A hexapod robotic platform for miniature drilling operations

Abstract

Product miniaturization is a key aspect of manufacturing nowadays. Computer numerically controlled (CNC) machine tools are the major tools used in manufacturing industries for producing miniaturized products. However, CNC machines are still big, bulky and stationary. This research is an effort to develop a robot which would be able to carry out machining operation as a mobile plaform. There have been several researches going on about the development and application of miniature multi legged robots. Hexapod robots are small and stable mobile robots which are developed having a lot of variety. But the main focus of researchers till now have been the structure and motion of hexapod robots. However, not much research has been conducted about the use of legged robot for machining application. In this project a Hexapod robot was designed and fabricated for machining operation. The research scope for this project is limited to 1-D machining i.e. drilling operation. This research demonstrates methodically for the first time the feasibility of meso-scale machining using linked mobile robotic platform. A suitable existing robot (hexapod) design was followed in this project. A drilling spindle was attached with the robot to carry out the machining operation. The robot was controlled using serial communication. A Graphical User Interface (GUI) was developed to control the Hexapod which had all the required algorithm inside. Machining operations were carried out with the prototype robot to test its performance. A new compensation algorithm has been proposed to improve the positional accuracy of the robot movement. The proposed algorithm takes into account spindle speed and linear velocity to compensate the positional error. The positional accuracy was improved by 85% after implementing the error compensation scheme. It was seen that for lowest spindle speed which is 2500RPM and point to point velocity 200mm/min the repeatability was the best which was less than 30?m. The positional accuracy of the robot movement was compared with that of an existing commercial micromachining system. The performance of the robot was found to be almost similar to that of the commercial machine. Finally, the machined hole quality was measured in terms of circularity and taperness. It was observed that at the best machining parameter setting, circularity deviation was as low as 0.016 mm and taperness was 0.547 degree.