Masahiko Kita

Creation of Cross-Section Changing Hole with a Hemisphere by Means of Electrical Discharge Machining

In general, machined holes have straight axes and their cross-sections are constant circles since holes are machined by drills. In other words, shapes of machined holes do not have so much variety. To solve the problem, the device was developed which can machine a certain shape on an inside wall of a straight hole by means of electrical discharge machining. This results in fabrication of holes whose cross-sections change variously. In the study, the holes are called cross-section changing holes. However, the device had only ability to make two-dimensional shapes. Therefore, the device has been improved so that three-dimensional shapes can be machined inside holes. From the result of the machining experiment, it is found that the improved device can machine a cross-section changing hole with a hemisphere.

DEVELOPMENT OF CURVED HOLE MACHINING METHOD – SIZE REDUCTION OF HOLE DIAMETER –

ABSTRACT This study deals with a diameter reduction of curved holes that can be machined by the method developed by the authors. In order to improve the productivity of molding, it is necessary to increase the efficiency of the cooling stage in a molding cycle. It depends on the shape and the arrangement of water channels, i.e., pipelines built in molds. However, water channels consist of a series of straight holes due to the fabrication by drilling. Accordingly, it is strongly required to develop a machining method of curved holes since curved water channels are desirable. To meet the requirement, the device has been developed, which can make an electrode move along a curved trajectory with electrical discharge machining. The device can fabricate curved holes. However, the fabricated curved holes have a problem that their diameter is too large to employ them as a water channel. In the study, thus, the size reduction of the curved holes is tried by improving the electrode and its peripheral parts.

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.