Surface roughness tests were performed on computer numerical controlled (CNC) incrementally formed sheet metal parts using various tool depth increments and spindle speeds. A non-contact method using white light interferometry was selected to avoid scratching the material surface. All parts were formed from annealed Al 3003 sheet to a shape with a flat 45° wall section for testing. A relationship was defined between peak-to-valley roughness and depth increment, which was then compared to theory for shear forming. The surface quality of modern incremental methods and shear forming was shown to depend on similar settings, and the defined relationship allows for knowledgeable control of surface roughness in future work on such applications as reflective surfaces.

The use of computers in manufacturing has enabled the development of several new metal forming processes that are based upon older technologies. In this case modifications have been made to traditional forming methods such as conventional spinning and shear forming. These two processes are similar in that the deformation mechanism is localized to a small region under the forming tool. Recent advances in computing power have enabled this localized deformation to be accurately controlled and studied. Spinning, shear forming and flow forming are limited to forming parts that are symmetrical about the revolving lathe axis. Current research has been focused on forming non-symmetrical parts using computer numerical control (CNC) technology, without the need for costly dies. A comparison of traditional and modern forming methods is presented here in an attempt to illustrate the evolution of different incremental sheet metal forming techniques. Emphasis is placed on conventional spinning, shear forming and modern computer-controlled forming methods that are currently being studied.

The forming parameters for incremental forming of aluminium alloy 3003 sheet are presented. Using two shapes for testing (a conical shape and a pyramid shape) and forming the sheet to various draft angles, the following data have been assembled: tensile tests, strain measurements, strength coe cient K and strain-hardening exponent n. The method of analysis of stress± strain diagrams used by Ford in the plane strain compression test are shown to be applicable. Relationships such as the sine law for spinning have been applied to the data and are presented.

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