The basic principles of laser modeling and its application in the machining of cylinder bores Laser modeling as a new process, until the beginning of the 21st century, was actually applied in the birthplace of a small number of companies in the automotive industry Germany, but in the cylinder for the engine In the practice of key processes such as body cylinder hole and connecting rod large head hole finishing, the superiority of this advanced technology has been fully demonstrated by improving the process performance of the mating surface and effectively improving the quality and reliability of the product. In recent years, this advanced manufacturing technology has been increasingly used in the European automotive engine industry. Since 2009, it has entered the domestic mainstream automotive engine production enterprises, demonstrating its very broad market prospects.
Simply put, this new technology is a process that uses the numerically controlled laser beam emitted by the laser head to produce a surface microstructure that meets the preset requirements on the surface being machined. In the process of surface sculpting, some of the high-energy beam will be reflected by the surface of the workpiece and some will be absorbed. The absorbed beam will heat the material in an instant and make it vaporized. The cutting ability of this "laser knife" generated beam depends on the pulse frequency, power, switching time, and feed rate. Since the temperature rise is instantaneous and has a high energy density, the beam is only cut in a limited part and the workpiece material is specially shaped by Volkswagen Powertrain (Shanghai) Co., Ltd. (201805). - "Platform structure" for the friction surface of the cylinder wall in a new process for finishing workpieces
In this case, it can be clearly seen that the wear resistance of the latter is much higher, and at the same time it is quite sufficient, using the cross-section c from the highest peak down to 1 μm down to intersect the surface microstructures of a and b, respectively. The oil storage capacity. This configuration ensures that enough lubricant is stored on the surface of the friction pair. The lubricant can completely separate the surfaces of the two friction pairs and minimize wear in any operating conditions. The mechanism is that the lubricating oil will be able to reside on the surface for a long time due to the special microstructure of the workpiece surface, and form a dynamic fluid pressure. Ideally, there will be no change in lubricants and carriers. In addition, residues of the cutting fluid adhered to the surface of the workpiece will be evaporated or burned without affecting the quality of laser beam cutting. The numerical control system of the laser modeling equipment can drive the laser head of cylinder bore finishing (see) to perform up and down and rotation movements, and control the switching time and energy of the laser beam accordingly, so that the inner surface of the workpiece with different requirements can be obtained. The microstructure. Therefore, the user can use this advanced manufacturing technology to produce a controllable microscopic appearance on the surface of the workpiece.
The cylinder head modeling equipment laser head (left) and working instructions but for the cylinder bore finishing, after introducing this new technology, did not abandon the previously used honing process. In fact, the finishing process at this time will consist of three processes: rough boring, laser styling and fine boring. The purpose of rough is to make the shape and size of the hole to a certain degree of precision, so that it can meet the requirements of the next process, and then perform the laser modeling. After finishing with this new process, there will be obvious melt deposits on both sides of the groove formed on the surface, and in order to remove these derived bonding melts and oxides, a lower surface roughness value is obtained. The surface of the platform structure, so that there must be another fine processing, in order to eventually get an ideal surface structure. The fundamental purpose of introducing the laser molding process into the inner surface finish of the cylinder bore is to obtain a controllable, adequate and sufficient microstructure, so that the engine oil has a longer residence time and a good fluid dynamic pressure. For this reason, it is generally preferred to use a regular, uniform groove scheme with staggered or intersecting pits. Three types of trenches are commonly selected: bag-shaped a, cup-shaped b, and block-shaped. Figure 3c. One of the common features of the above structure is that there is no crossover, no connectivity, and there is no connection between the grooves, and they can be effectively stored. Lubricating oil is not easy to lose, it is easy to form a uniform oil film, and the friction pair is in a fluid lubrication state.
As a result, not only sufficient lubrication is ensured, but also too much oil is prevented from intruding into the combustion chamber, the stress effect is reduced, and there is a great advantage in improving the friction performance.
(a)(b)(c) Schematic representation of the three commonly used groove modeling structures In contrast, the traditional honing process is often formed on the inner surface of the cylinder bore is interconnected mesh groove structure, and the surface roughness "Rough" leads to a large amount of oil storage. The result of the laser molding process is that the consumption of lubricating oil will be greatly reduced, and related to environmental protection indicators, such as particulate matter emissions and oil particle emissions are significantly reduced.
It is a real-life condition of the cylinder bore machined using this novel process. As can be seen from the figure, the actual laser modeling is performed only in the area near the top dead center of the cylinder bore subjected to high load to ensure that the piston ring is subjected to high loads in the area. Good lubrication. In fact, the surface of the cylinder wall after the automobile has operated for more than 100,000 kilometers and then dismantled. In the figure, both the regular groove formed by the shape and the mesh pattern of the lower honing process are clearly visible. This also shows that the use of laser modeling technology can significantly reduce wear, thereby extending the life of the engine.
The laser molding process of the connecting rod large head hole is different from the above mentioned piston ring - cylinder wall (cylinder hole inner wall or cylinder sleeve inner wall) friction set pair, in the engine piston - connecting rod - crankshaft movement mechanism, and the connecting rod shaft in the crankshaft The neck constitutes the friction pair of the movement, not directly the inner wall of the big head hole of the connecting rod, but a pair of (two and a half) bearing bushes. Therefore, the connecting rod large head hole is different from the previously studied cylinder bore. The inner wall and the bearing bush are tightly fitted together. There is not only a high frequency of relative motion between the two, but also requires the transfer of a high load of rotation. Moments when trying to avoid sliding, even if it is a small misalignment, so as not to affect the operation of the engine.
To this end, for a long time, in the product structure and process, methods have been adopted for machining the two-half-link bodies of the two bearing bushes and the split bodies to prevent slippage. This is a very mature manufacturing technology that is still in use today.
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