Feasibility and process analysis of helical gear manufacturing by sheet-bulk metal forming

Abstract The development of sustainable and efficient manufacturing strategies is accelerating the adoption of advanced forming processes for lightweight, high-performance components. Sheet-bulk metal forming (SBMF) enables near-net-shape production of thin-walled parts with integrated functional elements, offering advantages in material efficiency, process consolidation and geometric complexity. While the feasibility of straight-toothed gears has already been demonstrated, helical gears, which are widely used in industry due to their favorable load capacity and noise behavior, have not yet been experimentally validated. This study presents an experimental investigation into the SBMF-based production of helical gear structures. Starting from flat steel sheets, a combined process chain of deep drawing, upsetting and lateral extrusion is applied. The influence of material choice (DC04, CuZn37, DP600) is examined, complemented by reference tests on helix angle, punch stroke and lubrication strategy. Key process variables such as forming force, die filling and local strain hardening are analyzed and correlated with macroscopic defects and microstructural observations. The results demonstrate that the helix angle has negligible influence on process force or die filling, confirming the viability of transferring SBMF to helical gear geometries. Among the tested materials, DC04 exhibits the most advantageous forming response. Lubricant type and quantity exert minimal influence on die filling, indicating that global tribological adjustments are insufficient to steer material flow. Although high cavity engagement is achieved, localized defects such as folding, burrs and indentations highlight the need for improved material routing.