Research On Control System Of Double-station Connecting Rod Stress Slot Wire Edm Machine Tool

The cracking process of connecting rod has the great advantages of time saving,material saving and consumption reduction,and has gradually become the mainstream process in the processing of automobile connecting rods.The processing of the stress groove on the inner surface of the large-end hole of the connecting rod is one of the most important processes in the connecting rod cracking process,which affects the subsequent cracking quality.There are mechanical broaching,laser etching,wire EDM,and other methods for connecting rod stress groove processing,and mechanical broaching tools have serious wear and tear,which is not suitable for large-scale production processing of connecting rod stress grooves and other narrow grooves;The laser energy beam is processed to avoid the problem of tool wear in mechanical broaching.However,the laser equipment is expensive to manufacture,and after laser etching,it is easy to form hard spots at the exit of the connecting rod cracking groove and the product is bonded to the cracking groove.In the subsequent fine boring of the large end hole of the connecting rod,the tool is prone to chipping.The use of ordinary EDM wire cutting to process the stress groove is a feasible solution,which requires repeated threading,which is cumbersome and time-consuming.Based on the successful development of the first generation and second generation special threadless wire cutting stress groove processing machine tools,the paper uses uniform speed feed for the original equipment,which leads to the problem of short circuit during the processing process.This paper designs and develops a special servo control system for the double-station connecting rod stress slot wire EDM machine,and carries out the process verification.The servo control system is mainly divided into the following parts:(1)For single-station processing control,the gap average voltage detection method is used to collect the gap voltage signal,and the collection result is saved in the FX3U-4AD module.The fuzzy control method is used to classify the results of fuzzy collection,and the control results are obtained by formulating membership functions and fuzzy control rules.The min-max center of gravity method is used to de-obfuscate the control results to obtain an accurate control amount and control the servo feed.(2)Aiming at the double-station machining control,the two stations are independent of each other and do not interfere with each other.The PLC is used to simultaneously detect the discharge status of the two stations at the same time and independently control the processing of the experimental sample stress groove.(3)While designing the servo control system,the tension mechanism,liquid supply system and power supply module of the original machine tool are improved to reduce errors caused by defects in the machine tool itself.(4)Orthogonal experiments were conducted for single-station processing and dual-station processing,respectively.Verify the efficiency of single-station machining and double-station machining.The double-station machining experiment needs to ensure that the two stations have the same initial gap.Design the orthogonal experiment.The processing time is 20 s.The laser confocal microscope photographed the surface of the stress groove and observed the smoothness in the groove.After measurement,whether it is single-station machining or doublestation machining,the groove depth value can be kept within 0.4 ～ 0.7mm,and the groove width value is about 0.2mm,and it is connected with the two-way synchronous wire EDM machine tool.Compared with the processing efficiency of the stress groove on the inner surface of the large hole of the rod,not only can two rods be processed simultaneously in a unit time,but also the processing time of a single rod is shorter,which achieves the expected goal.