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Many process design factors effect the outcome of a sheet stamping operation. Particularly inner panel structures of hang-on panels are difficult to produce in aluminium. This paper deals with material behaviour issues related to formability and friction. Formability is characterized by the mechanical properties while friction is related to surface topography. Formability is evaluated by means of laboratory tests and stamping trials on actual inner panels. Optimum results are obtained with materials with high n value and isotropic r value. An improved AA5182 alloy has been developed to meet these demands on mechanical properties. This alloy creates the best condition for downgauging and cost saving targets.

An extended test program has been carried out at Volvo to determine the implications of the application of pretreated aluminium with dry lubrication. This should replace the standard route which is pressing with oil and subsequent pickling and passivation of panels. The separate results from each individual step in the production route are acceptable. However when a part is put through the whole route from pressing to assembly to paint line then it fails due to cratering after the e-coat. This is a result of incomplete removal of the dry-lubricant. To guarantee complete removal the pre-curing of the adhesives, the degreasing before phosphating and the composition of the dry-lube have to be optimized. Although pretreated aluminium with dry-lube offers great possibilities the application is at present not qualified at Volvo.