It is difficult to obtain an optimal servo feedrate. In traditional multi-axis EDM servo control systems, servo sensitivity is usually chosen as a smaller constant to avoid arc discharges. Thus, the servo feedrate is lower than the material removal rate in a machining process. The open circuit rate is high and the machining efficiency is decreased. This paper proposes an adaptive servo sensitivity control algorithm for multi-axis EDM of shrouded blisks. Servo sensitivity is adjusted according to discharge status, so as to decrease the open circuit rate and to improve the machining efficiency. Experiment results show that the proposed adaptive servo sensitivity control algorithm can improve the machining efficiency of shrouded blisks by 28.02% without deteriorating surface integrity. [ABSTRACT FROM AUTHOR]

Multi-axis electrical discharging machining (EDM) is the most commonly used manufacturing method for shrouded blisks. However, debris is difficult to be evacuated from a discharge gap, severely affecting the machining efficiency. Spatial planetary movements of a tool electrode can generate a non-uniform flow field in a discharge gap, promoting the evacuation of debris. This paper proposes a spatial planetary movement method for EDM of inclined holes. Screw theory is used to derive the kinematics of a spatial planetary movement, and the coordinate increments of each axis in an interpolation period can be calculated. The trajectories of the spatial planetary movements are simulated. The reliability of the method is confirmed by the simulation. Then, a multi-axis EDM machine can be controlled to drive a tool electrode to realize the spatial planetary movement. Machining experiments are carried out to explore the influences of the spatial planetary movement parameters on the machining performance of multi-axis EDM. Experiment results show that the increase in the amplitude of spatial planetary movements can improve discharge rate and gap status. The machining depth and machining efficiency of multi-axis EDM can be increased ulteriorly. And the speed of spatial planetary movements has no significant effect on the performance of multi-axis EDM. [ABSTRACT FROM AUTHOR]

With variations in gap discharge state or workpiece height, the servo feedrate of wire electrical discharge machining (WEDM) often fluctuates, and the machining process easily becomes unstable, thereby resulting in a decrease in material removal rate or an increase in risk of unexpected wire breakage. With developments of ISO-pulse discharge pulse power supplies and reciprocating traveling WEDM, a precise discharge state monitoring system for the servo federate control system is required. In this paper, with each single discharge pulse being precisely classified and counted, more accurate feedback information can be provided to the servo feedrate control system. Then a new adaptive servo feedrate control system with a self-tuning regulator and a variable gain linear proportional controller has been proposed to improve the material removal rate and control performance. The scheme of an adaptive servo feedrate control system is analyzed. It is found that the new adaptive servo feedrate control system by using a variable gain linear proportional component has a better control performance. By adjusting servo parameters, the discharge ratios are regulated, and the servo feedrate control system can keep the gap discharge state stable. Experimental results show that the material removal rate can be improved significantly by up to 19% with the new adaptive servo feedrate control system, without sacrificing the surface quality. [ABSTRACT FROM AUTHOR]