Strapping

Strap is a flat, flexible material, most commonly made from steel or various types of plastic.

Steel is used for heavy duty holding where high strength and minimal stretch are desired.

Common applications include steel coils, bundles of metal, baling wire, bricks and other pavers, and roll end-binding.

[1] Polypropylene strap (oriented or tensilized) is an economical material designed for light to medium duty unitizing, palletizing, and bundling.

This product offers higher elongation at break, but tends to have irrecoverable dead stretch with constant stress.

For instance, in cold climates a strap bonded in hot melt glue is used because it is weather-proof.

[citation needed] Nylon strap has the greatest specific strength of the three plastics, but it is rarely used due to its high price.

Because corded and woven polyester straps are light and soft, they are also a safer alternative to steel banding.

This allows the bundle to be introduced into the process without cutting the straps, which can lead to the product falling apart prematurely.

The polypropylene provides foam to the strap, but also improves the non-slip characteristic when combined with the wire buckle.

[citation needed] Examples include: Strapping is most often used in complete horizontal or vertical bands.

For lighter gauge strap, usually 16 mm (0.63 in) and narrower, heat is introduced with a hot knife system.

Then a platen comes up and compresses the straps and hot knife against an anvil on the order of tens of milliseconds.

Polypropylene and Polyester strapping can also be sealed in a similar manner with the heat being produced by sound in the form of Ultrasonic waves passing through the materials and exiting the molecular structure.

The interface of the two parts is specially designed to concentrate the energy for the maximum weld strength.

The joint is the weakest part of the system, therefore the type of joining method used is very important if strength is an issue.

The strength of a joint is defined as the force required to break the strap in uniaxial tension.

Well set up strapping machines or friction weld tools will aim for around 80% of break strength.

Non-powered separated dispensers have a pulley which releases and activates a brake to stop the inertia of the coil and keep the strap from over-running[definition needed] onto the floor.

A photocell is used to detect when the bundle is in the correct location, stop the conveyors, and activate the strapping machine.

Semi-automatic and fully automatic strapping machines substantially improve efficiency in a warehouse and also the overall presentation of a packaged product.

These machines are operated either by foot pedal or parcel sensor, which makes them ideal for volume throughput.