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This paper investigates a new tool, where the forming tip is constructed from acetal. The acetal tip is investigated because it is self-lubricating and more compliant than traditional SPIF tools. This work characterizes the topography of surfaces created by forming aluminum with both the acetal-tipped tool and a carbide tool. When the parts are compared visually, the parts formed with the acetal tool maintain the appearance of the unformed sheet metal. The surfaces of the parts are measured using an Olympus LEXT OLS4000, a vertical scanning laser confocal microscope. Surface height as a function of lateral position on both sides of the parts (contact and free surface) is measured. These measurements are analyzed quantitatively using areal surface texture parameters and qualitatively compared with micrographs of the surfaces. Comparisons of the surfaces that are in contact with the tool reveal that the surfaces produced with the acetal tool are rougher but more isotropic than those produced using the carbide tool. The surfaces produced by the carbide tool have a more anisotropic appearance, which is created by the tool as it steps down to form the part. The benefit of using the acetal tool rather than the carbide tool is the absence of the anisotropy caused by tool step down. The free surfaces produced by both tools are much rougher than the surfaces that contact the forming tools, since the tool does not affect roughness of the free surfaces.

A new method for applying statistical techniques with small data sets in surface metrology is demonstrated. This method allows for surfaces or surface-creation processes to be differentiated with as few as six measurement regions. A case study in surface roughness of single point incremental forming is used to demonstrate this method because previous work in this area has not provided quantitative statistical testing to support conclusions. The results from the case study indicate that surface roughness parameters Sz and relative length at scales less than 200 nm are greater when the roll marks on the surface are oriented perpendicular rather than parallel to the forming direction.

Forces are measured in Single Point Incremental Forming with a spindle mounted sensor. Results for AA3003 aluminum cones and pyramids are shown. Forces are measured for parts with a 75° forming angle, at which shear cracks are expected to occur. Forces in the three directions are measured on the spindle with force spikes being observed when the tool changes direction at pyramid corners, and reductions in force when stepping between contours. There is also a force variation as the forming tool moves along the pyramid wall. A comparison is made between the forces measured for cones and pyramids.