962 ISBN: 978-93-80689-28-9 Design and fabrication of Shape Memory Alloy actuated Stewart platform for automated laser assist micro-machining application Yogeshwaran SM 1 , Tameshwer Nath 2 , Reena Disawal 2 , I.A.Palani 2 1 Department of Mechatronics, Bannari Amman Institute of Technology 2 Opto-mechatronics Laboratory, Discipline of mechanical engineering Indian Institute of Technology Indore, Madhya Pradesh, India 1 smyogesh24@gmail.com*, 2 palaniia@iiti.ac.in Abstract In this work a Shape Memory alloy (SMA) actuated, automated Stewart platform has been designed and developed for laser based micro- machining setup. The Stewart platform are designed using SMA based actuators owing to their capability for precisely controlling displacement. The actuation studies were also performed through joule heating with linear displacement of 3 mm. The system is designed with a graphical user interface that can be integrated with the computer. The system has a capability to go have a displacement of 4 mm along the X and Y plane and 3 mm in the Z direction. The resolution is of the system is estimated to be around 0.2 mm and the accuracy will be up to 0.5 mm. The silicon wafer can be attached for the reflection of laser for micro machining. This platform is a parallel manipulator robot which converts linear motion into prismatic and two rotary axes in a planar motion. Design of Stewart platform equipped with Shape memory alloy spring and biased springs concentrically. This setup will be used for generating micro channels using lasers on the silicon wafer. Keywords: Shape Memory Alloy, Micro machining, on-off controller 1. INTRODUCTION The most novel mechanism used for flight simulators and position maintaining is Stewart platform or parallel manipulator. It is a classic example of a mechanical design that is used for positioning and orientating the platform with respect to a fixed base. Main application is to fulfill the requirement of high load carrying and precise positioning capability. Most of them available are actuated with hydraulics and pneumatics whose drawback is the control of position. The same platform can be used for the position control in other applications. Traditional actuators such as electric motors, hydraulic pump and pneumatic necessitate the use of large and heavy supported and are usually very noisy. Electric motors are bulky, revolve at very high revolution in which reduction gear is required to produce needed torque [1]. In recent decades, the parallel mechanisms have become attractive because they exhibit advantages in the manufacturing accuracy and speed. This plays an important role in developing the micro-scale positioning platform. Hassel Bach et al. have investigated several positioning platforms based on a parallel mechanism and emphasized the advantages of a parallel mechanism in the precision positioning field [2]. Yi et al. have designed and con ducted experiment on the stiffness of a platform consisting of several flexure hinges [3]. Dasgupta et al. have reviewed a parallel manipulator platform based on the Stewart–platform [4]. Various arrangements for stewart platform [5-9] have been studied to understand the behavior of platform. In this paper developed stewart platform is explained and experimentation of SMA spring performance were carried out to find important data such as speed of contraction, minimum and maximum weight that can be lifted and operating conditions. Fabrication and construction process of platform using SMA spring actuators was based on analysis of the experimental results. In the upcoming sections design, fabrication, experimentation and control strategy is discussed in detail. 2. DESIGN AND PRINCIPLE WORK The design of the Stewart platform is developed in a mini scale of 50 mm * 50 mm * 8 mm and attain three degree of freedom with rotation on x and y axis and prismatic in z axis. The platform consist of similar 4 SMA and 4 biased springs coaxially. The springs are hinged at both ends of the platforms. One side of the platform is fixed like a cantilever beam. The platform is designed in a CAD model with hooks for mounting the springs and converted to stereo lithography format for 3D printing (fig.1). The bottom platform is hinged with the table and SMA springs are mounted first in to the designed hooks. The Biased springs are installed coaxially with SMA springs and wires are commonly grounded and the positive supply pins are connected to separate relays for the control for actuation. Figure 1: Design of Stewart Platform 3. NITINOL SPRING SELECTION