Double modification of a rack cutter using a variable pressure angle and modulus

Abstract

This study modifies the straight edge of the rack cutter into an arc shape by changing the pressure angle. Using a variable modulus, the tooth surface is longitudinally modified along the axial direction of the rack cutter to create a bulge in the rack teeth in the center of the tooth width. This rack cutter with a double-crowned tooth is used to generate a pinion. An unmodified rack cutter is used to generate a gear. An undercutting analysis of the rack cutter is used to determine the undercutting condition for the double-crowned rack cutter and to determine the limits for the parameter. The transmission error for a gear pair is calculating using a tooth contact analysis. For this study, the assembly error for six cases is used to calculate the transmission error for the gear pair and the contact points for the gear pair are placed on a gear tooth. These contact points used to determine the contact for the gear pair. A transmission error analysis of the gear pair for a double-crowned gear gives a parabolic curve for the transmission error. The distribution of the contact points shows that, regardless of assembly errors, the contact points for the gear teeth are along the center of the tooth surface, starting from the top of the tooth, and gradually moving to the flank and away from the heel. The results show that the values for the transmission error for the modified gear pair for the proposed modification of the variable pressure angle and the variable modulus on a traditional rack cutter are small and the transmission error of the assembly errors are almost similar to those for an ideal assembly.