GETTING UNITIZED

Logistics Asia, 1/3/2008

What you want are neatly palletized, tightly wrapped unit loads. CORINNE KATOR explores some of the machines that can help deliver just that.

The vast majority of today’s palletizing operations are in manual mode, and while much of that palletizing is done without any mechanical assistance or with the help of all-purpose powered lift tables, there are suppliers that offer work positioners specifically designed to assist with theprocess of creating unit loads.

The positioners typically hold up to 2,000 kg and work best with uniform pallet loads. They require a lift truck for depositing and retrieving pallets and cost between US$1,700 and $2,500. As well as enabling major reductions in back injuries, productivity increases of up to 40 percent have been reported – an impressive result from an inexpensive piece of equipment that needs virtually no maintenance.

Although not widely used, semiautomatic palletizing machines are popular in some niche, low speed applications – such as bags of cement mix or cases of metal fasteners – where products are heavy and difficult to manually palletize.

A conveyor delivers products to the semi-automatic palletizer, where an operator arranges them into a layer on a plate. The operator then presses a button and the plate retracts, allowing the layer to fall onto the pallet just below.

Semi-automatic palletizers typically handle up to 20 cases or bags per minute and cost between $15,000 and $50,000, depending on the level of automation.

FULLY AUTO
Fully automated palletizing machines are the fastest, most efficient, most ergonomic type of palletizing equipment. But they are also the most expensive: costs range from $50,000 to $800,000, depending on the speed of the machine and the sophistication of the accumulators, conveyors and pallet dispensers that accompany it. Two categories of automatic palletizers are available: conventional and robotic.

Several varieties of conventional palletizers exist, but they all work on the same basic principle.w The machine forms a layer of products on a plate, it positions the plate above the pallet, and then it retracts the plate, letting the layer descend onto the pallet. The machine repeats the cycle until the load is complete. “It’s a version of the old tablecloth trick,” says Pat O’Connor, Product Manager at FKI Logistex, “where you pull the cloth out and leave the dishes behind.”

Most robotic palletizing systems operate through the use of a jointed robot arm to pick products from a production line and place them on a pallet. The robots, which often handle several cases at a time, can complete up to 25 pick-andplace cycles per minute. An entrylevel robotic system costs at least $125,000.

According to O’Conner, robotic systems have several advantages: a smaller footprint than conventional palletizers; the ability to build up to four pallets from four different product lines simultaneously, making them a good choice for some smaller volume operations; and though few buyers will admit it, robots are cooler.

“Robots are coming on strong in the palletizing business,” says O’Connor. “More and more of the low- to medium-speed applications are going robotic.”

Making the case for conventional palletizers is Jason Bennett, Director of Sales and Marketing at von Gal, who claims that that they are the best choice for many palletizing operations, with a basic conventional machine, costing less than half the price of a basic robot. Conventional palletizers also have a broader range of speeds, anywhere from 10 to 200 cases per minute.

As for trends in automatic palletizing, suppliers have traditionally focused on making high speed, high cost machines for high volume operations. But, says O’Connor, “there’s been a movement recently in automatic palletizing toward lower cost machines.” FKI, for example, offers a line of palletizers that handles fewer than 20 cases per minute and costs about $50,000.

Changes in consumer packaging are also influencing the palletizing market. As packaging gets cheaper and less durable, says Jason Bennet, palletizers must handle products more gently. And as package sizes get smaller, says Ted Yeigh of Columbia Machine, demand increases for faster palletizers that handle smaller cases. Yeigh says demand has increased for palletizing systems sophisticated enough to build mixed loads. An automatic palletizer can place multiple SKUs (stock keeping units) on the same load, he says, as long as the layers are about the same size.

STRETCH & WRAP
Once items have been placed on a pallet there has to be way to make them stay there as the pallet gets transported around. Stretchwrapping is considered to be the most cost-effective way to keep pallet loads together.

While manual stretchwrapping requires little equipment – at most, a $40 film dispenser and a $3 safety knife for cutting the film – a range of product options are available for automatically or semi-automatically wrapping loads.

An operation that stretchwraps more than 15 loads per day can likely justify some level of automation based on savings in labor, back strain and film costs, says Gordon Cooper, Sales Manager, Vestil Manufacturing, who also notes that because stretch film is a petroleum product, film prices have doubled in recent years.

Machines with pre-stretch devices can typically triple the life of a roll of film, and operations wrapping 20-25 loads per day can justify the cost of a machine with a prestretcher. A semi-automatic stretchwrapper needs an operator to tie the film to the load before wrapping begins, to cut the film after wrapping is complete, and – in the simplest machines – to guide the roll of film up and down the load during wrapping. Price tags range from about $3,500 to $15,000. Fully automatic stretchwrapping systems, on the other hand, attach and cut the film automatically, making use of optical sensors to detect loads so that operator is necessary. These machines, which range from $14,000 to more than $400,000, are best suited for routine operations where the same product comes down a conveyor line many times a day.

Two main types of stretchwrap machines are used for wrapping pallet loads: turntable and rotary. With turntable machines, the load spins as it is being wrapped. With rotary arm machines, which are best suited for heavy or unstable loads, the roll of film swings around a stationary load. While faster than turntable machines, rotary types also cost twice as much.

Advances in plastics technology mean that stretch films are getting thinner and stronger, and newer stretchwrap machines are designed to get maximum stretch from these films.

US manufacturers of stretchwrap machines report growing sales in low labor cost locations like South America and Mexico. An indication, they say, that the high price of film, rather than the potential for labor savings, is driving the market for stretchwrap machines.

Corinne Kator is Associate Editor, Modern Materials Handling (www.mmh.com).