Abstract
The spindle-turret coupling structure serves as a crucial component in Computer Numerical Control (CNC) spiral bevel gear milling machines. During the machining process, external loads are applied, causing radial deformation of the mating surface between the spindle and turret, which subsequently affects the coupling performance and machining accuracy of the machine tool. This paper focuses on the analysis and optimization of the spindle-turret coupling performance in a spiral bevel gear milling machine.
1. Introduction
The development of spiral bevel gear milling machines dates back to the 1980s, with companies like Gleason in the United States pioneering their creation. China introduced and subsequently developed its own CNC spiral bevel gear machine tools in the 1990s. These machines are characterized by their simple structure, high processing efficiency, and ease of programmatic control, enabling the informatization and intelligentization of spiral bevel gear processing. They are currently widely used in the automotive, aviation, and shipbuilding industries.
The spindle-turret coupling structure plays a vital role in the performance of these machines, with its coupling performance closely related to the machining accuracy of the machine tool. During the machining process, the spindle-turret coupling structure undergoes radial deformation due to external loads, impacting the coupling performance. Therefore, research on the spindle-turret coupling structure of spiral bevel gear milling machines is of great significance and practical value.
2. Theoretical Analysis of Spindle-Turret Coupling Performance
2.1 Structure and Force Analysis
The research object of this paper is the spindle-turret coupling structure of the YKH2235 CNC spiral bevel gear milling machine. The spindle is driven by a torque motor with full closed-loop control, with a speed range of 0-600 r/min. The spindle-turret coupling structure mainly consists of a spindle, turret, bearings, screws, and a spindle cover.
The turret adopts a short cone structure with a 1:24 taper, forming an initial fit with the spindle through the cone surface. Initially, there is a gap of approximately 0.15-0.25 mm between the turret end face and the spindle end face. By tightening the central screw, the turret end face is brought into contact with the spindle end face, eliminating the initial gap and achieving contact between the cone surface and the end face, allowing the spindle to transmit power and cutting loads.
2.2 Radial Deformation Model
Based on elastic mechanics theory and mechanical boundary conditions, a radial deformation theoretical model for the spindle-turret mating surface under no-load conditions is established. The model analyzes the influence of spindle speed on the radial deformation of the mating surface, providing theoretical support for subsequent finite element simulation analysis.
Table 2.1: Mechanical Boundary Conditions
| Boundary Condition | Description |
|---|---|
| r=0 | Radial displacement is finite |
| r=rb | Radial stress is zero |
3. Finite Element Simulation Analysis
3.1 Simulation Setup
The finite element simulation analysis process involves several steps: establishing a three-dimensional model, setting material properties, defining contact relationships, meshing, loading loads, constraints, and boundary conditions, and setting up simulation analysis parameters. The simulation results are then analyzed through pre- and post-processing.
3.2 Radial Deformation Analysis
Simulations are conducted under no-load conditions to study the radial deformation of the spindle-turret mating surface and its relationship with spindle speed. The results are compared with the theoretical model established in Section 2.2.
Table 3.1: Simulation Results under No-Load Conditions
| Spindle Speed (r/min) | Radial Deformation (mm) |
|---|---|
| 0 | X1 |
| 100 | X2 |
| 200 | X3 |
| 300 | X4 |
| 600 | X5 |
3.3 Influence of Cutting Force and Spindle Temperature Rise
Simulations are also conducted under actual machining conditions, considering the influence of cutting force and spindle temperature rise on the radial deformation of the spindle-turret mating surface.
4. Factors Affecting Spindle-Turret Coupling Performance
4.1 Spindle Speed
The simulation results indicate that spindle speed has a limited impact on the radial deformation of the spindle-turret mating surface. This is due to the sufficient axial tightening force provided by the screws, ensuring a tight fit between the spindle cone surface and the turret cone surface.
4.2 Cutting Force
The cutting force generated during the machining process affects the radial deformation of the spindle-turret mating surface. With an increase in cutting force, the coupling performance of the spindle-turret decreases.
4.3 Spindle Temperature Rise
The temperature rise of the spindle due to bearing friction heat generation enhances the coupling performance of the spindle-turret.
5. Optimization Design of Spindle-Turret Coupling Structure
5.1 Response Surface Optimization Design
Response surface methodology (RSM) is used to optimize the structure of the turret, aiming to reduce its mass while ensuring coupling performance.
5.2 Reliability-Based Robust Design
Reliability-based robust design (RBRD) further considers the reliability and robustness of the structure, optimizing the size parameters to meet these criteria.
Table 5.1: Comparison of Optimization Results
| Design Method | Mass Reduction (%) | Reliability | Robustness |
|---|---|---|---|
| Response Surface Optimization | Y1 | Z1 | W1 |
| Reliability-Based Robust Design | Y2 | Z2 | W2 |
The results show that while response surface optimization is more effective in reducing mass, reliability-based robust design is superior in terms of reliability and robustness.
6. Conclusion
This paper analyzes and optimizes the spindle-turret coupling performance of spiral bevel gear milling machine. Theoretical and simulation analyses are conducted to study the radial deformation of the spindle-turret mating surface under various conditions. The results indicate that spindle speed has a limited impact on coupling performance, while cutting force reduces it and spindle temperature rise enhances it. Based on these findings, the turret structure is optimized using response surface methodology and reliability-based robust design.
The research findings provide theoretical support for enterprises in the initial structural design stage and have practical reference value for improving the machining accuracy of spiral bevel gear milling machines. However, there are still areas for improvement in future research, such as establishing a more comprehensive theoretical model that considers the influence of cutting force and spindle temperature rise on radial deformation and adopting more reasonable experimental methods for comprehensive and systematic analysis.