CNC incremental forming.

摘要

CNC incremental forming of Al 3003 sheet was studied from both a qualitative and quantitative perspective. Development of two headlight reflector prototypes, for an automotive manufacturer, shows a practical application of the process with potential for further development in other areas. A qualitative analysis of incremental forming illustrates strains distributions, formable wall angle, material properties, and surface roughness. Calculated strains compare well with values given by the shear forming sine law, in which the material deforms by simple shear. The formable wall angle increases by 10° with a 1mm increase in blank thickness, however the percent reduction is reduced. Material properties, given by tensile testing, show increasing yield and necking stresses for larger wall angles. Stress-strain curves for each wall angle, averaged, and then offset by the corresponding measured major strain provide an extended curve for the material at high strains. A log plot of this data results in a straight line, and therefore, a Hollomon equation for the offset curves is proposed for Al 3003. Comparison of two empirical methods showed that both methods are satisfactory, however the Hollomon equation provides a better fit for the annealed curve, while Voce is more suitable for the cold worked material, especially beyond the necking point. Surface roughness tests, using various tool depth increments, provide a relationship for use when forming optical surfaces, or other roughness sensitive parts. Similarly, roughness tests at various tool RPM values provide indication that surface defects on the tool have a minor influence on roughness, and a minimum is reached at approximately 1500 RPM.