1. Introduction
Gears are fundamental components in mechanical transmission systems, widely applied in various industries such as aviation, marine, and automotive. With the continuous development of industrial technology, especially in high – end equipment manufacturing like aerospace, the requirements for gears are becoming more and more stringent. High – efficiency, high – precision, and high – reliability gears are in great demand. Grinding is a crucial process for gear manufacturing, significantly influencing the surface quality and service life of gears. However, gear grinding faces challenges due to the complex tooth structure and the difficulty of machining hardened surface materials. This article aims to comprehensively review the research progress of gear high – efficiency precision grinding technology, including grinding methods, material removal mechanisms, research status of high – efficiency and precision grinding, surface integrity, multi – energy – field composite manufacturing technology, and future development trends.
2. Gear Grinding Technologies
2.1 Gear Grinding Methods
According to the movement trajectories of the grinding wheel and the gear, gear grinding methods can be divided into generating grinding and form grinding. Table 1 summarizes the characteristics of these two methods.
| Grinding Method | Principle | Advantages | Disadvantages | Applications |
|---|---|---|---|---|
| Generating Grinding | Controls the tooth profile and pitch of the gear through the generating motion of the grinding wheel | High precision, high efficiency, adjustable precision | High – requirement for equipment and technology, high processing difficulty, high production cost | Suitable for various types of gears, especially those with high – precision requirements |
| Form Grinding | Forms the tooth profile of the gear through the shape and movement trajectory of the grinding wheel | High precision, good surface quality, wide processing range | Long processing time, especially for large or complex gears | Ideal for gears where accuracy control and gear strength are crucial |
Figure 1 shows the schematic diagrams of generating grinding and form grinding. In generating grinding (Figure 1a), the grinding wheel’s motion is carefully coordinated to replicate the gear’s tooth shape. For example, in the grinding of helical gears, the relative motion between the grinding wheel and the gear needs to be precisely controlled to ensure the correct tooth helix angle. In form grinding (Figure 1b), the shape of the grinding wheel is designed to match the gear’s tooth profile. This method is often used for gears with complex tooth shapes, such as some special – shaped gears in aerospace applications.
2.2 Material Removal Mechanism in Gear Grinding
Research on the material removal mechanism in gear grinding mainly focuses on aspects such as grinding force, grinding temperature, material removal mechanism, and surface quality. Scholars have used methods such as processing experiments, finite – element simulations, and mathematical modeling to conduct in – depth research. Table 2 shows some representative research results.
| Researcher(s) | Research Method | Research Content | Key Findings |
|---|---|---|---|
| KRUSZYŃSKI | Analyzed the tooth – shape formation and material – removal shape during grinding | Studied the thermal model of the gear – grinding process | Obtained the power – density distribution at the grinding – wheel – workpiece interface and calculated the temperature distribution |
| LISCHENKO et al. | Used finite – element software for simulation analysis | Conducted 2D/3D temperature – field calculations for gear – profile grinding | Discussed the accuracy of the simulation results |
| YI et al. | Based on the heat – source superposition principle, established a three – dimensional heat – source model and a residual – stress finite – element model | Studied the temperature – field simulation and residual – stress calculation in gear – tooth – profile grinding | Achieved the simulation of the tooth – profile – grinding temperature field and the calculation of residual stress considering thermal – mechanical coupling |
| XIAO et al. | Conducted experimental research and proposed models | Studied the measurement of residual stress on the tooth surface after gear – profile grinding and proposed a semi – analytical modeling method for material – removal mechanism and surface – topography generation | Developed a model to study the shape of chips and the thickness of undeformed chips and verified its effectiveness through experiments |
3. Research Status of High – Efficiency Precision Grinding of Gears
3.1 High – Efficiency Gear Grinding
3.1.1 High – Speed Grinding
High – speed grinding is an important method for high – efficiency gear grinding. It uses a high – speed rotating grinding wheel to grind gears, with the advantages of high processing speed and efficiency. Table 3 shows the comparison between high – speed grinding and traditional grinding.
| Grinding Method | Processing Speed | Efficiency | Heat – Affected Zone | Production Cycle | Surface Quality |
|---|---|---|---|---|---|
| High – Speed Grinding | High | High | Small | Short | Good |
| Traditional Grinding | Low | Low | Large | Long | Relatively poor |
Figure 2 shows the development of gear high – speed – grinding technology. EMURA et al. [55] carried out gear – grinding experiments using CBN grinding wheels and high – speed CNC gear – grinding machines to solve the problem of low production efficiency of spiral – shaped grinding – wheel gear – grinding machines. They increased the rotational speeds of the grinding spindle and the work spindle to 12000 r/min and 3000 r/min respectively, and developed a synchronous controller for a high – productivity NC gear – grinding machine using a multi – thread spiral – shaped CBN grinding wheel. XU et al. [59] used high – speed grinding technology to grind cycloid gears and found that high – speed grinding can reduce surface roughness and residual tensile stress and harden the surface.
3.1.2 Superhard – Material Grinding Wheels
With the development of superhard materials, superhard – material grinding wheels, such as those made of artificial diamond and cubic boron nitride (CBN), are widely used in gear grinding. Table 4 shows the characteristics and applications of different types of CBN grinding wheels.
| CBN Grinding – Wheel Type | Bonding Agent | Grinding Efficiency | Dressability | Characteristics | Applications |
|---|---|---|---|---|---|
| Electroplated CBN Grinding Wheel | Metal | High | Not dressable | Simple molding process, not dressable | Suitable for some simple – shaped gear – grinding tasks with high – efficiency requirements |
| Sintered CBN Grinding Wheel | Metal/Ceramic | High – precision | Dressable | High cost, high processing precision | Ideal for high – precision gear manufacturing, such as in aerospace and precision machinery |
| Resin – Bonded CBN Grinding Wheel | Resin | High | Difficult to dress | Simple molding process, difficult to dress | Can be used for general – purpose gear – grinding with high – efficiency requirements |
| Ceramic – Bonded CBN Grinding Wheel | Ceramic | High – efficiency, high – precision | Dressable | Durable, suitable for high – efficiency and high – precision processing | Commonly used in high – end gear – grinding applications, ensuring both efficiency and accuracy |
In 1992, Fang Qixian et al. from Xi’an Jiaotong University [61] conducted comparative experiments using CBN grinding wheels and corundum grinding wheels on 20CrMnMo carburized and quenched gears. The results showed that CBN grinding wheels have lower grinding temperatures, larger surface residual compressive stresses, shallower surface – modified layers, and improved contact – fatigue life compared with corundum grinding wheels.
3.2 Precision Gear Grinding
3.2.1 Research on Grinding Force
Grinding force is an important parameter in the gear – grinding process, affecting the stability of the grinding process, tool life, and processing accuracy. Table 5 shows the main factors influencing the grinding force.
| Influencing Factor | Influence Mechanism |
|---|---|
| Cutting Parameters | Increasing cutting speed and feed rate generally increases the grinding force. An increase in grinding depth also has an impact on the grinding force |
| Tool Geometric Shape | The shape and sharpening state of the grinding wheel affect the entry and exit of the cutting edge, thus influencing the grinding force |
| Grinding Fluid | Different types of grinding fluids and their usage methods can change the friction state at the grinding interface, affecting the grinding force. For example, traditional mineral – oil – based metal – working fluids can be replaced by micro – lubrication technologies to reduce the grinding force |
| Workpiece Material | Harder workpiece materials usually result in larger grinding forces |
Scholars have conducted a lot of research on the grinding force of gears or gear materials. For example, BOGDAN et al. [78] analyzed the gear – grinding process, clarified the influence of gear – grinding kinematics and grinding conditions on the grinding force, and established a relationship model between the grinding force and the grinding process.
3.2.2 Research on Grinding Temperature
The generation and transfer of grinding heat in the gear – grinding process are very complex. High grinding temperatures can cause problems such as thermal cracks, oxidation, and surface – quality degradation on the workpiece surface. Table 6 shows different grinding – temperature models and their applicability.
| Heat – Source Model | Model Conditions | Heat – Flux Density | Applicability |
|---|---|---|---|
| Rectangular Heat – Source Model | Uniform distribution of grinding power and energy | – | Small grinding depth (ordinary reciprocating grinding) |
| Triangular Heat – Source Model | Chip thickness varies from maximum to zero | – | Large cutting depth (high – efficiency deep – grinding) |
| Parabolic Heat – Source Model | Considers the real contact state and undeformed chip thickness | – | Continuous grinding |
WANG et al. [97] studied the influence of grinding process parameters and cooling coefficients on the temperature – field distribution of gear materials during grinding. They derived a temperature – model matrix using the heat – transfer control equation and conducted finite – element analysis to prove the accuracy of the model, providing a theoretical basis for grinding – temperature – field modeling and analysis.
4. Research Status of Gear Grinding Surface Integrity
4.1 Grinding Residual Stress
Grinding residual stress is a stress state formed by the coupling of grinding force and grinding temperature during the gear – grinding process. It has a significant impact on the fatigue strength and service life of gears. Table 7 shows the effects of different types of residual stress on gears.
| Residual – Stress Type | Influence on Gears |
|---|---|
| Residual Tensile Stress | Reduces the strength and service life of gears, may cause deformation and fatigue cracks |
| Residual Compressive Stress | Improves the anti – fatigue performance and strength of gears |
BALART et al. [107] conducted grinding experiments on four types of hardened steels, detected the distribution of grinding – surface residual stress using X – ray diffraction technology, and monitored the grinding temperature. They found that when the grinding temperature is too high, the stress state of the grinding surface is residual tensile stress.
4.2 Grinding Surface Topography
Grinding surface topography affects the surface integrity and service performance of gears. A good surface topography can reduce wear during meshing and improve transmission efficiency. Table 8 shows the relationship between surface topography and gear performance.
| Surface – Topography Feature | Influence on Gear Performance |
|---|---|
| Surface Roughness | Higher surface roughness leads to more severe wear and higher friction noise during gear meshing, reducing transmission efficiency |
| Surface Defects | Surface cracks and other defects can cause stress concentration, reducing the anti – fatigue performance and fracture strength of gears |
NOVOVIC et al. [114] studied the influence of different processing parameters and processes on the surface topography and integrity of workpieces. They believed that the fatigue performance of parts is affected by multiple factors, and surface – strengthening treatment and heat treatment can help improve the fatigue performance of workpieces.
4.3 Grinding Surface Micro – Hardness
The micro – hardness of the grinding surface is directly related to the surface quality of gears. Generally, the higher the micro – hardness, the better the surface quality. Table 9 shows the research on the influence of different factors on the micro – hardness of the grinding surface.
| Researcher(s) | Research Object | Influence Factors | Research Findings |
|---|---|---|---|
| WANG et al. | 20CrMnTi steel gears ground by micro – crystalline corundum grinding wheels | Metallographic structure transformation | As the carbon content in the surface structure decreases, the micro – hardness and retained – austenite content decrease, while the lath – martensite content increases |
| WANG Wei et al. | Carburized gears | Surface – hardening depth and surface hardness | An increase in the effective surface – hardening depth improves the anti – spalling ability, while the anti – pitting ability is hardly affected. Increasing the surface hardness reduces the pitting – failure risk but increases the deep – spalling – failure risk |
5. Gear Multi – Energy – Field Composite Manufacturing Technology
5.1 Electrochemical Composite Manufacturing
Electrochemical composite manufacturing combines electrochemical reactions with mechanical processing to achieve rapid, precise, and controllable material processing. Table 10 shows some research cases of electrochemical composite manufacturing in gear processing.
| Researcher(s) | Research Object | Processing Method | Research Findings |
|---|---|---|---|
| Pang Guibing et al. | Cylindrical gears | Electrochemical mechanical finishing | Significantly reduced the surface roughness value and improved the tooth – profile accuracy by 2 levels |
| SHAIKH et al. | Bevel gears | Electrochemical honing (ECH) | Established mathematical models for material – removal rate and surface roughness, and verified that gears processed by ECH have better operating performance |
| SINGH et al. | AISI 1040 carbon – steel bevel gears | Ultrasonic – assisted electrochemical honing | Found that the average surface roughness of the tooth surface after ultrasonic – assisted electrochemical honing is 91% of that of ordinary grinding |
5.2 Laser – Composite Manufacturing Technology
Laser – composite manufacturing technology combines laser processing and mechanical processing to manufacture high – precision and high – quality components. Table 11 shows the applications of laser – composite manufacturing technology in gear processing.
| Researcher(s) | Research Object | Processing Method | Research Findings |
|---|---|---|---|
| Bao Zhijun | Gears | Laser cladding | Solved the problem of uneven heat distribution during laser cladding of gears through parameter optimization, achieving non – damaged gear repair |
| Wang Zhijian | Parts | Laser remanufacturing | Realized high – precision repair of parts by controlling laser geometric characteristics and established a relationship model between process parameters and part – structure characteristics |
| Chen Xi | Large gears | Laser repair | Established a finite – element model of the laser – cladding temperature field for gears, studied the influence of process parameters on temperature distribution, and verified the feasibility of the laser – repair process for large gears |
5.3 Ultrasonic – Vibration – Assisted Machining
Ultrasonic – vibration – assisted grinding combines ordinary grinding with ultrasonic vibration to improve the grinding environment and surface quality. Table 12 shows the advantages of ultrasonic – vibration – assisted grinding compared with ordinary grinding.
| Comparison Item | Ultrasonic – Vibration – Assisted Grinding | Ordinary Grinding |
|---|---|---|
| Grinding Force | Smaller | Larger |
| Grinding Temperature | Lower | Higher |
| Surface Quality | Better | Relatively poor |
| Tool Life | Longer | Shorter |
VENKATESH et al. [137] carried out research on ultrasonic – assisted abrasive – flow processing technology for bevel – gear precision machining. They established a three – dimensional finite – element model based on fluid dynamics, simulated the flow state of the abrasive flow during ultrasonic – assisted and ordinary gear grinding, and verified the reliability of the model through experiments.
6. Conclusions
- Grinding is a key process in gear manufacturing, and research on high – efficiency precision grinding technology mainly focuses on aspects such as grinding force, grinding temperature, grinding – wheel wear, process – parameter optimization, and surface integrity. Gear grinding can be divided into generating grinding and form grinding, each with its own advantages and is suitable for different gear – manufacturing requirements.
- With the development of superhard materials and machine – tool performance, high – efficiency gear grinding can improve grinding efficiency while ensuring grinding quality. High – speed grinding and CBN superhard – abrasive grinding wheels have significant advantages in gear – grinding processes.
- Grinding force and grinding temperature are important parameters in the gear – grinding process. Research on grinding force mainly focuses on analyzing its influencing factors through mathematical models, experiments, and finite – element simulations. Research on grinding temperature focuses on the temperature – field distribution in the grinding area and its impact on the surface state.
- Grinding – surface residual stress, surface topography, and surface micro – hardness are important indicators of surface integrity, which have a crucial impact on the wear resistance, anti – fatigue strength, and contact stress of gears. Improving these indicators can enhance the performance of gears.
