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Gear High Efficiency, Accurate Transmission
Jun 13, 2017

Gear, is recognized as a symbol of industrialization, gear manufacturing level directly affects the performance and quality of mechanical products. Based on the significance of gear manufacturing in industry, this paper introduces the latest development of gear processing technology and lubrication technology, and the technical requirements and selection method of lubricating medium for gear processing.

As we all know, gear transmission is the most common mechanical transmission in modern machinery, mechanical products is an important basic parts. Compared with other mechanical transmission forms (chain drive, belt drive, hydraulic drive, etc.), it has the characteristics of high power range, high transmission efficiency, accurate transmission and long service life. Therefore, it has become an indispensable transmission parts of many mechanical products, but also the proportion of the largest machine in the form of transmission.

Gear design and manufacturing level will directly affect the performance and quality of mechanical products, for example, in the modern booming automotive industry, usually every car has 18 to 30 teeth, the quality of the gear directly affect the car noise, smooth Sex and service life. Gear processing technology and equipment usually greatly affect the industry can achieve the highest level of manufacturing, modern industrial developed advanced countries such as the United States, Germany and Japan are also gear manufacturing technology and equipment manufacturing power. Therefore, the status of gear in industrial development has been relatively prominent, is recognized as a symbol of industrialization. From this point of view, attention to the advanced processing technology and development trend of gear is extremely important.

2 gear development technology

In general, the gear manufacturing process includes material preparation, tooth blanking, cutting teeth, tooth surface heat treatment and tooth surface finishing and other five stages. The finishing of the toothed and heat treated is the key to gear manufacturing and also reflects the level of gear manufacturing. The gear manufacturing process development, to a large extent in the accuracy of the level of production efficiency and improve the two aspects. At present, the world mainly from the gear processing technology and processing equipment development in two areas to continuously improve the gear manufacturing level.

2.1 Hardened Hobbing Technology

In the traditional method, the machining of the hardened teeth of the gears requires grinding of the tooth surface, the processing cost is too low, the processing cost is too high, especially for some large diameter, large modulus gears in the processing more difficult Large, and thus from the 20th century, 80 years, domestic and foreign enterprises have gradually adopted hardened surface scraping as hardened gear (40 ~ 65HRC) semi-fine, finishing method.

Hard tooth hobbing technology, also known as scraping tooth processing, this process is the use of a special carbide hob, carburizing quenching after the tooth surface hardness HRC58-62 gear tooth surface scraping, scraping accuracy Reach level 7. This method can be processed arbitrary helix angle, modulus 1 ~ 40mm gear. General precision (6 ~ 7) Hardened gears, the general use of "roll - heat treatment - scraping" process, rough, finishing in the same hobbing machine can be completed; tooth surface roughness requirements of the higher gear, After the arrangement of honing; for high-precision gear, the use of "roll - heat treatment - scraping - grinding" process, with scraping semi-finishing process instead of rough grinding, remove the heat treatment of gear deformation, leaving a small and uniform margin Grinding, you can save 1/2 ~ 5/6 of the grinding time, the economic benefits are very significant. For large modulus, large diameter, large width of the hardened gear, because there is no corresponding large-scale grinding machine, generally only scraping.

Hardened surface scraping the biggest feature is the production efficiency is 5-6 times higher than the grinding teeth, in addition, the heat treatment carburizing quenching gear too large deformation of the grinding before grinding scratch, not only eliminates the deformation of the gear The amount of gear to ensure that the gear grinding in the smooth, but also improve the grinding efficiency, to protect the accuracy of grinding equipment.

Temperature control is extremely important when gearming is done with hardened hobbing technology, because too high a temperature will cause the tool to worn out and easy to collapse; thus it needs to be cooled by metalworking fluids while cutting the cuttings on the tool and the workpiece , To improve tool life and workpiece surface roughness. General use of special oil-based cutting fluid as a cooling and lubricating medium, such as KR-C20, through the appropriate control of the viscosity and the use of environmentally friendly extreme pressure anti-wear agent to meet the process of cooling, cleaning and lubrication requirements. 2.2 Dry cutting technology

Dry cutting is no lubrication cutting, metal cutting is one of the development trend. The technology in the last century 80's began to study, but has been subject to machine tools, tool material constraints and the development of slow, nearly a decade with the machine design technology, carbide cutting tools and surface coating technology, new ceramic tools, The development of research, dry cutting in a substantial increase in production efficiency, significantly improve the surface quality, but also to reduce production costs.

High-speed dry cutting is in the absence of cooling, the role of lubricants, the use of high cutting speed for cutting. High-speed dry cutting must use the appropriate cutting conditions. First, a very high cutting speed, try to shorten the contact time between the tool and the workpiece, and then use compressed air or other similar methods to remove the chip to control the temperature of the work area. Practice has proved that when the cutting parameters are set correctly, 80% of the heat generated by the cutting can be taken away by the chip.

High-speed dry cutting method not only makes the machine structure compact, but also greatly improves the processing environment and reduces the processing cost. In the gear processing, in order to further extend the tool life, improve the quality of the workpiece, can be dry during the cutting process, the use of 10 to 1000ml of lubricating oil per hour for micro-lubrication. The chips produced by this method can be considered as dry chips, the accuracy of the workpiece, the surface quality and internal stress from the negative effects of trace lubricants, but also with automatic control equipment for process monitoring.

According to statistics, the United States, Japan, Germany and other developed countries, the total cost of dry cutting is about 70% of the traditional cutting process. According to US companies statistics, in the centralized cooling processing system, cutting fluid accounted for 14% of the total cost of 16%, while the tool costs only 2% to 4%. It is estimated that if 20% of the cutting process using dry processing, the total manufacturing costs can be reduced by 1.6%. The advantages of dry cutting technology are also reflected in the improvement of surface quality and improvement of geometric accuracy. Foreign data show that the dry surface of the workpiece surface roughness value can be reduced by about 40%, in addition, dry cutting for the importance of resources and the environment is self-evident. Germany is a leader in high-speed dry cutting, with about 8% of existing dry cutting, which indicates that high-speed dry hobbing technology will be a direction for future gear processing.

It is foreseeable that domestic use of dry cutting technology in the field of hobbing, shaving, grinding and other processing will have great potential. With the gear machine tools, gear materials, gear cutting tools, processing technology, the replacement of traditional crafts is only a matter of time.

.3 gears without chip processing

Unlike the conventional gear tooth forming method such as hobbing, shaving, shaving and grinding, the gearless processing method is to use the plastic deformation of the metal or powder sintering to make the tooth part of the gear finally form or improve the tooth surface quality of. The method can be divided into the workpiece at room temperature for processing cold forming and the workpiece heated to about 1000 ℃ for the processing of hot forming two categories. The former includes cold rolling, cold forging, etc .; the latter includes hot rolling, precision die forging, powder metallurgy and so on.

No chip processing gear can make the material utilization from cutting 40 to 50% to 80 to 95% or more, the productivity can also be doubled. But due to the strength of the mold, the current general processing only smaller gears or other gear parts, while the higher precision gears, with no chip processing after the need to use the final finishing finishing teeth shape. No chip processing gears need to use a dedicated process equipment, the initial investment is large, only in the production of large quantities (generally more than 10,000 pieces) can significantly reduce production costs.