Zhuojin Pipe Fitting Co., LtdOverlay Welding Motion Simulation on Intersecting Surfaces Based on Pro/E
Literature Overview
This 2011 paper by Wang Xinhui, Yu Dan, Yang Kefei, and Meng Zhaolin from the Harbin Welding Research Institute (part of the China Academy of Mechanical Sciences), published in Transactions of the China Welding Institution (Volume 32, Issue 2, pages 72-76), presents a virtual prototyping approach for automated overlay welding on complex intersecting curved surfaces found in petroleum drilling and production valves. The work was supported by the China Academy of Mechanical Sciences Technology Development Fund (Project 200910126).
Application Context
Petroleum drilling and production valves (such as choke valves, flow control valves, and safety valves) often feature complex internal geometries that require overlay welding of wear-resistant or corrosion-resistant materials. These internal surfaces are characterized by:
- Intersecting cylindrical surfaces (e.g., valve seat and bore)
- Conical surfaces (tapered valve plugs)
- Toroidal surfaces (ball valve seats)
- Compound curves resulting from the intersection of multiple geometric elements
The overlay welding of these surfaces presents unique challenges:
| Challenge | Description |
|---|---|
| Complex geometry | Non-planar surfaces with varying curvature |
| Limited access | Internal surfaces with restricted torch approach angles |
| High precision requirements | Tight dimensional tolerances for sealing surfaces |
| Multi-axis coordination | Synchronized motion of multiple axes required |
| Process consistency | Reproducible bead quality across complex surfaces |
Mathematical Modeling
The paper describes the establishment of mathematical models for the intersecting curves on valve internal surfaces. The key steps include:
Surface Representation
The valve internal surface is mathematically represented using parametric equations. For example, a valve seat surface formed by the intersection of a cylinder and a cone can be expressed as:
- Cylinder: x² + y² = R² (valve bore)
- Cone: z = (R - r)/L × √(x² + y²) (tapered seat)
The intersection curve is then computed numerically, generating the path along which the weld torch must travel.
Torch Trajectory Planning
The weld torch trajectory must maintain:
- Constant standoff distance from the surface (typically 10–15 mm for GTAW, 8–12 mm for GMAW)
- Appropriate torch angle relative to the surface normal (typically 75–85° from horizontal)
- Constant travel speed to maintain consistent heat input
- Proper overlap between adjacent passes for multi-pass overlay
Virtual Prototyping with Pro/E
The paper describes the use of Pro/E (now Creo Parametric) software to create a virtual prototype of the overlay welding equipment and simulate its operation. The virtual prototyping process involves:
3D Model Development
- Workpiece model: The valve body is modeled with exact internal geometry, including all intersecting surfaces.
- Welding equipment model: The robotic or CNC welding system is modeled with all structural components.
- Kinematic chain definition: Motion joints are defined between components to represent the actual degrees of freedom.
- Servo motor parameterization: Motor specifications (torque, speed, acceleration) are defined to match the actual equipment.
Simulation Execution
The virtual prototype simulation provides:
- Motion trajectory curves: The actual path of the torch tip is computed and visualized.
- Collision detection: Potential collisions between the torch, workpiece, and equipment structure are identified.
- Kinematic analysis: Joint velocities, accelerations, and forces are computed.
- Error analysis: Discrepancies between planned and actual trajectories are quantified.
Simulation Results
The paper reports that the simulation successfully validated the mathematical model and trajectory planning algorithm. Key findings include:
| Parameter | Planned Value | Simulated Value | Error |
|---|---|---|---|
| Torch standoff distance | 12 mm | 11.8–12.2 mm | ±0.2 mm |
| Travel speed | 100 mm/min | 98–102 mm/min | ±2% |
| Torch angle | 80° | 79–81° | ±1° |
| Bead overlap | 1/3 | 1/3 ± 0.05 | Acceptable |
Engineering Practice Implications
The virtual prototyping approach offers several advantages for overlay welding equipment development:
- Risk reduction: Potential problems (collisions, unreachable positions, excessive forces) are identified before physical equipment is built.
- Parameter optimization: Process parameters can be iteratively refined in the virtual environment without consuming physical resources.
- Operator training: The simulation can be used to train operators on the equipment's capabilities and limitations.
- Documentation: The simulation provides a comprehensive digital record of the equipment design and capabilities.
Integration with Manufacturing
The virtual prototype serves as a bridge between design and manufacturing:
- CAM programming: The simulated trajectories can be directly converted to CNC or robot control programs.
- Process validation: The simulation results can be compared with actual welding results to validate the overall process.
- Design iteration: If problems are identified during actual welding, the simulation can be updated and re-run to develop corrective solutions.
Study Reflections
This paper represents an important application of virtual prototyping technology to welding equipment development. The approach is particularly valuable for complex overlay welding applications where the geometry is difficult to analyze analytically and where the cost of physical prototyping is high.
The use of Pro/E (Creo) for this application demonstrates the versatility of modern CAD software in supporting manufacturing process development. The integration of kinematic analysis, collision detection, and trajectory planning within a single software environment provides a powerful tool for welding process development.
For contemporary engineers, this paper illustrates the value of simulation-based process development in reducing development time and cost. As CAD/CAM/CAE capabilities continue to advance, the role of virtual prototyping in welding process development will become increasingly important, particularly for complex applications such as nuclear components, aerospace structures, and advanced energy equipment.