Abstract
The comprehensive analysis and optimization of the spur gear extrusion forming process. By employing finite element analysis (FEA), the influence of various process parameters on the extrusion forming quality of spur gears is investigated. The results provide valuable insights into the design and optimization of the extrusion die cavity and blank preforming to enhance the forming effectiveness and material utilization.
1. Introduction
Precision forging technology is a new method for net or near-net shaping, which allows for the production of parts with complex geometries and excellent mechanical properties while minimizing subsequent machining operations. The spur gear, as a critical component in transmission systems, has been a focus of research in precision forging due to its complex shape and high mechanical requirements. This paper aims to analyze and optimize the spur gear extrusion forming process through numerical simulations and experimental validations.
2. Literature Review
2.1 Cold Extrusion Forming Technology
Cold extrusion is a metal plastic forming process characterized by high efficiency, high quality, and low material consumption. It involves forcing a metal blank into a die cavity under high pressure, causing plastic deformation to obtain the desired shape and size. Cold extrusion can be classified into several types, including direct extrusion, indirect extrusion, composite extrusion, radial extrusion, and upsetting-extrusion.
Table 1: Classification of Cold Extrusion
| Type | Description |
|---|---|
| Direct Extrusion | Metal flows in the same direction as the punch movement. |
| Indirect Extrusion | Metal flows in the opposite direction to the punch movement. |
| Composite Extrusion | Part of the metal flows in the same direction as the punch, and part flows oppositely. |
| Radial Extrusion | Metal flows perpendicular to the punch axis. |
| Upsetting-Extrusion | Combines upsetting and extrusion, with metal flowing both axially and radially. |
2.2 Applications in Spur Gear Forming
Cold extrusion technology has been applied to spur gear forming to improve material utilization, reduce subsequent processing, and achieve better mechanical properties. Various process improvements have been proposed to address challenges such as tooth filling difficulties and high forming loads. These include the diversion process, floating die technology, streamlined die cavity, and composite forming processes.
3. Spur Gear Cold Extrusion Process and Die Structure
3.1 Process Analysis
The spur gear cold extrusion process involves several key parameters that affect the forming quality, including die entry angle, work zone length, blank diameter coefficient, friction coefficient, and extrusion speed. To study the influence of these parameters, an orthogonal test design was employed.
Table 2: Process Parameters for Orthogonal Test
| Parameter | Values Considered |
|---|---|
| Die Entry Angle (θ) | 30°, 45°, 60° |
| Work Zone Length (h) | 4mm, 6mm, 8mm, 10mm |
| Blank Diameter Coefficient (λ) | 1.05, 1.10, 1.15 |
| Friction Coefficient (μ) | 0.1, 0.15, 0.2 |
| Extrusion Speed (v) | 5mm/s, 10mm/s, 15mm/s |
3.2 Die Structure Design
The die structure for spur gear cold extrusion consists of a punch, a die with a streamlined cavity, and a blank holder. The streamlined die cavity is designed to improve metal flow and reduce forming loads.
4. Numerical Simulation and Analysis
4.1 Simulation Setup
The spur gear and its extrusion die were modeled in 3D using CAD software and imported into the DEFORM-3D finite element analysis software for simulation. The material selected for the blank was alloy steel 20Cr, corresponding to AISI-5120 in the DEFORM-3D database.
Table 3: Simulation Parameters
| Parameter | Value |
|---|---|
| Material | Alloy Steel 20Cr (AISI-5120) |
| Mesh Size | ~50,000 tetrahedral elements |
| Simulation Temperature | 20°C |
| Step Size | 1/3 of the smallest mesh size |
4.2 Results and Discussion
The simulation results provided insights into the metal flow patterns, velocity fields, forming morphologies, load-stroke curves, and effective stress and strain distributions during the extrusion process.
Table 4: Influence of Process Parameters on Spur Gear Extrusion Quality
| Parameter | Influence on Forming Quality |
|---|---|
| Die Entry Angle (θ) | Significant impact; smaller θ reduces upper surface shrinkage depth and forming load. |
| Work Zone Length (h) | Minimal impact on forming results. |
| Blank Diameter Coefficient (λ) | Varies; affects different indicators of forming quality. |
| Friction Coefficient (μ) | Significant but lesser impact compared to die entry angle and blank diameter coefficient. |
| Extrusion Speed (v) | Minimal impact on forming results. |
4.3 Optimization of Die Cavity and Blank Preforming
Based on the simulation results, three blank preforming designs and an optimized punch lower end shape were proposed to improve the upper surface shrinkage phenomenon. The results showed that modifying the punch lower end shape was more effective in reducing the shrinkage depth.
5. Conclusions
This paper presents a comprehensive analysis and optimization of the spur gear cold extrusion forming process. Through finite element simulations and orthogonal tests, key process parameters such as die entry angle, blank diameter coefficient, and friction coefficient were found to have significant impacts on the forming quality. Optimization of the punch lower end shape was effective in reducing the upper surface shrinkage depth, improving the forming effectiveness and material utilization. The results provide valuable guidelines for the design and optimization of spur gear extrusion dies and blank preforming processes.