How palletizers stack up

When deciding between conventional and robotic palletizers, speed, flexibility and other factors are key.

By Bernie Knill, Editor at Large -- Modern Materials Handling, 6/1/2005

If you haven't been keeping up with palletizers lately, now could be a good time. And while both conventional and robotic palletizers are focused on the same objective—uniformly stacking cases, bags and other units on a wooden or plastic pallet in a predetermined pattern—they get to that point somewhat differently.

In fact, the difference in their designs means that the strong suit of conventional palletizers is speed. And for robotic palletizers, it's flexibility. However, an increasing number of applications could go either way.

"While in the past, high-throughput applications have demanded a traditional high-speed palletizer, today many high-speed applications can be achieved with either robotic or conventional technology," says Pat O'Connor, product manager, palletizing systems, FKI Logistex Manufacturing Systems North America, (314-993-4700). The trick is determining which solution is the best fit to meet the other parameters in an application." Conventional palletizers

As production line speeds continue to increase, conventional palletizers are being improved to keep up. Low-speed palletizers handle 50 or fewer cases a minute while mid-speed units are more on the order of 75 to 100 cases. High-speed generally starts at 100 to 125 cases a minute and very high-speed units are 200 cases or more.

"Palletizers have changed electrically and electronically," says Bobby Edmonds, director of sales for von Gal palletizers, a division of HK Systems, Inc. (262-860-7000). "We've gotten away from hydraulic type units to pure electrics. Those moves have cleaned up the equipment."

Conventional palletizers come in several different models. Some accept cases at floor level while others at a higher level. Palletizing patterns can be easily modified even within a pallet load or from pallet to pallet, depending on the software available.

The latest development in conventional palletizers is the human machine interface (HMI). "An HMI is the panel or button of the screen that the operator sees to make the machine do what he wants it to do," says Richard Armstrong, national sales manager, Columbia Machines, Inc. (360-694-5010).

HMIs have changed over time, says Armstrong. In the previous generation, there was a CRT screen, that would specify error but would also detail where the malfunction was. "The current generation," says Armstrong, "is a complete overhaul of those screens to make it clear to the operator—with videos and pictures—that there's a lot more information and it's portrayed in a simpler way so that the average operator knows 's going on." Robotic palletizers

With conventional palletizers having the edge on speed, the question becomes where do robotic palletizers fit? Steve Stegora, manager, material handling,PaR Systems, Inc., (800-464-1320) says "a robot fits best where you're running multiple products at lower rates; conventional fits best in areas where you're running higher volumes and fewer SKUs [stock keeping units]."

Adds FKI's O'Connor: "Robotic solutions generally fit lower-speed lines where the palletizer needs to handle multiple lines simultaneously. Because of their typically smaller footprint, robotic solutions are also an option where floor space is at a premium."

When it comes to speed, the slowest robotic palletizers top out at 10 or 12 bags or cases a minute. Others operate in the 20 to 25 units a minute range. But speeds don't stop there.

Speeds have been increasing, says Columbia's Armstrong. He cites about a 20% increase in the past year alone. At the high end, robotic palletizers handle 120 cases a minute.

The strong suit of robotic palletizers is flexibility. The ability of the robot's arm to move in four, five or six axes makes possible a wide range of palletizing patterns. Robotic palletizers are often identified by their arm types.

The SCARA (selective compliant articulated robot arm) palletizer consists of a single fixed-mast unit with an arm able to rotate at the knuckles. It offers medium speed and price and generally handles one to three loads at a time.

The articulated arm robot is similar to SCARA except that the arm is jointed. It features high speed, a higher price than SCARA, and can handle five loads simultaneously.

Gantry palletizers, another type of robotic model, are typically used in manufacturing. They are slow and handle heavy loads as well as product coming from a large number of production lines. Gantry robots, known as "square robots," are linear motion robots that move up, down and across in a work envelope that can be more than 80 feet long. Economic justification

When it comes to justifying automated palletizers of any type, there are many factors to consider.

Two main criteria are at the top of the justification list, says Sandy Elfrink, executive vice president, PASCO(productive automation systems corporation, 800-464-1320), a manufacturer of conventional palletizers and an integrator of robotic palletizers.

First is the reduction in labor costs when switching from manual to automatic palletizing. The second criteria is throughput—the number of cases palletized in a given time.

There are other factors to consider too. One is the reliability of new equipment compared to manual labor or obsolete equipment.

Both safety and ergonomics are economic justification factors too. Says HK's Edmonds, "Ergonomics is the most prevalent justification for installing a palletizer system. The risk of serious back injuries is considerable. Claims could run as much as $50,000 to $100,000 per occurrence. It goes a long way toward justifying this type of operation."

"Energy consumption and maintenance are also justification factors," reminds Hanno Behm, senior vice president, Beumer Corp.(732-560-1155). Integration

There are also some options when integrating palletizers with existing materials handling systems. In some cases, the palletizer supplier will take responsibility for all materials handling equipment. In other cases, an independent integrator will do the job. And there are all gradations in between.

On the role of an integrator, Jay Wildner, vice president and general manager, Blackhawk Automation, Inc. (608-834-1453), has this to say. "The integrator specifies the correct machine based on collecting the data in the field and an analysis of that data. The integrator makes sure that all peripheral components are specified and, if necessary, manufactured, and that all controls meet customer's specifications." Blackhawk manufactures conventional styles and is an integrator of robotic palletizers.

In any case, automated palletizers offer several new options for building pallets and getting them out the door in short order. Now might be just the time to look at your options and determine if palletizers can be justified in your operation.

Click here to read more about robotic palletizers.
(The versatile robotic palletizer - web exclusive - June 2005)