A mold boom is emerging in the mold industry to further accelerate the technological update of China's mold industry. China's mold industry is facing a "big wave of sand and sand era", many new enterprises will emerge from the technological revolution, but more small businesses are on the line.
The modern mold industry is a technology- and capital-intensive industry. In recent years, the structural adjustment of China's mold industry has accelerated, mainly as follows: large, precise, complex, long-life molds and mold standard parts are developing faster than the industry's overall development rate; the proportion of plastic molds and die-casting molds has increased; market-oriented The number of professional mold manufacturers and their development capabilities have increased rapidly.
With the continuous deepening of the reform of the economic system, the development of "foreign capital" and private enterprises has grown rapidly. According to a survey by Luo Baihui, Secretary General of the International Mould Association, in August 2013, 1.477 million sets of molds were produced nationwide, a year-on-year increase of 5.7%; from January to August 2013, a total of 11.488 million sets of molds were produced nationwide, an increase of 17.67% year-on-year. 18 million sets of molds are produced, and the average monthly mold output is expected to be 1.5 million sets. At present, there are 1,314 enterprises above the designated size in the domestic mold manufacturing industry, with 244,155 employees, and the total industrial output value for the year is 55.561 billion yuan. Realized sales revenue and profit of 53.958 billion yuan and 4.675 billion yuan, and exported 1 billion US dollars. Imports amounted to $ 1.47 billion.
On September 24, Luo Baihui, Secretary-General of the International Mould Association, said in an interview with People's Daily at the strategic signing ceremony of Central China Mould City, "The average monthly production of 1.5 million sets of molds is equivalent to 50,000 mold companies producing only one set of molds per day. According to the calculation of the sales amount of only 100,000 yuan for each set of molds, the total output value of national molds in 2013 is expected to reach 1.8 trillion yuan. "
"The annual output value of China's mold industry has reached a trillion level. This is a very simple arithmetic problem, but it is less than 10 times the annual output value of China's molds calculated by China's local mold association less than 180 billion because the molds are only used as manufactured products. For a production tool, most of the molds have not been sold, resulting in sales value. "Luo Baihui further explained that China's molds have long been among the global mold manufacturing countries. According to the 1: 100 driving effect of the mold industry, China's molds have driven related industries to nearly two trillion.
Today, the market demand for machine tools that support efficient production systems is becoming more sophisticated and complex. As the rotating part of the machine tool, the rolling bearing is a part that cannot be ignored, and its performance directly affects the performance of the machine tool.
Development trends of machine tools
Machine tools are currently shifting in several major directions. The first is the increase in the use of 5-axis machining machines and composite machining machines. 5-axis processing machines and compound processing machines began to appear in the market around the second half of 1990 and are now widely used in the market. They are characterized by the addition of grinding, inspection, and robot handling functions in addition to cutting. In addition, there is a trend to further increase the number of control axes, a tendency to become more complex. Secondly, the machine tools have become easier to operate. For example, the function of automatically correcting the mechanical thermal displacement during machining is set in the machine tool; the function of checking the interference between the grinding tool and the workpiece; the function of monitoring the state of the spindle during operation; and the intelligence of the equipment. These changes will make the machine easier to operate. Then the development of machine tools towards high-precision, micro-machining. This improves the performance of components such as DD motors and linear motors, making it possible to determine the position of sub-precision precision. The other is that machine tools have become more space-efficient. At present, the demand for high performance of compact machines in mass production lines is also significant. In order to further suppress the width of the equipment and improve its maintainability, a 5-axis machining machine with a width of 1000 mm has been introduced. The last point is that machine tools are developing in the direction of reducing environmental load. The air flow of oil-air lubrication is reduced and the switch from oil-air lubrication to grease lubrication has appeared on the market. There are many machine tools designed with awareness of environmental issues.
Technical Trends of Spindle Bearings
1. Coexistence of high speed and high rigidity
In the context of the development of machine tools to compound, this tendency of multi-variety and low-volume production, variable variety and batch production, and engineering summation has become higher. Combine multiple machining of multiple workpieces on multiple machines on one machine, or combine multiple processes such as roughing and finishing into a few projects to contribute to improving production performance and saving space. Therefore, for the machine tool spindle, there is a need for a wide range of machining development from low-speed rotating heavy cutting to high-speed rotating light cutting. As a bearing, high speed and high rigidity are required to coexist. For high speed, the single dmn value of the bearing, the angular contact ball bearing is 4-5 million, and the cylindrical roller bearing is 2-3 million, which meets the requirements of machine tools. However, emphasis on high speed is detrimental to rigidity. For this reason, the design of the spindle has to pay attention to high speed and high rigidity. It can also be seen from this that maintaining high speed and having the necessary rigidity on the heavy cutting side is a subject of bearing development in the future.
2.New lubrication method
Lubrication is roughly divided into oil lubrication and grease lubrication. Generally, oil lubrication is used for high-speed processing, and grease lubrication is used for low-speed rotation, and costs, usability, and environmental load are reduced. However, with the advancement of machine tools, it is hoped that there can be a lubrication method that can meet both processing occasions.
As a bearing manufacturer, improvements are being made to oil lubrication to maintain high-speed machining while saving energy and improving environmental performance, or the development of technologies to improve grease lubrication. In other words, lubrication technology is a factor that has a great impact on bearing performance, and there are still many issues to be developed in the future.
3.Design of bearing
Bearings for machine tool spindles, according to various high-speed, high-rigidity, and reduced environmental load requirements, JTEKT currently offers four types of high-performance angular contact ball bearings: R, C, D, and F. The R-type ball has a large number of small balls, which is designed to emphasize rigidity; the C-type ball has a large diameter, which uses ceramic balls, to design for life; the D-type is designed to focus on high-speed performance in the oil supply method; Considering the centrifugal force, it is more suitable for high-speed designs than the D type. The user can choose the most suitable model according to the needs of use. The main dimensions of each bearing are in accordance with ISO standards. The minimum design changes of the shaft or housing can replace past products and can also improve the performance of existing equipment.
The performance of high-performance bearings is higher than that of the original high-speed bearings. The high-speed limit of the R-type bearings has been increased to about 1.3 times the original bearings, and the temperature rise has been reduced by 20% to 30%. Bearings also have the same tendency compared to the original bearings, making it possible to choose an R-type design that emphasizes rigidity and a C-type design that emphasizes load capacity according to the rotation speed during use. According to the effect of improving the high-speed performance of high-performance bearings and reducing the temperature rise, it is also possible to use high-precision positioning of the high-speed rotating spindle.
Under the condition of grease lubrication, the R-type bearing using ceramics for rolling elements and the temperature rising characteristics of the original bearing under the condition of oil and gas lubrication are compared with the original bearing. As a result, high-performance bearings have been confirmed to be able to use grease lubrication in areas where the original bearing requires oil and gas lubrication. Effects such as a reduction in environmental load due to the scattering of oil, and a reduction in cost due to the abandonment of the lubrication device. Regarding the R model, the standard type of sealing ring with a suitable amount of grease has been gradually raised.
These R and C type bearings have the same standard type that can use grease lubrication or oil and gas lubrication as the original bearings, but can be used at higher speeds with oil and gas lubrication special types D and F. This is the use of The bearing shape was developed in consideration of the effects of wind barriers that occur when these bearings rotate at high speeds.
As a result of the comparison between the D-type bearing and the R-type bearing, it has been confirmed that the D-type bearing has approximately 1.1 times the high-speed performance of the R-type bearing, and the temperature has been reduced by 5% to 10%. From the beginning, the air-oil lubrication to the orbital part is a direct-supply structure. It is not easily affected by wind barriers. Compared with the original oil-air lubrication, it can reduce the air flow by 20%. In addition, it is possible to reduce the wind noise generated by the ball. Good characteristics contribute a lot to energy saving or low noise. The F-type bearing is an ultra-high-speed rotating bearing that is provided with an oil filling area on the side of the original bearing and starts to supply oil and gas to the guide surface of the cage from the oil filling nozzle provided on the outer ring. The sliding guide surface of the cage may not be stable during rapid acceleration or deceleration or ultra-high-speed rotation. However, the cage can be stabilized by supplying oil and gas from the outer ring nozzle.
Compared with the current high-performance cylindrical roller bearings, it is confirmed that the high-speed performance is improved by about 1.5 times and the temperature rise is reduced by about 15%. The advantages brought by the high-speed cylindrical roller bearings make the structure of the spindle simple. Generally, the support structure on the rear side of the main shaft needs to be able to absorb the expansion and contraction of the shaft according to a change in temperature. Although cylindrical roller bearings are suitable for this role, since the high-speed performance of cylindrical roller bearings has not been complete so far, the structure of "angular contact ball bearings + sub-housing" is generally used for the support of the high-speed spindle rear side. However, the new high-performance cylindrical roller bearings developed this time can also support high-speed spindles, which can greatly simplify the structure around the bearings.
Current high-performance cylindrical roller bearings, when rotating at high speeds, will cause damage to the cage, which limits their high-speed performance, but as long as this shortcoming is improved, high-speed performance can be further improved. First, as for the material of the cage, compared with the original polyamide resin, a lightweight material suitable for high-speed rotation is used, and the high-strength resin has improved strength. Furthermore, it has a neck-like structure at the high-speed rotation at the contact portion between the cage and the roller, which optimizes the roller contact shape in the pocket of the cage and reduces friction and low temperature rise. In addition, the material of the ferrule is the same as the original product, and the bearing steel is easy to get started. The internal design suitable for high-speed rotation improves the high-speed performance.
4. High reliability
In order to improve the reliability of machine tools, the reliability of bearings must be improved. For this reason, the bearing life is established based on the detected bearing temperature or vibration, so prediction technology is indispensable. In addition, if the load on the bearing can be detected, the most suitable pretension and lubrication can be controlled according to the processing state. As a result, the corresponding processing field with high speed performance and high rigidity and wide width becomes the corresponding Maybe. Based on this, JTEKT has developed a unique mechanism that applies the most suitable preload to the bearing according to the speed. This mechanism can have sufficient rigidity from low to high speeds. In combination with a high-output built-in motor, it can make high-load processing more efficient get on. The original positioning pretensioning method will increase the rigidity of the spindle with the increase of the speed. However, when using this mechanism, the rigidity of the spindle in the low-speed rotation area will increase dramatically when high torque occurs. It is a preload suitable for high-load processing. the way.
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