Steel Coil and Copper Coil Packaging Machine for Eye-Through Film Wrapping

Executive Summary: Eye-through film wrapping (radial/toroidal wrapping) passes protective stretch film, paper, or VCI material through the central hollow core (“eye”) of steel and copper coils and across their radial circumference. By synchronizing coil rotation on heavy-duty polyurethane cradle rollers with high-speed orbital ring travel through the bore, this automated method delivers complete, hermetically sealed 360° protection. It eliminates internal condensation, edge chafing, and atmospheric oxidation during harsh intermodal transport and long-term storage, meeting strict ISO 9001 and EN 415-6 packaging standards.

How Eye-Through Wrapping Works

Eye-through coil wrapping (through-the-eye wrapping) protects heavy rolled metals by applying overlapping film spirals through the internal diameter (ID) and across the outer diameter (OD), encapsulating the coil body, side faces, and bore edges in a continuous, tight wrap.

Unlike conventional pallet wrappers that only wrap external cylindrical profiles, an eye-through wrapper coordinates two synchronized motion axes:

1. Toroidal Carriage Revolution: A high-precision circular ring or orbital shuttle carriage guides the pre-stretch film roll axially through the coil eye and loops back around the outer shell.
2. Axial Coil Rotation: The coil rests on motorized, polyurethane-coated support rollers (cradle rolls) that slowly index it around its horizontal centerline.

The automated industrial cycle runs through six controlled sequences:

1. Coil Infeed and Loading: A C-hook crane, walking beam, or automated guided vehicle (AGV) lowers the slitted or mill-run coil onto heavy-duty blocker/cradle rollers.
2. Geometric Centering and Clamping: A pneumatic or hydraulic overhead stabilizer roller (top hold-down roll) engages the top OD to prevent narrow coils from tilting or shifting under wrapping tension.
3. Bore Alignment and Shuttle Entry: The ring mechanism aligns with the coil’s core axis; optical sensors verify the internal diameter clearance before motion begins.
4. Synchronized Spiral Wrapping: The orbital ring drives the film carriage through the hollow center at up to 100 RPM while the cradle rollers rotate the coil at an electrically geared ratio. Overlap is adjustable between 30% and 70% to produce a continuous hermetic seal.
5. Film Clamping and Cutting: A pneumatic arm grips the film tail, cuts it with a heated impulse blade or mechanical shear, and wipes the flap against the coil body.
6. Ejection and Transfer: The hold-down roller releases and the wrapped coil advances onto an outfeed chain conveyor or downender for labeling and shipping.

Machine Specifications

Industrial-grade packaging systems handle varied coil gauges, slit bundles, and heavy master coils within rigid mechanical envelopes:

Eye-Through vs. Surface-Only Wrapping

Applying protective wrap exclusively across the outer cylinder diameter leaves the hollow bore and coil sidewalls exposed to moisture, airborne salts, and mechanical abrasion.

Metal-Specific Wrapping Sequences

Ferrous and non-ferrous metals demand different packaging layers due to differing surface reactivity, hardness, and sensitivity to staining.

Carbon Steel and Slit Steel Coils

Cold-rolled, galvanized, and silicon steel coils require high mechanical clamping forces and active chemical vapor barriers:

• Primary Inner Layer: Volatile Corrosion Inhibitor (VCI) film, whose molecules vaporize and create a non-reactive molecular layer across bare steel to block water vapor and oxygen.
• Secondary Structural Layer: High-puncture-resistant LLDPE cast film (25–35 µm) applied at 200%–250% pre-stretch to seal the VCI layer and resist sharp slit edges.
• Outer Protective Wrap (Optional for Export): High-density polyethylene (HDPE) woven tape or corrugated edge rings preventing mechanical damage during C-hook and fork handling.

High-Purity Copper and Brass Coils

Copper coils present high density (8.96 g/cm³), soft surfaces prone to scratching, and sensitivity to discoloration:

• Surface Protection: Low-tack, sulfur-free, neutral contact film applied under reduced tension to eliminate stretch adhesive residue and avoid scratching finished strip surfaces.
• Tension Control: Dual load-cell closed-loop unwinds maintain uniform, lower wrapping tension (15–30 N) to prevent edge folding or crimping on thin-gauge copper strips.
• Atmospheric Isolation: A multi-layer UV-blocking, anti-tarnish vapor barrier prevents black oxidation and patina development caused by humidity and acidic air.

Pre-Stretch Technology

Advanced coil wrappers use a powered dual-roller pre-stretch system mounted directly on the traveling film carriage.

Two rollers rotate via synchronized mechanical timing belts or independent servomotors. The downstream roller turns faster than the upstream roller, stretching the film before it leaves the carriage:

Pre-Stretch Ratio (%) = [(L_final - L_initial) / L_initial] × 100

A 250% pre-stretch ratio turns 1 meter of raw film into 3.5 meters of usable wrap:

• Material Cost Reduction: Pre-stretch cuts virgin film consumption by 45%–60% versus traditional friction-brake tensioners.
• Molecular Alignment: Pre-stretching aligns the polymer chains of linear low-density polyethylene (LLDPE), increasing tensile yield strength and puncture resistance while reducing neckdown.
• Residual Wrap Force: The film retains elastic memory, applying continuous radial compression across the coil pack without crushing soft copper edges or delicate slit coils.

Safety and Operational Integration

Heavy rotating rings and coils weighing several tons require engineered safety controls compliant with EN ISO 13849-1 and EN 415-6:

• Physical Guarding and Interlocks: Perimeter fencing (minimum 2,000 mm) with dual-channel magnetic safety interlock switches that trigger safe stops when service gates open.
• Optical Infeed/Outfeed Safety: Category 4 safety light curtains at the coil entry and discharge portals use muting sensors to distinguish moving coils from human entry.
• Anti-Drop Ring Retainers: Counterbalanced orbital rings feature secondary mechanical fall arresters and anti-derailment guide wheels, protecting operators during drive-chain or timing-belt fatigue.
• Automation and HMI: Siemens or Allen-Bradley PLCs linked to industrial touchscreens call up coil wrap recipes based on coil ID, OD, width, and metal type.

Maintenance Requirements

Reliable operation requires preventative maintenance on all mechanical drive and tensioning assemblies:

• Daily Inspections:
  • Check the film carriage cutter blade and clean away film dust or adhesive build-up.
  • Verify that emergency stop circuits, trip bars, and safety light curtain optics are unobstructed and functional.
• Weekly Services:
  • Lubricate orbital ring drive chains, guide rollers, and support tracks with specified synthetic grease.
  • Inspect cradle-roller polyurethane surfaces for embedded chips or wear that could mark finished metal coils.
• Monthly Preventative Audits:
  • Check drive belt tension on the powered pre-stretch rollers and clear accumulated plastic debris.
  • Confirm dynamic calibration of load-cell film tension dancers and ring proximity sensors.
• Quarterly Certification:
  • Check ring guide-bearing clearances to maintain rotation alignment within ±0.5 mm.
  • Measure motor current draw, inspect gearbox oil levels, and torque-test all main chassis anchor bolts.

Selection Considerations

To select the proper through-the-eye wrapping machine, evaluate your production requirements against these engineering parameters:

1. Dimensional Envelope: Determine the minimum bore ID, maximum OD, maximum width, and maximum weight per coil package.
2. Cycle Time and Capacity: Match required hourly throughput to line speeds and choose between an orbital continuous ring wrapper or a high-capacity shuttle wrapper.
3. Packaging Material Mix: Identify whether single stretch film, dual-layer film plus woven tape, or combined VCI protective films suit your shipping environments.
4. Plant Layout Integration: Confirm infeed/outfeed heights, floor loading ratings (MPa), overhead crane reach, and tie-ins to automated coil cars, walking beams, or downstream strapping tables.
5. Electrical and Control Architectures: Specify regional fieldbus protocols (Profinet, EtherNet/IP), control voltage standards, and industrial safety ratings.

Next Steps

To evaluate through-the-eye packaging systems for your steel or copper coil line:

1. Compile Production Data: Document your coil inner/outer diameters, strip widths, coil weights, and required processing counts per hour.
2. Submit Parameters for Engineering Review: Contact the engineering team at info@fhopepack.com with your dimensional matrix, plant floor drawings, and packaging specifications.
3. Receive a Customized Technical Proposal: We will deliver a complete layout package, including 3D line diagrams, cycle time calculations, film stretch analysis, and utility consumption estimates.
4. Approve Engineering Submittals: Complete collaborative design reviews with our mechanical engineering team to finalize your coil handling equipment.
5. Installation and Commissioning: Original factory engineers oversee field installation, electrical tie-in, recipe tuning, and full operator training.