PPGI Coil Packing Line: Surface & Edge Protection | FHOPE

PPGI Coil Packing Line: Preventing Edge and Surface Damage

In prepainted steel coil packaging, and on a prepainted galvanized steel (PPGI) coil in particular, the paint is the product. A chipped edge or a pressure mark on the coating is visible to the end customer and usually means a claim. When we design an automatic coil packing line for PPGI, we start by asking where the edges and the painted surface can be touched, from coil transfer to strapping, and we build each station to control that contact.

Critical PPGI Surface and Edge Damage Risk Points

For a PPGI coil, the risk points are the steps where the coil is moved or squeezed:

• Transfer and positioning: the coil car saddles and the rollers that rotate the coil
• Wrapping: the layer that touches the painted surface and how tightly it is applied
• Edges: the outer and inner edges of the coil during handling and stacking
• Strapping: the strap pressing on the edge and the coated surface

The image shows an automatic steel coil packing machine with an operator nearby. The finish risks begin before the wrapper: infeed support, side guidance, protector placement, and transfer can all touch the coating while the coil moves through the line.

Line Configuration for PPGI Coils

Our PPGI coil packaging line is built from these units:

Protecting the Painted Surface

PU-Covered Contact Rollers

The PU cradle rollers that carry and rotate the coil at the block roller station are covered with polyurethane, so the coil does not run on bare steel rollers.

Layer Sequence on the Coating

For eye-through wrapping we normally use stretch film. A film roll is long, so the wrapper keeps running without frequent reloading. Paper can also be wrapped, but paper rolls are short: on a large PPGI coil, one paper roll may not finish a complete package, so the operator must reload more often. Where a paper layer is specified, it is wrapped under the film against the coating (see our video on steel coil packing with paper and stretch film).

Wrapping Tension and Overlap

Film tension and overlap are adjustable. Our wrappers can set the overlap anywhere from 20% to 90%, so the number of film layers over the coating and edges can be matched to the shipping route.

The image shows an automatic film application station with an operator nearby. The recipe defines which film layer touches the coated surface and how the sequence is applied without trapping debris under the package.

Outer and Inner Edge Protection Systems

• Outer edge protectors: automatic (optional device). With the optional outer edge-protector device, the machine feeds outer edge protectors (plastic or kraft paper) together with the wrap during eye-through wrapping. Automatic application covers the outer edge only.
• Inner edge protectors: manual or robot. The inner bore edge protectors are fitted by an operator or by a robot. We plan this station into the line layout.

Strapping Without Marking the Coating

The strapping station on the PPGI line is optional and semi-automatic. Strapping happens after wrapping, so the strap sits on the film and edge protectors rather than on bare paint, and steel coils generally do not need extra pads at the strap points. Pads are mainly used for soft metals such as aluminum, and they are usually cardboard.

• Steel strap: holds the coil together so it does not unwind or spring loose during transport.
• PET strap: secures the package, for example to fix the coil to a pallet or to hold formed inner and outer edge protectors in place.

Wide coils, such as 1000 mm wide coils, can be strapped automatically or manually. Because strapping is done over the wrap, strap tension marking on the paint is kept off the bare coating.

Watch coil packing machinery and a coil stretch wrapper in operation:

Avoiding Contamination on Mixed Lines

PPGI is often packed on the same line as GI, CR and EGI coils. We have designed slit-coil lines for customers who run all of these products together.

Mixed-Coil Line Changeover Protocol

When the line changes over from bare steel to PPGI, we recommend cleaning the PU rollers and saddles, then checking the first coil before the batch is released.

Checking the Packed Coil

Before release, check that:

• edge protectors are present and in position
• where paper is specified, it lies fully under the film
• the straps sit on the wrapped package
• the label (weight and bar code) is correct

The image shows the labeling process on a coil packaging line. Final release for PPGI should confirm identity and label accuracy together with edge and surface checks, so the coil is not rejected later for a missing or mismatched record.

Slit PPGI Coil Packaging Specifications

For slit PPGI coils, our slit coil packing line equipment also applies:

• Slit coil line range: 100–3000 kg, OD 900–1400 mm, ID 508 mm, width 15–450 mm, 20–30 coils/h
• Down-ender with PU-covered conveyor; Siemens PLC + HMI
• See also our slit coil stretch wrapping and stacking line.
• Narrow slit coils of around 15 mm are generally strapped manually: secured with tape, tilted 90°, then strapped through the eye with PP or PET strap (2, 3, 4 or 6 straps).

FAQ

Which parts of the line touch the painted surface? The coil car saddles and the PU-covered rollers of the block roller station. Inside the package, the inner wrap layer (film, or paper where specified) sits against the coating.

Can edge protectors be applied automatically? Outer edge protectors, yes: with the optional outer edge-protector device, the machine applies them during eye-through wrapping. Inner edge protectors are fitted manually or by a robot.

Do strap points need pads on PPGI coils? Generally no. The coil is already wrapped when it is strapped. Cardboard pads are mainly used for soft metals such as aluminum.

When should steel strap or PET strap be used on PPGI coils? Steel strap keeps the coil from unwinding in transport. PET strap secures the package to a pallet and holds the edge protectors in place. A semi-automatic strapping station is available as an option.

What are the coil capacity limits? 1–30 t per coil, OD 800–1800 mm, width 500–1800 mm, ID 508–610 mm.

Film or paper? Stretch film is standard because film rolls run long. Paper is optional as an inner contact layer, but needs more frequent roll changes on large coils.

What warranty do you give? We give a 2-year warranty.

Can I add more film layers for long export routes? Yes. The overlap is adjustable from 20% to 90%, which increases the number of film layers over the coating and edges.

How do you avoid contamination when switching from bare steel to PPGI? We recommend cleaning the PU rollers and coil car saddles, then checking the first coil before the batch is released.

How are inner bore edge protectors applied? Manually by an operator or by a robot.

Can the line label coils? Yes. A weighing and labeling machine applies bar-code labels after wrapping.

Can it handle narrow slit PPGI coils? Yes. Our slit-coil packing line takes coils 15–450 mm wide and 100–3000 kg. Narrow coils of around 15 mm are generally strapped manually through the eye with PP or PET strap.

The image shows fully packaged steel coils prepared for shipment. The release record for PPGI should confirm the layer sequence, edge protection, strap-contact control, and changeover reset before the package leaves the line.

Every PPGI line carries our 2-year warranty and lifetime technical support. Send us your PPGI coil sizes and coating-protection requirements for a line layout on your automatic coil packing line, or contact us.