OPTIMISATION OF WELDING PARAMETERS IN A MOTOR VEHICLE STEERING TUBE USING EXPERIMENTAL DESIGN METHODOLOGY

The objective of this paper is to describe the optimisation of welding parameters in a motor vehicle steering tube of the Honda scooters using Experimental Design methodology. In the first phase the main variables were defined i.e. the factors (and the specific values related) influencing the welding process were chosen. Successively experimental runs were planned and carried out in two steps to refine the values (to reduce their variation range) of the factor levels considered. To evaluate the quality of the welding a destructive Macro-test was carried out, namely a survey at both macro-graphic and micro-graphic levels to ascertain the homogeneity of the materials. In the case of welded joints Macro-test is used to ascertain whether the welding has, in fact, created a continuous and permanent union of the mechanical parts of a component. Use of the macro-graphic survey makes it possible to evaluate the depth of penetration of the welded joint in order to meet safety standards. The penetration depth constituted the response of the welding process considered. Using ANOVA it was possible to evaluate the more significant factors of the process. Once the influence of all the factors and their interactions are known it is possible to trace the Response Surfaces and the relative iso-level curves. This means the values of these factors can be quantified and consequently it is possible to optimise the system's productivity response. At the conclusion of this activity compression tests were carried out on the steering tubes so as to characterise the mechanical resistance of the welded joint.