Executive summary Our radial steel coil strapping machine passes a high-tensile steel band through the coil eye and around the cross-sectional wall, mechanically locking the wraps to prevent coil telescoping, lateral shifting, and edge loosening during crane lifting and sea freight. Equipped with a 360-degree indexing strapping head and traversing arch, the system accurately applies multiple radial straps at any programmed angular increment while the heavy coil remains completely stationary. Engineered to feed standard and high-tensile steel straps from 19 mm to 32 mm wide, the machine operates in semi-automatic or fully integrated automatic modes. Circumferential (OD) strapping is handled by a complementary downstream station, forming a comprehensive coil packaging line.
Table of Contents
- Radial or circumferential bands
- How the radial machine works
- Work out band length
- Protecting the coil edges
- Machine data
- Utilities and safety
- Selection checklist
- Engineering FAQ
- Next step
- Related reading
- Sources
Radial or circumferential bands
Securing steel coils for transit requires two distinct strapping geometries, each addressing specific dynamic forces encountered during storage, handling, and logistics:
| Strap Type | Placement & Trajectory | Mechanical Function & Load Restraint |
|---|---|---|
| Radial (Eye-through) | Passes through the inner eye, across both radial faces, and around the coil wall | Mechanically binds coil wraps together; prevents axial telescoping and inter-wrap slipping during crane lifting |
| Circumferential (OD) | Encircles the external outer diameter along the strip face | Clamps the loose outer tail securely against the circumference; prevents unraveling caused by coil recoil |
A coil destined for overhead crane handling with C-hooks, coil grabs, or intermodal sea transport always requires radial eye strapping. Handling vibrations and tilting forces push the individual inner wraps sideways. Once telescoping begins, severe damage occurs to the strip edges, making decoiling in downstream processing lines impossible.
Circumferential bands retain strip tail tension, but they cannot resist axial thrust loads. Our automated packaging lines specify the required number of radial straps (typically 3, 4, or 6 bands placed at symmetric 120°, 90°, or 60° intervals) determined by coil weight, width, strip thickness, and transit distance.
How the radial machine works
The radial strapping system integrates a high-rigidity structural gantry, a traversing track arch, and an automatic strapping head mounted on a 360-degree precision rotating turret.
[Coil on Stationary Saddle]
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[Gantry Lowers Strapping Arch Through Coil Eye]
│
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[Feed & Track Clamping] ──► [High-Torque Tensioning] ──► [Sealless Notch / Weld Seal]
│
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[Arch Retracts] ──► [Turret Indexes to Next Angle (e.g., 90°)] ──► [Repeat Cycle]- Stationary Positioning: The master steel coil enters the strapping station via an automated coil car or walking beam conveyor and rests firmly on heavy-duty polyurethane-lined V-saddles.
- Arch Penetration: The horizontal track arch extends pneumatically or via servo drive, passing cleanly through the bore (eye) of the stationary coil to complete the guide loop.
- High-Speed Feed and Retract: The strapping head feeds steel strap around the modular guide track at up to 2.5 m/s, senses track arrival, initiates strap retract, and pulls the loop taut against the coil profile.
- Controlled Tensioning: Tension is applied dynamically via a secondary tensioning wheel, reaching adjustable loads between 5,000 N and 18,000 N to match specific strip thicknesses without exceeding strap yield points.
- Joint Execution: The machine joins the overlapping strap using one of two methods:
- Sealless Triple/Quadruple Notched Joint: Interlocking punched keys with joint efficiency of 75% to 80%, eliminating external seal clips.
- TIG / Resistance Welded Joint: A flat, flush welded seam providing up to 85% to 90% joint efficiency, ideal for automated uncoiler mandrel clearance.
- Angular Indexing: The arch retracts to clear the bore, and the rotating head assembly indexes to the next target angle via an absolute-encoder-controlled turntable. The coil never rotates on the saddle, eliminating surface scuffing and edge distortion on critical-finish strip.
Work out band length
Calculating strap consumption accurately is essential for production cost modeling and dispenser spool changeover scheduling. The physical perimeter of one complete radial loop encompasses both strip widths (inside bore face and outside circumference face) plus both radial wall thicknesses:
Theoretical Cross-Section Perimeter = 2 × Width + (OD − ID)To account for actual production conditions—including strapping head take-up stroke, track bend allowances, and sealing overlaps—use the practical shop-floor equation:
Total Radial Strap Length per Band = 2 × Width + (OD − ID) + L_allowance(Where L_allowance typically equals 150 mm to 200 mm for tensioner reverse stroke and seal overlaps).
Engineering Calculation Example
For a production steel coil with Outer Diameter (OD) = 1,500 mm, Inside Bore (ID) = 610 mm, Width = 1,200 mm, and L_allowance = 150 mm:
| Calculation Item | Mathematical Formula & Input | Total Consumption |
|---|---|---|
| Radial Wall Thickness (Single Side) | (OD − ID) / 2 = (1,500 − 610) / 2 | 445 mm |
| Combined Face Thickness (Both Sides) | OD − ID = 1,500 − 610 | 890 mm |
| Net Cross-Section Loop Length | 2 × 1,200 mm + 890 mm | 3,290 mm |
| Total Length per Radial Band (with Allowance) | 3,290 mm + 150 mm | 3,440 mm (3.44 m) |
| Complete 4-Radial-Band Pattern | 4 × 3,440 mm | 13.76 m |
| Circumferential Band (Outer Diameter) | π × OD + 150 mm = (3.1416 × 1,500) + 150 | 4.86 m |
Factoring in a scrap factor of approximately 3% for coil changeover threading ensures reliable inventory planning for shift-based high-output operations.
Protecting the coil edges
A 32 mm high-tensile steel strap pulled under 12,000 N of tension exerts extreme contact pressure over right-angle coil corners. Without proper protection, this causes two critical failure modes:
- Coil Defect: The band cuts into outer strip wraps, causing edge notch damage that forces end-users to crop and scrap the first 10 to 30 meters of material.
- Strap Rupture: Sharp slit-strip edges introduce shear stress raisers onto the strap, increasing the risk of premature band snapping during sea-freight vessel rolling.
To prevent product damage, our radial strapping machine can be integrated with an Automatic Edge Protector Applicator. The robotic arm feeds and positions heavy-duty paperboard corner angles (V-profiles) or plastic edge channels directly beneath the strap path at both the OD and ID corners prior to tensioning. The protection is clamped solidly into place during the sealing cycle without slowing line throughput.
Machine data
| Technical Specification | Standard Configuration | Heavy-Duty / High-Output Option |
|---|---|---|
| Strapping Orientation | Radial / Eye-through (vertical or horizontal eye) | Programmable multi-angle index |
| Strapping Head Rotation | 0° to 360° indexing via servo drive | Precision continuous indexing (±1° accuracy) |
| Strap Material Compatibility | Steel strap (Standard & High-Tensile) | Dual head: Steel or PET strap |
| Strap Width Range | 19 mm, 25 mm, 32 mm | 32 mm heavy-gauge (up to 1.0 mm thickness) |
| Joint Sealing Method | Sealless triple-notch interlock | High-efficiency electric weld / TIG joint |
| Strap Tension Range | 3,000 N – 14,000 N adjustable | 5,000 N – 18,000 N closed-loop control |
| Applicable Coil Width | 600 mm – 2,000 mm | Extended up to 2,500 mm |
| Applicable Coil Outer Diameter | 900 mm – 2,200 mm | Custom-engineered to 2,600 mm |
| Applicable Coil Inner Diameter | 508 mm, 610 mm, 760 mm | Down to 400 mm minimum bore |
| Head Service Life | Up to 1,000,000 cycles before major overhaul | Modular wear-part exchange kits |
| Auxiliary Options | Automated corner/edge protector applicator | Integrated optical strap presence verification |
Utilities and safety
Control Integration & Utilities
The electrical system accommodates global industrial line voltages (380V, 400V, 460V, 480V 3-phase, 50/60 Hz). The system is powered by an onboard Siemens S7-1500 or Allen-Bradley GuardLogix PLC system, communicating seamlessly via Profinet or Ethernet/IP with customer walking beams, coil cars, and higher-level MES architectures. Compressed air requires clean, dry air at 0.6 MPa to 0.7 MPa.
Operator Safety & Machine Guarding
Steel strapping pulled under high tension stores elastic energy. Under European CE and international industrial safety regulations, the following standards govern the machine layout:
- ISO 12100:2010: Comprehensive risk mitigation and machinery safety principles.
- EN 415-10:2014: Safety requirements for automated packaging, strapping, and handling machines.
- ISO 13849-1 (Category 4 / PL e): Safety circuit integration for all perimeter light curtains, interlocking service access gates, and safety dump valves for pneumatic/hydraulic motion.
All access zones around the rotating turret and lowering gantry are protected by perimeter safety fencing and dual-channel optical interlocks. Maintenance latch pins lock the head mechanically during cutter and jaw servicing.
Selection checklist for a radial coil strapping machine
- Coil Dimensional Envelope: Minimum and maximum Outer Diameter (OD), Inside Diameter (ID), and strip Width.
- Weight Parameters: Minimum and maximum coil mass (metric tons) to determine support saddle rating.
- Strip Grade & Surface Finish: Hot-rolled black, cold-rolled, galvanized, stainless steel, or silicon steel (critical for edge protection selection).
- Strapping Pattern: Target cycle time and number of radial bands (3, 4, or 6 bands).
- Strap Specification: Strap width (19 mm, 25 mm, or 32 mm), grade (regular duty vs. high-tensile), and joint type (notched vs. welded).
- Upstream & Downstream Integration: Coil delivery method (walking beam, overhead crane, saddle conveyor, or V-type coil car).
- Edge Protection Requirements: Manual pad placement or fully automated cardboard applicator.
- Utility Specifications: Plant operating voltage, frequency, and compressed air availability.
Engineering FAQ
Q: Why choose a stationary-coil radial strapping design over a roller-rotated system? A: Heavy steel coils weighing 15 to 35 tons cause significant friction when rotated on turning rollers, frequently leading to outer-wrap surface scratching, edge burring, or telescoping on high-surface-quality steels. Our design turns the lightweight head and arch 360 degrees around the coil, keeping the heavy load completely static.
Q: Do we still require a separate circumferential strapping machine? A: Yes. Radial straps secure the internal wraps through the eye to prevent axial shifting, but they do not clamp the outer strip tail. A circumferential strapping station wraps around the outer diameter to keep the tail flat, ensuring safe handling on conveyor beds. High-capacity mills utilize both units inline.
Q: When should we select a welded joint over a sealless notched joint? A: Sealless punch-notched joints are fast and cost-effective, eliminating consumable seal clips for general logistics. Welded joints provide higher joint efficiency (up to 90%) and leave a flat, flush seam. This eliminates snagging risks inside automated uncoiler jaws and prevents punch marks on sensitive sheet grades.
Q: Can the machine switch between steel strap and heavy-duty PET strap? A: Yes. We can configure the strapping gantry with modular, interchangeable heads. For lines transitioning lighter coil batches from steel to 25 mm or 32 mm heavy-duty polyester (PET) strap, our quick-disconnect mounting interface allows rapid conversion.
Next step
Optimize your coil packaging line throughput and secure your inventory against transit damage with our technical engineering team:
- Submit Line Data: Send your coil envelope dimensions, line cycle rate, and mill layout drawings to info@fhopepack.com.
- 48-Hour Engineering Review: Receive a preliminary 3D footprint layout, strapping pattern recommendation, and cycle-time calculation within 48 hours.
- Interface Alignment: Schedule a technical video conference with our project engineers to align PLC handshakes, safety zoning, and coil car transfer heights.
Related reading
- Radial Steel Coil Strapping Machine Engineering Specifications
- Automated Circumferential Steel Coil Strapping Machines
- Heavy-Duty PET Strap Solutions for Steel Coil Packaging
Sources
- Equipment Data: Radial Steel Coil Strapping Machine Technical Portal
- Process Integration: Circumferential Coil Strapping System Engineering Overview
- Machine Safety: ISO 12100:2010 Risk Assessment Principles
- Packaging Machinery Directives: EN 415-10:2014 Safety of Strapping Machines
Last reviewed: 2026-10-04
