Papers by Keyword: Cog Styling

Abstract: Sheet-bulk metal forming is an innovative process with a high potential to generate load-adapted parts with high precision. Bulk forming processes of sheet metals especially require high process forces, resulting in an intense contact pressure and, thus, in a very high abrasive and adhesive wear. As a method to reduce or avoid these common wear phenomena, even hardened or coated tool surfaces are not sufficient. The objective of this paper is to show an improvement of the tool resistance during an incremental forming process by an adapted tool design and the application of structured tool surfaces combined with coatings. For the tool surface the structure of the scarabaeus beetle serves as the basis for a bionic structure. This structure was manufactured by micromilling. Despite the high hardness of the tool material and the complex geometry of the forming tools, very precise patterns were machined successfully using ball-end milling cutters. The combination of bionic structures with coating techniques like physical vapor deposition (PVD) on plasma nitrided tool surfaces is very promising. In this work, the influence of process parameters (workpiece material, lubrication, tool design, stepwise infeed) on the tool resistance during the forming operation was analyzed experimentally. The results of the optimized forming tools were compared to conventional, unstructured, uncoated, and only plasma nitrided forming tools. The different tools were applied to 2 mm thick metal sheets made of aluminum (AlMg3) and steel (non-alloy quality steel DC04). As a result, the process forces could be reduced by a modified shape and surface of the tools. Thus, the lifetime of the tools can be enhanced.

Abstract: Sheet-bulk metal forming is a process used to manufacture load-adapted parts with high precision. However, bulk forming of sheet metals requires high forces, and thus tools applied for the operational demand have to withstand very high contact pressures, which lead to high wear and abrasion. The usage of conventional techniques like hardening and coating in order to reinforce the surface resistance are not sufficient enough in this case. In this paper, the tool resistance is improved by applying filigree bionic structures, especially structures adapted from the Scarabaeus beetle to the tool’s surface. The structures are realized by micromilling. Despite the high hardness of the tool material, very precise patterns are machined successfully using commercially available ball-end milling cutters. The nature-adapted surface patterns are combined with techniques like plasma nitriding and PVD coating, leading to a multilayer coating system. The effect of process parameters on the resistance of the tools is analyzed experimentally and compared to a conventional, unstructured, uncoated, only plasma nitrided forming tool. Therefore, the tools are used for an incremental bulk forming process on 2 mm thick metal sheets made of aluminum. The results show that the developed methodology is feasible to reduce the process forces and to improve the durability of the tools.