CLADDING TECHNOLOGY SHANXI CO., LTDDesign and Engineering Application of an Automatic Roll Cladding Machine
Literature Overview and Industrial Context
The design of an automatic roll cladding machine, as described by Liang Guangrui, Mo Shenghan, and Liao Zhenfei and published in the Electric Welding Machine journal in 2014, addresses a significant practical need in the pulp and paper industry. Paper machine rolls—particularly cylinder rolls, press rolls, and dryer rolls—are subjected to severe wear, corrosion, and mechanical damage during continuous operation. Traditional repair methods involving manual welding or manual grinding are labor-intensive, produce inconsistent results, and often require extended downtime. The automatic roll cladding machine presented in this research was developed under the Science and Technology SME Technical Innovation Fund (project number 13C26214504844) and represents a practical engineering solution for the efficient and consistent restoration of worn rolls.
Machine Design and Technical Configuration
The automatic roll cladding machine integrates several key subsystems to achieve automated, high-quality cladding of cylindrical workpieces:
| Subsystem | Function | Key Specifications |
|---|---|---|
| Workpiece rotation | Rotate the roll during cladding | Speed range: 0.1–10 rpm; torque: ≥500 N·m |
| Welding torch positioning | Guide the welding torch along the roll axis | Linear actuator with ±0.1 mm positioning accuracy |
| Welding power source | Provide stable arc energy | Submerged arc welding (SAW) or flux-cored arc welding (FCAW) |
| Wire feed system | Deliver consistent filler metal | Wire diameter: 1.6–2.4 mm; feed speed: 2–12 m/min |
| Flux delivery and recovery | Supply and recycle welding flux | Automated flux hopper and magnetic flux recovery system |
| Control system | Coordinate all subsystems | Programmable logic controller (PLC) with HMI interface |
| Cooling system | Control interpass temperature | Water spray or air cooling with temperature monitoring |
The machine design incorporates several innovative features that distinguish it from conventional manual welding setups. The workpiece rotation system uses a hydraulic or electric drive to ensure uniform rotational speed, which is critical for achieving consistent weld bead geometry and dilution control. The torch positioning system uses a linear guide with encoder feedback to maintain precise axial travel, ensuring that each cladding pass covers the full length of the roll without overlap or gaps. The flux recovery system is particularly important for submerged arc welding applications, as it ensures continuous flux supply and reduces material waste.
Welding Process Parameters and Quality Control
The automatic machine was designed to accommodate multiple welding processes, with submerged arc welding (SAW) being the primary process for heavy-duty cladding applications. The following process parameters were optimized for typical roll repair scenarios:
- SAW parameters: Current 500–800 A, voltage 28–36 V, wire feed speed 4–8 m/min, travel speed 150–400 mm/min, flux coverage 10–15 mm.
- Multi-pass strategy: For thick cladding layers (≥6 mm), a multi-pass sequence was implemented with the first pass providing full penetration into the base metal and subsequent passes building up the overlay thickness.
- Interpass temperature control: The cooling system maintained interpass temperatures below 250 °C for stainless steel cladding and below 350 °C for hard-facing alloy cladding, preventing excessive grain growth and cracking.
Quality control measures integrated into the machine design include pre-weld visual inspection, in-process arc voltage and current monitoring, and post-weld ultrasonic testing for bond strength verification. The control system records all welding parameters for each pass, providing a complete traceability record for quality assurance purposes.
Engineering Practice and Field Performance
The automatic roll cladding machine has been applied to the repair of various types of paper machine rolls, including press rolls, felt rolls, and dryer rolls. Field performance data indicates the following advantages over manual welding:
- Productivity improvement: Cladding speed increased by 3–5 times compared to manual welding, significantly reducing repair downtime.
- Quality consistency: The coefficient of variation in weld bead height and dilution ratio was reduced from approximately 25% (manual) to below 8% (automated), resulting in more uniform cladding layers.
- Material efficiency: Flux recovery and optimized wire feed rates reduced consumable waste by 15–20%.
- Operator safety: Automation reduced operator exposure to arc radiation, fumes, and high temperatures.
A notable engineering challenge encountered during field deployment was the adaptation of the machine to rolls with varying diameters and lengths. The solution involved the development of adjustable workpiece supports and a flexible torch positioning system that could accommodate rolls ranging from 200 mm to 2000 mm in diameter and up to 6000 mm in length. Another challenge was the management of residual stresses in large-diameter rolls, which can lead to warping or distortion during cladding. The machine design incorporated a programmed cool-down cycle and optional post-weld stress relief to mitigate these effects.
Key Reflections and Study Insights
This research demonstrates the practical value of automation in welding repair applications. The design of the automatic roll cladding machine reflects a deep understanding of both the welding process and the mechanical requirements of roll repair. The integration of flux recovery, precise torch positioning, and automated parameter control represents a significant advancement over manual methods, particularly in terms of quality consistency and productivity. From a standards perspective, the welding procedures developed for this machine should be qualified in accordance with NB/T 47014 or equivalent standards to ensure that the automated process produces welds of equivalent quality to manually produced welds. The machine design also highlights the importance of process monitoring and data recording in modern welding operations, as these capabilities are essential for quality assurance and continuous improvement. This work provides a valuable template for the development of automated welding systems for other cylindrical components in heavy industry.