CSR Qishuyan Locomotive Co., Ltd.
Diesel engines are widely used in various fields at present, such as ships, railways, construction machinery and electric power. In the face of wars and sudden disasters, diesel engines can more exert their advantages and functions. Due to the development of electric locomotives, the demand for diesel locomotives in the railway system has declined. Therefore, the original manufacturers of locomotive diesel engines have been transformed into marine engines.
In today's technological advancement and green environmental protection, users have higher requirements on the power, fuel consumption, noise, and machine breakage of diesel engines. This requires designers to have design ideas in line with international standards, manufacturers have advanced manufacturing processes and advanced high-end processing and manufacturing equipment to meet the needs of the market.
The diesel engine assembly will consist of thousands of parts, but the key is five parts, namely the body, crankshaft, camshaft, connecting rod and cylinder head. Taking the diesel locomotive of a diesel locomotive as an example, Figure 1 is an outline view of the assembly of a diesel locomotive diesel engine on the production line.
Figure 1 Diesel engine body assembly
Difficulties in machining and processing equipment
The diesel engine body is a typical complex box part, which is the basic part for assembling various parts. At present, there are two kinds of integral casting and plate welding parts. There are about a thousand bolt holes on each end face. The main precision dimensions of the V-type diesel engine body are reflected in the three-hole main bearing hole, the two-side camshaft hole, the cylinder bore and the spatial intersecting dimensions of the three holes. The accuracy of these apertures directly affects the life of the diesel engine and the probability of a machine break event. The accuracy of the spindle hole and camshaft hole of the diesel engine body has high precision. The straightness error of the spindle hole should be controlled at 0.08mm on the 5m long and 9th aperture, and the adjacent error should be controlled at 0.035mm. The degree of error should be controlled at 0.10mm, and the adjacent error should be controlled at 0.035mm. Therefore, the deformation of the body itself, the press-fit of the workpiece during machining, and the machining accuracy of the machine itself must be strictly controlled. Figure 2 shows the machining of the spindle bore and the camshaft bore.
When machining the machine body, the difficulty of machining is whether the straightness of the X-axis of the device itself meets the process requirements, and the repeating positioning accuracy index of each axis when the Y-axis and Z-axis run the interpolation program. Because the spindle hole and the camshaft hole are machined, the accessory milling head is processed in one block and one block. At the same time, the accessory milling head also has two precisions which affect the machining accuracy of the diesel engine body. The center deviation of the spindle centerline of the accessory milling head and the centerline of the ram main shaft and the offset accuracy of the 180° rotation center of the accessory milling head should be less than 0.015 mm, so the requirement for repeated positioning accuracy of the accessory milling head is relatively high, as shown in the figure. 3 is shown. At present, most of the domestic large-scale gantry machining centers are responsible for the roughing and semi-finishing of the diesel engine body. The finishing process is monopolized by the imported equipment of international brands such as Germany and Japan. Representative Waldrich Coburg and Hercules Special brand.
Crankshaft processing difficulties and processing equipment
The crankshaft (see Figure 4) is an important part of the engine that is subjected to impact loads and transmits power. During operation, it is subjected to alternating loads, bending and shear stresses, and has high performance indexes such as fatigue, wear resistance and strength. Requirements, at the same time have strict requirements on the material blank, heat treatment process.
A 5t full fiber extrusion of the crankshaft blank to the finished product requires a number of processes, the process is: rough car main neck → rough car connecting rod neck → semi-finished car main neck → semi-finished car connecting rod neck → fine car main neck → Finished car connecting rod neck → rough grinding spindle neck → rough grinding rod neck → fine grinding rod neck → fine grinding spindle neck and other heat treatment, inspection, test nearly 40 sub-processes. Such shaft-type workpieces are difficult to machine in one piece of the existing equipment because of the eccentricity, so there must be two types of equipment to machine the main journal and the connecting rod neck (see Fig. 5).
For more information, please download the attachment or view Metalworking (Cold Processing), Issue 23, 2013:
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