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Factors affecting the machining accuracy of the cylinder head

Table of Content

The cylinder head of a diesel engine is a core component and its machining accuracy can affect the comprehensive performance of the engine. The machining accuracy of the cylinder head bore is an important requirement to improve the overall accuracy of the cylinder head. Through the study of several typical processing methods of diesel engine cylinder head bore, we carefully analyze the factors affecting the machining accuracy of the bore and think about the targeted improvement process.

Nowadays, the equipment manufacturing industry, as a national weapon, has set higher standards for the machining accuracy and process quality of different products. In the field of motor vehicle manufacturing, the optimization of the machining accuracy of the cylinder head duct bore of diesel engines can better enhance valve sealing and thus optimize engine performance. In the actual processing, there are factors that can affect the accuracy of the processing of the duct hole under different process methods, which need to be given sufficient attention and should be effective scientific means to eliminate the impact of undesirable factors.

1. diesel engine cylinder head tube hole processing accuracy requirements

Diesel engine cylinder head valve guide hole processing accuracy requirements are high, the cylindricity of the tube bore should be 0.005mm, the coaxiality of the inner and outer circle is 0.2mm, the axis to the bottom verticality should be 100:0.10mm, the surface roughness of the tube bore should be maintained at 0.8m below.

Cylinder head

2. Conventional machining process of cylinder head valve guide bore and factors affecting accuracy

2. 1 Manual reamer processing

The manual reaming method is guided by the valve guide bore, and the measurement is carried out in time during the reaming process to make the runout parameters of the bore and the bevel taper of the valve seat ring reach the standard. In this method, there is little major process equipment and the accuracy parameters such as diameter, cylindricity, straightness and perpendicularity of the duct bore are mainly referred to the initial accuracy of the duct bore at the beginning of the cylinder head machining. The main factor affecting the accuracy is the uneven strength in the manual operation, making the hole position angle and other deviations prone to occur, while the continuity of the manual operation is not strong, making the process of lowering the tool with obvious force stagnation process, easily resulting in surface roughness not reaching the high precision requirements. The manual reaming process also requires the addition of a grinding machine to the assembly line, which requires a grinding process of more than 10min, and will also affect the accuracy of the process. The more obvious drawback of the manual reaming process is that it is labor-intensive, and many processes are challenging for a single person to complete, so more than one person is required to work with each other, and the level of proficiency of each other will also lead to errors in machining accuracy.

Cylinder head

2.2 Vertical or horizontal machining centres

Manual machining methods are inadequate in terms of labor intensity, production efficiency and operational safety, so the use of mechanical machining methods can better improve operational The promotion of the vertical/horizontal machining center method is able to amplify the performance of the equipment and achieve a high degree of refinement and precision, while also guaranteeing a reliable demonstration of mechanical performance, effectively alleviating the accuracy problems in manual machining, but there are still factors that affect machining accuracy. The actual application of the machining center has strict positioning methods and requirements, which may make the centreline of the valve guide hole to the centreline of the outer circle of the guide hole appear to be out of alignment. In the actual process, with the flow of workpieces between different combinations of equipment in the machining center, the workpieces will experience more frequent switching of positioning systems, which will result in certain positioning errors and make the position of the valve guide hole vulnerable to other positions in terms of accuracy. The workpiece undergoes more frequent positioning system changes. Once the bottom hole is out of position, then the center axis of the tube hole and the bottom hole are offset and a more refined workpiece cannot be produced.

2.3 Gun Boring Equipment

With the increasing use of gun boring equipment, the simultaneous machining of multiple workpieces can be achieved. The bore of a valve guide in a diesel engine cylinder head can be formed in one operation with a high-speed boring process. On the whole, the accuracy of the bore is not affected by the cylinder head itself and the own accuracy of the mounting holes of the bore, etc. Of course, the process for many cylinder head professional manufacturers, its processing is more targeted, can provide a single type of product cylinder head and other key sectors of high precision machining, but the equipment used in the tooling costs are high, and powerful part of the use of internal combustion engine, internal combustion engine updates, there may be a lack of power and other circumstances, to a certain extent affect the accuracy of the workpiece under the gun boring process.

Cylinder head

3. Conclusion

The machining of diesel engine valve guide bores can be accomplished by a variety of method processes. Regardless of which process, while improving operational efficiency, it is more important to focus on optimizing the process and improving machining accuracy. The factors influencing machining accuracy are not static, so staff should continue to summarise the factors influencing accuracy and actively consider improvements in concrete practice, so as to truly master the mechanical machining methods with higher accuracy and efficiency.

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