New spinning technology for producing square section die-less spun parts in the sheet metal forming process

Abstract

Sheet metal spinning is one of the main forming processes, being characterized by flexibility, low cost, reduced manufacturing time, and high formability. Where a flat metal blank is rotated at a high speed and this spun part is formed by pressing a forming tool into the blank, however, this process is limited to axisymmetric parts. This research thus aimed to design and build a simple and flexible mechanism for producing asymmetrical spun parts to allow non-circular forms (polygons) to be formed without interrupting the rotation of the turned blank, being synchronized with the rotation of the special forming tool. The proposed mechanism is based on developing a synchronous spinning machine in which the rotational motion and traditional lathe machine feed are monitored to maintain synchronization with the tool rollers (special forming tool), where the latter controlled by electric motors. The speed of the electric motors is controlled by a variable frequency drive (VFD), pulse-controls and specialized software. The proposed machine can be applied to multiple product shapes by changing the pulse-control in the software code, making the machine much more flexible than other options. Square cross-section parts were formed by cutting aluminum alloy sheets (1050) into a circular shape of 1.5 mm in thickness and 150 mm diameter. The experimental study then examined the effects of various process parameters on the spinning process, spindle speed of the lathe, feed ratio, and forming tool diameter. Three values were adopted for the three parameters, spindle speeds of 48, 68, and 135 RPM, feed ratios of 0.16, 0.22 and 0.32 mm/rev, and forming tool ball diameters of 16, 22, and 25 mm. The results showed that the maximum average in wall thickness reduction was about 27.44 %, and the maximum average error in dimensional accuracy was 6.47 % for spun parts made with a 45 mm mandrel.