Pallet equipment: All wrapped up

When buying pallet wrapping equipment, one of the most fundamental choices is whether to spend a little on a manual, a little more on a semi-automatic or a lot more on an automatic model. Which of these you go for will determine the speed at which pallets are wrapped, the level of operator intervention needed and the amount of film used.

Martin Taylor, sales manager with Sontex Machinery, explains the basic design differences between manual, Semi-automatic and automatic machines.

A manual machine requires the operator to tie the stretch film to the pallet, press the start button to begin the rotation of the turntable and then use a lever or up/down buttons to control the rise and fall of the stretch film carriage. “The operator manually controls the number of wraps at the top and bottom of the pallet, stops the film carriage at the desired height and is required to remain with the machine throughout the cycle.”

A semi-automatic machine requires the operator to attach the stretch film to the pallet, then press the start button. The machine is operated via a programmable PLC to control the number of wraps at the top and bottom of the pallet. It also uses a light beam sensor to automatically detect the top of the pallet. “These features mean an operator does not need to stand next to the machine during its wrapping cycle,” he says.

“A fully automatic machine is presented with pallets via an infeed conveyor and needs no operator intervention. It is completely enclosed in a safety cage and the pallets are ejected at the end of the cycle.”

Making the choice
To an extent, the budget and number of pallets that will be wrapped each day will determine which of these is most suitable.

According to Jacqueline Glover, sales executive with Inpac Automation, as a guide, if you need to wrap more than two pallets per hour you should consider semi-automatic. She says you can generally expect to achieve up to 20 pallet loads per hour from a semi-automatic machine and up to 130 pallet loads per hour from a fully automatic machine.

Aetna national sales manager Paddy McCartney adds that anything over 10 pallets an hour calls for either a semi or a fully automatic machine, and puts the throughput range of automatic machines at between 20 and 160 pallets per hour.

Price-wise, Glover says semi-automatic machines tend to fall into the £4,000-£8,000 bracket, while fully automatic machines cost upwards of £40,000. Operater-controlled manual machines can be picked up for as little as £2,000.

But although capital cost and speed are important, there are other factors to take into account, such as film costs, health and safety and space constraints. Manual machines might cost the least, are portable and can wrap awkward loads, but these benefits are set against high film costs and poor film economy.

“You pay a premium for hand film as the film is made to machine film size and you have to pay for the time taken to wind the film on to smaller reels, says McCartney. It is also difficult to hand wrap to the base of the pallet, the maximum stretch you will get is 20% and wastage is generally about 20%.”

He says film economy is slightly improved on a semi-automatic machine, as standard machine film is used, but maximum stretch is 40-50%.

For really good film economy, you have to go to a fully automatic machine with power pre-stretch. “Power pre-stretch is the most cost-effective method of stretch wrapping pallets and gives the best load containment, says McCartney. Our Rotoplat 507PFS stretches the film 250%.”

McCartney advises any company wrapping 40 pallets or more a day to invest in a power pre-stretch machine on the basis of the film savings they will make. “Wrap costs are up to 50% less than for a standard machine on a like-for-like wrap and pallet stability will be better,” he says. “Very light items, such as empty plastic bottles, can only be wrapped correctly with power pre-stretch.”

His advice is echoed by Malcolm Dykes, general sales manager at Orion Packaging Machinery, who estimates that pre-stretching typically results in film savings of up to 70% over hand wrapping, and says that machines for wrapping fragile products should have power pre-stretch, as this not only reduces the possibility of product damage, but also optimises film use.

He warns against cheaper ‘core brake’ systems on the grounds that they can suffer from ‘necking down’ – in other words reducing the width of film applied. This means more film is used, and the film is not properly stretched and therefore will not contract sufficiently to hold the load in place.

Additional benefits
Semi-automatic and automatic machines score more favourably on the health and safety front too. By law, all automatic machines must be fully guarded, minimising the risk of operator injury.

“As companies seek to reduce the amount of manual handling and decrease days lost due to medical problems arising from hand wrapping, this is driving the increased use of automated and semi-automatic stretch wrappers,” says Dykes.

Even once you’ve decided on the level of automation for your wrapping operation, you still need to know what type of wrapper is going to be most suited to the task in hand.

Low- and medium-speed applications (up to 40 pallets per hour) tend to be best carried out by a ‘rotating’ or ‘turntable’ pallet wrapper.

Rotating arm and ring machines are usually chosen where speed is a priority. Both of these wrap film around a stationary pallet as opposed to rotating the pallet on a turntable. Ring machines have a slight edge in speed terms, according to McCartney, as they tend to be capable of up to 100 pallets per hour with top sheet or without, while rotary arm wrappers max out at 80 pallets per hour without top sheet or 45 pallets with top sheet. That said, there are now double-arm systems available, which can wrap up to 160 pallets per hour.

McCartney says robotic wrappers are ideal for extremely large pallets, heavy items, low-speed applications and when a portable machine is needed.

Cheap not cheerful?
There’s also the question of who to buy from. Spain and Italy have a reputation for building the best quality stretch wrappers, but the prices of equipment imported from the Far East are more attractive. However, as Sontex’s Martin Taylor warns, cheaper imports may turn out to be a false economy.

“To cut costs, cheaper components such as motors and gearboxes and thinner metals are used for the fabrication and turntable and their frailties soon become apparent when they are faced with two-tonne pallets. Some are also supplied with very questionable CE certificates.”

His concerns are shared by Orion’s Dykes, who warns that not all imported machines comply with UK law. “Current UK health and safety regulations stipulate a 50mm clearance on all four corners of the turntable and a 500mm gap around the turntable. However, not all CE standards of conformity are published yet, meaning imported machines need only comply with the national standards in their country of origin. Many overseas machines are only fitted with a 1,500mm turntable, which can lead to pallet overhang and could cause ‘entrapment’, where a person is caught between the rotating pallet and either a wall or the fixed part of the machine.”

He adds that UK law also requires all control panels to have a safety reset button and protected wires, but that again, this does not apply to imported machines.

Ultimately, the adage ‘buyer beware’ applies – the more you know about pallet stretch wrappers before you buy, the more likely you are to pick a winner.

EQUIPMENT ROUND-UP
The newest piece of kit at Chronos Richardson Systems is the RP500 Cartesian robot palletiser, which uses four-axis mobility to transfer up to 350 bags an hour from the feed conveyor to the pallet.

Cyklop’s range of semi-automatic wrappers has increased with the introduction of the GL300. The machine can be started by remote control from the truck and when a pallet wrap has been completed, the film is automatically cut and the trailing end attached to the load.

Cyklop has also added the CP500 pneumatic hand-strapping tool to its range of strapping equipment. This tool is said to be ideal for securing heavy and difficult products that previously had to be secured with a steel strap.

At Interpack 2008, Krones launched its high-speed Modupal 1 ADR palletiser, which removes the need for a double-position palletiser.

2008 saw several new introductions from the Aetna Group. These included the Helix HS40/2 double-rotating arm winder, which can wrap up to 160 pallets per hour.

Since December 2008, the Walsall Engineering Group has been acting as the sales and engineering partner of Italian stretch wrapping kit specialist Bema in the UK and Irish markets.

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