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Process processing methods and testing research of diesel engine cylinder head

Table of Content

The design and processing of diesel engine cylinder heads generally take injector holes, duct holes and valve seats as the key parts for precision control. The scribing process and the processing method of the top and bottom hole system of the cylinder head are discussed, and the machining accuracy inspection operation of the key parts of the cylinder head is briefly described for reference of the industry.

The diesel engine cylinder head is a typical casting part of the box class. In the processing before, should take the initiative to implement the casting scribing process, in order to determine a good processing benchmark, to facilitate the control of injector holes, conduit holes, valve seats and other key parts of the size specifications. Only by actively mastering the important processes of diesel cylinder heads and standardizing the machining methods in different processes can we obtain more ideal machining accuracy.

1 Cylinder head machining process

For the cylinder head, the conventional processing process or process mainly has several steps:

  • scribing process;
  • turning bottom and top surface process;
  • casting peripheral processing process;
  • processing top and bottom hole system process;
  • the first cleaning process of the casting;
  • after cleaning organization inspection and confirm no quality situation after the organization of grinding and sand cleaning process;
  • the second cleaning process of the casting;
  • the implementation of the finished product inspection process.

2 The processing methods of the important processes of the cylinder head

machine line
cylinder head cleaning machine

2. 1 Scribing process

The main purpose of scribing is to determine the processing benchmark, so after scribing the line can be organized according to the position of the scribe’s precise processing. In the case of cylinder heads, the level of workmanship of the casting itself may lead to certain errors in the casting process, while the rigidity and hardness of the tool are limited in lathe machining, thus affecting the quality of the machining. In the scribing process, it should first be recommended that the design of the drawing should take full account of the comprehensive performance of the cylinder head, and design the positioning benchmark in a reasonable position of the cylinder head, which can be completed by specific professional processing units according to the design drawing to determine the processing benchmark. Pay attention to the bottom surface of the cylinder head is placed upwards, flexible adjustment of the level of stability of the entire casting, find the bottom surface near the water cavity hole to determine the processing line of the bulkhead, marked as a benchmark line and then determine the processing line of different surfaces, different holes in turn.

2.2 top and bottom hole machining process

In the processing of the top and bottom holes of the cylinder head, box-type jigs, bent-plate jigs and frame-type jigs can be used for clamping, while the specific processing should be done in strict accordance with the design drawings that have passed the technical meeting. For box jigs or bent plate jigs, the bottom hole system and the top hole system of the cylinder head are mainly second clampings, so that the machining tool can be flexibly controlled in order to cope with the limitation of the machining machine axis in terms of travel. The bent plate fixture is generally used when the type and style of tooling is not available and allows the process to be refined into a more specific process, creating a more time-sensitive production pattern. The frame fixture is used for primary clamping, where the pallet is rotated during the operation of the machine, thus allowing for a higher degree of adaptability to the position of the hole system on the underside of the ding.

Cylinder head CMM

In the machining of the top and bottom faces of the cylinder head, attention is also paid to the positioning of the faces and holes. In the positioning of the face, the focus of attention should be on the flexibility of the clamping and dismantling of the cylinder head, as far as possible, the design reflects the uniformity and flexibility of positioning, to reduce the adverse effects of positioning errors on machining accuracy. The positioning of holes often requires a high degree of accuracy, and the hole system on the cylinder head often has small specification parameters, so the positioning should be considered to reduce or avoid damage from other operations with multiple holes, thus affecting the accuracy control.

The top surface of the cylinder head and the bottom surface of the hole system processing, the processing of the conduit hole problem is more critical. The conduit holes are usually filled with mandrels of different materials such as cold iron, which can reduce the probability of shrinkage during the hole casting process. The machining of the conduit hole requires a certain amount of machining allowance. When feeding the tool to the bottom position, the boring tool and the reaming tool should be started at the same time, first with the reaming tool and then with the boring tool to correct the conduit hole and complete the semi-finish machining.

3 Cylinder head key parts of the processing test

The design and processing of diesel engine cylinder head is generally based on injector holes, conduit holes and valve seats as the key parts of precision control, and the machining accuracy of these parts can be measured by means of mechanized automatic measurement to complete the dimensional measurement of holes and elevations, and also to determine the accuracy between different measured holes. For example, in the inspection of the conduit hole, automatic measurement inspection tool can be used, mainly by the fast thermal extraction data line, valve seat hole detection inductor, conduit hole detection inductor, etc., the use of data lines to connect the device with the computer, while the computer software program can be organized in different parts of the hole must be induction detection, the computer directly calculates the hole size and coaxial and other accuracy parameters, with a high degree of accuracy.

4 Conclusion

The accuracy of the diesel engine cylinder head process is an important indicator of its overall performance, and setting up important processes and strengthening the process methods of different processes is an important part of enhancing the quality of cylinder head design and processing. Continuously optimize the processing methods of each process, enhance the processing level and improve the inspection means, in order to better enhance the production and processing quality of cylinder head.

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