HXD series freight locomotive driven gear weight reduction hole cutting processing

Abstract

To ensure the overall operational performance of railway locomotives and tracks, axle load control is a critical requirement. In this context, the driven gears of HXD₂ series freight locomotives are equipped with eight 130 mm diameter weight-reduction holes to achieve precise weight distribution. To enhance the machining process and reduce complexity, this paper explores the use of flame cutting combined with fine boring as an effective method for manufacturing these holes. It also presents improvements aimed at ensuring high-quality results throughout the flame cutting process.
1. Introduction
In order to enhance the capacity for both passenger and freight transportation in Chinaâ€™s railways, and to advance the modernization of railway technology and equipment, the Datong Electric Locomotive Company, part of China North Locomotive Group, has introduced and independently developed the HXD₂ series high-power AC-driven freight electric locomotives. The drive unit of these locomotives is designed with strict axle weight control to guarantee optimal performance of both the locomotive and the track. These gears feature eight 130 mm diameter weight-reduction holes, which reduce the gear's weight from 500 kg to 440 kg. The structure is illustrated in Figure 1.

To reduce the difficulty of machining the driven gear and improve its production efficiency, this paper compares several methods for processing the eight 130 mm diameter weight-reduction holes. Based on practical considerations, the flame cutting and fine boring approach was selected as the most efficient and cost-effective solution. Several improvement measures were proposed to ensure the quality and reliability of the final product.
2. Comparison of Processing Methods for Weight-Reduction Holes
Since the locomotive gear must meet high standards of reliability and safety, the surface of the weight-reduction hole should be in a cold-worked condition. Therefore, three machining methods were evaluated: milling using a machining center, CNC boring, and flame cutting combined with fine boring. A comparison of their processing efficiency, economic viability, and other factors is shown in Table 1.

From the analysis, it is clear that the flame cutting plus fine boring method offers the shortest processing time and the best cost-effectiveness, making it the preferred choice in actual production. This method not only improves productivity but also ensures the required quality standards. For more detailed information, please refer to the attached document or read the 18th issue of Metalworking Magazine (Hot Processing).
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