High-precision gear manufacturing requires advanced technology

Under the trend of high-precision manufacturing upgrades in the gear industry and the rapid development of the new energy automobile industry, the "High-precision Gear Manufacturing Technology Development Seminar" was held in Baoji. Nearly two hundred guests attended the meeting and discussed related topics such as gear modification design and processing, cutting process stability, thermal effect control and other related topics in gear processing. The participating experts made wonderful technologies on the new challenges brought by high-precision gear manufacturing. report.

High-precision gear manufacturing requires new design and new technology
High-precision gear manufacturing must be designed with reasonable modification to control noise. Mao Shimin, professor of Xi'an Jiaotong University and general technical consultant of Qinchuan Machine Tool Group Co., Ltd., summarized 3 main reasons when talking about gear modification:
1. The elastic deformation of the transmission system and the gear itself under the working load, such as the dislocation, tooth deformation, and irregular changes in the meshing stiffness caused by the deformation of the gear support;
2. Thermal deformation of high-speed gear transmission system and deformation caused by centrifugal force, such as uneven temperature distribution in the tooth width direction, and pressure angle change caused by centrifugal force;
3. Manufacturing and assembly accuracy. In addition, Professor Mao Shimin exemplified various failure modes of gears in practical applications and examples of gear repairs of electric vehicle reducers, and vividly explained the optimization of gears in gear design, reasonable transmission layout, tooth top chamfering and teeth. Standard design of end chamfering, etc.

 "The key technology of gears is a systematic project involving all aspects of design, manufacturing, heat treatment, raw materials, etc. It requires close coordination of multiple departments such as design and process, and develop appropriate processes and standards according to actual needs." Vice President of Fast Group The engineer Sun Feng preached. Sun Feng shared some special details in the design of Fast transmission gears, such as the use of non-standard small pressure angle, small modulus, and large tooth tip height, which can achieve three-tooth and two-tooth alternate meshing instead. Traditional single-tooth and double-tooth alternate meshing; the single-arc tooth root design with a larger radius of curvature not only helps to suppress the crack growth of carburizing and quenching, but also improves the bending strength of the gear; Fast’s specific tooth profile K Xiuxian's design can effectively enhance the ability of pitting corrosion resistance and reduce the impact of meshing. In terms of gear processing technology, Chief Engineer Sun Feng and the participants shared the advanced processing methods currently used by Fast Group, such as: high-speed dry cutting, precision grinding, powerful rolling, powerful honing, and fast Specially researched balance shaving processing technology, etc.

Because of the high reliability, long life, and high precision requirements of gear parts in the aviation field, it must be quality first and efficiency cost second in manufacturing. Du Gaimei, a researcher-level senior engineer of China Aviation Development Xi’an Power Control Technology Co., Ltd., took the oil pump gear of an aero engine as an example to introduce the processing and manufacturing technology of superhard tooth surface gears. In recent years, with the development of domestic aeroengines, the design has put forward higher and stricter requirements on oil pump gears, as well as the application of new materials. The corresponding processing technology needs to be developed and verified in time. At the same time, the requirements for tools, fixtures, equipment, etc. are correspondingly improved, so whether it is a gear manufacturing company or a gear manufacturing equipment provider, it can be said that opportunities and challenges coexist.

Efficient equipment helps high-precision gear processing
With the upgrading of domestic gear manufacturing, the requirements for fixtures are getting higher and higher, and new gear fixtures are also constantly being used in production. The general manager of Xi’an Donglong Precision Tools Co., Ltd. Wang Chunlin introduced at this meeting that Donglong’s products can meet the rapid change of fixtures in automated production; the clamping accuracy of 0.003μm can ensure the high precision of the processed gears; in small batches, In multi-variety manufacturing enterprises, flexible and modularized group fixtures are customized for workpieces to reduce the production cost of the enterprise; and its patented product vulcanized rubber expansion sleeve realizes the localization of imported fixtures.

Low cost is an enterprise's competitive advantage in the industry. Therefore, under the premise of ensuring quality, low cost is the goal that every enterprise is pursuing. Global cutting tool manufacturers have been working hard to find effective ways to reduce costs. Manager Zhou Haolei from Iscar Tool Company introduced Iscar through a large number of experimental studies and data analysis, and adopted to improve the structure of cutting tools to reduce orders. Piece cost. The vertical clamping indexable milling insert designed by Iscar realizes more efficient, economical and higher productivity gear milling processing. The effective use of multiple cutting edges of the indexable milling insert can greatly reduce the processing cost of a single piece.

High-precision gears put forward higher requirements for tooth surface quality
The development trend of high-precision gear transmission is light weight, low noise, and higher power transmission efficiency. In this case, it is necessary to have strict deformation control measures for the heat treatment of the gear, and cold processing such as grinding needs to take necessary measures to control its deformation.
"The natural failure and deformation phenomenon of carburized and hardened gears (this is very important for gears that have been stored for a long time with high precision)" said Li Zhiyi, a failure analysis expert at Chongqing Yiyang Electromechanical Equipment Co., Ltd., "The main reasons for the phenomenon of natural failure and deformation are as follows: 1. The escape of hydrogen and the relaxation of stress during the natural failure process; 2. The stress-induced residual austenite transformation caused by gear grinding or wire cutting, and insufficient stress relief and tempering, resulting in delayed stress relaxation; 3. Natural The relaxation and selective release of stress during the failure process may cause a very small amount of residual austenite transformation. Solution: Correction, grinding, wire cutting and other processing should be immediately stress-relieved and tempered; measures for manufacturing measuring tools are used to increase cryogenic treatment After the cryogenic treatment, immediate tempering is also required. Generally speaking, the amount of retained austenite should be controlled at about 3%." He was 81 years old and shared his experience in failure analysis work for many years.

The "large" and "small" deformations in the gear heat treatment determine the quality of the gear finishing. Li Xiaoshuan, Senior R&D Manager of Nanjing Kerun Industrial Media Research Institute, said: "The heat treatment deformation control of gears is a "system engineering" problem. From a technical point of view, it involves multiple disciplines; from a production point of view, it involves multiple processes. The factors that affect deformation are too much. Too much and too complicated. Kerun gear carburizing and quenching product KR498 can control deformation between 0.03-0.04. Reasonable selection of gear quenching oil can optimize the deformation control of gear parts to a certain extent and realize the improvement of product quality."

In order to obtain higher gear tooth surface quality, grinding is usually carried out. "During the gear grinding process, due to the high hardness of the gear tooth surface, the cutting fluid impacts the grinding surface of the grinding wheel and the gear tooth surface under high pressure when the grinding wheel rotates at a high speed, which is very likely to generate air bubbles and cause burns on the grinding surface. Houghton has developed grinding oil products with different formulations for different grinding conditions to meet the cooling and lubrication of gear grinding and hobbing." Chen Youxu, Technical Manager, Houghton Industrial Media (Shanghai) Co., Ltd. Introduced.

In addition, the problem of residual stress of gears was also discussed enthusiastically in this meeting. Cheng Shimei, the technical manager of EST Stress Technology Co., Ltd. said: “Due to the effects and influences of various manufacturing processes, gear parts have undergone uneven plastic deformation. After the external force and influence disappear, these uneven elastic deformations will cause gears to wait. The stress of the parts reaches a balance. The internal stress corresponding to these elastic deformations is called the residual stress in the engineering.” Regarding the inevitable existence of residual stress in gear parts, the manager of Xi’an Ouyi Instrument Co., Ltd. Haibin also affirmed this. The effects and effects of various processes have produced uneven plastic deformation on the parts, which is the source of residual stress. For example, the extreme uneven temperature changes of gear parts caused by welding will inevitably produce residual stress. Fortunately, although the residual stress is invisible and intangible, both companies have provided solutions to detect residual stress. The residual stress detection instrument produced by X-ray diffraction method has been successfully applied in production. Instrument Co., Ltd. also introduced grinding and burn detection equipment. There are more than one advanced testing instruments, which play a role in escorting the quality of the tooth surface of high-precision gears.

Advanced technology improves gear surface treatment
 The gear design is in accordance with the ISO standard, and its main indicator is the bending fatigue strength. Professor He Jiawen from Xi’an Jiaotong University used carburized gears as the object to divide the bending fatigue factors in the ISO standard into four categories: clear quantitative regulations, qualitative or semi-quantitative prompts, and pointed out that the analysis of various factors of bending fatigue is more important for improving the process and failure analysis. Realistic, the use of shot peening technology to process the gear tooth surface, the positive effect of its residual compressive stress and homogenization, can make the gear strengthen the actual resistance to bending fatigue. For gear tooth surface shot peening, Dr. Bai Tao from Changyu Stress Technology (Shanghai) Co., Ltd. added that shot peening and contact fatigue have the same hardening mechanism, and the degree of grip is the key to the pros and cons. Strengthening accompanied by damage: high shot peening strength, high residual compressive stress, and large damage. Low-strength shot peening is also difficult to avoid micro-cracks, so the upper limit of residual compressive stress should be limited. Eliminating and inhibiting the influence of black tissue and reducing the dispersion of the pre-processed surface can control the negative effect of shot peening.

Corrosion of metal parts such as gears can easily lead directly to the scrapping of gear parts and cause irreparable losses. A certain amount of rust removal can be used to recover the loss. How to quickly remove rust from corroded gear parts in batches without damaging the machining dimensions and mechanical properties of the parts? This is a problem that many manufacturers are eager to solve. To this end, Chen An, sales director of Shanghai Sriven Special Oil Technology Co., Ltd., specially introduced XA130 neutral rust remover and supporting rust removal technology. "XA130 neutral rust remover combined with the ultrasonic rust removal equipment independently designed by Sriven can achieve batch integration of rust removal, cleaning and rust prevention of metal parts such as gears. It can be completed in 2-5 minutes under normal working conditions. .XA130 neutral rust remover has excellent permeability, only has a strong ability to adsorb and dissolve some metal oxides; it has high safety and has no adverse effects on the human body or metal parts." Chen An’s The introduction aroused the interest of many participants.

High-precision gear manufacturing is inseparable from excellent equipment suppliers
Gear accuracy grade has a great influence on transmission noise; through strict control of certain accuracy parameters, gear noise and transmission errors can be reduced. This also requires high-performance machine tools to ensure. The co-organizer of this conference, Qinchuan Machine Tool Group Co., Ltd., will build a digital assembly workshop based on Internet technology for users based on the existing digital workshop construction and system integration capabilities, aiming at mid-to-high-end automotive automatic transmission gearboxes, so that the products will be " The new form of output of "physical objects + data packets" realizes the integrated development of digital technology and industrial ecology.

Long Xingyuan, Secretary of the Party Committee and Chairman of Qinchuan Machine Tool Group Co., Ltd., said in the opening speech of the meeting. "In recent years, Qinchuan Machine Tool Group has always adhered to the development idea of'Technology Leading, Model Winning', with'struggling to make money for users' as its original intention, with'reducing costs and improving efficiency for enterprises' as its foundation, and based on'precision and complexity'. 'The advantage of technological equipment manufacturing, expand the digital manufacturing process equipment chain of medium and high-end automobile automatic transmission gears (boxes), which includes multiple business units such as sophisticated and complex cutting tools, high-efficiency and high-precision gear processing machines, gear measuring instruments, etc. Development mode It also shifted from “mainly focusing on machine tool production and machine tool sales” to “mainly providing services such as fault warning and remote diagnosis based on industrial Internet technology”, creating an intelligence guided by user technology and supported by design consultation. Comprehensive service system."

“After years of rapid growth, China’s auto industry has become a veritable power in the auto industry. For gear manufacturers, it is necessary to realize that the domestic high-end sedan market is still growing, and we need to integrate and share development models and develop technologies. Make breakthroughs and upgrades, and achieve high-quality development of the company in accordance with the industry’s own development laws.” said Chairman Long Xingyuan.

Speed ​​up technological innovation and upgrading, and enhance independent innovation capabilities

"The current problems facing the gear industry include: the gear industry’s weak independent innovation capabilities, high-end gear products rely heavily on imports, and core technologies are restricted by others; high-end product R&D and manufacturing capabilities are insufficient, medium and low-end products have a serious overcapacity, and homogeneity competition is intensified; The gear product quality and stability are poor, the early failure rate of the product is high, the service life is short, the reliability is low, and it cannot meet the needs of the main engine; high-level research and development and high-skilled talents are generally lacking, and the overall quality of personnel needs to be improved; many small and medium-sized gears in the gear industry Enterprises are caught in difficulties such as financing difficulties, heavy tax and fee burdens, and weak anti-risk capabilities." said Yin Xibing, deputy secretary general of the Gear Technology Branch of the China Society of Automotive Engineers and deputy general manager of Anhui Xingrui Gear Transmission Co., Ltd. Yin Xibing urged that as long as the gear industry faces challenges correctly, speeds up technological innovation and technological upgrading, enhances independent innovation capabilities, and vigorously explores a diversified domestic market and a diversified international market, we will surely be able to usher in a new round of the gear industry Rapid development.