Processing and equipment of key parts of diesel engine

CSR Qishuyan Locomotive Co., Ltd.

Diesel engines are widely used across various industries today, including maritime, rail, construction machinery, and power generation. In situations like wars or natural disasters, diesel engines play a crucial role due to their reliability and versatility. However, with the rise of electric locomotives, the demand for diesel locomotives in railways has decreased. As a result, original manufacturers have shifted their focus from railway diesel engines to marine engines. With the rapid development of technology and growing environmental concerns, users now demand higher performance, lower fuel consumption, reduced noise, and improved durability from diesel engines. This means that designers must follow international standards, while manufacturers need advanced production processes and high-end machining equipment to meet market expectations. A diesel engine assembly consists of 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, the engine assembly involves precise integration of these components. Figure 1 shows an overview of the 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 casting or welded part, serving as the base for assembling other components. It contains around a thousand bolt holes on each end face. For V-type engines, the main precision dimensions include the three main bearing holes, two camshaft holes, cylinder bore, and the spatial intersection of the three holes. These dimensions directly impact the engine's lifespan and the likelihood of mechanical failure. The spindle hole and camshaft hole require extremely tight tolerances. The straightness error of the spindle hole should be within 0.08 mm over a 5-meter length, and adjacent hole errors must not exceed 0.035 mm. The angular deviation should be controlled to less than 0.10 mm, with adjacent deviations under 0.035 mm. Therefore, controlling deformation, workpiece clamping, and machine accuracy is essential during machining. Figure 2 illustrates the machining of the spindle and camshaft holes. During the machining of the engine block, one major challenge is ensuring the straightness of the X-axis meets the required specifications, along with the repeat positioning accuracy of the Y and Z axes when running interpolation programs. Since the spindle and camshaft holes are machined using an auxiliary milling head, this tool must maintain high precision. The center deviation of the milling head’s spindle and the rotation accuracy of its 180° axis must be less than 0.015 mm, making the repeated positioning accuracy requirement very strict. Figure 3 demonstrates this precision. Currently, most large gantry machining centers in China handle roughing and semi-finishing of the engine block, while the finishing process is dominated by imported equipment from brands like Waldrich Coburg and Hercules Special.

Difficulties in Crankshaft Machining

The crankshaft (see Figure 4) is a critical component that withstands impact loads and transmits power. It experiences alternating stresses, bending, and shear forces, requiring high fatigue resistance, wear resistance, and strength. Additionally, strict requirements apply to the material blank and heat treatment process. Producing a 5-ton crankshaft from raw material to finished product involves nearly 40 sub-processes, including rough turning of the main journal and connecting rod journal, semi-finishing, fine turning, and grinding. Due to the eccentric nature of the shaft, it is typically machined on two different types of equipment, 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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