Investigations on the Formability of Incrementally Sheet Formed Al Alloys

Abstract

Incremental sheet forming (ISF) is an advanced flexible manufacturing process to produce complex shaped products without the use of heavy toolings, such as punch, die and blank holder etc., using a CNC milling machine and acts as a substitute to the conventional stamping process. The present work focusses on the investigation of formability, forming time, and geometric accuracy of an axisymmetric CP-Al alloy component manufactured using the ISF process for different values of process parameters, spindle speed and feed rate. Hardness and microstructure of the alloy sheet before forming was characterized. ISF experiments were carried out on CP-Al alloy sheets of 2 mm thickness using a 10 mm diameter hemispherical forming tool in a CNC milling machine for three different values of spindle speed (50, 500 and 3000) and feed rate (50, 1000 and 2500). A dome shaped component of 75 mm diameter was modeled using the CAD software and the corresponding G-codes of the geometry for a spiral tool path strategy were generated to run the CNC milling machine. Formed components were scanned using the FARO Edge Laser Scanner non-contact measuring system and the forming depth, amount of thinning and springback were measured using the solid works software in order to check the formability and dimensional accuracy of the incrementally formed components. The results showed that at constant feed rate, when the spindle speed was increased, the forming depth and thinning were increased, while the springback was decreased. Similarly, at constant spindle speed, when the feed rate was increased, the forming depth and thinning were decreased, and the springback was increased. No failure of the component was observed in any of the above cases. A maximum forming depth of 32.46 mm and minimum springback of -9.45% (at the bottom of the dome) was observed for the combination of lower feed rate and higher spindle speed. A minimum forming depth of 28.34 mm and maximum springback of -20.94% (at the bottom of the dome) was observed for the lower spindle speed and higher feed rate combination. Similarly, maximum thinning was found to occur along the sidewalls of the dome for all the components and a maximum thinning of 66% was observed for the medium spindle speed and lower feed rate combination.