| Nickel-based superalloys are widely used in key areas of the national economy,such as aero-engines,energy sources,and gas turbines,because of their excellent properties in thermal stability,corrosion resistance,tensile strength,and better thermal fatigue performance at temperatures above 600°C.However,nickel-based superalloys are prone to processing problems such as high cutting temperature,work hardening,and tool wear during machining.The micro-EDM technology uses non-contact pulse discharge to convert electrical energy into heat energy for metal erosion.Because the electrode does not directly contact the workpiece,it is not affected by the plasticity and hardness of the workpiece material.It is the type of alloy micro-hole processing in an effective method.However,high-efficiency Nickel-based superalloys EDM processing greatly depends on the control performance of the discharge system.It not only needs to monitor the discharge status in real time,but also needs to dynamically adjust the pulse and servo system.Although domestic and foreign scholars have also proposed some control methods in this regard,they have not reached unanimous conclusions in the actual application process.Therefore,this paper conducts a certain degree of exploration in nickel-based superalloy micro-hole MEDM machining technology by carrying out research on nickel-based superalloy micro-hole variable group pulse power supply and servo control technology mainly represented by GH4169.This article first explains the basic principles of EDM,and on this basis,collects the waveform trends and discharge waveform states of different processing stages in the entire processing process through basic process experiments;further explores the conditions of a single discharge energy with different energy levels.The influence of parameters such as discharge current and single discharge energy on material removal rate and relative loss of electrodes.Aiming at the problems in actual machining,a pulse power supply and control system that dynamically adjusts the number of pulses and servo feed according to the discharge state between electrodes is designed,and a power supply structure scheme based on the coordinated control of ARM and CPLD is proposed.The power system hardware is mainly composed of main discharge and power conversion,pulse detection and identification,main control board and configuration circuit.The algorithm of pulse recognition detection based on edge detection and delay detection method recognizes and distinguishes different pulse discharges and counts the actual discharge rate.The variable group pulse and adaptive control algorithm based on discharge detection are designed.based on the CARMA model,A two-loop nested variable packet pulse power control structure is proposed,also a least-squares direct selftuning controller is built,and the software programs of each part are written.The installed test of the micro-EDM power supply system completed through the experiment verifies the effectiveness of the design of the power supply system.The comparison experiment of the nickel-based superalloy micro-hole machining process is carried out.The experimental results show that when the variable group pulse power system is used for machining,the Under the condition of micro-energy discharge,the processing efficiency of small holes is nearly doubled.Combined with adaptive control,the depth-to-diameter ratio of the micro-hole during 150?m electrode processing is increased by about half. |
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