Development of Crank-Connecting Rod Attachment for Electric Discharge Machining of Curved Holes

摘要

Devising a best possible design is often considered as the main important stage in the development of a new device for making curved holes effortlessly. This study deals with the development of a crank-connecting rod attachment for the circular motion of the electrode into the metal body to generate a curved hole by electric discharge machining (EDM). This attachment helps to convert the periodical linear motion of EDM ram to the electrode (curved) circular motion into the metal object. To make the curved hole in the metal body, the electrode also should be in a curved shape. In electric discharge machining, both tool and workpiece are in interaction during sparking; therefore, while producing the curve hole, the curved electrode also gets melted and is not useful for the next production. The fabrication of the curved electrode is also a difficult task. Hence, the attachable electrode inserts (copper) have developed to protect the curved electrode during the EDM process. So that, the combined setup (electrode element + insert) could move in a circular motion during EDM machining to generate the circular holes. Hence, the copper insert only gets melted during ED machining, and it is changeable. The insulating bearings (nylon bushes) were also developed for a rotating shaft to avoid the short circuit between the electrode linkages (electrically negative) and supporting base (electrically positive). By using this device, the EDM experiments were conducted with four rough setting parameters consists of pulse-on time (T_(on)), pulse current (IP), sensitivity of ram (SEN), lifting time of ram (LFT). Finally, the curved hole was generated successfully in a hard metal block using this device.