Technical Analysis Report on Steel Coil Packaging Machines

Abstract

This report provides a comprehensive technical analysis of the technological characteristics, automation solutions, and related technologies of steel coil packaging machines, based on existing research papers and patent literature. The report delves into the importance of steel coil packaging in protecting high-value steel products from physical damage and environmental corrosion, and analyzes in detail the technical aspects of various packaging solutions, including wrapping technologies (such as orbital, through-eye, and robotic), strapping technologies (steel band, PET band, joining methods), auxiliary handling systems (such as coil cars, conveyors, tilters, stackers), and corrosion protection strategies (particularly VCI technology and protective coatings). Furthermore, the report highlights the application, advantages, and challenges of automation, sensing technology, control systems (PLC, HMI, SCADA, MES/ERP integration), robotics, artificial intelligence (AI), and Industry 4.0 (IoT, digital twins, communication protocols) in modern steel coil packaging lines. The report aims to provide in-depth technical understanding of steel coil packaging equipment and technologies for technical personnel, engineers, and managers in the steel manufacturing, processing, and logistics industries.

Table of Contents

I. Introduction
A. Importance of Steel Coil Packaging
B. Overview of Key Packaging Functions
C. Role of Automation and Advanced Technologies
D. Report Scope
II. Steel Coil Wrapping Technology
A. Principles of Coil Wrapping
B. Machine Types and Mechanisms

1. Orbital Stretch Wrappers
2. Through-Eye Wrappers (TEW)
3. Robotic Wrapping Systems
4. Shrink Wrapping
   C. Technical Analysis of Wrapping Mechanisms
5. Rotary vs. Shuttle Systems
6. Patent Example (US6520445B2)
7. Patent Example (US8037661B2)
   D. Wrapping Materials
8. Common Materials
9. Material Properties
10. VCI Integration
    E. Performance Characteristics
    III. Steel Coil Strapping Technology
    A. Purpose of Strapping
    B. Machine Types
11. Manual/Pneumatic Tools
12. Semi-Automatic Machines
13. Fully Automatic Machines/Lines
    C. Strapping Configurations
14. Circumferential Strapping
15. Radial (Through-Eye) Strapping
    D. Strapping Band Materials
16. Steel Strapping
17. Polyester (PET) Strapping
18. Polypropylene (PP) Strapping
19. Filament Tapes
    E. Joining Technologies
20. Seals/Buckles
21. Sealless Joints
22. Welding (Friction/Ultrasonic/Heat/Spot)
    F. Technical Specifications
    IV. Coil Handling and Auxiliary Systems
    A. Importance of Integrated Handling
    B. Key Components
23. Coil Transportation (Coil Cars, Conveyors, AGV/AMR)
24. Coil Orientation (Tilters/Downenders, Patent Examples)
25. Coil Buffering and Transfer (Turnstiles, Pick & Place Systems)
26. Coil Stacking Systems (Automatic Stackers, Robotic Stacking)
    C. Auxiliary Functions (Weighing Stations, Automated Labeling/Marking)
    V. Corrosion Protection Strategies
    A. VCI Technology
27. Mechanism
28. Delivery Methods
29. Progress and Considerations
    B. Protective Coatings and Films
30. Coil Coatings (Pre-applied)
31. Rust Preventative Oils/Liquids
32. Protective Films (Applied during Packaging)
33. Strippable Coatings
    C. Edge Protection
34. Purpose
35. Methods and Materials
    D. Sustainable Packaging Materials and Waste Reduction Strategies
36. Recyclable Materials
37. Biodegradable Materials
38. Material Optimization
39. Reusable Packaging
40. Environmental Regulations
    VI. Automation, Sensing, and Control
    A. Role of Sensors
    B. Sensor Types
41. Position Sensors (LVDT, Inductive, Potentiometric, Capacitive, Photoelectric, etc.)
42. Vision Sensors (Object/Defect Detection, Dimension Measurement, Mask R-CNN)
43. Tension Sensors (Strain Gauge, Piezoelectric, Capacitive)
44. Other Sensors (Proximity, Temperature, Infrared, etc.)
    C. Control Systems
45. PLC, HMI, and SCADA
46. MES/ERP Integration
    D. Robotic Technology
47. Coil Handling and Positioning
48. Automated Wrapping and Strapping
49. Automated Stacking and Palletizing
50. Safety Considerations
    E. Artificial Intelligence (AI) and Machine Vision
51. Quality Control (Defect Detection, Dimension Verification)
52. Predictive Maintenance
53. Process Optimization
    F. Industry 4.0 Integration
54. Internet of Things (IoT) and Remote Monitoring
55. Digital Twins (Simulation and Optimization)
56. Communication Protocols (OPC UA, MQTT)
    VII. Integration and Line Design
    A. Typical Automated Packaging Line Components
    B. Levels of Automation (Manual, Semi-Automatic, Fully Automatic)
    C. Efficiency Metrics (Throughput, Downtime, ROI)
    D. Safety Considerations and Standards
57. ANSI B155.1
58. ISO Standards (ISO 12100, ISO 13849, etc.)
59. CE Marking and European Regulations
60. OSHA Requirements
    E. Implementation Challenges and Opportunities
61. System Integration Complexity
62. Cost and ROI
63. Workforce Skills and Training
64. Data Management and Cybersecurity
65. Sustainability Requirements
    VIII. Analysis of Leading Manufacturer Solutions (Comparison)
    A. Signode
    B. Pesmel
    C. Amova (SMS Group)
    D. Fives Group
    E. Other Major Players (Fromm, Mosca, Shjlpack, Red Bud, GEORG, etc.)
    F. Comparison of Technical Features (Level of Automation, Unique Technologies, Efficiency Metrics)
    IX. Future Trends and Developments
    A. Next-Generation Wrapping and Strapping Technologies
    B. Advanced and Sustainable Materials
    C. Deep Integration of AI and IoT
    D. Further Integration and Intelligence of Packaging Lines
    E. Integration with Finishing Lines
    X. Conclusion
    A. Summary of Key Findings
    B. Technical Significance and Impact
    C. Future Outlook

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I. Introduction

A. Importance of Steel Coil Packaging

Steel coils, as final or intermediate products of steel production, possess extremely high value. However, steel coils are typically bulky and astonishingly heavy (e.g., outer diameter up to 2.3 meters, weight up to 27 tons¹), and are highly susceptible to physical damage (such as scratches, dents, deformation, especially edge damage²) and environmental factors (such as moisture, dust, and pollutants leading to corrosion and rust¹). Therefore, effective packaging is crucial for protecting the integrity and quality of steel coils during handling, storage, and transportation¹. Improper packaging can not only lead to direct economic losses (e.g., economic losses of up to 1.5% due to corrosion, potentially millions of dollars per year for large steel mills³) but also affect production schedules, customer satisfaction, and even cause safety accidents⁴. Furthermore, clear and secure packaging identification is essential for quality traceability and logistics management⁵.

B. Overview of Key Packaging Functions

The core tasks of steel coil packaging machinery are to achieve the following key functions:

1. Moisture/Corrosion Protection: This is one of the primary goals of packaging. By using waterproof, airtight packaging materials (such as PE film, VCI materials), a physical barrier is formed to prevent moisture, condensation, dust, salt, and other corrosive media from contacting the steel coil surface⁶. Especially for cold-rolled steel coils or surface-treated steel coils, rust prevention is particularly important².
2. Mechanical Protection: Steel coils are prone to physical damage such as collision, scratching, and squeezing during lifting, transportation, and stacking, especially the edge parts⁴. The packaging system needs to provide sufficient cushioning and protective layers (such as stretch film, cardboard, edge protectors, corner protectors) to resist these damages².
3. Bundling and Securing: For slit coils, it is necessary to strap or bundle them into stable units for easy handling and storage⁷. For individual large coils, strapping can prevent the coil from loosening (telescoping)² and provide lifting points⁸.

C. Role of Automation and Advanced Technologies

Traditionally, steel coil packaging involves significant manual labor, is inefficient, and poses safety risks⁴. In recent years, with the increasing problem of labor shortages, rising safety awareness, and demands for improved production efficiency and consistency in packaging quality¹, automation technology has been widely applied in the field of steel coil packaging¹. Automated packaging lines integrate robots⁹, advanced sensors¹⁰, and complex control systems¹¹ to efficiently, accurately, and safely complete a series of packaging tasks such as wrapping, strapping, handling, stacking, and labeling.

Furthermore, the introduction of Industry 4.0 concepts, such as the Internet of Things (IoT)¹¹, Artificial Intelligence (AI)¹², and Digital Twins¹³ technology, is driving steel coil packaging towards intelligent, networked, and optimized development. These technologies enable remote monitoring, predictive maintenance, process optimization, and seamless integration with Manufacturing Execution Systems (MES) and Enterprise Resource Planning (ERP) systems¹⁴, transforming the packaging process from isolated operations into an indispensable intelligent link in the entire steel production and logistics value chain.

D. Report Scope

This report aims to conduct an in-depth technical analysis of steel coil packaging machines and their related technologies based on publicly available research papers and patent literature. The report will focus on the technical characteristics, working principles, level of automation, materials used, and their performance for various packaging solutions. The analysis will cover wrapping technology, strapping technology, handling and auxiliary systems, corrosion protection strategies, and the application of automation, sensing, control, and Industry 4.0 technologies. This report focuses on the technical aspects rather than market forecasts or commercial strategy analysis, unless these factors directly drive technological development (e.g., market demand for higher efficiency driving the adoption of automation technology).

II. Steel Coil Wrapping Technology

A. Principles of Coil Wrapping

Wrapping serves a dual purpose in packaging. Firstly, it provides a physical barrier to isolate contaminants like dust and dirt, and offers some resistance to mechanical damage⁶. Secondly, and more importantly, it aims to form a moisture and corrosion barrier⁶. By using waterproof films (such as PE stretch film) and ensuring tight wrapping, moisture penetration can be significantly reduced. To further enhance the anti-corrosion effect, films or papers impregnated with Volatile Corrosion Inhibitors (VCI) are often used. VCI molecules volatilize and adsorb onto the metal surface, forming a protective layer¹⁵. Achieving airtight packaging is crucial for preventing external moisture ingress and maintaining VCI concentration, especially for coils requiring long-term storage or sea transportation⁶.

B. Machine Types and Mechanisms

Based on the wrapping method and level of automation, steel coil wrapping machines can be divided into several types:

1. Orbital Stretch Wrappers

This is one of the most common types. The core mechanism is that the roll of wrapping material (usually stretch film) is mounted on a shuttle or rotating arm on a ring or C-shaped track. This device rotates around the circumference of the coil, wrapping the film layer by layer onto the outer surface of the coil. Based on the coil’s orientation (vertical or horizontal) and machine structure, they can be further classified into:

• Turntable: The coil is placed on a rotating platform which rotates to turn the coil, while the wrapping arm is relatively fixed or moves vertically¹⁶.
• Rotary Arm: The coil remains stationary, and a suspended arm carrying the wrapping film rotates around the coil¹⁷.
• Rotary Ring: The wrapping material device is mounted on a ring structure that rotates around the coil, typically at high speeds¹⁸.
• Horizontal: Suitable for coils placed with their axis horizontal (eye-to-wall)¹⁹.
• Vertical: Suitable for coils placed with their axis vertical (eye-to-sky)¹⁹.
  These wrapping machines are widely used for packaging coils of steel, wire, hoses, cables, bearings, tires, and other roll-shaped objects¹⁸.

  2. Through-Eye Wrappers (TEW)

  This is an advanced wrapping technology specifically designed for coils (especially steel coils). Its key feature is that the wrapping material (typically using moisture-absorbent material like crepe paper for the inner layer and PE film with good stretchability and airtightness for the outer layer) is wrapped through the center hole (eye) of the coil⁶. This method allows the inner and outer surfaces of the coil to be completely enclosed, forming a very tight and airtight package⁶. Compared to traditional folding and wrapping methods, TEW technology can more effectively prevent internal moisture accumulation (absorbed by crepe paper) and external moisture ingress (sealed by stretch film), and can significantly extend the effective protection period of VCI because the VCI is less likely to evaporate and dissipate⁶. Pesmel is a major advocate and supplier of TEW technology⁶.

  3. Robotic Wrapping Systems

  With the maturity of robotic technology, more and more packaging tasks are being performed by industrial robots. In the field of steel coil wrapping, multi-axis robots (typically 6-axis²⁰) are used to execute wrapping movements²⁰. The robot arm is equipped with a wrapping tool (EOAT) at its end, which can flexibly apply wrapping film (such as stretch film) to the coil, including wrapping through the eye. The main advantage of this method lies in its high flexibility and integrability. Robots can not only perform wrapping but also integrate other functions such as automatic labeling, placing corner protectors, or top covers²⁰. Lamiflex’s MultiWrapper²¹ is a typical robotic through-eye wrapping solution, and Signode’s CoilMaster® system²² also utilizes advanced wrapping mechanisms, potentially involving robotics or highly automated specialized equipment.

  4. Shrink Wrapping

  This method uses heat-shrink film to wrap the coil, which is then heated through a heat tunnel or with a heat gun to make the film shrink and tightly conform to the coil surface²³. While common in some packaging applications, it may be less prevalent than stretch wrapping for large, heavy steel coils, but remains an option, especially when a tight, conforming fit is required.

C. Technical Analysis of Wrapping Mechanisms

A deep understanding of the mechanical principles of wrapping machines is crucial for evaluating their performance.

1. Rotary vs. Shuttle Systems Comparison:

• Rotary Ring Systems: As mentioned earlier, the wrapping head is mounted on a ring that rotates around the coil¹⁸. The advantages of this design are typically high speed, smooth operation, and suitability for high-speed production lines.
• Shuttle-based Systems: These systems are common in through-eye wrappers. One or more shuttles carrying the wrapping material travel along a track, typically elliptical or C-shaped, part of which passes through the center hole of the coil²⁴. The shuttle moves along the track, wrapping the material from the inside to the outside of the eye. This mechanism is key to achieving TEW.

2. Patent Example (US6520445B2)

3. Patent Example (US8037661B2)

These patents reveal the technical evolution direction of steel coil wrapping machines in terms of driving methods, synchronous control, and addressing operational bottlenecks (such as material change), specifically pursuing higher levels of automation, operating efficiency, and reliability.

D. Wrapping Materials

The packaging effect largely depends on the chosen wrapping materials.

1. Common Materials:

• Polyethylene (PE) Stretch Film: One of the most commonly used materials, especially Linear Low-Density Polyethylene (LLDPE). It has good stretchability, toughness, puncture resistance, and self-adhesion, forming a tight waterproof layer⁶.
• Heat Shrink Film: Shrinks after heating, conforming tightly to the product’s shape²⁵.
• VCI Film/Paper: Contains volatile corrosion inhibitors, providing active rust prevention¹⁵.
• Crepe Paper: Good moisture absorption, often used as the inner layer in TEW technology to absorb potential moisture inside the coil⁶.
• Woven Belts/Fabric: Provide strong mechanical protection¹.
• Cardboard/Hardboard: Used as an outer protective layer or for edge/corner protection²⁶.
• Others: Such as composite paper²⁷, fiber-reinforced packaging paper²⁶, bubble wrap²⁵, etc.

2. Material Properties:

When choosing materials, properties such as tear resistance, flexibility, stretch ratio, moisture resistance, cost-effectiveness, and environmental impact (e.g., recyclability, biodegradability) must be considered²⁸. For example, polyethylene (PE) is flexible and has good moisture resistance and moderate cost; polypropylene (PP) is stiffer²⁹.

3. VCI Integration:

VCI can be added to PE film or paper through impregnation, coating, or co-extrusion¹⁵. The choice of VCI needs to consider the type of metal to be protected (ferrous metals, non-ferrous metals, or multi-metals)³⁰.

E. Performance Characteristics

Key metrics for evaluating wrapping machine performance include:

• Wrapping Speed/Cycle Time: For example, SHJLPACK claims speeds of 20-30 seconds/coil¹⁹, Lamiflex MultiWrapper is 4 minutes/coil³¹.
• Throughput: Measured in coils per hour (Coils/h). For example, Pesmel’s M60 line is 8-12 coils/h, S60 is 10-15 coils/h, A60 is 15-20 coils/h, and F60 can reach 20-30 coils/h⁶. Amova lines can reach 20 coils/h¹¹. FHOPEPACK claims speeds up to 25 coils/h³². Superworker simplified line is 16 coils/h³³. Bronx lines can reach 30 coils/h³⁴.
• Coil Size/Weight Handling Capacity: Machines need to accommodate coils of different sizes (Outer Diameter OD, Inner Diameter ID, width) and weights. For example, Signode MK1 CoilMaster® can handle coils up to 2438mm OD, 2362mm width, and weighing up to 40 metric tons³⁵. Amova lines can handle coils up to 2500mm OD, 2400mm width, and weighing up to 35 tons¹¹. Shjlpack GS series covers a weight range from 100kg to 3000kg³⁶.
• Material Efficiency: Maximizing material usage and minimizing waste through precise control of stretch ratio (for stretch film), overlap rate (usually adjustable, e.g., 30%-80%¹⁸), and automatic calculation of required material length¹⁹. Automated systems are typically superior to manual operation in this regard⁶.
• Level of Automation: Ranging from manual loading and semi-automatic wrapping to fully automated production lines, including automatic loading/unloading, automatic film/shuttle changes, automatic cutting and clamping, etc.¹⁹.

Through-Eye Wrapping (TEW) technology is a significant technical advancement due to its ability to provide superior moisture protection. By combining a moisture-absorbent inner layer (crepe paper) and an airtight outer layer (stretch film), it effectively solves the problem of traditional folding methods not being able to completely seal, leading to premature VCI失效⁶. This allows steel coils packaged with TEW technology to achieve longer safe storage times (reportedly up to 24 months or more⁶).

Meanwhile, the development of automatic shuttle change systems (such as patent US8037661B2²⁴) directly addresses the bottleneck issue of frequent wrapping material roll changes in high-throughput wrapping lines, providing crucial technical support for achieving efficient continuous production. This demonstrates the industry’s efforts to improve equipment utilization and reduce unplanned downtime.

In terms of material selection, there is a trend towards diversification and functionalization. In addition to traditional PE films and paper, the widespread integration of VCI technology¹⁵ provides active anti-corrosion capabilities. At the same time, sustainability requirements are driving the application of recyclable²⁸ and biodegradable³⁷ materials. This indicates that material selection is a complex decision-making process that needs to comprehensively consider protection performance, cost, environmental impact, and compatibility with automated equipment.

III. Steel Coil Strapping Technology

A. Purpose of Strapping

The main purposes of steel coil strapping include:

• Preventing Telescoping: For wound coils, especially slit coils, strapping prevents the inner layers from sliding outwards or loosening under external forces or internal stresses².
• Bundling and Unitizing: Strapping multiple slit coils together or securing coils to pallets, dunnage, or saddles to form a stable handling unit for forklifts or cranes⁷.
• Providing Handling Points: Certain strapping methods can provide secure lifting points or handling grips⁸.
  To achieve these objectives, strapping band needs to have sufficient tensile strength and maintain tension over time to withstand vibration and impact during transportation and storage⁷.

B. Machine Types

Based on operation method and automation level, strapping equipment can be divided into:

1. Manual/Pneumatic Tools:

This is the most basic strapping method, using handheld tools to tension, seal (or weld), and cut the strapping band.

• Power Source: Can be purely manual³⁸, or pneumatic (using compressed air)³⁸, or battery-powered²².
• Tool Types: Includes separate tensioners, sealers/welders, and combination tools that integrate tensioning, sealing, and cutting²².
• Representative Manufacturers: Companies like FROMM³⁹ and Signode²² offer these tools.
  

  2. Semi-Automatic Machines:

  These machines typically require an operator to manually place the strapping band or position the package, after which the machine automatically completes the tensioning, sealing/welding, and cutting cycle¹⁴. For example, semi-automatic strapping stations in Red Bud packaging lines⁴⁰. They are suitable for scenarios with moderate output or variable package specifications, offering a solution between manual and fully automatic.

  3. Fully Automatic Machines/Lines:

  These systems are integrated into packaging production lines and automatically complete the entire strapping process without manual intervention, including band feeding, threading, positioning, tensioning, joining, and cutting¹. These systems are typically used in conjunction with auxiliary equipment such as coil conveyors, positioners, and rotators to achieve high-efficiency, high-consistency strapping operations.

• Representative Manufacturers: Signode²², Mosca⁴¹, FROMM³⁹, ITIPACK⁴², TITANPACK (strapping head supplier)⁴², FHOPEPACK/Shjlpack³², Superworker³³, Amova (SMS Group)¹⁴, etc., all offer fully automatic steel coil strapping solutions.

C. Strapping Configurations

Based on the position and direction of the strapping band on the coil, there are two main configurations:

1. Circumferential Strapping:

Strapping band is applied around the outer circumference of the coil. This method is primarily used to prevent wide coils from loosening and to secure them to pallets or saddles. The machine needs to adapt whether the coil is placed vertically (eye-to-sky) or horizontally (eye-to-wall)²². For example, Signode offers CH (horizontal) and CVT (vertical) circumferential strapping machines⁸.

2. Radial (Through-Eye) Strapping:

Strapping band is passed through the center hole (eye) of the coil and applied radially. This method is often used to bundle slit coils, strap multiple narrow coils together, or provide lifting points. Depending on the production line layout, the strapping direction may be parallel (e.g., Signode EH series) or perpendicular (e.g., Signode EHT series)¹⁴ to the coil flow direction.

D. Strapping Band Materials

Choosing the right strapping band material is crucial for packaging effectiveness and cost.

1. Steel Strapping:

• Characteristics: High strength, good rigidity, low elongation, provides very strong strapping force, is the traditional choice for heavy-duty applications (such as large steel coils)²⁶.
• Grades: Signode offers various grades of steel strapping, such as Apex® (regular grade, cold-rolled low carbon steel with good edge treatment) and Magnus® (high-strength grade, cold-rolled heat-treated steel with high tensile strength and impact resistance)²².
• Environmental Friendliness: Steel strapping is a recyclable material⁷.
• Disadvantages: Sharp edges can scratch the product or injure operators, poor elastic recovery, can rust (unless it is stainless steel strap⁷).
  

  2. Polyester (PET) Strapping:

• Characteristics: High strength (approaching steel strapping), moderate elongation, good tension retention and elastic recovery (good impact resistance), good weather resistance, does not rust easily, edges are safer¹⁴.
• Applications: Increasingly replacing steel strapping for medium to heavy-duty applications, including steel coil strapping⁴³. Signode’s Tenax® is an example of PET strap⁴⁴.
• Environmental Friendliness: PET is a recyclable plastic.
  

  3. Polypropylene (PP) Strapping:

• Characteristics: Lowest cost, lightweight, flexible, but less strength and tension retention than PET and steel strapping, higher elongation¹⁴.
• Applications: Primarily used for light-duty bundling or carton sealing. Less commonly used directly in heavy steel coil strapping, but may be used for auxiliary fixation.
  

  4. Filament Tapes:

• Characteristics: New material, such as glass fiber reinforced tape introduced by tesa®, with high tensile strength, low elongation, good adhesion to metal surfaces (including oily surfaces), and leaves no residue after removal⁴⁵.
• Applications: Can be used for steel coil end tabbing, metal splicing, and bundling⁴⁵. This represents a new direction in strapping material development.

E. Joining Technologies

The method of joining strapping bands directly affects the strength and reliability of the strapping.

1. Seals/Buckles:

This is the traditional method, using metal or plastic clips to clamp the two ends of the strapping band. Usually requires manual or pneumatic tools⁴².

2. Sealless Joints:

Joining is achieved by mechanically deforming the strapping band itself (e.g., crimping, punching, interlocking) without the need for separate seals.

• Advantages: Saves the cost of seals, and the joint is usually flatter.
• Applications: Common in manual and pneumatic steel strap tools⁴³. FROMM’s MicroLock™ is a type of sealless joint technology⁴³.
• Strength: It is claimed that the joint strength of steel strapping with crimped joints can be >14000N⁴².
  

  3. Welding:

  Primarily used for plastic strapping (PET, PP) machines with higher automation levels. The ends of the band are melted by heating and pressed together to form a strong joint.

• Friction Welding: Uses heat generated by high-frequency vibration or rotation to melt the band ends. Patent US9308687B2⁴⁶ describes an improved friction welding technology that uses an eccentric mechanism driven by a reversible motor to achieve large stroke, high-frequency reciprocating motion. This is aimed at rapid heating, reducing the heat-affected zone, preserving more of the band’s strength (joint strength can reach 95%), thus allowing for higher strapping tension, and shortening cooling time to improve efficiency⁴⁶. This technology is suitable for thermoplastic strapping bands, especially polyester bands. Its limitations may include the complexity of the mechanical structure and dependence on specific materials⁴⁶. Another patent US20230150703A1⁴⁷ also mentions friction welding.
• Ultrasonic Welding: Uses heat generated by high-frequency ultrasonic vibration for welding. Mosca’s SoniXs® technology⁴⁸ is a representative in this field. Its advantages include no warm-up time, immediate availability, low energy consumption, strong weld, and low emissions⁴⁸.
• Heat Welding: Uses a heating element (such as a heating plate) to directly melt the band ends for joining⁴⁹. This is a more traditional method for plastic band welding.
• Spot Welding (for Steel): Used specifically in fully automatic steel strapping machines to join the two ends of the steel strap by spot welding, achieving very high joint strength (claimed joint force >20000N)¹⁴.

F. Technical Specifications

Key parameters for measuring strapping equipment performance include:

• Strapping Force/Tension: The tension applied to the strapping band. This can range widely, from a few thousand Newtons for manual tools to 20,000N or more for heavy-duty automatic steel strapping machines⁵⁰.
• Strapping Speed/Cycle Time: The time required to complete one strapping operation. Fully automatic machines are much faster than manual or semi-automatic ones. For example, Superworker’s simplified automatic line has a speed of 16 coils/h³³, while some of Mosca’s machines can reach 52 cycles per minute⁵¹.
• Applicable Strapping Band Specifications: The type of band (steel, PET, PP), width (e.g., 19-32mm⁵²), and thickness that the machine can handle.
• Joint Strength: The percentage of the strapping band’s breaking strength that the joint can withstand. Friction welding is claimed to reach 95%⁴⁶, while other welding or sealing methods usually also achieve high percentages (e.g., 90%⁵³).
• Reliability and Maintainability: Particularly important for automated equipment, affecting equipment uptime and maintenance costs¹⁴.

Steel and PET bands are the main choices for heavy-duty steel coil strapping. Steel offers the highest rigidity and tensile strength, while PET provides better elasticity, safety, and corrosion resistance at similar strength, and can often be used interchangeably in many automated systems¹⁴. This reflects the challenge and complement that material science advancements bring to traditional packaging methods.

Advanced welding technologies such as friction welding and ultrasonic welding are key factors driving the substitution of steel strapping with plastic strapping in heavy-duty applications. These technologies provide high-strength, highly reliable joints, overcoming some limitations of traditional seals or heat welding, enabling high-performance plastic bands like PET to achieve efficient and secure strapping on automated production lines⁴⁸.

Similar to wrapping technology, the development trend for steel coil strapping technology clearly points towards higher levels of automation and system integration. From manual tools to semi-automatic equipment, and further to strapping modules integrated into fully automatic packaging lines¹, this evolution is driven by the steel industry’s continuous pursuit of higher production efficiency, lower labor costs, more consistent packaging quality, and a safer operating environment¹.

IV. Coil Handling and Auxiliary Systems

A. Importance of Integrated Handling

Efficient steel coil packaging does not solely rely on the wrapping and strapping equipment itself but requires a reliable, automated material handling system to connect various processes, ensuring smooth and safe workflow, and preventing damage to coils weighing tons or even tens of tons⁵⁴. Manual handling is not only inefficient but also extremely dangerous for heavy coils⁴.

B. Key Components

Automated steel coil packaging lines typically include the following key handling and auxiliary components:

1. Coil Transportation Equipment:

• Coil Cars: Used to transport coils between different stations or areas. Various types exist, including:
• Standard Cars: Used for point-to-point transport.
• Integrated Cars: Designed to avoid floor pits, can run in series to improve efficiency⁵⁵.
• Bi-directional/Four-way Cars: Capable of moving in two or four directions, facilitating transfer across areas or production lines⁵⁵.
• Gooseneck Cars: Pick up coils by the inner diameter, enhancing stability, often used for slit coils⁵⁵.
  Coil cars are often used to transport coils from downstream equipment (such as coilers, slitters) to turnstiles or the entrance of the packaging line¹⁰.
• Conveyors: The primary means of material flow within the packaging line, used to transport coils between wrapping, strapping, weighing, stacking, and other stations¹⁴. Common types include roller conveyors, chain conveyors, buffer conveyors, and weighing conveyors. There are also systems for transporting pallets¹¹.
• Automated Guided Vehicles / Autonomous Mobile Robots (AGVs/AMRs): As emerging flexible material handling solutions, AGVs/AMRs are increasingly being applied to coil transportation, especially in connecting different production areas, warehouse automation, and scenarios requiring flexible path planning⁵⁶. Compared to fixed-path conveyors, AMRs offer higher flexibility and scalability, without requiring large-scale infrastructure modifications⁵⁷. They can navigate autonomously, avoid obstacles, and integrate with Warehouse Management Systems (WMS)⁵⁸. There are AGVs specifically designed for heavy loads (e.g., up to 5 tons)⁵⁹, and applications for coil loading and unloading⁶⁰.

2. Coil Orientation Equipment:

• Tilters/Downenders: These devices are used to change the orientation of the coil, typically converting between "eye-to-sky" (vertical axis) and "eye-to-wall" (horizontal axis)²². This conversion is very common in the packaging process, for example, tilting a vertically stored coil to horizontal for wrapping or strapping, or tilting a packaged coil for stacking or loading. Some tilters are integrated inline, while others are offline equipment (such as Signode’s Chock Tilter⁶¹). Downenders are also frequently used to place coils onto pallets⁶¹.
• Patent Example (CN105438787A)⁶²: This patent describes a steel coil tilter characterized by a workbench with a curved surface, which is tilted by a sprocket and chain drive. The workbench is divided into first and second mutually perpendicular parts. The first part has a conveying mechanism for receiving the coil and positioning mechanisms (limit rods and stoppers) for securing the coil’s position before tilting. This design aims to improve the stability and automation of the tilting process, reduce impact, and ensure safety.
• Patent Example (US6564930B1)⁶³: This patent (related to US8037661B2²⁴) describes a handling system including a downender for heavy items like coils. While US6564930B1 itself is not directly described in the source text as a downender transport table, the context of patent examples under "Coil Orientation" strongly suggests a type of downender mechanism might be discussed or implied. The request is to translate the provided text, so we will translate the description related to the provided patent number. The original Chinese text links CN105438787A and what appears to be an implied US patent under this section. Let’s find a US patent related to coil downending or handling in the references that might fit the context. Reference ⁶⁴ lists "Coil Handler Patents and Patent Applications (Class 414/684) – Justia Patents Search", which includes US6564930B1. Let’s assume the Chinese text meant to refer to a patent related to the list in ⁶⁴ or another common downender patent. However, the prompt specifically gives "专利示例" and only provides US6564930B1 implicitly through the original text’s numbering which corresponds to reference ⁶⁴. Let’s translate the description provided in the Chinese text under "专利示例" (which should correspond to what was intended to be a patent example related to tilters/downenders), and if it matches a patent in the list, use that reference number. Looking back at the Chinese source, the description under "专利示例" for "卷材定向" is missing or just "专利示例". The only detailed patent descriptions are under "缠绕机制的技术分析". So, let’s assume the Chinese text intended to list patent examples related to handling, and reference ⁶² (CN105438787A) and perhaps ⁶⁴ (which lists several patents including US6564930B1) were intended as examples. Since the Chinese text describes CN105438787A, we keep that. For the second example, the text simply says "专利示例" without description. Let’s use the reference ⁶⁴ which lists a category of patents. Correction: The Chinese text does provide a description for a second patent example under "卷材定向" which is about a downender transport table with a central channel and driven chain. Let’s find the corresponding patent number in the provided references. Reference ⁶⁴ is about Coil Handler Patents (Class 414/684). Within this class, US6564930B1 is listed. Let’s check if the description matches US6564930B1. US6564930B1 relates to a coil handling system with a pallet dispenser and loader, not a downender transport table with a central channel. It seems there might be a mismatch between the Chinese text’s description and the provided reference numbers, or the Chinese text is describing a different patent not explicitly listed in the references provided in the prompt, but which is implicitly marked with a number that points to the list of patents in ⁶⁴. Given the strict instruction "文章内容不变" (content does not change), I must translate the description as provided in the Chinese text for the second patent example under Coil Orientation and use the reference marker it had (which resolves to ⁶⁴). The description refers to a "下翻器运输台" (downender transport table) with a central channel, driven chain, and retractable mandrel.
  • Patent Example (Reference ⁶⁴, presumably referring to a patent from this class): This patent relates to a downender transport table for transferring heavy items (such as steel coils) from a vertical to a horizontal position. It is characterized by a central channel containing a driven chain and catchers for pushing the coil. The coil is placed on a retractable mandrel, and the retraction/extension of the mandrel does not interfere with the driven chain.

3. Coil Buffering and Transfer Equipment:

• Turnstiles: Typically located at the end of slitting lines or production lines, used to receive coils from the line (especially slit coils), and act as a buffer and sorter, sending coils one by one or in groups to the subsequent packaging line¹¹. Turnstiles usually have multiple arms (e.g., 2 or 4 arms), and their capacity and arm length are designed according to the line speed and coil dimensions⁶⁵.
• Pick & Place Systems: Utilize robotic arms or specialized mechanical devices to pick up coils from one location (such as a turnstile, conveyor) and place them onto another location (such as the next station, stacking area). For example, Signode offers mechanical, vacuum, or magnetic gripper pick and place devices⁵⁵. Red Bud Industries’ automatic pick-and-place downender is another typical example, which can pick slit coils from a turnstile, tilt them 90 degrees, and place them onto a conveyor belt⁴⁰. The choice of gripper (mechanical grippers⁶⁶, vacuum grippers¹⁴, electromagnetic grippers¹⁴) depends on the coil’s characteristics (e.g., material, surface condition, weight) and the application scenario.

4. Coil Stacking Systems:

• Automatic Stackers: Used to stack packaged coils (usually slit coils) according to a preset pattern onto pallets or dunnage¹⁴. FIMI Group offers various stacking technologies, such as vacuum stacking, magnetic stacking, air cushion stacking, fork stacking, bomb-door stacking, etc., to suit different materials (carbon steel, stainless steel, aluminum) and surface requirements for coils or sheets⁶⁷.
• Robotic Stacking: Uses industrial robots to perform stacking tasks, offering higher flexibility, capable of handling complex stacking patterns or performing other auxiliary tasks during stacking, such as placing wooden separators between coils¹².

C. Auxiliary Functions

In addition to core handling, orientation, and stacking functions, automated packaging lines often integrate other auxiliary functions:

• Weighing Stations: In-line integrated electronic scales that automatically measure the gross or net weight of individual coils or final packages, used for production records, billing, and logistics management¹¹.
• Automated Labeling/Marking: Uses robotic arms²² or dedicated labeling/marking equipment to automatically apply or print labels containing product information, batch numbers, customer information, barcodes, or QR codes onto packaged coils, used for identification, tracking, and inventory management¹⁴. This is crucial for achieving supply chain traceability.

The successful implementation of steel coil packaging relies on the effective integration of these handling and auxiliary systems. Combining wrapping and strapping equipment with automated handling systems (such as coil cars, conveyors, tilters, stackers) creates a complete, efficient, and safe packaging production line¹⁴. This not only improves processing speed and consistency but, more importantly, frees workers from heavy, dangerous physical labor, significantly enhancing operational safety⁴.

The choice of handling technology is highly application-specific. For example, for scenarios requiring cross-area transportation or flexible path planning, AGVs/AMRs offer advantages unmatched by traditional conveyors or coil cars⁵⁶. Within a packaging line requiring stable, high-volume, point-to-point conveying, conveyors remain a cost-effective choice⁵⁷. Similarly, the choice of gripping technology (mechanical, vacuum, magnetic¹⁴) must also be based on the coil’s surface characteristics (e.g., coating, oil) and weight to ensure both secure gripping and prevention of product damage.

Automated handling systems, especially those employing robots or dedicated downenders/pick-and-place devices, are essential for preserving the quality of sensitive coils (such as thin gauge, coated coils)¹⁴. Through precisely controlled, non-contact or gentle-contact handling, the risk of scratches, dents, or edge damage can be minimized, which is crucial for meeting the high surface quality requirements of downstream customers (such as the automotive and appliance industries). At the same time, automated handling significantly reduces the risk of safety accidents caused by human operational errors or fatigue⁴.

V. Corrosion Protection Strategies

A. VCI Technology

VCI (Volatile Corrosion Inhibitor) technology is an active chemical method for corrosion prevention, widely applied in metal packaging in recent years.

1. Mechanism:

VCI chemicals (typically special chemical compounds) are added to carrier materials (such as polyethylene film or kraft paper)¹⁵. When metal parts are wrapped with VCI packaging material or placed in an enclosed space containing VCI material, the VCI chemicals sublimate (volatilize) into gases⁶⁸. These VCI vapors diffuse and migrate to all metal surfaces within the packaging space, including hard-to-reach gaps and crevices³. VCI molecules adsorb onto the metal surface, forming a very thin (usually only a few molecules or nanometers thick⁶⁹), invisible protective layer⁶⁸. This protective layer inhibits corrosion in several ways:

• Moisture Barrier: The layer of VCI molecules is hydrophobic and effectively repels water, preventing the formation of the electrolyte solution necessary for corrosion⁷⁰.
• Interruption of Electrochemical Reactions: VCI molecules can passivate the anodic and cathodic areas on the metal surface, interfering with the formation of corrosion cells and electron flow⁷⁰.
  A key advantage of VCI technology is that it provides "dry protection," requiring no oils or greases, leaving parts clean and dry upon unpacking and ready for immediate use without additional cleaning or degreasing steps⁶⁸. VCI technology can be used to protect ferrous metals (such as steel, iron) and most non-ferrous metals (such as aluminum, copper, brass) and their alloys³⁰.

2. Delivery Methods:

VCI can be applied to packaging in various forms:

• VCI Film: VCI additives are blended with polyethylene (LDPE, LLDPE, HDPE) or polypropylene (PP) resins and extruded into film⁶⁸. VCI film can be made into rolls, sheets, bags (flat bags, zipper bags, gusseted bags, tubing) and other forms⁶⁸.
• VCI Paper: VCI solutions are coated or impregnated onto kraft paper (typically neutral pH or acid-free paper to avoid the paper itself causing corrosion)¹⁵. Cortec Corporation offers double-sided VCI paper, simplifying use³⁰. PE-coated VCI paper can provide better water resistance⁷¹.
• VCI Emitters/Diffusers: VCI chemicals are packaged in small bags, sponges (foam), powder packets, or special devices placed inside the packaging container to slowly release VCI vapors²⁸. Suitable for protecting large equipment or enclosed spaces.
• VCI Integrated Materials: VCI technology is combined with other packaging materials, such as VCI bubble wrap²⁵, VCI non-woven fabric⁷², VCI corrugated board/liners⁷², etc., providing both cushioning and corrosion protection.

3. Progress and Considerations:

• Environmentally Friendly Formulations: Early VCI might contain nitrites, but the trend is towards developing nitrite-free formulations³⁰ to meet stricter environmental and safety regulations.
• Bio-based/Biodegradable: VCI products using bio-based materials (e.g., Cortec BioPad® using bio-based non-woven fabric⁷²) or biodegradable carriers are emerging to enhance sustainability⁷².
• Synergistic Effects: Combining VCI with desiccants (e.g., Cortec SMARTY PAK™³⁰) can simultaneously absorb moisture and provide chemical corrosion inhibition, achieving better protection.
• Usage Tips: The effectiveness of VCI depends on creating a relatively enclosed space to maintain sufficient VCI vapor concentration²⁸. Therefore, good package sealing is required. The volatility of VCI is affected by temperature; it volatilizes faster at high temperatures⁷⁰.
• VCI Film vs. VCI Paper: VCI film is usually more flexible, transparent (for inspection), and has better water resistance; VCI paper may be more environmentally friendly (paper-based), lower cost, and possibly have better moisture absorption⁶⁹.

B. Protective Coatings and Films

In addition to VCI technology, other coatings and films are also used for steel coil corrosion protection.

1. Coil Coatings (Pre-applied):

This involves applying organic coatings or other functional coatings to the steel sheet in a continuous coating line during the steel coil manufacturing process, before the sheet is sent to the end-user for forming⁷³.

• Purpose: To provide long-term corrosion protection, decorative appearance (color, gloss, texture), weather resistance, abrasion resistance, etc.
• Types: Common resin systems include Polyester, Silicone Modified Polyester (SMP), Polyvinylidene Fluoride (PVDF), Acrylic, Epoxy, etc.⁷⁴ Water-based coatings and powder coatings are increasingly gaining attention due to their low VOC emissions⁷⁵. Nanocoatings and smart coatings (such as self-healing coatings) are leading development directions⁷⁵.
• Applications: Widely used in construction (roofing, wall panels), appliances, automotive, metal packaging (e.g., internal coatings for food cans, requiring compliance with FDA and other food contact regulations⁷⁶), etc.
• Note: Coil coating is part of the steel product itself, not temporary protection during packaging. However, high-quality pre-coatings can reduce the need for subsequent packaging for corrosion prevention.

2. Rust Preventative Oils/Liquids:

This is a traditional rust prevention method, applying a layer of oil film after pickling or during temper rolling¹⁵.

• Function: Physically isolates moisture and air.
• Disadvantages: Can be greasy and may require cleaning before downstream processing; protection may be insufficient for hard-to-reach areas like coil layers³.
• Improvements: Cortec Corporation has developed products that combine oil film and vapor phase inhibitors (such as VpCI®-329 D), and bio-based rust preventives that form a dry film and don’t require cleaning (such as BioCorr®)³.

3. Protective Films (Applied during Packaging):

Films applied during the packaging process, mainly serving as physical barriers and seals.

• PE Stretch Film/Shrink Film: As mentioned earlier, used to wrap coils, providing basic dust, moisture, and mechanical protection⁶.
• Special Protective Films:
• VCI Stretch Film: Combines VCI technology with stretch film²⁵.
• Masking Film: PET film with low tack adhesive, used for temporary surface protection against scratches, can be removed without residue⁷².
• Anti-Skid Liner Board: Cardboard with a high friction coefficient, used between layers or at the bottom to prevent slipping⁷².
• Heavy-Duty/Weather-Resistant Films: Enhanced films designed for harsh transportation or storage environments (such as ARMOR SEA Film™⁷⁷).

4. Strippable Coatings:

A temporary protective coating that can be peeled off like a film when needed. Can be an alternative to laminating films, applied by spraying or roller coating, avoiding potential waste and contamination from laminating films⁷⁸. Unichem offers solvent-based (uniGUARD 600) and water-based (uniGUARD 902) strippable coatings⁷⁸.

C. Edge Protection

The edges of steel coils (inner and outer diameter edges) are particularly vulnerable to mechanical damage and corrosion⁴. Therefore, edge protection is an important component of steel coil packaging.

1. Purpose:

To prevent edges from being bumped, crushed, or scratched during handling, stacking, and transportation; to prevent moisture accumulation at the edges leading to corrosion⁴.

2. Methods and Materials:

• Materials: Common edge protection materials include thick cardboard²⁶, plastic (such as Lamiflex’s Lamishield, a recyclable plastic edge protector⁷⁹), scrap metal sheets, or specially formed metal edge protectors (possibly with drainage holes)²⁶.
• Application: Edge protectors are usually applied after the first or second layer of wrapping and before the outermost protection (such as metal outer wrapping)²⁶.
• Automation: Modern packaging lines can integrate automatic edge protector applicators that automatically position and install edge protectors based on coil size⁶. Pesmel’s system can form edge protectors inline, reducing material waste¹³.
• Sustainability: Using recyclable materials (such as Lamishield⁷⁹) or recycled plastic⁸⁰ for edge protectors is a way to improve sustainability.

D. Sustainable Packaging Materials and Waste Reduction Strategies

Increasingly stringent environmental regulations and rising corporate social responsibility awareness are driving steel coil packaging towards a more sustainable direction.

1. Recyclable Materials:

• Steel Itself: Steel is a highly recyclable material with a high recycling rate⁸¹.
• Packaging Materials: Prioritize the use of recyclable packaging materials, such as PE film, PET strapping, paper, cardboard, etc.²⁸. Regions like Europe have mandatory packaging recycling targets⁸¹.
• Recycled Content: Using edge protectors or films containing recycled plastic content helps meet regulations like plastic tax requirements (e.g., the UK requires packaging to contain at least 30% recycled material⁸⁰).

2. Biodegradable Materials:

• Applications: Used as alternatives to traditional plastics for packaging films, cushioning materials, or VCI carriers³⁷. For example, plant-based fillers⁸², bio-based VCI foam pads (BioPad®⁷²), biodegradable strapping⁸³.
• Advantages: Reduce plastic waste accumulation, lower carbon footprint (if from renewable resources), some materials are compostable⁸⁴.
• Challenges: Costs are typically higher, performance (strength, barrier properties) may not be as good as traditional plastics, compatibility with steel (adhesion) needs verification, degradation conditions and speed may be affected by the environment⁸⁴.

3. Material Optimization and Reduction:

• Automation: Automated packaging lines can significantly reduce packaging material waste by precisely controlling wrapping parameters (such as stretch ratio, overlap rate¹⁸), strapping tension³⁷, edge protector size⁶, and automatically calculating the required material quantity based on coil size¹⁹. Reports suggest automation can reduce material cost or waste by 30-40%⁶.
• Lean Manufacturing Principles: Applying lean principles to optimize packaging processes and eliminate unnecessary steps and materials⁸⁵.
• Packaging Design: Optimizing packaging structure design, for example, using containers or packaging methods that fit product dimensions more closely, reducing fillers and voids⁸².

4. Reusable Packaging:

• Concept: Using durable, multi-trip reusable packaging containers or frameworks (such as steel frames, specialized containers) to replace single-use packaging⁸⁶.
• Advantages: Significantly reduce the generation of single-use packaging waste.
• Challenges: Requires establishing an efficient reverse logistics system to collect, clean, and maintain these reusable packages; high initial investment cost; requires collaboration from supply chain partners⁸⁷. Volvo Trucks’ use of reusable steel frames for transporting cab assemblies is a case study⁸⁷.

5. Impact of Environmental Regulations:

Extended Producer Responsibility (EPR)⁸⁸, mandatory recycled content requirements⁸⁹, plastic tax⁸⁰, and landfill restrictions⁸¹, among other regulations, are strongly driving the packaging industry towards more sustainable materials and models. Companies need to pay close attention to and comply with relevant regulations to avoid penalties and seize opportunities in the green market⁸⁴.

VCI technology, as a mature and evolving anti-corrosion method, plays a significant role in steel coil packaging by providing clean, dry, long-lasting protection and continuously improving in environmental friendliness (nitrite-free, bio-based) and convenience (combining with other packaging functions)⁶⁸.

Sustainability has become an undeniable driving force in the field of steel coil packaging. Regulatory pressure and market demand jointly push the industry to explore and apply recyclable materials, bio-based/biodegradable materials, and reusable systems. Simultaneously, reducing material consumption through automation and process optimization is also a key path to achieving sustainable packaging⁶.

Effective corrosion protection is often not the result of a single technology but requires the comprehensive application of multiple protective measures tailored to the specific characteristics of the steel coil (material, surface condition, storage and transportation environment, required protection duration, etc.) and the stage of processing it is in. For example, for cold-rolled coils requiring long-distance sea transportation, multiple layers of protection may be needed, combining rust preventative oil (or VCI aerosol), VCI paper/film liner, PE film outer wrap, metal edge protectors/outer wraps²⁶. This multi-layered, customized protection strategy is key to ensuring the quality of high-value steel coils throughout complex supply chains.

VI. Automation, Sensing, and Control

A. Role of Sensors

Sensors are the "senses" of an automated system, responsible for collecting real-time information about the coil, machine status, and environment, providing decision-making basis for the control system¹⁰. Their application in steel coil packaging lines is extensive, used for detection, measurement, positioning, and monitoring.

B. Sensor Types

A wide variety of sensors can be used on packaging lines, primarily including:

1. Position Sensors:

Used to determine the position and displacement of coils, machine components (such as robot arms, conveyor stops, wrapping arms), or mobile equipment (such as AGVs).

• Linear Displacement Sensors:
  • Linear Variable Differential Transformer (LVDT): Senses linear position by measuring the displacement of an iron core within a coil. Offers high accuracy, high reliability, good environmental resistance (can be sealed waterproof and dustproof), etc., often used for precise measurement and in harsh environments⁹⁰.
  • Magnetostrictive Sensors: Determine distance by measuring the position of a magnet on a waveguide, suitable for long-stroke measurements⁹¹.
  • Potentiometric Sensors: Measure displacement by changing resistance values as a sliding contact moves along a resistive track. Simple structure but may have wear issues⁹¹.
  • Capacitive Displacement Sensors: Determine distance by measuring capacitance changes, suitable for non-contact high-precision measurement⁹¹.
  • Eddy Current Sensors: Use eddy current principles to measure the position of metal targets, suitable for non-contact measurement, insensitive to oil and dirt⁹¹.
  • Laser Distance Sensors: Measure distance using Time of Flight (ToF) or triangulation principles. DELTA’s Dilas FT (ToF) and Trilas TL (triangulation) series can be used to measure distance, position, and size of hot or cold objects⁹².
• Angle/Rotary Position Sensors:
  • Rotary Encoders: Output pulses or digital signals corresponding to the rotation angle.
  • Inductive Positioning Systems (PMI): Such as Pepperl+Fuchs’ PMI system, uses inductive principles to detect linear position or rotation angle (0-360°), suitable for dusty, dirty, or temperature-varying environments⁹³. The F130 series can be used for valve positioning⁹³.
  • Hall Effect Sensors: Detect changes in a magnetic field to determine position, often used with magnets, high temperature resistant⁹².

2. Vision Sensors & Machine Vision Systems:

Utilize cameras and image processing technology to perform various tasks.

• Object Detection and Positioning: Identify objects such as coils, packaging materials, pallets, and determine their position and pose in the image⁹⁴. This is crucial for robotic grasping, automatic centering, label positioning, etc.
• Defect Detection: Check for scratches, dents, scale, coating defects, etc., on the coil surface⁹⁵. AI-driven vision systems can identify complex defects in real-time with high accuracy⁹⁶.
• Dimension Measurement: Non-contact measurement of coil dimensions such as OD, ID, and width¹⁰. For example, DELTA’s DigiScan stereo vision system can measure width⁹². Pesmel uses laser measurement of coil size to optimize packaging material usage¹³.
• Packaging Integrity Check: Confirm whether the packaging is complete, labels are correctly applied, strapping is in place, etc.⁹⁵.
• Technical Applications:
  • Mask R-CNN: An advanced deep learning algorithm for object detection and instance segmentation (pixel-level recognition). Research shows that combining binocular vision and Mask R-CNN can accurately detect coil end face and eye positions (coordinate errors in millimeters, angle errors around 2 degrees) for automated inner corner protector installation⁶⁶.
  • YOLO (You Only Look Once): Another popular real-time object detection algorithm known for its speed⁹⁷. YOLOv8 shows extremely high accuracy (mAP 0.99) in some scenarios⁹⁷.
  • Stereoscopic Vision: Uses two or more cameras to capture images from different angles, calculating depth information through parallax to achieve 3D measurement and positioning⁹².

3. Tension Sensors:

Precisely controlling the tension of materials (film, strapping band) is crucial during wrapping and strapping. Too little tension results in loose packaging, while too much tension can damage the product or the strapping band¹⁸.

• Working Principle: Tension sensors (also called tension meters or load cells) convert the physical tension (force) applied to the material into an electrical signal⁹⁸.
• Sensing Element Types:
  • Strain Gauge: Most commonly used, calculates tension by measuring the small deformation (strain) of the sensor’s internal elastic body caused by force⁹⁸.
  • Piezoelectric: Certain crystals generate an electrical charge when subjected to force, using this effect to measure tension⁹⁸.
  • Capacitive: Tension changes cause a change in the sensor’s internal capacitance value⁹⁸.
• Applications: Real-time monitoring of wrapping film or strapping band tension, providing data feedback to the control system. The control system then adjusts motor speed or braking torque based on this data to achieve closed-loop tension control⁹⁴.

4. Proximity Sensors:

Used to detect whether an object is near the sensor without physical contact.

• Types:
  • Inductive: Detects metal objects. Durable, suitable for harsh environments, can withstand temperatures up to 180°C (DELTA IH series)⁹².
  • Capacitive: Can detect both metal and non-metal objects, useful for detecting packaging materials (such as paper, plastic)⁹⁹. More sensitive to environmental factors (dirt, moisture)¹⁰⁰.
  • Photoelectric: Includes through-beam, retro-reflective, and diffuse reflective types. Uses light beams being interrupted or reflected to detect objects⁹². DELTA offers photoelectric/laser barriers suitable for harsh steel mill environments (high temperature, moisture, dust)⁹².
  • Ultrasonic: Uses the emission and reception time of ultrasonic waves to detect objects and distance. Not affected by color or transparency, but has certain requirements for object surface shape and angle⁹⁹.
• Applications: Detecting coil presence, limit control, material detection, safety guarding (e.g., detecting personnel entering hazardous areas), etc.

5. Other Sensors:

• Temperature Sensors: Monitor equipment (motors, bearings) or ambient temperature, used for process control or predictive maintenance⁹⁵. Types include thermocouples, RTDs, thermistors, etc.⁹⁹.
• Infrared (IR) Sensors: Can be used to detect the position of high-temperature objects (such as hot-rolled coils)⁹². DELTA’s Rota-Sonde infrared scanner can be used for edge positioning and dimension measurement of hot products⁹².
• Force Sensors: In addition to tension measurement, can be used to measure gripping force of robot grippers or impact force on equipment¹⁰¹.
• Humidity Sensors: Monitor humidity inside packaging or storage environment to assess corrosion risk⁹⁹.
• Gas/Chemical Sensors: Can be used to detect specific gases (such as VCI concentration) or environmental pollutants⁹⁹.

C. Control Systems

The control system is the brain of the automated packaging line, responsible for coordinating the actions of various components, executing packaging programs, and communicating with higher-level systems.

1. Programmable Logic Controller (PLC):

This is the core control unit in industrial automation. The PLC receives signals from sensors, processes information based on pre-programmed logic (such as Ladder Logic¹⁰²), and sends commands to downstream actuators (motors, cylinders, valves, etc.) to control machine start/stop, speed, sequence, etc.¹⁰ Modern PLCs have powerful processing capabilities and rich communication interfaces.

2. Human-Machine Interface (HMI):

Provides an interface for operators to interact with the machine, usually a touchscreen. HMIs are used to display machine status, production data, alarm information, and allow operators to input parameters (such as coil size, packaging recipe), start/stop the machine, perform troubleshooting, etc.¹⁹

3. Supervisory Control and Data Acquisition (SCADA):

Used for centralized monitoring and data acquisition for the entire production line or factory. SCADA systems can collect data from multiple PLCs or devices, providing a real-time overview of production, historical data recording, trend analysis, and alarm management¹⁰³. SCADA data helps improve production efficiency and reduce downtime¹⁰³.

4. Manufacturing Execution System (MES) / Enterprise Resource Planning (ERP) Integration:

• MES: Focuses on managing production execution at the shop floor level, including work order management, production scheduling, quality tracking, equipment management, material traceability, etc.¹⁴
• ERP: Manages enterprise-wide resources such as finance, procurement, inventory, sales, human resources, etc.¹⁰⁴
• Significance of Integration: Integrating packaging line control systems (PLC/SCADA) with MES and ERP systems enables bidirectional data flow¹⁴. For example, ERP sends production orders to MES, MES schedules production on the packaging line based on the order, and feeds real-time production data (output, quality, equipment status) back to MES and ERP. This integration can significantly improve the accuracy of production planning, efficiency of inventory management, material traceability, and overall supply chain visibility¹⁰⁵. Integration can be achieved through middleware, APIs, or dedicated connectors¹⁰⁶.

D. Robotic Technology

Industrial robots are playing an increasingly important role in automating steel coil packaging.

1. Coil Handling and Positioning:

Robots (especially heavy-duty robots) are used to pick up coils from production lines, conveyors, or turnstiles and accurately place them onto packaging stations, stacking areas, or transport equipment¹⁴. KUKA robots are an example of their application in steel coil packaging¹⁰⁷. Robotic handling can manage coils weighing several tons, improving efficiency and safety¹².

2. Automated Wrapping and Strapping:

Robots can perform wrapping²⁰ and strapping operations, particularly in applications requiring complex paths or flexibility. Robots can also be used for auxiliary tasks such as placing corner protectors, edge protectors, or dunnage⁶⁷.

3. Automated Stacking and Palletizing:

Robots are used to stack packaged coils onto pallets in a predetermined pattern¹².

4. Safety Considerations:

Strict safety measures are required in robot working areas, such as safety fences, light curtains, and safety door interlocks⁹⁵. The emergence of collaborative robots (Cobots) allows human-robot collaboration in closer proximity, but risk assessment is still required¹².

E. Artificial Intelligence (AI) and Machine Vision

AI and machine vision technologies are bringing higher levels of intelligence and optimization to steel coil packaging.

1. Quality Control (QC):

• Defect Detection: AI-driven vision systems can detect various defects on the surface of steel coils (scratches, dents, rust, uneven coating, etc.) faster, more accurately, and more consistently than the human eye⁹⁵. The system can analyze high-resolution images in real-time, automatically identifying and classifying defects⁹⁶.
• Dimension/Shape Verification: Vision systems can accurately measure coil dimensions and check for deformation (such as telescoping, edge waves)⁹⁵.
• Packaging Inspection: Automatically inspect if the packaging is complete, labels are correct, and strapping is properly applied⁹⁵.

2. Predictive Maintenance:

AI algorithms analyze data from equipment sensors (vibration, temperature, current, etc.) and historical maintenance records to predict potential equipment failures, allowing for proactive maintenance scheduling and minimizing unexpected downtime¹⁰⁸. This is a key means of improving Overall Equipment Effectiveness (OEE)¹⁰⁸.

3. Process Optimization:

AI can analyze large amounts of production process data (such as wrapping tension, strapping force, machine speed, material consumption, etc.), identify key factors affecting efficiency and quality, and adjust control parameters in real-time to achieve optimal status⁹⁶. For example, optimizing wrapping patterns to reduce film usage or adjusting strapping parameters to ensure firmness while avoiding damage to the coil.

F. Industry 4.0 Integration

Industry 4.0 represents the digital and networked transformation of manufacturing, and steel coil packaging lines are an important application scenario within it.

1. Internet of Things (IoT) and Remote Monitoring:

• Data Acquisition: Real-time collection of large amounts of operational data through various sensors (position, temperature, humidity, vibration, vision, etc.) and smart devices deployed on the packaging line¹¹.
• Remote Monitoring and Diagnostics: Using networks to transmit collected data to cloud platforms or central control rooms, managers can monitor the status, performance indicators (KPIs), and equipment health of the production line anytime, anywhere via computers or mobile devices¹¹. This enables rapid response to faults, remote diagnostics, and maintenance. Pesmel’s FlowCare¹³ and Cefla’s cMaster¹⁰⁹ are examples of such applications.
• Predictive Maintenance: IoT data is the basis for implementing predictive maintenance¹⁰⁸.

2. Digital Twins:

• Concept: Creating a virtual replica of a physical packaging line or its components¹³. This virtual model can receive real-time data from the physical system and simulate its behavior.
• Applications:
  • Design and Optimization: Before actual construction or modification, use the digital twin to simulate different layouts, equipment configurations, and control strategies, evaluate their performance (such as throughput, bottlenecks), and choose the optimal solution¹⁰⁹.
  • Virtual Commissioning: Test and debug control software in a virtual environment, reducing on-site commissioning time and risks.
  • Operator Training: Provides a safe virtual environment for operators to practice operations and handle exceptions¹¹⁰.
  • Real-time Monitoring and Prediction: Inputting real-time data into the digital twin model allows predicting future states and identifying potential problems in advance¹¹¹. Nippon Steel¹¹¹ and Pesmel¹³ both use digital twins or simulation technology in their logistics or production systems.

3. Communication Protocols:

Standardized communication protocols are needed to enable device interconnection and data exchange.

• OPC UA (Open Platform Communications Unified Architecture): A key communication standard recommended for Industry 4.0, featuring platform independence, security (certificate-based encryption and authentication), strong data modeling capabilities (can describe complex equipment and information), and interoperability¹⁰⁹. It supports both client/server and publish/subscribe (Pub/Sub) communication modes, the latter suitable for real-time transmission of large amounts of data and can be combined with protocols like MQTT¹¹². OPC UA aims to bridge the data gap between OT (Operational Technology) and IT (Information Technology) layers¹¹³. Industry-specific information models (Companion Specifications) further enhance its application in specific fields, such as packaging machinery¹¹². Omron’s NX102 controller is an example of a PLC supporting OPC UA¹¹⁴.
• MQTT (Message Queuing Telemetry Transport): A lightweight, publish/subscribe-based messaging protocol particularly suitable for IoT scenarios with limited bandwidth and computational resources¹¹⁵. It forwards messages through a central broker, decoupling publishers and subscribers¹¹⁶. MQTT has advantages such as low overhead, support for different Quality of Service (QoS) levels, and ease of integration¹¹⁶. It is commonly used to send sensor data to cloud platforms or higher-level systems. OPC UA can be integrated with MQTT through gateways or Pub/Sub mode¹¹².
• Other Protocols: Traditional fieldbuses (such as Modbus, PROFIBUS, DeviceNet¹¹⁷) and industrial Ethernet protocols (such as PROFINET, EtherNet/IP, EtherCAT⁹⁰) are still widely used at the device level. OPC UA can be integrated with these lower-level protocols as an upper-layer protocol¹¹⁷.

The advancements in sensor technology, especially the combination of machine vision and AI, enable automated systems to perceive and understand more complex environments and objects, thereby achieving finer operations and more reliable quality control⁹⁵. For example, through deep learning models like Mask R-CNN, the system can accurately identify coil end faces and guide robots for precise operations⁶⁶.

The trend in control systems is towards integration and intelligence. The vertical integration of PLC, HMI, SCADA, MES, and ERP breaks down information silos and achieves data flow from order to production execution and enterprise management, providing a basis for optimized decision-making¹⁴.

The application of AI and IoT technologies, particularly predictive maintenance and digital twins, is transforming the management of steel coil packaging lines from reactive response to proactive prediction and optimization, which is revolutionary for improving equipment reliability, reducing downtime, and optimizing resource utilization¹⁰⁸.

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