Zhuojin Pipe Fitting Co., LtdResearch on the Mechanism of Rotary Drawing Tee Pipe Formation
Literature Overview
This paper by Tang Yong, Zhang Faying, and Chen Chengzhou, published in Tool Engineering (Vol. 32, No. 6, 1998), presents fundamental research on the mechanism of rotary drawing (spinning-drawing) for tee pipe formation. The study analyzes the formation characteristics and conditions of tee pipes produced by this method, with experimental findings on the relationships between drawing force, oblique surface inclination angle, rotary drawing allowance, feed rate, and the resulting side hole height.
Core Technical Content
Rotary drawing (also known as rotary spinning-drawing or swaging with rotation) is a specialized forming process for producing tee-shaped tubes from cylindrical stock. Unlike conventional tee manufacturing methods such as bending, welding, or forging, rotary drawing forms the tee geometry through controlled material flow under combined axial compression and rotational deformation.
Formation Mechanism
The rotary drawing tee pipe process involves:
- Initial configuration: A cylindrical tube is positioned with a forming die that includes an oblique surface at the tee junction.
- Rotational deformation: The tube is rotated while being axially fed through the die.
- Material flow: The oblique die surface deflects material laterally, creating the branch opening.
- Wall thinning: Material at the tee junction experiences localized thinning as it flows from the axial direction into the lateral branch.
- Continuous formation: The rotation and feed continue until the full tee geometry is formed.
Key Process Parameters and Their Effects
The experimental results revealed the following relationships:
| Process Parameter | Effect on Drawing Force | Effect on Side Hole Height |
|---|---|---|
| Oblique surface inclination angle (↑) | Increases | Secondary effect |
| Rotary drawing allowance (↑) | Increases | Primary determining factor |
| Feed rate (↑) | Increases | Minor effect |
| Tube material properties | Influences magnitude | Influences uniformity |
Formation Characteristics
The study identified the following formation characteristics:
- The drawing force increases monotonically with oblique surface inclination angle, rotary drawing allowance, and feed rate.
- The side hole height is primarily determined by the rotary drawing allowance, with secondary influence from other parameters.
- The material flow at the tee junction is non-uniform, leading to thickness variation that must be controlled through process parameter optimization.
- The rotational speed affects surface finish and deformation uniformity.
Process Window and Engineering Considerations
For practical implementation of rotary drawing tee pipe production, the following process windows should be considered:
| Parameter | Typical Range | Notes |
|---|---|---|
| Oblique surface angle | 15°–45° | Higher angles increase force but improve branch opening |
| Rotary drawing allowance | 5%–25% | Controls branch height; excessive values cause cracking |
| Feed rate | 0.5–5 mm/rev | Must be coordinated with rotation speed |
| Rotation speed | 50–300 rpm | Affects surface quality and deformation uniformity |
| Material | Carbon steel, stainless steel, copper alloys | Ductility requirements vary by alloy |
Engineering Practice Applications
The rotary drawing process for tee pipes has particular relevance in:
- Heat exchanger manufacturing: Where complex tube geometries are required for efficient heat transfer, as mentioned in the paper's keywords.
- Refrigeration systems: Where copper tee fittings are commonly used for refrigerant flow distribution.
- Automotive exhaust systems: Where stainless steel tees are required for exhaust manifold connections.
- Hydraulic systems: Where precise flow control tees are needed for fluid distribution.
The process offers advantages over welding-based tee fabrication in that it produces a homogeneous material structure without heat-affected zones, eliminates the risk of welding defects, and provides improved fatigue resistance at the tee junction.
Study Insights and Reflections
This research, though published in 1998, addresses a fundamental forming mechanism that remains relevant to modern manufacturing. The rotary drawing process represents an elegant solution to the tee pipe formation problem—one that exploits rotational symmetry to achieve complex geometry from simple cylindrical stock. The key insight is that the oblique die surface converts axial material flow into lateral flow, and the rotation ensures uniform circumferential deformation.
From a metallurgical perspective, the process is advantageous because it avoids the thermal cycles associated with welding. The tee junction, which is typically the weakest point in welded fittings due to heat-affected zone degradation, is instead formed through cold or warm deformation that can actually improve material properties through strain hardening and grain refinement.
The quantitative relationships identified in this study—drawing force versus process parameters—provide essential design data for process development. Modern finite element analysis (FEA) simulations can build upon these experimental foundations to optimize die geometries and process parameters for specific applications. The study's emphasis on the rotary drawing allowance as the primary control parameter for branch height is a valuable design principle that simplifies process control.