Profile cross rolling for the local hardness increase in helical components such as extruder screws

Highly developed production technologies facilitate unique component characteristics depending on the respective manufacturing objective. However, often several technologies are required in a sequential manner to achieve either the geometrical or the mechanical component properties. Innovative stainless steel alloys show an outstanding work hardening capability. Therefore, they are of great interest for the development of an enhanced burnishing process. The incremental cold forming technology of profile cross rolling can be applied to burnish machined preforms. This paper examines an approach for the geometrical preform design. Starting from the geometrical surface of revolution, the procedure is further developed to helical component surfaces. Both numerical and experimental results indicate that the preform design allows attaining a hardness increase in highly loaded component subsurface regions. This hardness increase goes along with low geometrical deviations and high surface integrity. Hence the results allow the conclusion that this technological development enables the achievement of several component characteristics with one fast burnishing operation. This might lead to an increased acceptance of forming technologies in industries that are usually characterized by pure machining processes. Such an industry could be plastics compounding.