CLADDING TECHNOLOGY SHANXI CO., LTDPLC Based Automatic MIG MAG Welding Equipment Development for Industrial Applications
Literature Overview
This 2012 publication from Shandong Jiaotong Vocational College, authored by Song Jinhua, addresses the development of a PLC-based automatic MIG/MAG welding system. The work represents an important milestone in the automation of gas metal arc welding (GMAW) processes, particularly relevant to engineers engaged in cladding operations, bimetal pressure vessel fabrication, and multi-pass welding of thick-section components where repeatability and parameter consistency are critical. The document focuses on the integration of programmable logic controllers with welding power sources to achieve automated wire feed control, travel speed regulation, and process parameter optimization.
Core Technical Content
The fundamental approach involves using a PLC as the central control unit to coordinate multiple welding subsystems simultaneously. The system architecture typically comprises the following functional modules:
- Wire feed motor speed control via pulse counting
- Travel carriage speed regulation synchronized with welding current
- Gas flow rate management and pre-flow/post-flow timing
- Multi-pass welding sequence programming
- Real-time monitoring and fault diagnosis
Key Control Parameters
| Parameter | Typical Range | Control Method | PLC Signal Type |
|---|---|---|---|
| Welding Current | 150–500 A | Power source setpoint | Analog output (0–10 V) |
| Arc Voltage | 18–32 V | Power source setpoint | Analog output (0–10 V) |
| Wire Feed Speed | 2–12 m/min | Motor encoder feedback | Pulse train (0–20 kHz) |
| Travel Speed | 200–1200 mm/min | Servo motor control | Pulse train (0–50 kHz) |
| Gas Flow Rate | 10–25 L/min | Solenoid valve + flowmeter | Digital I/O + analog |
| Pre-flow Time | 0.5–2.0 s | Timer output | Digital output |
| Post-flow Time | 1.0–3.0 s | Timer output | Digital output |
Engineering Practice Relevance
For cladding and weld overlay applications, the PLC-based automation approach offers significant advantages. In multi-layer cladding operations such as electroslag welding (ESW) overlay or submerged arc welding (SAW) overlay of nickel-based alloys onto carbon steel substrates, maintaining consistent heat input across dozens or hundreds of passes is essential to prevent intermetallic compound formation at the cladding/base metal interface. The PLC system ensures that current, voltage, travel speed, and wire feed speed remain within tight tolerances throughout the entire cladding sequence.
In the context of bimetal pressure vessel fabrication, particularly for hydrogenation reactors requiring 304/316L stainless steel or Inconel 625 cladding layers, the automated welding system enables:
- Consistent dilution ratio control between the cladding layer and the base metal
- Reproducible interpass temperature management through integrated thermocouple monitoring
- Sequential multi-pass welding without operator fatigue-induced parameter drift
- Documentation and traceability of welding parameters for quality records per NB/T 47014 and ASME IX requirements
FMEA Analysis of PLC Control System
| Failure Mode | Effect | Severity | Detection Method | Countermeasure |
|---|---|---|---|---|
| Wire feed speed deviation | Porosity, undercut | 8 | Current fluctuation alarm | Encoder feedback loop, belt tension monitoring |
| Travel speed loss | Excessive penetration, burn-through | 9 | Voltage/current ratio monitoring | Servo motor with closed-loop position control |
| Gas shutoff timing error | Oxidation of weld pool | 7 | Flowmeter feedback | Redundant timing logic in PLC program |
| Power source communication failure | Process interruption | 10 | Signal integrity check | Watchdog timer, automatic restart sequence |
Study Insights and Reflections
The PLC-based approach described in this literature, while developed in 2012, remains fundamentally relevant to modern welding automation. The key insight is that the reliability of automated welding depends not merely on the welding power source capability but on the precision and robustness of the control system that coordinates all process variables simultaneously. For engineers working on cladding operations where the overlay layer thickness must comply with standards such as ASTM A263/A264/A265 or EN 10028-7, the ability to program and repeat complex multi-pass sequences with minimal deviation is indispensable.
One reflection worth noting is that the PLC approach described focuses primarily on trajectory and parameter control but does not extensively address adaptive control strategies. Modern implementations have evolved to include real-time arc sensing, seam tracking, and feedback-based parameter adjustment. However, the foundational architecture of using a PLC as the master controller coordinating wire feed, travel, gas, and power source remains the backbone of most automated welding cells in pressure vessel fabrication shops today.
The practical implication for engineers is that investment in a robust PLC control system for cladding operations yields compounding quality benefits across every component produced, reducing the need for excessive NDT coverage and minimizing the risk of interfacial defects that could compromise the long-term integrity of bimetal pressure vessels in aggressive service environments.