Design of an adaptive fixturing system for aerospace component machining
Govindan Dhanasekaran Murallikrishna
Date of Issue2016
School of Mechanical and Aerospace Engineering
An aircraft engine has numerous components like fuel lines, combustion chamber, turbine and compressor rotor stator blades and honeycomb segments, where constant maintenance and repair need to be carried out in escalating the life time of these parts. The part families of turbine Outer Air Seal (OAS) normally have different stages and have unique common features for datuming as well as repairing. In order to perform repair operations on these parts, a significant amount of time has to be spent in design and fabrication of dedicated fixtures for the particular stage which eventually increases the fixtures count. After a detailed review on the various flexible fixturing systems, vacuum based fixtures were found to be more suitable when compared to the other systems. Vacuum fixtures offers high degree of flexibility, low set up time and effective clamping ability on the OAS parts. The fixturing method consists of a common base plate designed in such a way that it could be easily fastened on any machining bed in different orientations for chiseling and milling operations. Due to the dimensional constrain of the OAS stages, individual vacuum chucks were designed accordingly in such a way it can be easily mounted on to the base plate using dowel pins and fasteners. Vacuum suction and mechanical clamps were employed to clamp the workpiece rigidly on the vacuum chuck. The fixture components were analyzed using FEA packages, to determine the exactness of fixturing dimensions and boundary conditions assumed. This design methodology reduced the tooling count from six to one. The set up time is reduced considerably and the initial tooling cost is reduced by 43% when compared to the existing fixturing method.