Palletizing applications pile up for robots: robots, faster and cheaper than ever, can be...

When it comes to the end of the line, robots may be the end of the line.

Traditionally, robotic palletizing has been viewed as an intermediate step between strictly manual and fully automatic. For a robot to make sense at the end of the line, the application had to be low-volume and/or

That's still true, of course. But reliability and other factors have improved in robotic palletizing systems to the point where, in some applications, they can compete directly as a alternative to fully automatic ram-based systems.

End users who are moving away from manual palletizing often have to choose between robotic and traditional palletizers. That's the choice faced by English Mountain Spring Water, Dandridge, Tenn., which supplies the Cracker Barrel restaurant chain with water in customized polyethyelene terephthalte (PET) bottles for diners and store customers.

English Mountain considered a conventional palletizer, but settled on a KR 180 robot system from Kuka Robotics, installed by Aidco International. The robotic system was only about $10,000 more than the conventional one, and offered more versatility, says company president John Burleson.

"We felt that down the road, we could actually take [the robot] and put it anyplace in the plant and maybe even retool it to do some additional work," Burleson says.

Robotic future

Palletizing is "going away from hard automation and going more and more toward robotics," asserts Matthew Job, senior engineer for material handling, palletizing and packaging at Fanuc Robotics.

Robots can compete on equal terms with many conventional palletizers because they're more robust. It's not uncommon for a robot to be rated at more than 60,000 hours of mean time between failures.

"You look at a hard automation palletizer, there's drives and chains and pulleys and many different things that can break," Job says. "In a robot there's four motors and four [speed] reducers and beyond that, it's all linkage, so there's very few things that can go wrong."

FKI Logistex markets both robotic and conventional palletizers. Pat O'Connor, the company's product manager for palletizing systems, says the competition between the two has become more direct.

"I would say there is no question that robotic palletizers compete head to head with conventional ones," O'Connor says. "I think customer preference or customer fascination with the technology sometimes encourages the use of robots where conventional palletizers could be less expensive."

In some applications, robots compete by moving cases just like conventional palletizers do: in entire layers at a time. Kevin Alberts, regional sales director at Brenton Engineering, says some customers use robots to replace worn-out conventional palletizers. Such robot systems usually have layer-forming tables and robot end-of-arm tooling that allow it to pick tip and move a whole layer of cases.

"Application-wise, it's almost similar to a [conventional palletizer]," Alberts says. "We would still form a layer pattern and pick and place that pattern. With that, we have seen rates approaching--or exceeding, with small cases--100 cases a minute." End-user benefits can include a low-level case infeed, a flexible system footprint to fit existing room layouts, robot reliability and the flexibility to quickly adapt to product changes through user-friendly software.

O'Connor says FKI Logistex has had similar installations, but he doesn't believe that it represents the future of robotic palletizing.

"I think that over the long term, direct pick-and-place will be the solution, and not combining some alternate technology to try to get the robot to speed up," O'Connor says.

Flexibility advantage

Robotic palletizing still retains its traditional advantages. "The underlying advantage we have over any hard automation is flexibility," Job says.

The most common need for flexibility in palletizing stems from the need to change pallet loading patterns. Retailers are demanding a greater variety in both case sizes and load make-ups. Many retailers want what Kevin Kozuszek, marketing manager of Kuka Robotics, calls "rainbow loads," consisting of numerous product types.

Robots, of course, can handle this kind of variety much more easily than conventional palletizers. With the latter, changing a pallet pattern is a major mechanical project; for robots, it's a simple matter of programming.

How simple is a factor that varies among suppliers. Most of them provide the initial programming but allow end users to add new patterns as needed. In most cases, such programming would have to be done by electricians or other trained plant personnel. But some robot manufacturers are touting systems that allow pallet pattern programming through the operator interface, presumably by anyone on the plant floor.

"The robot industry has pushed this concept of easy pattern creation," says one manufacturer. "I can be a little cynical about it. It's not anywhere near as easy or flexible as advertised."

In any case, software for pallet changes is usually proprietary. Fallas Automation, which has specialized up to now in robotic case packing, is waiting for Allen-Bradley to develop open-architecture software for pallet programming before coming out with a palletizing system.

"We don't want to have proprietary boxes on our machine to make life difficult for the people at the plant level," says Fallas spokesperson David Mitchell. "We want them to be able to get into the program to do what they need to as they grow with different needs."

Lines slow down

Flexibility also is needed at the end of the line when it's instituted upstream. Many plants are getting away from high-speed dedicated lines that rarely change case sizes or other parameters. The tendency is toward slower lines and more of them, which makes it easier to increase product variety.

One of the most common uses of robotic palletizers is for servicing two or more lines. Using conventional palletizers on multiple lines would require overhead case conveyors converging on the palletizer, which would bring problems of noise and maintenance, O'Connor says.

Robotic palletizers also are well suited to applications where space constraints can make conventional systems unusable. A beam or support in the wrong place, or simply not enough room at the end of the line, can crowd out a conventional palletizer. But robots need only enough room to be able to reach the end of the line with their arms.

Robotic palletizers come in a variety of configurations, but they can be broadly divided into two classes: fixed-base and gantry. The latter hang the robot off an overhead rail, which often is at the top of a gantry, or large bracket-shaped frame.

Gantry-based systems cover more ground than fixed-base ones. FKI Logistex has installed gantry-based systems, for end users such as chewing-gum and cigarette manufacturers, that fill as many as 20 pallets. They also usually can handle heavier payloads than fixed-based robots. Gantry-based systems are more expensive, slower and take up more room than fixed-base ones; they are most appropriate for multiple lines with large cases and low throughput.

One of the final frontiers for robotic palletizing is the freezer. "There are people who believe one of greatest untapped potential applications for palletizing is freezers," O'Connor says.

Manually stacking cases onto pallets inside a frozen-storage area is one of the hardest, most distasteful jobs to be found in any food plant. But the cold that makes humans uncomfortable can be fatal to robots, coagulating their lubricants and contracting their metal. Even minuscule contraction can ruin the fine tolerances needed in a robot's bearings.

Until recently, robot manufacturers could only cope with the cold the same way humans do: by dressing for it. Many robots in freezers wear "suits" of vinyl or other material with electric heating elements inside.

"They tended to take a Band-Aid approach, if you will, by putting a suit over the arm, so that the arm thought it wasn't in the freezer, even though it was," O'Connor says. "The downside to that is, the customer has invested a lot of money in trying to keep this area cool, and then you put heating elements in it."

But some robot manufacturers, including Motoman and Kuka, have come out with robots designed especially for freezers. These models have lubricants and bearings that take the effects of a cold environment into account, enabling them to work without being heated.

Robotic palletizing has evolved into one of the most versatile options for the end of the packaging line. Technology improvements are making robots suitable for all sorts of applications.

For more information

The following companies helped with the research of this article:

Aidco International

517-265-7165; www.aidcoint.com

Arrowhead Systems

920-235-5562; www.arrowheadsystems.com

Brenton Engineering

800-535-2730; www.brentonengineering.com

Fallas Automation

254-772-9524; www.fallasautomation.com

Fanuc Robotics America Inc.

800-4T-ROBOT; www.fanucrobotics.com

FKI Logistex

800-325-1596; www.fkilogistex.com

Kuka Robotics

248-819-0230; www.kukarobotics.com