Abstract
Cold forging of toothed components by extrusion is associated with high punching forces and tool loads, which requires the use of expensive and high-strength tool steels. High process forces result into a substantial tool deflection, which significantly reduces the precision of the toothed components. Thus, the development of alternative processes in order to reduce acting process forces in cold forging is of high interest. A potential process enhancement approach is to use a preform operation where the resulting preform can be formed partwise either in the same or in a subsequent die. Preforms allow to systematically control the material flow in subsequent forming operations. For this reason, the Institute for Metal Forming Technology in Stuttgart has developed a new cold extrusion process for manufacturing toothed components based on the conventional Samanta process. The newly developed die design of the Guided Material Flow—Samanta (GMF—Samanta) process enables efficient cold forging of gears. By means of numerical simulations and forging experiments it was successfully demonstrated that the new Guided Material Flow—Samanta process results into a significant reduction of punch force and normal pressure while simultaneously improving the die filling.
Highlights
The two processes are compared based on the die filling, normal pressures, equivalent stress distributions and required punch forces
A new cold forging process was developed and numerically investigated for cold forging of gear shapes and gear wheels based on established Samanta process
Objective of the investigation was to verify the feasibility of the process and to compare the numerical results with the conventional Samanta process sequence
Summary
Cold forging of toothed components is until today a technological challenge because narrow die cavities have to be filled with a high degree of precision. These studies have shown that improved die filling, a decrease in die load and punch forces can be accomplished by the use of a preform. Extrusion processes have become very important in the industrial production of gear components. Main reason for this can be found in simple design of the tools and the straight forward process in which a blank is pressed axially through an internally toothed die with adapted inlet geometry. Disadvantages of the Samanta process are high notch stresses in the forming zone and gear inaccuracies (Fig. 1b; [6]). In order to overcome these disadvantages, the conventional Samanta process was optimized at the Institute for Metal Forming Technology in Stuttgart by an innovative die design [7, 8]
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