Processing and equipment of key parts of diesel engine

CSR Qishuyan Locomotive Co., Ltd.

Diesel engines remain a crucial power source across various industries, including maritime, rail, construction, and energy. In critical situations like wars or natural disasters, diesel engines prove their reliability due to their durability and versatility. However, with the rise of electric locomotives, the demand for diesel-powered trains has decreased, prompting manufacturers to shift focus toward marine applications. As technology advances and environmental concerns grow, users are now placing higher demands on diesel engine performance, fuel efficiency, noise levels, and reliability. This means that designers must follow global standards, while manufacturers need advanced production techniques and high-end machinery to meet market expectations. The assembly of a diesel engine involves thousands of components, but five key parts stand out: the engine block, crankshaft, camshaft, connecting rod, and cylinder head. For example, in a diesel locomotive, Figure 1 shows an overview of the engine assembly process on the production line.

Figure 1: Diesel Engine Block Assembly

Challenges in Machining and Processing Equipment

The diesel engine block is a complex component that serves as the foundation for assembling other parts. It can be either a cast integral or a welded plate structure. Each end face typically contains around a thousand bolt holes. The precision of the main bearing holes, camshaft holes, cylinder bores, and the spatial intersection dimensions directly impacts the engine's lifespan and failure rate. The spindle hole and camshaft hole require extremely tight tolerances. For instance, the straightness error of the spindle hole should not exceed 0.08mm over a 5-meter length, and adjacent hole errors must be within 0.035mm. These strict requirements mean that deformation control, workpiece clamping, and machine accuracy are all critical factors. Figure 2 illustrates the machining of these critical areas. When machining the engine block, one of the main challenges is ensuring that the X-axis of the machine meets the required straightness and that the repeated positioning accuracy of the Y and Z axes is consistent during interpolation operations. Additionally, the accessory milling head used for processing the spindle and camshaft holes must maintain high precision. Any deviation in the centerline of the milling head or the rotational accuracy of its 180° axis could affect the final product. As shown in Figure 3, this level of precision requires advanced equipment. Currently, most domestic large gantry machining centers handle rough and semi-finished processes, while the finishing stage is dominated by imported machines from brands like Waldrich Coburg and Hercules Special.

Crankshaft Machining Challenges and Equipment

The crankshaft (see Figure 4) is a vital part of the engine that experiences heavy impact loads and transmits power. It undergoes alternating stresses, bending, and shear forces, requiring high fatigue resistance, wear resistance, and strength. The material and heat treatment process also play a significant role in its performance. Producing a finished crankshaft from a 5-ton fiber extrusion involves nearly 40 sub-processes, including rough turning, semi-finishing, and fine grinding of the main and connecting rod journals. Due to the eccentricity of the shaft, it’s difficult to machine the entire piece in one setup, so two different types of equipment are needed to process the main journal and connecting rod neck, as shown in Figure 5. For more detailed information, please download the attachment or refer to *Metalworking (Cold Processing)*, Issue 23, 2013.

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