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This paper presents the modelling of the mechanical properties of the bobbin friction stir welded of 6 mm thick AA1100 with control factors of spindle and welding speeds. Face-centered composite design (FCCD) was used to design the experimental work and the results of the responses and the combination of factors were analyzing through analysis of variance (ANOVA). From ANOVA, the result indicates that both spindle and welding speed influence significantly the tensile strength and average hardness at SZ of AA1100. The optimum factors for maximum tensile strength and average hardness of the AA1100 were 950 rpm and welding speed of 130 mm/min. Both models giving a relative small percentage error of 0.8 % and 1.64 % for tensile strength model and average hardness in stir zone (SZ) region, respectively, thus indicate the models were adequate.

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Understanding process response through measuring process signal provides on-site information in the area of process monitoring, which saves time and costs. The type of signals depends upon the type of process, equipment and machines used through sensors attached on the equipment used in the process. This is an important method for detecting changes in the process that reflect the condition or quality of the weld. The benefits of this method, however, has not been well performed for Bobbin friction welding. This process is different from conventional friction welding due to the different process set-up in term of tooling and parameters, hence the need to evaluate the signal response. Consequently, signal measuring for welding plate AA1100 was carried out. Tool rotation ranged from 750 rpm to 950 rpm with a fixed travel rate of 130 mm/min on a CNC milling machine and a fixed spacing tool. During the joining process, welding temperature, current consumption and welding force were measured. The resulting data were then plotted on the X-Y axis chart and mapped using the welded plate identifying the welding phase. From the welding force and current measurement, it is found that high force and current is detected at the tool entry phase and exit. As the tool moves towards the end of the plate, the temperature increased. The highest current and strength are measured when the spindle speed is at the lowest, while the highest temperature is at the fastest spindle speed. In weld phase, a current of approximately 6.5 A, a force of 1 kN and a temperature of 320º was measured. A maximum weld strength of 102.860 MPa achieved using a speed of 950 rpm. A slow spindle speed at the entrance area and a high spindle speed at the weld phase are needed to optimise the process.