Single point incremental forming of aluminum sheet metal: The development of maximum forming angle forming limits, measured strains, surface roughness and dimensional accuracy.

摘要

Single Point Incremental Forming (SPIF) is a new sheet metal forming process which does not require expensive dedicated dies to replicate the part.;In this thesis, the Box-Behnken solves five factors at three levels in forty six runs. The five factors investigated are: material type, material thickness, formed shape, tool size and incremental step sizes (depth of each step into forming). The response to the forming factors, defined as the measure of formability, is maximum forming angle. The parts manufactured to maximum forming angle were also measured for strain, dimensional accuracy and surface roughness.;Traditional sheet metal forming tests for Aluminum alloys show a maximum strain of 40%, while SPIF shows maximum strains of more than 120%. Hence, traditional sheet metal forming tests severely underestimate the forming capabilities of the SPIF process and are not applicable to SPIF. The forming limits in sheet metal forming are typically defined by a forming limit diagram (FLD). These are inadequate for SPIF and FLDs specific to SPIF are required. These are developed in this thesis.;Dimensional accuracy and tolerance is a characteristic of most manufacturing processes. A dimensional accuracy study is undertaken for SPIF, for the first time. The deviations from dimensions specified for a part, to the actual manufactured part, are measured to a maximum deviation of 5 mm. The average deviation is 1 mm.;The forming parameters and forming limits in SPIF are not fully understood. In this thesis the effect of the critical forming factors on formability is studied. Experimental studies are undertaken to determine the forming limits in SPIF with the use of a Box-Behnken designed experiment. This is the first time the Box-Behnken designed experiment has been applied in sheet metal forming. It enables the definition of a 3D response surface, with good accuracy, in a relatively low number of experimental runs - hence its usefulness in experimental work.;Surface roughness is another important characteristic of manufacturing processes. Previous studies in SPIF investigated surface roughness based on the factors of step size and spindle speed, this study investigates the surface roughness based on the five critical forming factors. The average surface roughness measurements range in value from 0.88 to 3.70 mm and are most dependant on the part shape.