Cylinder block, cylinder head is the foundation of the engine, its production line has been a new engine plant must be built two production lines. Because the cylinder block, cylinder head is the rest of the engine parts of the installation of the benchmark, but also to ensure the key to engine performance. The rest of the parts can be outsourced processing, such as piston, connecting rod, crankshaft and oil pump, as far as possible to let the professional factory organization production, they are professional, high production efficiency, low cost, according to the quality of the price, good selection, avoid the early factory scale is too large, too high capital investment.
When compiling the processing technology of cylinder block and cylinder head, it is necessary to understand the structure of cylinder block and cylinder head, the important elements of the parts and functions, which are the key points of compiling the processing sequence, in addition, attention should be paid to the reasonable selection of the processing process, as well as equipment, tools and auxiliary machinery.
The following is an example of the production line of MR479Q engine block to discuss the selection of process, equipment and tools.
1. Preparation of cylinder block processing technology
(1) selection of crude, transitional and fine standards for cylinder block processing.
Crude benchmark refers to the cylinder body completely blank choice under the conditions of processing benchmark, engine companies both at home and abroad, in the cylinder body design, general design transition datum plane in the side of the cylinder block, has been in use today, such as MR479Q cylinder, on the right side up and down four discrete nonfunctional small plane design, the bottom surface and cylinder liner blank hole crude benchmark selected for processing transition of datum plane and fine boring ipsilateral 2 out of the sand hole, to transition of datum plane and fine boring ipsilateral 2 sand holes as benchmark to machining precision and 2 f 14 h7 benchmark bottom plane positioning hole, so technology choice, the end result?
Due to the design of four discontinuous non-functional planes, the distance between the upper two planes and the lower two planes from the center of the cylinder hole is different (not in the same plane), so it is difficult to adjust the positioning element. 4 discontinuous non-functional plane, in the delivery of blank inevitably bump or cylinder block casting collapse, some small plane milling out, no transition datum, unable to locate, resulting in the scrap of blank cylinder block.
Transition datum plane and two fine boring and out of the sand hole and the location of the plane has no strict degree, to locate the bottom of the machining fine benchmark plane and 2 f 14 h7 positioning hole, easy to cause fine benchmark bottom and top surface position error is too big, make the individual cylinder top plane relative to the large plane tilted at the bottom of the benchmark, top surface machining allowance is not enough, the top plane milling out.
It can be seen that the transition datum plane specially designed by domestic and foreign engine companies is not ideal and still has some problems. The author took part in group processing technology research of the country's practice, through the analysis, if not by traditional design method of transitional datum plane in advance, and with the plane of cylinder body itself functions such as the bearing cover combine transition datum for the thick datum processing (rough milling plane), rough milling head plane as transition datum plane and cylinder blank hole positioning, to processing and fine benchmark bottom plane 2 f 14 h7 positioning hole, can make fine benchmark bottom plane and 2 f 14 h7 positioning hole and plane position degrees increase, the follow-up process for cylinder surface, hole and other elements, relative to the top of cylinder body plane, cylinder, easy to guarantee the position of the hole.
Because the main bearing cover joint surface and the top surface of the cylinder block in casting, to ensure a better degree of parallelism.
Specially designed transition datum plane, increase the weight of the blank, also increase the chance of defect factors in transition datum plane.
The precision base plane and the top plane are each other's base plane machining error.
(2) prepare the machining process and comprehensively analyze the cylinder structure.
Notable is the top plane and cylinder hole machining process, mechanical processing technology in preparation of engine cylinder block, cylinder head flat flatness, cylinder hole and verticality of the top plane and cylinder hole itself the cylindricity is the key of the process, selecting equipment, often used in combination machine tools is a composite processing, namely a positioning to complete the rough boring cylinder hole, half fine milling surface process.
In the cylinder bore grinding processing, mechanical processing. After the arrangement of fine boring cylinder hole, fine milling top plane composite processing of the combination of machine tools. Because the cylinder block in the whole production line, in order to process the different elements of the cylinder block, the workpiece conveying plane is constantly changing, in order to prevent the top plane in the process of conveying abrade, ensure the flatness of the top plane, the process is specially.
The verticality machining of the main bearing bore and the crankshaft thrust face of the cylinder block is arranged in a double-position modular machine tool to ensure the verticality of the shaft thrust facing the main bearing bore of the cylinder block. In the fine boring station and the main bearing hole have location requirements of elements such as crankshaft rear oil seal 2 f 6H7 positioning holes, transmission 2 f 10H7 positioning holes are also in the fine boring of the main bearing hole work step.
2. Equipment selection
(1) selection of production line structure. Combination machine tools automatic line: China's auto industry has just started in the 1980 s, few varieties of cars, combination machine tools automatic line has been widely used in the private car industry, the group has to purchase domestic combination machine tools automatic line, but because of the characteristics of modular machine tool automatic line, although efficiency is high, but the piecewise line covers an area of big, can't increase or decrease. Into the 1990s, has been unable to adapt to the innovation and development of automotive technology, the combination of machine tool automation line is basically eliminated from the automotive manufacturing field.
Composed of machining center machine tool automatic line production line: in the late 1990 s, our country automobile industry into the high speed development, the domestic start machining center machine imported from foreign companies made of flexible automatic production line, all greatly improve the level of engine manufacturing technology and production efficiency, but a large investment, high maintenance costs, foreign companies maintenance and parts supply cycle is long.
Combination machine tools and machining center machine tool of mixed production line: in the 20th century, China's auto industry into the stable period, the domestic automobile market shows the pattern of small batch and many varieties, both to ensure the quality of production, and to reduce the high input upfront money, combination machine tools and machining center machine tool of mixed production line just to satisfy this requirement. It has the high efficiency (the modular machine tool efficiency is high) and the flexibility (the machining center machine tool starts the step to be flexible), by most domestic automobile company adoption. Our company also USES the combination machine tool and the processing center machine tool composition mixed production line.
(2) the selection of equipment not only considers the efficiency, but also requires the balance of the beat of the whole production line. Some procedures are not suitable for processing in the machining center on the machine tool, the reason is the beat is long, low efficiency, such as the front and rear with thick, fine large dense tooth cutter disk, coarse precision milling double position combination machine tool.
Main bearing hole 8 side milling using vertical feed transverse special milling head, the main shaft according to the main bearing hole 8 side position arranged 8 three face edge milling cutter disk vertical feed, a feed is completed, and the machining center machine tool is very difficult or unable to complete. In short, for the cylinder block unchanged elements, should give full play to the characteristics of high rigidity and high efficiency of modular machine tools.
The small plane on other surface of the cylinder, such as generator, water pump and hydraulic steering pump and other dense screw thread installation hole processing, the spindle center distance limit of the modular machine tool (that is, the workpiece center distance) must be divided into more than one modular machine tool processing, the hole center distance is difficult to guarantee, and the processing center is not subject to this condition.
The use of special machine type machining center machine tool, it is more professional than general machining center machine tool, can be configured rotary dial, easy to complete the same side of different angles of the plane and hole processing, so that work step more concentrated.
In order to balance the rhythm of production line, the machine tool of machining center adopts compound tool reasonably. Machining center machine tool used more composite tool, the purpose is to reduce the work step, ensure the beat. Choosing composite cutting tools, in improve efficiency at the same time, also want to consider the composite technology of cutting tool processing, such as processing screw side cylinder body hole bottom hole, and to reduce the process of beats, drilling, chamfering, and milling phi 18 mm round son flats three step composite with a knife, because the drilling bit first round partner is rough surface contact, bit deflecting force, often occur bit broken. At the beginning of the production line acceptance, can only be replaced by milling 18mm circle sub plane, and then drilling, chamfering compound drill bit processing, to solve the problem.
(3) auxiliary equipment, such as the transmission mode of the workpiece, sealing test equipment, intermediate and terminal cleaning equipment, etc., can be reasonably arranged according to the amount of investment, the arrangement form of the production line (line or loop).
3. The conclusion
The combination machine tool and the mixed production line composed with the machine tool of the processing center are a kind of rigid and flexible production line structure, which fully accords with the national conditions of the automobile development in China. It is worth noting that after decades of development, the domestic equipment manufacturing industry has greatly improved its manufacturing technology and processing accuracy, and its maintenance and technical services have advantages that foreign companies do not have. The author thinks that the hybrid production line is more in line with the pattern of China's small-batch multi-variety automobile market.
Process preparation to consider all kinds of factors, such as the environment of the factory, the size of the investment, the technology of the blank cylinder manufacturers, innovation is fundamental. Process preparation should not be restricted by rules and regulations, pay more attention to the domestic and foreign processing technology innovation results, according to the possibility and need to learn, apply to process preparation. But the process is not a matter of one person, multi-party research, discussion, innovation, brainstorming, in order to ensure the quality of the process, gradually improve the overall level of processing technology.
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