Paper Title
Design And Analysis Of Welding Fixture For Motor Case Assembly

This paper focuses on the Design and Analysis of the Welding Fixture for Motor Case Assembly. A Motor case assembly is a part of the rocket boosters which is made of Maraging steel MDN 250 grade a well known material in the aerospace domain for it high strength to weight ratio and it also possesses a good weldabilty property. The application of a motor case is to store the solid propellant such as Black powder (BP) propellants [Composed of charcoal (fuel), potassium nitrate (oxidizer), and sulfur (additive)], Zinc–sulfur (ZS) propellants [Composed of powdered zinc metal and powdered sulfur (oxidizer)] etc. Motor case assembly consists of four main parts i.e. Head end sub-assembly, Tube I, Tube II and Rear end which have to be manually welded using TIG Welding sequentially in an corresponding order. The welding has to be carried out to meet the specified tolerance and weld quality. Since, the length of the motor case assembly is approximately about 4 meters the need for welding fixture is established and also some of the brackets and ducts have to be welded on the motor case assembly. To meet the required tolerances on the motor case assembly the shaft/support pipe is designed as a main part of the welding fixture and the different parts are mounted on this shaft /support pipe. The analysis is carried out to have a optimum shaft dimension so has to have minimum deflection on it. To have a proper clamping effect on the components of Motor case assembly the finger clamps are used and corresponding lifts are evaluated using Analysis. All the analysis part is carried out using CATIA V5 R17. To meet the required weld quality on the motor case assembly the welding is carried out in the presence of the Arsenic Copper Weld backup tool with the purging facility which possesses a high thermal conductivity than Maraging Steel. Since, the mass plays an effective role in dissipating the heat produced during the welding operation, the mass of the Arsenic copper is found and the inert gas used in purging is Argon. All the modeling of the components has been carried out using UNIGRAPHICS NX8.0.