Size Reduction and Performance Improvement of Automatic Discharge Gap Controller for Curved Hole Electrical Discharge Machining

The study deals with size reduction and performance improvement of automatic discharge gap controller (ADGC) for a microrobot which can fabricate a long curved hole by electrical discharge machining (EDM). It is strongly required that curved hole machining method is developed so that the pipelines can be made which have arbitrary shape and are located in arbitrary position. However, such pipelines cannot be fabricated since holes are generally formed by drilling. To solve the problem, the authors have proposed the curved hole machining method by means of a microrobot with an EDM function. The microrobot has to have the function of performing stable EDM in the limit space such as the bottom of a long curved hole, in other words, the function of always keeping the equipped electrode in the appropriate position automatically and autonomously so as to maintain stable EDM. To realize the function, ADGC has been devised. Actually, the prototype of ADGC was developed and it had been proved that the prototype had the function. However, the prototype was too large to install on a microrobot and did not achieve the full performance designed. Therefore, in the study, the improvements of ADGC are done so that its size is reduced and its full performance is achieved. From the experimental results, it is found that the improved ADGC, whose size is reduced so that the installation to a microrobot is enabled, realizes the designed full performance.